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A phylogenetic and biogeographic perspective on the evolution of Poeciliid fishes
Abstract
Phylogenetic relationships of members of the subfamily Poeciliinae (Cyprinodontiformes) are investigated to test alternate hypotheses of diversification resulting from the assembly of the Central America and the Caribbean from the Cretaceous period onwards. We use 4333 aligned base pairs of mitochondrial DNA and 1549 aligned base pairs of nuclear DNA from 55 samples representing 48 ingroup and seven outgroup species to test this hypothesis. Mitochondrial genes analyzed include those encoding the 12S and 16S ribosomal RNAs; transfer RNAs coding for valine, leucine, isoleucine, glutamine, methionine, tryptophan, alanine, asparagine, cysteine and tyrosine; and complete cytochrome b and NADH dehydrogenase subunit I and II; nuclear gene analyzed included the third exon of the recombination activation gene 1 (RAG1). Analyses of combined mtDNA and nuclear DNA data sets result in a well-supported phylogenetic hypothesis. This hypothesis is in conflict with the classical taxonomic assignment of genera into tribes and phylogenetic hypotheses based on the taxonomy; however, the molecular hypothesis defines nine clades that are geographically restricted and consistent with the geological evolution of Central America and the Caribbean. Our analyses support multiple colonization events of Middle America followed by a mix of vicariance and dispersal events.
... Molecular phylogenetics have also challenged the taxonomic assignment of genera to tribes based on morphological characters (Rosen and Bailey, 1963). These studies have consistently recovered tribes as nonmonophyletic (Hrbek et al., 2007;Reznick et al., 2017). ...
... Likewise, our understanding of the diversity and evolutionary relationships at the generic and species levels within Poeciliidae has significantly changed over the last ten years (e.g., Agorreta et al., 2013;Alda et al., 2013;Kang et al., 2013;Bagley et al., 2015;Jones et al., 2016;Thomaz et al., 2019;Rodríguez-Silva et al., 2020;Spikes et al., 2021;Palacios et al., 2023), including the description of four new species and a new genus (Fricke et al., 2023). In fact, a striking result based on molecular phylogenetic analyses is the hypothesis regarding the placement of Xenodexia ctenolepis, a species endemic to the upper reaches of the Usumacinta River in northern Middle America (Hubbs, 1950;Elías et al., 2020), as the sister taxon to all other poeciliids (Hrbek et al., 2007;Reznick et al., 2017). On the contrary, morphological hypotheses placed Tomeurus gracilis as the sister taxon of all other poeciliids (Rosen and Bailey, 1963;Lucinda and Reis, 2005). ...
... On the contrary, morphological hypotheses placed Tomeurus gracilis as the sister taxon of all other poeciliids (Rosen and Bailey, 1963;Lucinda and Reis, 2005). Interestingly, modern biogeographic models support a South American origin for the family (Hrbek et al., 2007;Reznick et al., 2017;Tagliacollo et al., 2017). ...
Poeciliids (Cyprinodontiformes: Poeciliidae), commonly known as livebearers, are popular fishes in the aquarium trade (e.g., guppies, mollies, swordtails) that are widely distributed in the Americas, with 274 valid species in 27 genera. This group has undergone various taxonomic changes recently, spurred by investigations using traditional genetic markers. Here we used over 1,000 ultraconserved loci to infer the relationships within Poeciliidae in the first attempt at understanding their diversification based on genome-scale data. We explore gene tree discordance and investigate potential incongruence between concatenation and coalescent inference methods. Our aim is to examine the influence of incomplete lineage sorting and reticulate evolution on the poeciliids’ evolutionary history and how these factors contribute to the observed gene tree discordace. Our concatenated and coalescent phylogenomic inferences recovered four major clades within Poeciliidae. Most supra-generic level relationships we inferred were congruent with previous molecular studies, but we found some disagreements; the Middle American taxa Phallichthys and Poecilia (Mollienesia) were recovered as non-monophyletic, and unlike other recent molecular studies, we recovered Brachyrhaphis as monophyletic. Our study is the first to provide signatures of reticulate evolution in Poeciliidae at the family level; however, continued finer-scale investigations are needed to understand the complex evolutionary history of the family along with a much-needed taxonomic re-evaluation.
... Molecular phylogenetics have also challenged the taxonomic assignment of genera to tribes based on morphological characters (Rosen and Bailey, 1963). These studies have consistently recovered tribes as nonmonophyletic (Hrbek et al., 2007;Reznick et al., 2017). ...
... Likewise, our understanding of the diversity and evolutionary relationships at the generic and species levels within Poeciliidae has significantly changed over the last ten years (e.g., Agorreta et al., 2013;Alda et al., 2013;Kang et al., 2013;Bagley et al., 2015;Jones et al., 2016;Thomaz et al., 2019;Rodríguez-Silva et al., 2020;Spikes et al., 2021;Palacios et al., 2023), including the description of four new species and a new genus (Fricke et al., 2023). In fact, a striking result based on molecular phylogenetic analyses is the hypothesis regarding the placement of Xenodexia ctenolepis, a species endemic to the upper reaches of the Usumacinta River in northern Middle America (Hubbs, 1950;Elías et al., 2020), as the sister taxon to all other poeciliids (Hrbek et al., 2007;Reznick et al., 2017). On the contrary, morphological hypotheses placed Tomeurus gracilis as the sister taxon of all other poeciliids (Rosen and Bailey, 1963;Lucinda and Reis, 2005). ...
... On the contrary, morphological hypotheses placed Tomeurus gracilis as the sister taxon of all other poeciliids (Rosen and Bailey, 1963;Lucinda and Reis, 2005). Interestingly, modern biogeographic models support a South American origin for the family (Hrbek et al., 2007;Reznick et al., 2017;Tagliacollo et al., 2017). ...
... Both theories, vicariance and overwater dispersal hypotheses, have disagreed with each other with no consensus over many decades. However, some authors have suggested that both processes could have played important roles in the biogeography of different groups in the Caribbean (Hrbek et al., 2007;Newton, 2003). ...
... Several poeciliid species show varying levels of tolerance to water salinity, which could made possible overseas dispersal from the mainland (Briggs, 1984;Darlington, 1938;Myers, 1938;Rosen & Bailey, 1963). In fact, much of the controversy between dispersal and vicariance advocates in relation to the origin of the Antillean freshwater fish fauna revolves around the fact that poeciliids are a group that ecologically lies between terrestrial and purely freshwater species so that both models can explain the biogeographic distribution observed in this group (Hrbek et al., 2007;Palacios et al., 2016;Reznick et al., 2017;Rivas, 1958;Rosen & Bailey, 1963;Weaver et al., 2016). ...
... The oldest radiation event documented for poeciliids in the West Indies was related to the ancestors of today's genus Girardinus and its sister genus Quintana, both endemic to Cuba (Doadrio et al., 2009;Hrbek et al., 2007;Reznick et al., 2017;Rivas, 1958). ...
Studies of the biogeography of the West Indies are numerous but not all taxonomic groups have received the same attention. Many of the contributions to this field have historically focused on terrestrial vertebrates from a perspective closely linked to the classical theory of island biogeography. However, some recent works have questioned whether some of the assumptions of this theory are too simplistic. In this review, we compiled information about the West Indies biogeography based on an extensive and rigorous literature search. While we offer some background of the main hypotheses that explain the origin of the Caribbean biota, our main purpose here is to highlight divergent diversification patterns observed in terrestrial versus aquatic groups of the West Indian biota and also to shed light on the unbalanced number of studies covering the biogeography of these groups of organisms. We use an objective method to compile existing information in the field and produce a rigorous literature review. Our results show that most of the relevant literature in the field is related to the study of terrestrial organisms (mainly vertebrates) and only a small portion covers aquatic groups. Specifically, livebearing fishes show interesting deviations from the species‐area relationship predicted by classical island biogeography theory. We found that species richness on the Greater Antilles is positively correlated with island size but also with the presence of elevations showing that not only island area but also mountainous relief may be an important factor determining the number of freshwater species in the Greater Antilles. Our findings shed light on mechanisms that may differently drive speciation in aquatic versus terrestrial environments suggesting that ecological opportunity could outweigh the importance of island size in speciation. Investigations into freshwater fishes of the West Indies offer a promising avenue for understanding origins and subsequent diversification of the Caribbean biota.
... America to the Polochic-Motagua-Jocotán fault system in Guatemala and Honduras in Central America. The ichthyofauna of the region is primarily hypothesized to have diversified from South American origins between the late Cretaceous to the Miocene (Hrbek, Seckinger, & Meyer, 2007;McMahan, Chakrabarty, Sparks, Smith, & Davis, 2013;Tagliacollo, Duke-Sylvester, Matamoros, Chakrabarty, & Albert, 2017), pre-dating estimated ages (~20 to ~6 Ma) for the closure of the Panamanian Isthmus (Bacon et al., 2015). This region has been subjected to everything from shifting tectonic plates, volcanic activity and sea-level changes to river reversals that have made for a complex geological history, particularly for its freshwaters (Brocard et al., 2012;Iturralde-Vinent & MacPhee, 1999;Rosen, 1975Rosen, , 1979Rosen, , 1985. ...
... Characiformes and Siluriformes) dominate the diversity. This pattern has been explained by the Ostariophysan vacuum hypothesis (Myers, 1966) in which cichlids and poeciliids colonized and diversified in Northern Middle America (Hrbek et al., 2007;Ríčan, Piálek, Zardoya, Doadrio, & Zrzavy, 2013) in the absence of Ostariophysan fishes (which are hypothesized to have arrived after the initial closure of the Panamanian isthmus; Reeves & Bermingham, 2006). But the discovery of the monotypic family Lacantunidae in the upper reaches of the Usumacinta River (Rodiles-Hernández, Hendrickson, Lundberg, & Humpries, 2005) and the hypothesis of its phylogenetic relationships based on molecular data (Lundberg, Sullivan, Rodiles-Hernández, & Hendrickson, 2007) do not support the Ostariophysan vacuum hypothesis and instead suggest that a more diverse group of Ostariophysans fishes (i.e. ...
... Thus, their discovery, diagno- The five endemic areas recovered were primarily supported by the distribution of poeciliids and cichlids but only the non-dominant taxon category provided strong support for the distinctiveness of the Northern Maya Block. Cichlids and poeciliids dominate the species pool of freshwater fishes in the region (Chakrabarty & Albert, 2011;Matamoros et al., 2015;Miller, 1966) and it is hypothesized that these taxa colonized and diversified in the region prior the initial closing of the Panamanian isthmus (Chakrabarty & Albert, 2011;Hrbek et al., 2007;Ríčan et al., 2013;Tagliacollo et al., 2017) in contrast with other taxa like modern Ostariophysi, which began dispersing into the Northern Neotropics only after initial closing of the Isthmus of Panama (Reeves & Bermingham, 2006) up to 20 million years ago (Bacon et al., 2015). Such differences in the timing of colonization in Africa (Lundberg et al., 2007) and Xenodexia ctenolepis, a species of livebearer (family Poeciliidae) that has been hypothesized to be the sister to all other New World members of the family based on molecular data (Hrbek et al., 2007), are both endemic to the Upper Usumacinta. ...
Aim
The processes that generate biodiversity occur at finer scales than are often studied, particularly in freshwater systems of the northern Neotropics. We investigate whether fine‐scale biogeographic patterns are present within the larger Grijalva–Usumacinta Area of Endemism (AoE) —a region in Middle America where nearly 60% of freshwater fishes are endemic—and if present‐day river basins are single historical units.
Location
Northern Central America and southern Mexico.
Taxon
Freshwater fishes (e.g., Cichlidae, Poeciliidae, Ostariophysi)
Methods
We used fine‐scale distributional data for freshwater fishes in northern Middle America (based on museum records and fieldwork) and performed cluster analyses on a presence/absence data matrix of 117 species. We assessed statistical support of geographic clusters using global one‐way analysis of similarity and recovered endemic areas that were further supported by species indicator analyses. Endemic areas were diagnosed by the distribution of endemic species within these areas. For a broader scale we also performed phylogeographic analyses for widespread species representing the dominant families of the region.
Results
We found unrecognized biogeographic structure within the Grijalva‐Usumacinta AoE. Different lineages possess varying degrees of geographic structuring and endemic species were not homogeneously distributed across the riverscape.
Main conclusions
We redefine the geographic boundaries of two northern Middle American areas of endemism. We identify five endemic areas nested within the larger Grijalva‐Usumacinta AoE. We demonstrate that the upper reaches of the Usumacinta and Grijalva river basins are independent historical biogeographic units and can be differentiated from their lower reaches based on their assemblage and molecular diversity. The recognition of these endemic areas can help us define the geographic landscape and develop hypotheses about the processes that generated the ichthyofauna of northern Middle America.
... Without specific attention to Lake Miragoâne, some studies of Limia have resolved the general phylogeny of the genus. Current literature suggests Limia to form a monophyletic group with the genera Pamphorichthys, Mollienesia, Micropoecilia, and Poecilia, with Limia as sister taxon to Poecilia [51][52][53]. Limia melanogaster is the most basal species, branching off early and colonizing Jamaica [2]. Limia melanogaster's divergence was followed by the colonization of Hispaniola, where the species diverged into over 20 recognized species [44]. ...
... Via Polymerase Chain Reaction (PCR), we amplified 1127 bp of the mitochondrial cytochrome b gene. Primers and reaction profiles were modified from Hrbek et al. ( [51]; Additional file 4). Except for L. vittata, P. dominicensis, and P. hispaniolana, the primer combinations L14725 and H15981 were used. 1 µl DNA isolate was used during amplification (increased to 2 µl if DNA concentration was below 20 ng/µl). ...
Objective The Caribbean is an important global biodiversity hotspot. Adaptive radiations there lead to many speciation events within a limited period and hence are particularly prominent biodiversity generators. A prime example are freshwater fish of the genus Limia, endemic to the Greater Antilles. Within Hispaniola, nine species have been described from a single isolated site, Lake Miragoâne, pointing towards extraordinary sympatric speciation. This study examines the evolutionary history of the Limia species in Lake Miragoâne, relative to their congeners throughout the Caribbean. Results For 12 Limia species, we obtained almost complete sequences of the mitochondrial cytochrome b gene, a well-established marker for lower-level taxonomic relationships. We included sequences of six further Limia species from GenBank (total N = 18 species). Our phylogenies are in concordance with other published phylogenies of Limia. There is strong support that the species found in Lake Miragoâne in Haiti are monophyletic, confirming a recent local radiation. Within Lake Miragoâne, speciation is likely extremely recent, leading to incomplete lineage sorting in the mtDNA. Future studies using multiple unlinked genetic markers are needed to disentangle the relationships within the Lake Miragoâne clade.
... Without specific attention to Lake Miragoâne, some studies of Limia have resolved the general phylogeny of the genus. Current literature suggests Limia to form a monophyletic group with the genera Pamphorichthys, Mollienesia, Micropoecilia, and Poecilia, with Limia as sister taxon to Poecilia [51][52][53]. Limia melanogaster is the most basal species, branching off early and colonizing Jamaica [2]. Limia melanogaster's divergence was followed by the colonization of Hispaniola, where the species diverged into over 20 recognized species [44]. ...
... Via Polymerase Chain Reaction (PCR), we amplified 1127 bp of the mitochondrial cytochrome b gene. Primers and reaction profiles were modified from Hrbek et al. ( [51]; Additional file 4). Except for L. vittata, P. dominicensis, and P. hispaniolana, the primer combinations L14725 and H15981 were used. 1 µl DNA isolate was used during amplification (increased to 2 µl if DNA concentration was below 20 ng/µl). ...
Objective
The Caribbean is an important global biodiversity hotspot. Adaptive radiations there lead to many speciation events within a limited period and hence are particularly prominent biodiversity generators. A prime example are freshwater fish of the genus Limia , endemic to the Greater Antilles. Within Hispaniola, nine species have been described from a single isolated site, Lake Miragoâne, pointing towards extraordinary sympatric speciation. This study examines the evolutionary history of the Limia species in Lake Miragoâne, relative to their congeners throughout the Caribbean.
Results
For 12 Limia species, we obtained almost complete sequences of the mitochondrial cytochrome b gene, a well-established marker for lower-level taxonomic relationships. We included sequences of six further Limia species from GenBank (total N = 18 species). Our phylogenies are in concordance with other published phylogenies of Limia . There is strong support that the species found in Lake Miragoâne in Haiti are monophyletic, confirming a recent local radiation. Within Lake Miragoâne, speciation is likely extremely recent, leading to incomplete lineage sorting in the mtDNA. Future studies using multiple unlinked genetic markers are needed to disentangle the relationships within the Lake Miragoâne clade.
... Introduction M e m b e r s o f P o e c i l i i n a e s e n s u P a r e n t i ( 1 9 8 1 ) (Cyprinodontiformes: Poeciliidae) comprise approximately 275 species in 27 genera, which are widely distributed in the Americas, from the southern USA to Argentina, as well as on many islands throughout the Caribbean (Lucinda 2003;Reznick et al. 2017). The highest diversity occurs in Central America (Hrbek et al. 2007), especially in Mexico, where 81 species are known (Miller 2005), whereas only 5 species have been reported in Argentina (Mirande and Koerber 2015). Due to their diversity and broad distribution, poeciliids have played a prominent role in studies of biogeography (Hrbek et al. 2007), which have recently postulated that the family originated in South America, although its major diversification dates to a later colonization of Central America (Reznick et al. 2017). ...
... The highest diversity occurs in Central America (Hrbek et al. 2007), especially in Mexico, where 81 species are known (Miller 2005), whereas only 5 species have been reported in Argentina (Mirande and Koerber 2015). Due to their diversity and broad distribution, poeciliids have played a prominent role in studies of biogeography (Hrbek et al. 2007), which have recently postulated that the family originated in South America, although its major diversification dates to a later colonization of Central America (Reznick et al. 2017). In addition to their remarkable biological diversity, variation in reproductive traits displayed by this group of fishes, ranging from egg laying to live-bearing and including morphological Verónica Taglioretti and Adriana García-Vásquez contributed equally to this work. ...
In this study, we followed an integrative taxonomy approach to describe two new species of Gyrodactylus von Nordmann, 1832, and to identify specimens of G. breviradix Vega, Razzolini, Arbetman, and Viozzi, 2019, all three collected from ten spotted live-bearer Cnesterodon decemmaculatus (Jenyns, 1842), an endemic and widespread poeciliid from the Pampean region, which is the southernmost occurring species of the Poeciliidae in the Americas. Gyrodactylids were first characterized morphologically and mophometrically, and when possible, sequences of the Internal Transcribed Spacers (ITS1-5.8S-ITS2) and the cytochrome oxidase II (COII) were used to delimit species. Gyrodactylus breviradix, Gyrodactylus marplatensis n. sp., and Gyrodactylus pampeanus n. sp. were found on the fins and body surface of C. decemmaculatus in La Tapera Creek, Mar del Plata, Buenos Aires province, Argentina. A phylogenetic analysis combining newly generated sequences of one of the new species, G. marplatensis n. sp., and of G. breviradix, along with those available in GenBank for a further 36 species of Gyrodactylus, revealed that G. marplatensis n. sp. is a sister taxon of Gyrodactylus decemmaculati Vega, Razzolini, Arbetman, and Viozzi, 2019. Genetic distances for the ITS and COII gene were estimated among Gyrodactylus spp. and further supported the validity of the new species. Overall, morphometric and molecular data coincided in delimiting the new taxa, thus demonstrating the value of integrative taxonomy for the erection of new species of Gyrodactylus and species identification.
... Previously phylogenetic hypotheses for Poeciliidae using morphological data evidenced that Cnesterodontini would encompass Cnesterodon Garman, 1895, Phallotorynus Henn, 1916, Phalloceros Eigenmann, 1907, Phalloptychus Eigenmann, 1907(Rosen and Bailey 1963Parenti and Rauchenberger 1989), and Tomeurus Eigenmann, 1909(Ghedotti 2000. Even though phylogenies based on molecular data pointed out discrepancies regarding the monophyly of the tribe Cnesterodontini (see Hrbek et al. 2007), Cnesterodon, Phallotorynus, and Phalloceros are very closely related to each other and form a well-recognized clade within the tribe, based on both more robust morphological data and character states than others used in previous works (see Lucinda 2005Lucinda , 2008. Thus, species of Cnesterodon, Phalloceros, and Phallotorynus are the currently known cnesterodontines and present taxonomic revisions that address their phylogenetic relationships based on morphological (Lucinda 2005(Lucinda , 2008Lucinda et al. 2006;Aguilera et al. 2009;Lucinda and Graça 2015) as well as on molecular (Thomaz et al. 2019) data. ...
Distributional, phylogenetic, molecular, and paleontological data may be integrated to discover biogeographic patterns exhibited by the organisms. Cladistic biogeography uses information on the phylogenetic relationships between taxa and their geographic distribution to infer a sequence of area fragmentation. Brooks Parsimony Analysis (BPA) was performed based on the phylogenetic proposals for Cnesterodontini to hypothesize on the historical relationships among nine areas previously recognized by endemism of freshwater fish from South America. Additionally, we investigated the conservation scenario for cnesterodontines based on biogeographic, phylogenetic, and extinction criteria to establish a priority ranking for the analyzed areas. We found that the area relationships for Cnesterodontini are strongly linked to the historical patterns of evolution of the hydrographic basins, revealing well-defined scenarios of the formation of hydrological barriers between coastal river basins (i.e., Atlantic Slope) and mainly drainages running into the La Plata River system (i.e., Inland Slope). Dispersal events through headwater capture and sea-level changes explain the congruences evidenced among other fish lineages that exhibit similar diversification patterns in the Central Brazil drainages and in drainages on the Atlantic coast of South America. The ranking of priority areas for conservation established for Cnesterodontini indicates that greater attention should be directed to the regions located in the Central Coastal and Upper Parana areas, mainly in the Atlantic Forest, which represents one of the most threatened biodiversity hotspots on the planet with serious threats to freshwater biodiversity.
... Helminths of Nearctic origin in Southern Mexico and Central America's neotropical host lineages are very rare, the only case currently known being that of the monogenean genus Salsuginus (Mendoza-Franco et al. 2006;Salgado-Maldonado 2006;Salgado-Maldonado 2008). Most models of colonisation and dispersal of Central American and Southern Mexico freshwater fishes of neotropical origin currently propose northwards expansion of the southern taxa (Myers 1966;Martin and Bermingham 1998;Doadrio et al. 1999;Concheiro-Pérez et al. 2007;Hrbek et al. 2007;Říčan et al. 2013;Matamoros et al. 2015b;Tagliacollo et al. 2015). However, some fish lineages like the poeciliid Pseudoxiphophorus likely originated in Central Mexico and dispersed from this area southwards (Agorreta et al. 2013). ...
... A total of 47 individuals from all sampling sites were subjected to molecular analysis. Putative tRNA gene regions and conserved sequences or motifs feature segments were localized and verified by alignment and comparison with homologous sequences of reported poeciliids (Hrbek et al. 2007;Meredith et al. 2010;Kong et al. 2014;Pollux et al. 2014;Bruno et al. 2016) and other fish species (Lee et al. 1995;Nian Shui et al. 2008;Zhang et al. 2013;Satoh et al. 2016). Sequences obtained were submitted to GenBank under the accession numbers MT628341 to MT628348. ...
The biodiversity of Neotropical region is affected by anthropogenic disturbance. Throughout Brazil, Argentina and Uruguay, the native fish, Cnesterodon decemmaculatus, is well distributed and widely used as an excellent bioindicator of environmental quality. We investigated the diversity and genetic structure of its populations along a water pollution gradient to answer the following questions: 1- Does the genetic diversity decrease under the stressful conditions of a severe water quality gradient? and 2- Is there any relationship between the haplotypes registered along the studied basin and those recorded in other distant basins? Two mitochondrial DNA markers, Cytochrome b and D-loop, were analyzed and four haplotypes were registered for both markers along the basin. H1 was present throughout all the river sections in high frequencies leading to a low genetic diversity. We suggest that only a few haplotypes tolerate the stressful conditions of mountain rivers. On the other hand, the presence of H4 at the site located downstream suggests a history of recent colonization from the southeast to the northwest of the biome. These results, together with the abundance decrease along the pollution gradient, and the non-migratory characteristic of C. decemmaculatus suggest that its populations may be at risk of local extinction.
Graphical abstract
... Studies of systematic, biogeography and population genetics have revealed that the upper regions of the two basins have independent evolutionary histories (Elías et al. 2021;Beltrán-López et al. 2021;Terán-Martínez et al. 2021). The presence of relic endemic species such as the catfish of Chiapas (Lacantunia enigmatica Rodiles-Hernández, Hendrickson et Lundberg, 2005) and the livebearer (Xenodexia ctenolepis Hubbs, 1950) of the upper Usumacinta are evidence of the region's unique biogeographic history (Rodiles-Hernández et al. 2005;Hrbek et al. 2007;Elías et al. 2021). ...
Historical hydrological changes and the environmental characteristics of northern Middle America have promoted diversification and determined the distribution of fishes in the Grijalva and Usumacinta river basins of Mexico. In several taxa with wide distributions, cryptic diversity has been identified through molecular and morphological analyses. This study evaluated the intraspecific morphological variation of Dorosoma anale Meek, 1904 and Dorosoma petenense (Günther, 1867) along the Grijalva and Usumacinta river basins through geometric morphometric and linear biometric analyses. Little intraspecific differentiation was detected for either species. However, differences were identified between populations in the Grijalva basin and those from the upper Usumacinta River basins with respect to body height, head size, pelvic fin position, and anal fin size. The phenotypic expression of these attributes appears to be closely related to habitat type and geographic isolation. The morphological differences within D. petenense support the molecular hypothesis of two lineages existing in the Usumacinta River basin.
... milleri) and two other species (H. echeagarayi, H. rachovii) comprise a sister clade to the rest of the genus Gambusia(Hrbek et al., 2007;Miller, 2005;Radda, 1987; R. B. Langerhans et al. unpubl. data), and disagreement exists regarding whether these species belong to the Gambusia genus or their own genus Heterophallus. ...
Cannibalism, the act of preying on and consuming a conspecific, is taxonomically widespread, and putatively important in the wild, particularly in teleost fishes. Nonetheless, most studies of cannibalism in fishes have been performed in the laboratory. Here, we test four predictions for the evolution of cannibalism by conducting one of the largest assessments of cannibalism in the wild to date coupled with a mesocosm experiment. Focusing on mosquitofishes and guppies, we examined 17 species (11,946 individuals) across 189 populations in the wild, spanning both native and invasive ranges and including disparate types of habitats. We found cannibalism to be quite rare in the wild: most populations and species showed no evidence of cannibalism, and the prevalence of cannibalism was typically less than 5% within populations when it occurred. Most victims were juveniles (94%; only half of these appeared to have been newborn offspring), with the remaining 6% of victims being adult males. Females exhibited more cannibalism than males, but this was only partially explained by their larger body size, suggesting greater energetic requirements of reproduction likely play a role as well. We found no evidence that dispersal‐limited environments had a lower prevalence of cannibalism, but prevalence was greater in populations with higher conspecific densities, suggesting that more intense resource competition drives cannibalistic behavior. Supporting this conclusion, our mesocosm experiment revealed that cannibalism prevalence increased with higher conspecific density and lower resource levels but was not associated with juvenile density or strongly influenced by predation risk. We suggest that cannibalism in livebearing fishes is rare in the wild because preying on conspecifics is energetically costly and only becomes worth the effort when competition for other food is intense. Due to the artificially reduced cost of capturing conspecifics within confined spaces, cannibalism in captive settings can be much more frequent. We assessed the occurrence of cannibalism in mosquitofishes (genus Gambusia) and guppies (Poecilia reticulata) by examining 17 species (11,946 individuals) across 189 populations in the wild, and by conducting a mesocosm experiment for one species (Gambusia affinis). Cannibalism was rare, its occurrence was associated with resource competition, but it was not associated with juvenile density or strongly influenced by predation risk, and cannibals were predominantly female. Cannibalism in captive settings might be higher due to an artificially reduced cost of capturing conspecifics within confined spaces.
... Emel'yanova and Pavlov reported on p.97 that for Gambusia affinis, the "proximal centriole (pc) is electron dense and no longer contains distinct tubules" [71]. This species is an internal fertilizer [72]. ...
The sperm competition theory, as proposed by Geoff Parker, predicts that sperm evolve through a cascade of changes. As an example, internal fertilization is followed by sperm morphology diversification. However, little is known about the evolution of internal sperm structures. The centriole has an ancient and evolutionarily conserved canonical structure with signature 9-fold, radially symmetric microtubules that form the cell's centrosomes, cilia, and flagella. Most animal spermatozoa have two centrioles, one of which forms the spermatozoan flagellum. Both are delivered to the egg and constitute the embryo's first two centrosomes. The spermatozoa of mammals and insects only have one recognizable centriole with a canonical structure. A second sperm centriole with an atypical structure was recently reported in both animal groups and which, prior to this, eluded discovery by standard techniques and criteria. Because the ancestors of both mammals and insects reproduced by internal fertilization, we hypothesized that the transition from two centrioles with canonical composition in ancestral sperm to an atypical centriolar composition characterized by only one canonical centriole evolved preferentially after internal fertilization. We examined fish because of the diversity of species available to test this hypothesis-as some species reproduce via internal and others via external fertilization-and because their spermatozoan ultrastructure has been extensively studied. Our literature search reports on 277 fish species. Species reported with atypical centriolar composition are specifically enriched among internal fertilizers compared to external fertilizers (7/34, 20.6% versus 2/243, 0.80%; p < 0.00001, odds ratio = 32.4) and represent phylogenetically unrelated fish. Atypical centrioles are present in the internal fertilizers of the subfamily Poeciliinae. Therefore, internally fertilizing fish preferentially and independently evolved spermatozoa with atypical centriolar composition multiple times, agreeing with Parker's cascade theory.
... In addition, mitochondrial DNA is highly heterogeneous and harbors the genetic characteristics associated with maternal traits (O'Brien 1971;Michot et al. 1990; Bartlett and Davidson 1991;Meyer 1993;Beheregaray and Sunnucks 2001;Liu et al. 2002;Yoshizawa and Johnson 2003). Hence, mitochondrial DNA can be used to identify fish groups at the molecular level and explore geographic distribution, species origin, and species differentiation (Avise et al. 1987;Kai et al. 2002;Hrbek et al. 2007). As fish are a large group with a complex origin in the vertebrate subphylum, studies on their phylogenetic and evolutionary relationships performed using traditional morphological methods often provide limited information. ...
Comparative analysis of the mitogenomes of two Corydoras (Siluriformes, Loricarioidei) with nine known Corydoras, and a phylogenetic analysis of Loricarioidei. ZooKeys Abstract Corydoras is a speciose catfish genus from South America with widely investigated phylogenetic and evolutionary relationships. The complete mitogenomes of C. aeneus and C. paleatus were sequenced, assembled , and annotated using next-generation sequencing. The genome arrangements, gene contents, genome structures, base compositions, evolutionary features, codon usage, and tRNA structures of the two mi-togenomes were compared and analyzed with nine published mitogenomes of Corydoras. Phylogenetic analysis was performed using concatenated nucleotide sequences with 13 protein-coding genes and two rRNAs with 44 mitogenomes of Siluriformes. These results provide information on the mitogenomes of eleven Corydoras species and evolutionary relationships within the suborder Loricarioidei, which may be applicable for further phylogenetic and taxonomic studies on Siluriformes and Loricarioidei.
... Mosquitofish are members of the live-bearing fish subfamily Poeciliinae (Parenti, 1981), a 68 million-year-old group which diversified in Central and North America after dispersal from South America starting 5 million years ago (Hrbek et al., 2007;Reznick et al., 2017). ...
The most widespread and numerous inland fish in the world is likely the mosquitofish (Gambusia affinis and G. holbrooki, Poeciliidae). Much has been written about the basic biology, the current distribution and the negative impacts of non‐native populations of mosquitofish. Here, we instead review the relationship of humanity with mosquitofish. First, we review the early literature on the species and aim to resolve its path towards becoming the globally dominant fish for biological control of mosquitoes. We identify the initial advocates of mosquitofish use, we examine the reasons behind their advocacy, and we document the spread of their viewpoints into and from the globally foundational mosquito control texts. Second, we identify the people and institutions that facilitated early international translocations of mosquitofish, including, among others, David Starr Jordan, the Rockefeller Foundation and the International Red Cross. Third, we discuss the reduction in mosquitofish translocation and use during and after WWII, initially stemming from the discovery and use of other methods, like DDT and later from a recognition of the negative ecological consequences of non‐native mosquitofish populations. Fourth, we propose that the future utility of mosquitofish is largely in its value as a model study organism. We provide an overview of the contributions mosquitofish have made to some major fields in biology. Finally, we suggest that the value of mosquitofish as a model system should increase into the future, behind a momentum of research advances, and as human‐mediated range expansion will permit access to mosquitofish by yet greater numbers of biologists worldwide.
... Caracterización molecular. Para la caracterización molecular se utilizaron fragmentos del gen mitocondrial Citocromo b (Cyt b) (Hrbek et al., 2007;Schories et al., 2009;Tobler et al., 2011). El ADN total (ADNt) se obtuvo de músculo del pedúnculo caudal empleando el kit Puregene (Qiagen) y su cuantificación con espec-trofotómetro Nanodrop. ...
This book Mexican Biodiversity and Ecology: New knowledge and technologies for current challenges is a compilation of scientific studies carried out by researchers from various institutions in the country. Its objective is to present current information on issues of biological diversity and ecology of relevant species in terms of conservation, as well as aspects of sustainable use of natural resources. Bio-logical diversity comprises the accumulation of living organisms considering all levels of their organization (genes, populations, species, communities, habitats, ecosystems and landscapes). Ecology, on the other hand, seeks to understand the relationships that exist between organisms and the biotic and abiotic elements in their environment. Both lines of research are closely related and form the basis for the appropriate use of available natural resources. In this context, the studies presented in this book deal with the diversity of bacterial genes, microbiotas, yeasts, snails, shrimps, insects, fish, dinosaurs, avifauna and vegetation. In the ecological aspect, varied information is offered covering climatic issues, fires, the effect of growth-promoting bacteria in plants, as well as relevant topics on fish, herpetofauna, birds, mammals, fungi, lichens and vegetation. Regarding the use of natural resources, the book contains information on the use of species for economic and human health purposes, biological control, biostimulants, bacterial biocontrol activity, meliponiculture and environmental education through botanical gardens.
It is hoped that this work will provide the reader with a broad overview of the topics that are currently being studied in these lines of research and that seek to increase knowledge of living beings, promoting their conservation and sustainable use.
conservation and sustainable use.
... Para ello se examinaron 126 lotes de museos, definiendo Poeciliinae (sensu Parenti & Rauchenberger 1989). Las unidades taxonómicas operacionales se seleccionaron de acuerdo a material disponible en museos y a la información filogenética existente con relación a este grupo (Rosen 1979;Parenti 1981;Greenfield 1985;Rodríguez 1997;Costa 1998;Ghedotti 1998Ghedotti , 2000Lucinda & Reis 2005;Hrbek et al. 2007). Los datos morfológicos, disecciones e ilustraciones fueron realizados en un estereoscopio Olympus SZX -12. ...
PRESENTACIÓN /
El Simposio de Biodiversidad y Servicios Ambientales 2010 nace de la necesidad de brindar espacios académicos para la divulgación de conocimiento, experiencias, ideas y proyectos de investigación
científica que se han generado en el contexto de la conservación, valoración y el manejo de la diversidad biológica y los servicios ambientales que ésta presta, en respuesta a las amenazas globales como la pérdida de hábitat y especies, así como el cambio climático.
El simposio permite la presentación de resultados de investigaciones científicas y favorece la generación de propuestas en donde el conocimiento se transforme y derive en posibles soluciones y aportes para reducir el impacto de las amenazas sobre los recursos naturales, la biodiversidad y las poblaciones humanas que de ellos dependen.
Para lograr estos objetivos, se instituye en un inicio, una plataforma académica a iniciativa del Instituto de Agricultura y Recursos Naturales de la Universidad Rafael Landívar, el Centro de Estudios Ambientales y de Biodiversidad de la Universidad del Valle de Guatemala, la Fundación Defensores de la Naturaleza y Fondo para el Sistema Arrecifal Mesoamericano. Posteriormente se unieron al esfuerzo el Centro de Estudios Conservacionistas de la Universidad de San Carlos de Guatemala, el Ministerio de Ambiente y Recursos Naturales, el Consejo Nacional de Áreas Protegidas, con el apoyo de la línea FACYT del Consejo Nacional de Ciencia y Tecnología y el aval de la Red de Formación e Investigación Ambiental, REDFIA.
Este documento contiene los resúmenes de las conferencias magistrales, que para el tema de servicios ambientales, fue dictada por la Dra. Carla Restrepo de la Universidad de Puerto Rico-Río Piedras, Puerto Rico, abordando en el tema “Deslizamientos de tierra y presupuestos de carbono en la Sierra de las Minas de Guatemala: Implicaciones para la provisión de servicios ambientales en sistemas montañosos tropicales”. Para reflexionar sobre la importancia de la investigación en biodiversidad para la toma de decisiones, se contó con la conferencia magistral de la Dra. Mariel Aguilar-Støen de la Universidad de Oslo, Noruega, titulada “Biodiversidad, política e investigación: ¿decisión, negociación o imposición?”
Luego se presentan 29 resúmenes de las ponencias de 27 investigadores. En total 21 resúmenes en temas de biodiversidad y 8 en el tema de servicios ambientales. En el tema de biodiversidad, se abordaron los subtemas sobre investigación en ecosistemas terrestres, investigación en ecosistemas marino-costeros
y aguas continentales, gestión de la biodiversidad y aplicación de la biotecnología en el estudio de la biodiversidad.
En el subtema de ecosistemas terrestres se destaca el interés de los investigadores en los grupos de mamíferos menores y aves, aunque también se encuentran investigaciones en temas como paisajes,
insectos o mamíferos mayores. En el tema de investigación en ecosistemas marino-costeros, se abordan temas variados en ecología de aves, peces y mamíferos. En el subtema de gestión se hace énfasis en la inclusión de los pueblos indígenas en Guatemala en la toma de decisiones y en la generación del conocimiento biológico. También se reflexiona sobre aspectos de política y administración pública, así
como el papel de la diversidad genética para enfrentar al cambio climático. El aspecto legal de los recursos genéticos se aborda en el subtema de Biotecnología.
Con respecto a servicios ambientales se tratan subtemas sobre seguridad alimentaria, mecanismos de pagos por servicios ambientales, donde se destacan metodologías para cuantificar servicios de ecosistemas de ribera y el importante servicio de la polinización. En el subtema de metodologías de estimación de servicios ambientales, destacan esfuerzos realizados para la estimación de carbono en bosques con vistas a programas REDD, así como la metodología para calcular la cuenta nacional de agua.
El Comité Científico agradece los esfuerzos de personas e instituciones que han hecho posible este evento y la impresión del presente ejemplar. Esperamos que este documento ayude a los investigadores a divulgar sus temas de interés, sus resultados y conclusiones, y más aún, apoye el avance de la ciencia y la
construcción del conocimiento conjunto en Guatemala.
Dra. Doris Eugenia Martínez Melgar
Comité Científico del Simposio de Biodiversidad
Coordinadora General
... Hubungan kekerabatan fenetik pada spesies ikan Famili Poeciliidae yang telah diidentifikasi sebagai berikut: a) Menentukan Satuan Taksonomi Operasional spesies ikan Faimili Poeciliidae yang dibandingkan; b) Menyeleksi karakter morfologi dari masing-B A Gambar 4. Struktur Gonopodium A. Poecilia rositae (Meyer et al., 2004), B. Xiphophorus hellerii (Hrbek, 2006) masing sampel yang dapat dibandingkan untuk memberi gambaran secara umum dari ciri satuan taksonomi operasional yang dinyatakan dengan kode-kode biner. Kode tersebut yaitu: angka 1 untuk karakter yang dimiliki dan apabila tidak terdapat karakter yang dimiliki diberi angka 0; c) Menyusun data ciri-ciri morfologi ke dalam bentuk tabel atau matriks untuk semua spesies yang dikarakterisasi; d) Data yang diperoleh selanjutnya dianalisis dengan menggunakan NTSYS 2.02i. ...
Anggota Famili Poeciliidae merupakan ikan introduksi dengan karakteristik berukuran kecil, live-bearers, dimorfi seksual dari segi ukuran tubuh, pola warna dan struktur gonopodium sebagai ciri diagnostik pada ikan jantan. Ikan ini berperan sebagai pengontrol perkembangan nyamuk malaria dan model pembelajaran biologi. Sejauh ini kajian taksonomi dan penelusuran hubungan kekerabatan didalam famili Poeciliidae belum ada. Tujuan penelitian ini adalah mengidentifikasi jenis, kekerabatan dan pengelompokkan berdasarkan karakter morfologi (morfometrik, meristrik, gonopodium dan ciri diagnostiknya). Jenis penelitian ini adalah deskriptif eksploratif, dengan pendekatan survey. Pada penelitian ini ditemukan tiga spesies ikan Poeciliidae yaitu Xiphoporus helleri, Poecilia mexicana dan Poecilia reticulata. Dendogram hasil analisis morfologi menggunakan metode UPGMA diperoleh dua kelompok percabangan apomorfi yaitu kelompok Genus Xiphoporus dan Genus Poecilia. Sub Clade automorfi antara Xiphoporus helerri A dan B dengan nilai kesamaan 92%. Pengelompokkan ikan Poeciliidae dibedakan berdasarkan lima karakter utama terpilih yaitu: SL (standart length), Hdl (Panjang kepala), Panjang gonopodium, panjang sirip ekor dan PreDL (Panjang sebelum sirip dorsal).Kejelasan identifikasi ikan introduksi khas Telaga Sari menjadi modal utama dalam aquaculture, manajemen, konservasi, biodiversitas dan perkembangan ilmu pengetahuan.
... The guppy Poecilia reticulata originates from Venezuela and South America, and the mosquitofish Gambusia affinis is originally from North America (Hrbek et al., 2007;Reznick et al., 2017). According to the ancestral area reconstruction based on the molecular phylogeny of the family Poeciliidae, the genus Poecilia diversified mainly in South and Central America, whereas the genus Gambusia diversified after it dispersed from Central America to North America (Reznick et al., 2017). ...
Sexual conflict can result in coercive mating. Because males bear low costs of heterospecific mating, coercive males may engage in misdirected mating attempts toward heterospecific females. In contrast, sexual selection through consensual mate choice can cause mate recognition cues among species to diverge, leading to more accurate species recognition. Some species show both coercive mating and mate choice‐associated courtship behaviors as male alternative reproductive tactics. We hypothesized that if the selection pressures on each tactic differ, then the accuracy of species recognition would also change depending on the mating tactic adopted. We tested this hypothesis in the guppy (Poecilia reticulata) and mosquitofish (Gambusia affinis) by a series of choice experiments. Poecilia reticulata and G. affinis males both showed imperfect species recognition and directed all components of mating behavior toward heterospecific females. They tended to direct courtship displays more frequently toward conspecific than heterospecific females. With male P. reticulata, however, accurate species recognition disappeared when they attempted coercive copulation: they directed coercions more frequently toward heterospecific females. We also found that heterospecific sexual interaction had little effect on the fecundity of gravid females, which suggests that prepregnancy interactions likely underpin the exclusion of G. affinis by P. reticulata in our region.
... Family Anablepidae: This family is represented by a total of 19 species distributed in the Neotropics from Mexico to South America (Fricke et al., 2020). The origin of the family is still debated, with some studies suggesting that the clade originated in the Lower Cretaceous (130-110 Ma), before Africa and South America split (Rosen, 1975;Ghedotti, 2000;Hrbek et al., 2007) or between the Upper Cretaceous and the Early Palaeocene (62-67 Ma) (Reznick et al., 2017). Recent molecular studies suggest that Anablepidae originated in South America during the Oligocene (~29.6 Ma) (Amorim & Costa, 2018), followed by a separation between the oviparous brackish and marine genus Oxyzygonectes Fowler 1916 and the clade comprised by the viviparous anablepids including the brackish and marine genus Anableps Scopoli 1777 and the predominantly freshwater genus Jenynsia Günther 1866 (27.9 Ma), which eventually diverged from each other in the Miocene (12.5 Ma). ...
Introduction:
The Cyprinodontiformes are a group of secondary freshwater fishes widely distributed in El Salvador. Currently, many species of this group are usually incorrectly identified for lack of adequate tools. Additionally, their taxonomy and distribution have changed in recent years.
Objective:
To provide updated information about the taxonomy and distribution of El Salvador Cyprinodontiformes through identification keys, distribution notes, and general descriptions for all species.
Methods:
We carried out an extensive review of the literature, electronic databases, and museum specimens to generate a list of valid species present in El Salvador.
Results:
Eleven species in three families are confirmed: Profundulidae (two species), Anablepidae (one species), and Poeciliidae (eight species). We also include distribution data, both vertical and by main basins, and an illustrated guide. Conclusions: There are 11 species of Cyprinodontiformes in El Salvador and they can be found and identified with this article.
... Caracterización molecular. Para la caracterización molecular se utilizaron fragmentos del gen mitocondrial Citocromo b (Cyt b) (Hrbek et al., 2007;Schories et al., 2009;Tobler et al., 2011). El ADN total (ADNt) se obtuvo de músculo del pedúnculo caudal empleando el kit Puregene (Qiagen) y su cuantificación con espec-trofotómetro Nanodrop. ...
El cambio climático puede influenciar la frecuencia, severidad y extensión de los incendios forestales. Los incendios son perturbaciones comunes en el medio ambiente que pueden tener repercusiones ecológicas y económicas graves e impredecibles; no obstante, también es un conductor importante del funcionamiento del ecosistema, la dinámica de la biota y el ciclo de nutrientes. Es por lo anterior, que el presente trabajo tuvo como objetivo identificar el impacto en la actividad microbiana total del suelo después de un incendio ocurrido en el Cañón de San Lorenzo. Los resultados demostraron un incremento en el pH, CE y MOS en comparación a la zona testigo no incendiada, mas no fue significativo estadísticamente. Por otro lado, la respiración basal sí presentó diferencia significativa entre la zona incendiada y testigo durante todo el tiempo de incubación, presentando una disminución en la zona perturbada, lo que pudo deberse a factores como la transferencia del calor del fuego en el subsuelo que incrementa directamente la mortalidad de las comunidades microbianas, disminuyendo así la biomasa y metabolismo, así como a una menor humedad en el suelo, el cambio de las
propiedades fisicoquímicas o la baja disponibilidad de nutrientes fácilmente degradables.
... Caracterización molecular. Para la caracterización molecular se utilizaron fragmentos del gen mitocondrial Citocromo b (Cyt b) (Hrbek et al., 2007;Schories et al., 2009;Tobler et al., 2011). El ADN total (ADNt) se obtuvo de músculo del pedúnculo caudal empleando el kit Puregene (Qiagen) y su cuantificación con espec-trofotómetro Nanodrop. ...
Se describe la abundancia y diversidad de bacterias fecales de un pool de muestras de caballo en libre pastoreo en la reserva de la Biosfera Mapimí. Se realizó secuenciación masiva V3-V4 del gen 16S rRNA con Illumina.
Los resultados se analizaron con QIIME y la referencia taxonómica EzBioCloud. Se identificaron 10 phyla, 16 clases, 26 órdenes, 46 familias, 134 géneros y 136 especies. Los phyla Proteobacteria, Firmicutes y Actinobacteria fueron los más abundantes. El género de mayor abundancia fue Brevudimonas; se identificaron cinco géneros asociados a infecciones en caballos (Clostridium, Fusobacterium, Klebsiella, Nocardia y Rhodococcus).
... However, recent work revealed male livebearing fishes in the family Poeciliidae have altered this ancestral body plan with a novel three-part body plan composed of the two aforementioned regions plus a third region known as the ano-urogenital vertebral region (Rosa-Molinar et al., 1994, 1996Rivera-Rivera et al., 2010). This body plan appears to have evolved at least 44 million years ago (Hrbek et al., 2007). Because of the relatively little research conducted on this novel body plan to date, and the emphasis on Poeciliidae so far, its origination and extent is not fully understood-this body plan could be more widespread throughout much of Atherinomorpha. ...
Major evolutionary innovations can greatly influence subsequent evolution. While many major transitions occurred in the deep past, male live-bearing fishes (family Poeciliidae) more recently evolved a novel body plan. This group possesses a three-region axial skeleton, with one region—the ano-urogenital region—representing a unique body region accommodating male genitalic structures (gonopodial complex). Here we evaluate several hypotheses for the evolution of diversity in this region and examine its role in the evolution of male body shape. Examining Gambusia fishes, we tested a priori predictions for (1) joint influence of gonopodial-complex traits on mating performance, (2) correlated evolution of gonopodial-complex traits at macro- and microevolutionary scales, and (3) predator-driven evolution of gonopodial-complex traits in a post-Pleistocene radiation of Bahamas mosquitofish. We found the length of the sperm-transfer organ (gonopodium) and its placement along the body (gonopodial anterior transposition) jointly influenced mating success, with correlational selection favoring particular trait combinations. Despite these two traits functionally interacting during mating, we found no evidence for their correlated evolution at macro- or microevolutionary scales. In contrast, we did uncover correlated evolution of modified vertebral hemal spines (part of the novel body region) and gonopodial anterior transposition at both evolutionary scales, matching predictions of developmental connections between these components. Developmental linkages in the ano-urogenital region apparently play key roles in evolutionary trajectories, but multiple selective agents likely act on gonopodium length and cause less predictable evolution. Within Bahamas mosquitofish, evolution of hemal-spine morphology, and gonopodial anterior transposition across predation regimes was quite predictable, with populations evolving under high predation risk showing more modified hemal spines with greater modifications and a more anteriorly positioned gonopodium. These changes in the ano-urogenital vertebral region have facilitated adaptive divergence in swimming abilities and body shape between predation regimes. Gonopodium surface area, but not length, evolved as predicted in Bahamas mosquitofish, consistent with a previously suggested tradeoff between natural and sexual selection on gonopodium size. These results provide insight into how restructured body plans offer novel evolutionary solutions. Here, a novel body region—originally evolved to aid sperm transfer—was apparently co-opted to alter whole-organism performance, facilitating phenotypic diversification.
... The gonoduct has been described in other species of oviparous and viviparous teleosts such as the cyprinid Alburnus alburnus Linnaeus (Lahnsteiner et al., 1997), and the poeciliids P. reticulata (Campuzano-Caballero & Uribe, 2014), P. gracilis (Campuzano-Caballero & Uribe, 2017). Because P. reticulata and P. gracilis are viviparous species and because they are phylogenetically closely related with C. decemmaculatus(Hrbek et al., 2007;Reznick et al., 2017), we will compare these species with the observations analyzed in C. ...
During embryogenesis, teleost females do not develop Müllerian ducts, which form the oviducts in all other vertebrates. Thus, when they reach sexual maturity they do not have oviducts. In viviparous teleosts, the lack of oviducts means that the development of the embryos occurs as an intraovarian gestation, unique among vertebrates. The ovary is an unpaired hollow organ whose cavity is continuous with the caudal portion, the gonoduct, characterized by the absence of germinal cells, which opens to the exterior at the gonopore. The gonoduct attains essential function as a barrier between the germinal region of the ovary and the exterior during all reproductive stages. This study describes the functional morphology of the gonoduct in the viviparous teleost Cnesterodon decemmaculatus during non‐gestation (previtellogenesis and vitellogenesis) and gestation. The ovaries were processed using histological techniques and stained with hematoxylin‐eosin, and periodic acid Schiff. The gonoduct has two regions: cephalic and caudal, and is formed by three histological layers, which are, from inside to the periphery: 1) tunica mucosa; 2) tunica muscularis; and 3) tunica serosa. In the cephalic region there are mucosal folds extending into the lumen and forming a structure similar to a cervix. The histology of the gonoduct indicates essential functions, i.e.,i) the control of the luminal diameter in the limit to the germinal region of the ovary by the presence of a cervix; ii) during insemination the gonoduct receives the spermatozoa, may store and transport them to the germinal region; iii) the presence of melano‐macrophage centers indicates support of immunological processes, especially during gestation when these centers increase in size; iv) production of exocrine secretions; and v) it is the birth canal , internally lined by an ciliated epithelium and surrounded by smooth musclesboth tissues supposedly supporting the birth process. .
... The sterlet reference genome analysis has led to an estimate for the duplicate retention rates of ≈70% after the acipenseridae-specific WGD (180 MYA), which is much higher than the about 15-20% ohnolog retention rate after the teleost WGD (320 MYA) [49]. It was shown that the sterlet genome is generally characterized by very slow evolutionary rates and it may serve as a useful representative of the conserved ancestral actinopterygian genome [11]. ...
MicroRNAs play a crucial role in eukaryotic gene regulation. For a long time, only little was known about microRNA-based gene regulatory mechanisms in polyploid animal genomes due to difficulties of polyploid genome assembly. However, in recent years, several polyploid genomes of fish, amphibian, and even invertebrate species have been sequenced and assembled. Here we investigated several key microRNA-associated genes in the recently sequenced sterlet (Acipenser ruthenus) genome, whose lineage has undergone a whole genome duplication around 180 MYA. We show that two paralogs of drosha, dgcr8, xpo1, and xpo5 as well as most ago genes have been retained after the acipenserid-specific whole genome duplication, while ago1 and ago3 genes have lost one paralog. While most diploid vertebrates possess only a single copy of dicer1, we strikingly found four paralogs of this gene in the sterlet genome, derived from a tandem segmental duplication that occurred prior to the last whole genome duplication. ago1,3,4 and exportins1,5 look to be prone to additional segment duplications producing up to four-five paralog copies in ray-finned fishes. We demonstrate for the first time exon microsatellite amplification in the acipenserid drosha2 gene, resulting in a highly variable protein product, which may indicate sub-or neofunctionalization. Paralogous copies of most microRNA metabolism genes exhibit different expression profiles in various tissues and remain functional despite the rediploidization process. Subfunctionalization of microRNA processing gene paralogs may be beneficial for different pathways of microRNA metabolism. Genetic variability of microRNA processing genes may represent a substrate for natural selection, and, by increasing genetic plasticity, could facilitate adaptations to changing environments.
... Para la caracterización molecular se utilizaron fragmentos del gen mitocondrial Citocromo b (Cyt b) (Hrbek et al., 2007;Schories et al., 2009;Tobler et al., 2011). El ADN total (ADNt) se obtuvo de músculo del pedúnculo caudal empleando el kit Puregene (Qiagen) y su cuantificación con espectrofotómetro Nanodrop. ...
... They represent a widely studied taxon (e.g., Rosen 1960Rosen , 1979Parenti 1981). Hrbek et al. (2007) hypothesized that they dispersed from South America to North America in the Late Cretaceous (ca. 68 m.y.a.). ...
The biota of the Mexican Transition Zone was assembled through the successive dispersal of four cenocrons from North and South America and their incorporation to the Paleoamerican biota, which was the original North American (Holarctic) biota that extended in Mexico in the Jurassic-Cretaceous. The Mexican Plateau cenocron dispersed to southern North America from South America (Gondwana) in the Late Cretaceous-Paleocene. The Mountain Mesoamerican cenocron dispersed from South America to the mountain forests of Central America and southern Mexico in the Oligocene-Miocene and then northward in the Pliocene. The Nearctic cenocron dispersed from northern North America to the mountains of the Mexican Transition Zone in the Miocene-Pliocene. Finally, in the Pleistocene the Typical Neotropical cenocron dispersed from the Neotropical region, being represented by genera widespread in South America. Based on the successive assembly of these cenocrons, three horobiotas are distinguished: Paleogene horobiota (original Paleoamerican biota plus Mexican Plateau cenocron), Neogene horobiota (Paleoamerican biota plus Mexican Plateau, Mountain Mesoamerican, and Nearctic cenocrons), and Quaternary horobiota (Paleoamerican biota plus Mexican Plateau, Mountain Mesoamerican, Nearctic and Typical Neotropical cenocrons)
... They represent a widely studied taxon (e.g., Rosen 1960Rosen , 1979Parenti 1981). Hrbek et al. (2007) hypothesized that they dispersed from South America to North America in the Late Cretaceous (ca. 68 m.y.a.). ...
Several authors have considered that the complex area where the Neotropical and Nearctic biotas overlap corresponds to a transition zone. In the strict sense that is followed in this book, the Mexican Transition Zone includes the highlands of Mexico, Guatemala, Honduras, El Salvador, and Nicaragua north of Lake Nicaragua, whereas northern Mexico, the United States and Canada belong to the Nearctic region, and the lowlands of the Pacific coast and the Gulf of Mexico, the Yucatán Peninsula, and Central America belong to the Neotropical region. In a series of contributions, Gonzalo Halffter provided a coherent theory that explains how cenocrons that evolved in different geographic areas assembled in the Mexican Transition Zone. I review herein the historical development of Halffter’s theory, including the characterization of the dispersal or distributional patterns recognized by this author. These distributional patterns are considered to represent cenocrons, namely, sets of taxa that share the same biogeographic history and constitute identifiable subsets within a biota by their common biotic origin and evolutionary history. The biotic assembly of the Mexican Transition Zone is summarized into five stages, from the Jurassic-Cretaceous to the Pleistocene.
... They represent a widely studied taxon (e.g., Rosen 1960Rosen , 1979Parenti 1981). Hrbek et al. (2007) hypothesized that they dispersed from South America to North America in the Late Cretaceous (ca. 68 m.y.a.). ...
The Mexican Transition Zone is the area where the Neotropical and Nearctic regions overlap. In its strict sense followed in this book, it corresponds to the moderate- to high-elevation highlands of Mexico, Guatemala, Honduras, El Salvador, and Nicaragua. This area is considered a transition zone between the Nearctic and Neotropical regions, so from the perspective of biogeographic regionalization, it should be assigned simultaneously to both regions. Within the Mexican Transition Zone, I recognize 5 biogeographic provinces and 22 districts. The Sierra Madre Occidental province is situated in western Mexico at elevations between 200 and 3000 m, with most of the area above 2000 m; it includes the Apachian and Durangoan districts. The Sierra Madre Oriental province is situated in eastern Mexico at elevations above 1500 m; it includes two subprovinces: Austral-Oriental (with the Saltillo-Parras and Potosí districts) and Hidalgoan (with the Sierra Gorda and Zacualtipán districts). The Transmexican Volcanic Belt province is situated in central Mexico, at elevations above 1800 m; it includes two subprovinces: West (with the Otomí and Tarascan districts) and East (with the Aztec and Orizaba-Zempoaltepec districts). The Sierra Madre del Sur province comprises south central Mexico at elevations above 1000 m; it includes three subprovinces: Western Sierra Madre del Sur (with the Jaliscian and Jaliscian-Manantlán districts), Central Sierra Madre del Sur subprovince (Michoacán district), and Eastern Sierra Madre del Sur (with the Guerreran and Oaxacan Highlands districts). The Chiapas Highlands province comprises southern Mexico, Guatemala, Honduras, El Salvador, and Nicaragua, basically corresponding to the Sierra Madre de Chiapas, from 500 to 2000 m altitude; it includes the Sierra Madrean, Comitanian, Lacandonian, Soconusco, Guatemalan Highland, and Nicaraguan Montane districts.
... They represent a widely studied taxon (e.g., Rosen 1960Rosen , 1979Parenti 1981). Hrbek et al. (2007) hypothesized that they dispersed from South America to North America in the Late Cretaceous (ca. 68 m.y.a.). ...
Most of the authors involved in the theoretical development of evolutionary biogeography assume that dispersalism, panbiogeography, cladistic biogeography, and phylogeography represent alternative approaches. Instead, I consider that different biogeographic methods may be used to answer different questions, which are different steps of an integrative biogeographic analysis. This stepwise approach comprises five steps, each corresponding to particular questions and methods. Track analysis and methods for identifying areas of endemism are used initially to identify biotas (graphically represented on maps as generalized tracks or areas of endemism), which represent hypotheses of primary biogeographic homology and are the basic units of evolutionary biogeography. Then, cladistic biogeography uses available phylogenetic data to test the historical relationships between these biotas (secondary biogeographic homology). Based on the results of these analyses, a biogeographic regionalization is achieved. Intraspecific phylogeography, molecular dating, and fossils are incorporated to help identify the different cenocrons (set of taxa that share the same biogeographic history, which constitute identifiable subsets within a biota by their common biotic origin and evolutionary history) that became assembled in a biota. Finally, the geological and biological knowledge available is integrated to construct a geobiotic scenario that helps explain the way different dispersal and vicariance events contributed to biotic assembly and how the cenocrons dispersed to the biota analyzed. I present the concepts implied in these steps and some of the methods that may be applied to answer particular biogeographic questions and discuss how they can be integrated to explain biotic assembly within an integrative framework.
... They represent a widely studied taxon (e.g., Rosen 1960Rosen , 1979Parenti 1981). Hrbek et al. (2007) hypothesized that they dispersed from South America to North America in the Late Cretaceous (ca. 68 m.y.a.). ...
A biogeographic transition zone is a geographical area of overlap, with a gradient of replacement and partial segregation between different biotas (sets of taxa sharing a similar geographic distribution as a product of a common history). It is an area where physical features and environmental conditions allow the mixture and co-occurrence of species belonging to two or more biotas, but also constrain their distribution further into one another. The biogeographic affinities of the taxa assigned to these biotas are the most fundamental information considered to analyze accurately biogeographic transition zones. Ecological biogeographers have plotted the frequency of different distribution patterns on maps, detecting gradual changes in their relative contribution to a given area and identifying the most heterogeneous places in terms of distributional patterns as transition zones. Evolutionary biogeographers have found transition zones particularly interesting for analyzing causal connections between evolutionary and geological processes at large spatial and temporal scales. Biogeographic transition zones constitute natural laboratories for investigating evolutionary and ecological principles shaping biotic assembly. Additionally, they represent places where different evolutionary lineages coexist, having important implications for conservation, particularly when they also exhibit high diversity.
... They represent a widely studied taxon (e.g., Rosen 1960Rosen , 1979Parenti 1981). Hrbek et al. (2007) hypothesized that they dispersed from South America to North America in the Late Cretaceous (ca. 68 m.y.a.). ...
This book presents an evolutionary biogeographic analysis of the Mexican Transition Zone, which is situated in the overlap of the Nearctic and Neotropical regions. It includes a comprehensive review of previous track, cladistic and molecular biogeographic analyses and is illustrated with full color maps and vegetation photographs of the respective areas covered.
Given its scope, the book will be of interest to students and researchers whose work involves systematic and biogeographic analyses of plant and animal taxa of the Mexican Transition Zone or other transition zones of the world, and to ecologists working in biodiversity conservation, who will be able to appreciate the evolutionary relevance of the Mexican Transition Zone for establishing conservation areas.
... However, most of the species occur in inland waters including species locally distributed in mountain streams. Most of the recent studies aimed to determine the origins of this genus in the Caribbean, agree on the South American derivation of Limia fishes via dispersal or vicariance (Hrbek et al., 2007;Palacios et al., 2016;Weaver et al., 2016b;Reznick et al., 2017) Hispaniola is considered to be the center of endemism for Limia since at least 18 species are known from this island whereas only one endemic species is reported from Cuba, Jamaica, and Grand Cayman each (Chambers, 1987;Burgess & Franz, 1989;Hamilton, 2001;Weaver et al., 2016b). A notable radiation is particularly observed in Lake Miragoane located in southwestern Haiti where eight endemic species are currently reported. ...
Limia mandibularis, a new livebearing fish of the family Poeciliidae is described from Lake Miragoane in southwestern Haiti on Hispaniola. The new species differs from all other species in the genus Limia by the presence of a well-developed lower jaw, the absence of preorbital and preopercular pores, and preorbital and preopercular canals forming an open groove each. The description of this new Limia species from Lake Miragoane confirms this lake as an important center of endemism for the genus with a total of nine described species so far.
... The gene balance hypothesis posits that ohnologues persist because the loss of one copy would lead to a detrimental change in the stoichiometry of macromolecular complexes, the interactome and signalling pathways 47 . The majority of duplicates, however, are predicted to become non-functional or get lost (degeneration)-for example, the ohnologue retention rate from the teleost WGD in the extant teleosts is estimated to be only 15-20% 48 . On the basis of noncoding microsatellites, the sterlet was proposed to have undergone extensive duplicate gene degeneration and has been classified since then even as a functional diploid species 10 . ...
Sturgeons seem to be frozen in time. The archaic characteristics of this ancient fish lineage place it in a key phylogenetic position at the base of the ~30,000 modern teleost fish species. Moreover, sturgeons are notoriously polyploid, providing unique opportunities to investigate the evolution of polyploid genomes. We assembled a high-quality chromosome-level reference genome for the sterlet, Acipenser ruthenus. Our analysis revealed a very low protein evolution rate that is at least as slow as in other deep branches of the vertebrate tree, such as that of the coelacanth. We uncovered a whole-genome duplication that occurred in the Jurassic, early in the evolution of the entire sturgeon lineage. Following this polyploidization, the rediploidization of the genome included the loss of whole chromosomes in a segmental deduplication process. While known adaptive processes helped conserve a high degree of structural and functional tetraploidy over more than 180 million years, the reduction of redundancy of the polyploid genome seems to have been remarkably random.
... Molecular evidence sustains that several clades of frogs (Crawford and Smith, 2005;Moen and Wiens, 2009;Alonso et al., 2012), freshwater fishes (Murphy et al., 1999;Perdices et al., 2005;Concheiro Pérez et al., 2007;Hrbek et al., 2007;Hulsey et al., 2011;Rican et al., 2013), spiders (Crews and Gillespie, 2006;Binford et al., 2008), and plants (Fritsch, 2003;Pennington and Dick, 2004;van Ee et al., 2008), may have also dispersed through GAARlandia. Further, detailed analyses by Dávalos (2004) agree in that most non-volant Caribbean mammalian lineages arrived in the West Indies before the Middle Miocene. ...
Resumen: Tradicionalmente América del Sur fue considerado como un continente isla durante la mayor parte del Terciario. Sin embargo, evidencia biológica y paleontológica dispersa indica que un intercambio biótico entre Norte y Sudamérica habría ocurrido en tiempos pre-Pliocenos. En contraposición, la evidencia geológica que sugiere que el Istmo de Panamá se habría cerrado en el Mioceno es todavía débil, y esto constituye una importante inconsistencia entre los datos geológicos y biológicos. Con la finalidad de explicar el poblamiento de las Islas Caribeñas por fauna y flora terrestres, diversos autores propusieron que entre el Eoceno y Oligoceno existió una lengua de tierra emergida llamada GAARlandia que uníría América del Sur con esas islas. Si este fuera el caso, habrían ocurrido intercambios bióticos entre las Islas del Caribe y ambas américas en una estrecha ventana temporal. Esta nueva hipótesis tiene implicancias profundas en el entendimiento de las fases tempranas del intercambio biótico entre las Américas en tiempos pre-pliocenos.
Scombridae is a family of pelagic marine fishes that comprises 16 genera and 51 species. This family has been of significant commercial importance throughout history; however, the phylogenetic relationships within the Scombridae have been disputed due to the unclear taxonomic boundaries of the suborder Scombroidei, which includes six families, including Scombridae. Despite this, only a limited number of studies have been conducted on the Scombridae. In our study, eight species covering five genera of the Scombridae were selected, and one nuclear (ITS) and three mitochondrial DNA markers (CO1, Cytb, and D-loop) were used to amplify gene fragments. Additionally, we included homologous sequences from other Scombridae fishes obtained from GenBank. Our analysis constructed phylogenetic relationships of 48 Scombridae species in 14 genera. The results demonstrated that the three phylogenetic trees (NJ, ML, and BI) exhibited similar topologies, containing three major clades. One major clade indicated that Grammatorcynus bilineatus and Grammatorcynus bicarinatus did not cluster with other species in the Scombridae; another clade comprised the genera Scomber and Rastrelliger ; the third clade consists of the remaining Scombridae species. Notably, the study showed that Gasterochismatinae and Scombrinae were not sister groups; Allothunnus (tribe Thunnini) and Cybiosarda (tribe Sardini) clustered into a clade, suggesting that Sardini and Thunnini were non-monophyletic. Overall, this research enhances the understanding of phylogenetic relationships within the Scombridae and provides basic information to aid further research.
In biogeography, vicariance and long-distance dispersal are often characterised as competing scenarios. However, they are related concepts, both relying on collective geological, ecological, and phylogenetic evidence. This is illustrated by freshwater fishes, which may immigrate to islands either when freshwater connections are temporarily present and later severed (vicariance), or by unusual means when ocean gaps are crossed (long-distance dispersal). Marine barriers have a strong filtering effect on freshwater fishes, limiting immigrants to those most capable of oceanic dispersal. The roles of vicariance and dispersal are debated for freshwater fishes of the Greater Antilles. We review three active hypotheses [Cretaceous vicariance, Greater Antilles-Aves Ridge (GAARlandia), long-distance dispersal] and propose long-distance dispersal to be an appropriate model due to limited support for freshwater fish use of landspans. Greater Antillean freshwater fishes have six potential source bioregions (defined from faunal similarity): Northern Gulf of México, Western Gulf of México, Maya Terrane, Chortís Block, Eastern Panam a, and Northern South America. Faunas of the Greater Antilles are composed of taxa immigrating from many of these bioregions, but there is strong compositional disharmony between island and mainland fish faunas (>90% of Antillean species are cyprinodontiforms, compared to <10% in Northern Gulf of México and Northern South America, and ≤50% elsewhere), consistent with a hypothesis of long-distance dispersal. Ancestral-area reconstruction analysis indicates there were 16 or 17 immigration events over the last 51 million years, 14 or 15 of these by cyprinodontiforms. Published divergence estimates and evidence available for each immigration event suggests they occurred at different times and by different pathways, possibly with rafts of vegetation discharged from rivers or washed to sea during storms. If so, ocean currents likely provide critical pathways for immigration when flowing from one landmass to another. On the other hand, currents create dispersal barriers when flowing perpendicularly between landmasses. In addition to high salinity tolerance, cyprinodontiforms collectively display a variety of adaptations that could enhance their ability to live with rafts (small body size, viviparity, low metabolism, amphibiousness, diapause, self-fertilisation). These adaptations likely also helped immigrants establish island populations after arrival and to persist long term thereafter. Cichlids may have used a pseudo bridge (Nicaragua Rise) to reach the Greater Antil-les. Gars (Lepisosteidae) may have crossed the Straits of Florida to Cuba, a relatively short crossing that is not a barrier to gene flow for several cyprinodontiform immigrants. Indeed, widespread distributions of Quaternary migrants (Cyprinodon, Gambusia, Kryptolebias), within the Greater Antilles and among neighbouring bioregions, imply that long-distance dispersal is not necessarily inhibitory for well-adapted species, even though it appears to be virtually impossible for all other freshwater fishes.
Genes are often selected for molecular taxonomy citing their agreement to taxonomically derived species trees. These results are then used to define and edit existing taxonomic hierarchies of species. We counter the validity of this practice experimentally using mitochondrial genes routinely employed for the purpose. We constructed trees from complete mitochondrial DNA sequence (except D-loop) and its thirteen protein-coding genes namely ND1, ND2, ND3, ND4, ND4L, ND5, ND6, ATP6, ATP8, COI, COII, COIII & CYTB of 255 species of Cypriniformes fish using maximum likelihood (ML) and Bayesian methods. While ND4, ND5, COI, COII, COIII and CYTB formed trees at par with the species tree, no gene produced complete concurrence. Similarly, while few genes formed similar branching patterns at family (COI & COIII) or broad group (ND1, ND2 & ND3 and ND5 & COII) levels, no two gene trees fully agreed with each other. Tajima’s D estimates of all studied genes indicated non-random evolution, violating the basic assumption of molecular phylogenetics. Bootstrap or Posterior probability values were also poor for several taxa indicating low robustness. Our findings reiterate that tree concurrence noted in studies involving smaller sample sizes is not a reflection of the evolutionary signature of the species.
Mexico is a megadiverse region with a complex geological history, but it remains unclear to what extent the distribution of freshwater fish has been influenced by geographic barriers. This study examines the population level genetic divergence and phylogenetic relationships of species in the shortfin group of the subgenus Mollienesia (genus Poecilia), a group of live-bearing fishes that are widely distributed across Mexico, with sampling at a small geographic scale. Samples from over 50 locations were analyzed for six species by using phylogenetic and haplotype network approaches to assess genetic diversity across geographic ranges and to refine the distributions of species in this group. The results indicate that Mexican species have diversified following multiple, independent invasions from Middle America. Two species found north of the Trans-Mexican Volcanic Belt (TMVB) and one transversal species exhibited weak phylogenetic structure, likely due to the lack of physiographic barriers, recent colonization, and high dispersal rates among regions. In contrast, three species found south of the TMVB exhibited strong phylogenetic structure, reflecting a longer presence in the area and multiple physiographic barriers that isolated populations. This study identified mechanisms driving divergence and speciation, expanded the known range of several species, and resolved taxonomic uncertainties of populations.
This datasheet on Phalloceros caudimaculatus covers Identity, Overview, Distribution, Dispersal, Diagnosis, Biology & Ecology, Environmental Requirements, Natural Enemies, Impacts, Uses, Prevention/Control, Further Information.
This datasheet on Belonesox belizanus covers Identity, Overview, Distribution, Dispersal, Diagnosis, Biology & Ecology, Environmental Requirements, Natural Enemies, Impacts, Uses, Prevention/Control, Further Information.
The karst aquifer of the Yucatán Peninsula (YP) in southeastern Mexico is a unique ecosystem in which water-filled sinkholes, locally known as cenotes, connect subterranean waters with the surface. This system is home to around 20 species of freshwater fishes, including several that are endemic and/or threatened. Studies on this unique ichthyofauna have been partially hampered by the technical difficulties associated with sampling these habitats, particularly submerged caves. In this proof-of-concept study, we use environmental DNA (eDNA) metabarcoding to survey the diversity of freshwater fishes associated with the YP karst aquifer by sampling six cenotes from across the Ring of Cenotes region in northwestern Yucatán, a 180-km-diameter semicircular band of abundant karst sinkholes. Through a combination of conventional sampling (direct observation, fishing) and eDNA metabarcoding, we detected eight species of freshwater fishes across the six sampled cenotes. Overall, our eDNA metabarcoding approach was effective at detecting the presence of fishes from cenote water samples, including one of the two endemic cave-dwelling fish species restricted to the subterranean section of the aquifer. Although our study was focused on detecting fishes via eDNA, we also recovered DNA from several other vertebrate groups, particularly bats. These results suggest that the eDNA metabarcoding approach represents a promising and largely noninvasive method to assay aquatic biodiversity in these vulnerable habitats, allowing more effective, frequent, and wide-ranging surveys. Our detection of DNA from aerial and terrestrial vertebrate fauna implies that eDNA from cenotes, besides being a means to survey aquatic fauna, may also offer an effective way to quickly survey non-aquatic biodiversity associated with these persistent water bodies.
Poeciliopsis (Cyprinodontiformes: Poeciliidae) is a genus comprised of 25 species of freshwater fishes. Several well-known taxonomic uncertainties exist within the genus, especially in relation to the taxonomic status of Poeciliopsis pleurospilus and P . gracilis . However, to date, no studies have been conducted to specifically address the taxonomic status of these two species. The goal of this study was to examine the taxonomic validity of P . pleurospilus and P . gracilis using genomic data (ddRADseq) in phylogenetic, population genetic, and species delimitation frameworks. Multiple analyses support the recognition of both taxa as distinct species and also permits us to revise their respective distributions. A species delimitation analysis indicates that P . pleurospilus and P . gracilis are distinct species, each of which consists of two distinct lineages that are geographically structured. Phylogenetic and population genetic analyses provide clear evidence that individuals of P . gracilis are distributed north and west of the Isthmus of Tehuantepec in both Pacific and Atlantic river systems in Mexico, whereas individuals of P . pleurospilus are distributed in both Atlantic and Pacific river systems south and east of the Isthmus of Tehuantepec, from southern Mexico to Honduras.
The fish fauna occurring in Brazilian small streams comprises 36 families of teleost freshwater fishes. The systematics and phylogenetic knowledge about this fauna greatly expanded during the last two decades, but is still very heterogeneous. For some taxonomic groups there are taxonomic identification keys and well-documented phylogenetic hypotheses, while other groups are mostly comprised by poorly known species. The increase in the knowledge of Neotropical fish diversity was associated with the significant growth of hypotheses about their evolution and contributed to the understanding of the phylogenetic history of fish comunities and their structure in small streams.
Rich fossil evidence suggests that many traits and functions related to terrestrial evolution were present long before the ancestor of lobe- and ray-finned fishes. Here, we present genome sequences of the bichir, paddlefish, bowfin, and alligator gar, covering all major early divergent lineages of ray-finned fishes. Our analyses show that these species exhibit many mosaic genomic features of lobe- and ray-finned fishes. In particular, many regulatory elements for limb development are present in these fishes, supporting the hypothesis that the relevant ancestral regulation networks emerged before the origin of tetrapods. Transcriptome analyses confirm the homology between the lung and swim bladder and reveal the presence of functional lung-related genes in early ray-finned fishes. Furthermore, we functionally validate the essential role of a jawed vertebrate highly conserved element for cardiovascular development. Our results imply the ancestors of jawed vertebrates already had the potential gene networks for cardio-respiratory systems supporting air breathing.
The Caribbean is one of the most important biodiversity hotspots on the planet due to the high level of species diversity and endemism in plants and animals. As elsewhere, adaptive radiations in the Caribbean lead to many speciation events within a limited period and hence are particularly prominent biodiversity generators. The general prediction from Island Biogeography that relates species richness to island size is valid for livebearing fishes in general in the Greater Antilles, where larger islands have higher numbers of species mainly due to in situ speciation. A prime example of this speciation process can be seen in the genus Limia , endemic to the Greater Antilles. Within Hispaniola, nine species have been described from a single isolated site, Lake Miragoâne, pointing towards extraordinary sympatric speciation in Limia . Few studies have examined the evolutionary history of the fishes found in Lake Miragoâne. Here, we address the gaps in present knowledge by providing a preliminary phylogeny of Limia and testing whether the species found in Lake Miragoâne may originated from an in situ radiation. We targeted the mitochondrial cytochrome b gene, a well-established marker for lower-level taxonomic relationships for which we obtained almost complete sequences for 13 species. The general topology of the phylogenies we produced are in concordance with other published phylogenies of Limia . There is also strong support that the species found in Lake Miragoâne in Haiti are indeed monophyletic (BS=97; PP=1.0), confirming the hypothesis of a recent local radiation. Within Lake Miragoâne, speciation is likely extremely recent, leading to incomplete lineage sorting in the mtDNA. Future studies are needed using multiple unlinked genetic markers to disentangle the relationships within the Lake Miragoâne clade.
The Neotropical freshwater fish fauna represents 20% of the known fish species diversity. Although several historical and ecological mechanisms involved in the distribution of this diverse ichtyofauna have been explored, few studies have analyzed a complete community. Here, we report a study of the distribution and diffusion of eco-morphological traits across the phylogeny of the fish community of the Maroni Basin, located at the border between French Guiana and Suriname. We also test the eco-morphological hypothesis stating that morphology can be used as a predictor of ecology. Nuclear (five markers) and mitochondrial (one marker) sequences of 236 species were collected to reconstruct their phylogeny, morphometric measurements of 680 individuals were taken and a data table of each species’ general ecology was compiled. Multivariate analyses showed a strong structuration of morphometric data on the axes segregating the orders and successive ranks. Axis 1 (27.14%) was a component of shape, and separated compressed, deep-bodied big-eyed fishes (negative values) from depressed, long-snouted fishes with small eyes positioned upward (positive values). The second axis (25.47%) was mainly related to fin-based locomotion and showed a negative correlation between length of anal fin (negative values) and the relative area of pectoral, dorsal and caudal fins. Ecological traits showed a more diffuse pattern since some niches can be occupied by several species belonging to different orders. Co-inertia analyses showed that morphological and ecological traits were significantly linked (RV=0.23; p<0.001) but that this correlation becomes very weak once the influence of phylogeny is removed (RV=0.05; p<0.02), thus challenging the universal application of the eco-morphological hypothesis. Furthermore, Abouheif tests showed that all ecological and morphological traits, as well as the main co-variations between them, were significantly auto-correlated to phylogeny. Evolutionary patterns of some of these traits were mapped across the community’s evolutionary tree: thus we observed that shifts to a benthic lifestyle occurred twice during the evolution of Characiformes and Siluriformes and that they were both times simultaneously followed by body depression and anal fin reduction, and that body depth and relative eye size have a tendency to co-evolve.
Using molecular dated phylogenies and biogeographic reconstructions, the species diversity, biogeography and time frame of evolution of the genus Herichthys were evaluated. In particular, we test the role of Punta del Morro (PdM) as a vicariant brake along the Mexican Transition Zone in the context of local and global time frame of cichlid diversification using several sets of calibrations. Species diversity in Herichthys is complex and the here employed dating methods suggest young age and rapid divergence for many species while species delimitation methods did not resolve these young species including both sympatric species pairs. Based on our molecular clock dating analyses, Herichthys has colonized its present distribution area significantly prior to the suggested vicariance by PdM (10-17.1 Ma vs. 5 to 7.5 Ma). The PdM constraint is in conflict with all other paleogeographic and fossil constraints including novel ones introduced in this study that are, however, congruent among each other. Our study demonstrates that any cichlid datings significantly older or younger than the bounds presented by our analyses and discussion have to be taken as highly questionable from the point of view of Middle American paleogeography and cichlid biogeography unless we allow the option that cichlid biogeography is completely independent from ecological and geological constraints.
Limia islai, a new species of livebearing fish, is described from Lake Miragoane in south‐western Haiti on Hispaniola. The new species has a conspicuous barred pattern consisting of several (4–12) black bars along the body, ray 4p serrae of the gonopodium in males with 10 segments and origin of dorsal fin in females slightly behind the origin of the anal fin. Although the new species colour pattern is similar to that of the humpbacked limia Limia nigrofasciata Regan 1913, L. islai sp. nov. has exclusive morphological features, such as slender body, lack of hump anterior to dorsal fin in males and presence of specific features in the gonopodial suspensory, which allow an unambiguous diagnosis from L. nigrofasciata. L. islai further differs from L. nigrofasciata in reproductive behaviour since L. islai males rely on sneak copulations and gonopodial thrusting, whereas L. nigrofasciata display an elaborate courtship behaviour. The new species is also genetically distinct in both nuclear (Rh, Myh6) and mitochondrial (12S, ND2, D‐loop, Cytb) genes from other species in the genus showing reciprocal monophyly. The description of this new Limia species from Lake Miragoane confirms this lake as an important centre of endemism for the genus, with a total of eight endemic species described so far.
A new method is presented for inferring evolutionary trees using nucleotide sequence data. The birth–death process is used as a model of speciation and extinction to specify the prior distribution of phylogenies and branching times. Nucleotide substitution is modeled by a continuous-time Markov process. Parameters of the branching model and the substitution model are estimated by maximum likelihood. The posterior probabilities of different phylogenies are calculated and the phy-logeny with the highest posterior probability is chosen as the best estimate of the evolutionary relationship among species. We refer to this as the maximum posterior probability (MAP) tree. The posterior probability provides a natural measure of the reliability of the estimated phy-logeny. Two example data sets are analyzed to infer the phylogenetic relationship of human, chimpanzee, gorilla, and orangutan. The best trees estimated by the new method are the same as those from the maximum likelihood analysis of separate topologies, but the posterior probabilities are quite different from the bootstrap proportions. The results of the method are found to be insensitive to changes in the rate parameter of the branching process.
This paper* presents a series of detailed paleogeographical analyses of the Caribbean region, beginning with the opening of the Caribbean basin in the Middle Jurassic and running to the end of the Middle Miocene. Three intervals within the Cenozoic are given special treatment: Eocene-Oligocene transition (35-33 Ma), Late Oligocene (27-25 Ma), and early Middle Miocene (16-14 Ma). While land mammals and other terrestrial vertebrates may have occupied landmasses in the Caribbean basin at any time, according to the interpretation presented here the existing Greater Antillean islands, as islands, are no older than Middle Eocene. Earlier islands must have existed, but it is not likely that they remained as such (i.e., as subaerial entities) due to repeated transgressions, subsidence, and (not incidentally) the K/T bolide impact and associated mega-tsunamis. Accordingly, we infer that the on-island lineages forming the existing (i.e., Quaternary) Antillean fauna must all be younger than Middle Eocene. The fossil record, although still very poor, is consistent with the observation that most land mammal lineages entered the Greater Antilles around the Eocene-Oligocene transition. Western Laurasia (North America) and western Gondwana (South America) were physically connected as continental areas until the mid-Jurassic, ca. 170 Ma. Terrestrial connections between these continental areas since then can only have occurred via landbridges. In the Cretaceous, three major uplift events, recorded as regional unconformities, may have produced intercontinental landbridges involving the Cretaceous Antillean island arc. The Late Campanian/Early Maastrichtian uplift event is the one most likely to have resulted in a landbridge, as it would have been coeval with uplift of the dying Cretaceous arc. However, evidence is too limited for any certainty on this point. The existing landbridge (Panamanian isthmus) was completed in the Pliocene; evidence for a precursor bridge late in the Middle Miocene is ambiguous. We marshal extensive geological evidence to show that, during the Eocene-Oligocene transition, the developing northern Greater Antilles and northwestern South America were briefly connected by a "landspan" (i.e., a subaerial connection between a continent and one or more off-shelf islands) centered on the emergent Aves Ridge. This structure (Greater Antilles + Aves Ridge) is dubbed GAARlandia. The massive uplift event that apparently permitted these connections was spent by 32 Ma; a general subsidence followed, ending the GAARlandia landspan phase. Thereafter, Caribbean neotectonism resulted in the subdivision of existing land areas. The GAARlandia hypothesis has great significance for understanding the history of the Antillean biota. Typically, the historical biogeography of the Greater Antilles is discussed in terms of whether the fauna was largely shaped by strict dispersal or strict continent-island vicariance. The GAARlandia hypothesis involves elements of both. Continent-island vicariance sensu Rosen appears to be excludable for any time period since the mid-Jurassic. Even if vicariance occurred at that time, its relevance for understanding the origin of the modern Antillean biota is minimal. Hedges and co-workers have strongly espoused over-water dispersal as the major and perhaps only method of vertebrate faunal formation in the Caribbean region. However, surface-current dispersal of propagules is inadequate as an explanation of observed distribution patterns of terrestrial faunas in the Greater Antilles. Even though there is a general tendency for Caribbean surface currents to flow northward with respect to the South American coastline, experimental evidence indicates that the final depositional sites of passively floating objects is highly unpredictable. Crucially, prior to the Pliocene, regional paleoceanography was such that current-flow patterns from major rivers would have delivered South American waifs to the Central American coast, not to the Greater or Lesser Antilles. Since at least three (capromyid rodents, pitheciine primates, and megalonychid sloths) and possibly four (nesophontid insectivores) lineages of Antillean mammals were already on one or more of the Greater Antilles by the Early Miocene, Hedges' inference as to the primacy of over-water dispersal appears to be at odds with the facts. By contrast, the landspan model is consistent with most aspects of Antillean land-mammal biogeography as currently known; whether it is consistent with the biogeography of other groups remains to be seen.
Osteological and soft anatomical features of representatives of poeciliine genera were studied to test the monophyly of the poeciliine tribes and to advance a hypothesis of relationships within the subfamily. The resultant hypothesis supports the proposal of a new classification for the subfamily Poeciliinae. Diagnoses are provided for suprageneric clades. The tribe Tomeurini is resurrected and the new tribes Brachyrhaphini and Priapichthyini as well as the supertribe Poeciliini are described. New usages of old tribe names are proposed based on the phylogenetic framework. Caracteres osteológicos e da anatomia mole de representantes dos gêneros de poeciliíneos foram estudados para se testar a monofilia das tribos de Poeciliinae e para propor uma hipótese de relações dentro da subfamília. A hipótese resultante suporta a proposição de uma nova classificação para a subfamília Poeciliinae. São fornecidas diagnoses para os clados supragenêricos. A tribo Tomeurini é ressuscitada e as novas tribos Brachyrhaphini e Priapichthyini bem como a supertribo Poeciliini são descritas. Novos usos para antigos nomes de tribos são propostos com base no arranjo filogenético.
Nucleotide sequences for a 402-base segment of the mitochondrial cytochrome b gene were determined from 25 species of live-bearing fishes. A total of 34 sequences representing 24 species of the genus Gambusia and 1 species of Belonesox were generated via the polymerase chain reaction. The levels of overall variation were consistent with those from other genera of fishes. In total, 137 of 402 (34.1%) nucleotides exhibited variation within or among the species. Observed differences at 24 (17.9%) of the 134 cytochrome b codons would result in amino acid replacements. Phylogenetic analyses employing various weighting schemes resulted in several clades representing traditionally recognized taxonomic groups. However, precise relationships among species-groups remained uncertain. Randomization tests indicated that these topologies contained significant nonrandom phylogenetic information. As with other fishes, the overall rate of divergence appeared to be slower than that of other vertebrates and the overall replacement/substitution pattern was suggestive of nonrandom evolutionary input.
The complete sequence of the 16,569-base pair human mitochondrial genome is presented. The genes for the 12S and 16S rRNAs, 22 tRNAs, cytochrome c oxidase subunits I, II and III, ATPase subunit 6, cytochrome b and eight other predicted protein coding genes have been located. The sequence shows extreme economy in that the genes have none or only a few noncoding bases between them, and in many cases the termination codons are not coded in the DNA but are created post-transcriptionally by polyadenylation of the mRNAs.
A 505-bp sequence from the control region (D-loop) and the complete 1047 bp of the NADH dehydrogenase subunit 2 (ND2) gene were examined for individuals from 11 species of mollies included in the group Mollienesia. All three species of sailfin mollies of the Poecilia latipinna species complex were included (P. latipinna, P. petenensis and P. velifera); this group is named after the strikingly large dorsal fin in males. Six members of the shortfin P. mexicana complex (P. gilli, P. mexicana, P. orri, P. catemaconis, P. latipunctata and P. sulphuraria) and two members of the shortfin P. sphenops complex (P. butleri and P. sphenops) were examined. To test the monophyly of the Molliensia group, two species of mollies outside of this group were included: P. caucana and P. vivipara. The guppy P. reticulata was used as the outgroup taxon. Similar topologies were recovered using three phylogenetic methods (maximum parsimony, neighbour joining and maximum likelihood) and revealed several interesting relationships. First, all members of Mollienesia form a monophyletic group, which supports the more traditional taxonomy and classification of these species as comprising the subgenus Mollienesia as proposed previously. Second, the species of mollies outside of the Mollienesia group are only loosely allied with the Mollienesia clade; P. caucana is the sister taxon to Mollienesia, but P. vivipara lies outside of this Mollienesia-P. caucana clade. Third, the three sailfin molly species form a monophyletic group within the Mollienesia clade, but interestingly, shortfin species are paraphyletic due to the inclusion of a single shortfin species, P. latipunctata, within this sailfin clade. The exact placement of P. latipunctata within the sailfin clade is unclear. Fourth, the remaining shortfin species form a monophyletic sister clade to the sailfins and are separated into two groups, one containing P. sphenops and P. catemaconis and a second lineage leading to the remaining shortfin species. This arrangement does not support the morphological separation of shortfins into a P. sphenops and a P. mexicana species complex. Bootstrap analyses support the monophyly of Mollienesia (78–85%), the sailfin clade (100%) and the shortfin clade (79–95%).
A maximum likelihood method for inferring evolutionary trees from DNA sequence data was developed by Felsenstein (1981). In evaluating the extent to which the maximum likelihood tree is a significantly better representation of the true tree, it is important to estimate the variance of the difference between log likelihood of different tree topologies. Bootstrap resampling can be used for this purpose (Hasegawa et al. 1988; Hasegawa and Kishino 1989), but it imposes a great computation burden. To overcome this difficulty, we developed a new method for estimating the variance by expressing it explicitly.The method was applied to DNA sequence data from primates in order to evaluate the maximum likelihood branching order among Hominoidea. It was shown that, although the orangutan is convincingly placed as an outgroup of a human and African apes clade, the branching order among human, chimpanzee, and gorilla cannot be determined confidently from the DNA sequence data presently available when the evolutionary rate constancy is not assumed.
A new method is presented for inferring evolutionary trees using nucleotide sequence data. The birth-death process is used
as a model of speciation and extinction to specify the prior distribution of phylogenies and branching times. Nucleotide substitution
is modeled by a continuous-time Markov process. Parameters of the branching model and the substitution model are estimated
by maximum likelihood. The posterior probabilities of different phylogenies are calculated and the phylogeny with the highest
posterior probability is chosen as the best estimate of the evolutionary relationship among species. We refer to this as the
maximum posterior probability (MAP) tree. The posterior probability provides a natural measure of the reliability of the estimated
phylogeny. Two example data sets are analyzed to infer the phylogenetic relationship of human, chimpanzee, gorilla, and orangutan.
The best trees estimated by the new method are the same as those from the maximum likelihood analysis of separate topologies,
but the posterior probabilities are quite different from the bootstrap proportions. The results of the method are found to
be insensitive to changes in the rate parameter of the branching process.
The program MRBAYES performs Bayesian inference of
phylogeny using a variant of Markov chain Monte Carlo.
Availability: MRBAYES, including the source code, documentation,
sample data files, and an executable, is available at http://brahms.biology.rochester.edu/software.html.
Contact: johnh{at}brahms.biology.rochester.edu
Cyprinodontiforms are a diverse group of approximately 900 pantropical and temperate fishes, mostly found in freshwater. Whereas the vast majority of fishes lay eggs (i.e. are oviparous), this group is unusual in that four groups of cyprinodont fishes give birth to living young (i.e. are viviparous). A molecular phylogenetic hypothesis was based on partial DNA sequences of the tyrosine kinase gene X-src. The study included the major lineages of fishes of the suborder Cyprinodontoidei, order Cyprinodontiformes. Our phylogeny agrees with some but not all of the conclusions of a previous morphological cladistic analysis (Parenti (Bull. Am. Mus. nat. Hist. 168, 335 (1981)). The differences are: (i) the Profundulidae are the sister group to the Goodeidae, not the sister group to all other cyprinodontoids; (ii) Fundulidae are the sister group to the Profundulidae and Goodeidae; (iii) Cubanichthys and the Cyprinodontinae might not be sister taxa; (iv) Cubanichthys, and not the Profundulidae, might be the most basal member of the cyprinodontoids; and (v) the Anablepinae and Poeciliinae might be sister groups. The molecular phylogeny was used to reconstruct the evolution of major life-history traits such as internal fertilization, copulatory organs, livebearing and placentas. Internal fertilization, modifications of the male's anal fin to form a copulatory organ, and viviparity probably evolved independently three times in cyprinodontiform fishes: in the subfamilies Goodeinae, Anablepinae and Poeciliinae (sensu Parenti 1981). The evolution of bundled sperm, spermatozeugmata, is probably not a prerequisite for internal fertilization because at least one species with internal fertilization has free spermatozoa. Livebearing (viviparity), which takes the form of ovoviviparity (where embryos are nourished by their yolk sac only), evolved only in the subfamily Poeciliinae. Advanced forms of viviparity, in which the mother provides additional nourishment to the embryos through placenta-like structures, apparently evolved at least three times from egg-laying ancestors: in the subfamilies Goodeinae, Anablepinae, and more than once in the Poeciliinae.
DARWIN believed that sexual selection accounts for the evolution of exaggerated male ornaments, such as the sword-like caudal fin extensions of male fishes of the genus Xiphophorus, that appear detrimental to survival. Swordtails continue to feature prominently in empirical work and theories of sexual selection; the pre-existing bias hypothesis has been offered as an explanation for the evolution of swords in these fishes. Based upon a largely morphological phylogeny, this hypothesis suggests that female preference to mate with sworded males arose in ancestrally swordless species, thus pre-dating the origin of the sword itself and directly driving its evolution. Here we present a molecular phylogeny (based on mitochondria! and nuclear DNA sequences) of Xiphophorus which differs from the traditional one: it indicates that the sword originated and was lost repeatedly. Our phylogeny suggests that the ancestor of the genus is more likely to have possessed a sword than not, thus questioning the applicability of the pre-existing bias hypothesis as an explanation for the evolution of this sexually selected trait.
Phylogenetic relationships were reconstructed using partial mitochondrial DNA sequence data for the cytochrome b gene among all nine described species of Brachyrhaphis and several members of the tribe Gambusiini. We included three of the more than 40 members of the genus Gambusia and Belonesox belimnus, the third, monotypic genus of the tribe Gambusiini. Xiphophorus malinche served as the outgroup. Phylogenetic trees were generated using maximum-parsimony, maximum-likelihood, and neighbor-joining analyses. Hypotheses of relationships withii the tribe and genus Brachyrhaphis made by previous authors were tested. The existence of a slim- and a deep-bodied clade within the monophyletic genus Brachyrhaphis was supported. Brachyrhaphis hariwegi is the basal member of the deep-bodied clade, whereas B. punctifer is the basal member of the slim-bodied clade.
Mitochondrial DNA sequences are often used to construct molecular phylogenetic trees among closely related animals. In order to examine the usefulness of mtDNA sequences for deep-branch phylogenetics, genes in previously reported mtDNA sequences were analyzed among several animals that diverged 20-600 million years ago. Unambiguous alignment was achieved for stem-forming regions of mitochondrial tRNA genes by virtue of their conservative secondary structures. Sequences derived from stem parts of the mitochondrial tRNA genes appeared to accumulate much variation linearly for a long period of time: nearly 100 Myr for transition differences and more than 350 Myr for transversion differences. This characteristic could be attributed, in part, to the structural variability of mitochondrial tRNAs, which have fewer restrictions on their tertiary structure than do nonmitochondrial tRNAs. The tRNA sequence data served to reconstruct a well-established phylogeny of the animals with 100% bootstrap probabilities by both maximum parsimony and neighbor-joining methods. By contrast, mitochondrial protein genes coding for cytochrome b and cytochrome oxidase subunit I did not reconstruct the established phylogeny or did so only weakly, although a variety of fractions of the protein gene sequences were subjected to tree-building. This discouraging phylogenetic performance of mitochondrial protein genes, especially with respect to branches originating over 300 Myr ago, was not simply due to high randomness in the data. It may have been due to the relative susceptibility of the protein genes to natural selection as compared with the stem parts of mitochondrial tRNA genes. On the basis of these results, it is proposed that mitochondrial tRNA genes may be useful in resolving deep branches in animal phylogenies with divergences that occurred some hundreds of Myr ago. For this purpose, we designed a set of primers with which mtDNA fragments encompassing clustered tRNA genes were successfully amplified from various vertebrates by the polymerase chain reaction.
Caribbean biogeography is reviewed to illustrate within a particular geographic framework how evidence of plant and animal distribution may be interpreted without commitment to special assumptions other than allopatric speciation (vicariance). The distributional data are examined with respect to whether or not they form recognizable patterns within the Caribbean region. Four main patterns and one lesser pattern are identified. The patterns or generalized distributional tracks are regions or geographical features (e.g., islands, coastlines, oceanic and continental regions) inwhich the distributions of monophyletic groups of diverse organisms are coincident. The generalized tracks are compared with geophysical theories of Caribbean history. The one geophysical theory which is strongly consistent with the distributional evidence (generalized tracks) specifies that Antillean land was originally or had its origin as part of anearly lower Central American archipelago that was later replaced by the tectonically and topographically similar, presentday, lower Central American land. The postulated events associated with this replacement involve continental drift, the main effect of which would have been to intrude a portion of the eastern Pacific sea floor into the tropical western Atlantic, carrying the early lower Central American archipelago with it. The hypothesized intruded sea floor, now forming the Caribbean Sea, is bounded on the north and east by a transposed, original archipelago, the Antilles, and onthe west by a new archipelago, now represented by the continuous land of present-day lower Central America. The separate parts of each generalized track are interpreted as the remnants of an ancestral biota that underwent geographical fragmentation followed by allopatric speciation (vicariance). This vicariance model of Caribbean biogeography specifieswhere dispersal, rather than vicariance, is the most parsimonious interpretation of a particular individual distribution, and contrasts strongly with other biogeographic interpretations in which dispersal is assumed aprioristically to be the sole, or single most important, feature of Caribbean biotic history. The vicariance model is also shown to predict, and therefore to be tested by, phylogenies (cladograms) of geographically included taxa. [Biogeography; Caribbean;vicariance; continental drift; plate tectonics.].
The scientific study of fishes of the Great Lakes of Nicaragua began in 1864 with the description by Gunther of Heros labiatus (=Cichlasoma labiatum) from Lake Managua. Subsequently, Gunther reported on several other species collected in the Great Lakes by Captain J. M. Dow. Astorqui (1967) reviewed the sparse ichthyological literature dealing with Nicaraguan fishes and pointed out the paucity of recent studies. Since then Villa (1971) has produced a provisional list of the freshwater and brackish water fishes of Nicaragua and Astorqui (1972) has analyzed the ichthyofauna of the Great Lakes Basin. Riedel (1972) discussed the geological history of the Great Lakes in relation to the composition and evolution of its fish fauna.
The modern herpetofauna of Central America is comprised of approximately 625 species that have developed in response to ecologic diversity and historical opportunities provided by the stimulus of Cenozoic changes in physiography and climate. Of the 159 genera of amphibians and reptiles known from the region, 12 have widespread tropical distributions, 62 have patterns of differentiation and distribution centered on South America, 67 are essentially tropical Middle American groups, and 18 have distributions centered in extratropical North America. Genera with South American distributions are poorly represented in Central America north of Panamá and make up only 14% of the fauna north of Costa Rica. Under these circumstances the tropical Middle American assemblage is regarded as a distinctive unit, the Mesoamerican herpetofauna, equivalent in rank to the Nearctic and Neotropical units. The distribution of this fauna determines the limits of the Mesoamerican region, which extends from central Panamá to the limits of tropical conditions in México. Six major herpetofaunal assemblages are recognized in Central America: Mesoamerican-Eastern Lowland, Western Lowland, Guatemalan Highland, and Talamancan; Neotropical-Panamanian and Chocoan. Each of these assemblages is restricted to a particular geographic area (or biogeographic subregion) characterized by a series of tropical bioclimates and vegetation. The most important influences making it possible to estimate time of arrival and history of Middle American groups that today have similar distribution patterns are: 1) isolation of Central America from South America during late Mesozoic; 2) connection of the two areas by an intercontinental land bridge during Paleocene; 3) separation of Nuclear Central America from South America by the Panamanian marine portal from Eocene to Pliocene; 4) reconnection of the two areas by the Isthmian Link from early Pliocene onward; 5) uplift of the highlands of northern and lower Central America from Miocene to the present; 6) development of xeric climate and vegetation along the Pacific Coast during Pliocene to Recent. Four basic distribution patterns that correlate with these key events of Cenozoic history indicate primary historical units that have contributed to the Central American herpetofauna. These fundamental historical units or elements and their basic distribution patterns are: 1) South American Element, groups principally South American in distribution, but in some cases now ranging northward into Central America; 2) Middle American Element, groups that are primarily tropical Middle American in distribution and have their closest allies in Middle or South America or are endemics; 3) Old Northern, groups that are essentially extratropical in North America and the Old World and have their closest allies outside tropical America; 4) Young Northern, taxa with distributions centered on xeric extratropical portions of México and the southwestern United States, that appear to have been derived originally from tropical American ancestors. Historical complexes are subdivisions of the elements composed of species with similar distributional histories. It appears that in early Cenozoic the Americas were dominated by two major faunal assemblages. In subtropical and tropical America to at least as far as 40° N lat. a generalized tropical herpetofauna existed. To the north occurred ancestral Old Northern groups. The inundation of the Isthmian Link from Nicaragua to Colombia in late Paleocene eliminated the continuity of the tropical fauna north and south of the broad marine portal. The South American Element underwent evolution in the South American island from Eocene until Pliocene when the Isthmian Link was re-established. Sixty-nine genera belonging to this element are found in Central America, but only 23 of them occur north of Costa Rica. Two principal distribution patterns are shown by representatives of this element that occur in Central America: a) species associated with mesic conditions in Pacific Colombia and Ecuador, members of the Western South American Complex; and b) species associated with the xeric habitats of Caribbean Colombia and Venezuela, members of the Northern South American Complex. The Middle American Element differentiated to the north of the Panamanian portal during the Eocene-Pliocene separation from South America. Seventy-two genera belong to this element in Central America. Two basic distribution patterns are shown by taxa included in the element, indicating separate histories during middle to late Cenozoic: a) species found in the xeric lowlands from western México to central Costa Rica, the Western Mesoamerican Complex; and b) species with distributions centered on the mesic lowlands of the Caribbean versant, the Eastern Mesoamerican Complex. In some cases tropical families that had not penetrated across the Isthmian region by Eocene evolved in isolation: to the north as part of the Middle American Element, the Rhinophrynidae, Kinosternidae, Xantusiidae, Helodermatidae, and Xenosauridae; to the south as part of the South American Element, the Pipidae, Dendrobatidae, Centrolenidae, Atelopodidae, Pelomedusidae, Chelidae, and Aniliidae. In other cases elimination of the link led to evolution of clusters of genera north and south of the water barrier as shown in the Microhylidae, Iguanidae, Teiidae, Boidae, and Crocodylidae. The Young Northern Element is composed of groups that appear to have evolved during middle to late Cenozoic in the extratropical arid regions of western North America. Only seven genera belonging to this element are found in Central America. The Old Northern Element is represented in Central America by 18 genera. Three patterns of distribution suggest centers of differentiation and common origins. Apparently representatives of this element first reached Middle America in Eocene through migration southward along the developing Rocky Mountains. These groups later became fully isolated from their congeners in the eastern and western areas of the United States by the development of temperate arid conditions across northern México. The isolated tropical stocks became the Central American Complex, whose subsequent history was in close association with the Middle American Element. One group of species within the complex appears to have invaded the lowlands of Central America early in its history, while another group seems to have been associated with the margins of the Mexican Plateau. Several Old Northern taxa with affinities to the southeastern United States appear to be recent immigrants into the Caribbean lowlands. From Eocene onward, Central America has been dominated by the Middle American Element. The crucial period in the development of the Central American herpetofauna into modern aspect was the Pliocene. At the beginning of this period Middle American Element and Central American Complex groups were widespread over the region, with local centers of differentiation in the emerging highlands of north and lower Central America. Further uplift from Pliocene to Recent has emphasized the highlands as minor evolutionary centers and as barriers to lowland dispersal. Reconnection of Central America and South America through the Isthmian Link also permitted northward movement of South American Element groups south of Nicaragua. By middle to late Pliocene four additional historical components appear to have contributed to the fauna: 1) Middle American taxa associated with xeric climatic conditions in west México moved south along Pacific Central America as xeric habitats developed; 2) Young Northern Element groups apparently invaded the xeric Pacific lowlands and the Guatemalan highlands from the north; 3) upland Mexican groups of Old Northern relations also seem to have moved into the highlands of Chiapas and Guatemala; 4) South American xeric-adapted groups invaded Pacific coastal Panamá. From Pliocene onward these components expanded into Central America along a series of physiographic and climatically controlled dispersal routes while many groups of the basic Middle American and Central American units expanded their range southward into South America. The principal dispersal routes utilized by the faunal units are: a) an Atlantic lowland route from México to eastern Panamá that crosses over to the Pacific versant and continues to Ecuador, followed by expanding Middle and Central American groups, particularly southward, and by South American groups northward; b) a series of Pacific lowland routes that permitted Western Mesoamerican Complex and Young Northern Element forms to move southward to Costa Rica and some South American Element groups to disperse from northern South America to western Panamá. A moist area in the Golfo Dulce region effectively blocks the penetration of many South American forms into the xeric corridor of Pacific Central America and conversely limits the distribution of Middle American groups to the corridor; c) a highland route across the Isthmus of Tehuantepec that permitted exchange in both directions between the Chiapas-Guatemala-Honduras highlands and the mountains of southern México; followed southward by Mexican groups of Old and Young Northern affinities; d) a route across the Talamancan highlands of Costa Rica and Panamá; used by endemic groups and a few invaders of Old and Young Northern relations from the northern highlands. In every part of Central America, except in eastern Panamá and on the highest peaks, the fauna expresses in its distinctness from both the Nearctic and Neotropical assemblages its long and independent history, and fully validates the concept of the Mesoamerican unit as a separate major herpetofauna.
Caribbean biogeography is reviewed to illustrate within a particular geographic framework how evidence of plant and animal distribution may be interpreted without commitment to special assumptions other than allopatric speciation (vicariance). The distributional data are examined with respect to whether or not they form recognizable patterns within the Caribbean region. Four main patterns and one lesser pattern are identified. The patterns or generalized distributional tracks are regions or geographical features (e.g., islands, coastlines, oceanic and continental regions) in which the distributions of monophyletic groups of diverse organisms are coincident. The generalized tracks are compared with geophysical theories of Caribbean history. The one geophysical theory which is strongly consistent with the distributional evidence (generalized tracks) specifies that Antillean land was originally or had its origin as part of an early lower Central American archipelago that was later replaced by the tectonically and topographically similar, presentday, lower Central American land. The postulated events associated with this replacement involve continental drift, the main effect of which would have been to intrude a portion of the eastern Pacific sea floor into the tropical western Atlantic, carrying the early lower Central American archipelago with it. The hypothesized intruded sea floor, now forming the Caribbean Sea, is bounded on the north and east by a transposed, original archipelago, the Antilles, and on the west by a new archipelago, now represented by the continuous land of present-day lower Central America. The separate parts of each generalized track are interpreted as the remnants of an ancestral biota that underwent geographical fragmentation followed by allopatric speciation (vicariance). This vicariance model of Caribbean biogeography specifies where dispersal, rather than vicariance, is the most parsimonious interpretation of a particular individual distribution, and contrasts strongly with other biogeographic interpretations in which dispersal is assumed aprioristically to be the sole, or single most important, feature of Caribbean biotic history. The vicariance model is also shown to predict, and therefore to be tested by, phylogenies (cladograms) of geographically included taxa.
The distribution of freshwater fishes in Central America is reviewed. Major parts of the region, especially in Honduras and Nicaragua, have yet to be explored ichthyologically, and systematic revision of important groups, notably the cichlids, is long overdue. The continental area from the Isthmus of Tehuantepec to the Colombian border contains approximately 456 species, of which over 75% comprise the Cyprinodontidae, Poeciliidae, Cichlidae, and marine invaders (peripheral fishes); about one-third of the latter (57 species) have taken up more or less permanent residence in fresh water. There are 104 primary species in 10 families, 165 secondary forms in 6 families, and 187 peripheral species distributed among 30 families (nearly half of the latter are ariids, atherinids, gerrids, and gobies). Poeciliids and cichlids are particularly rich and diverse, together comprising 139 species. Characins are numerous only in the Panamanian region, into which they and five South American catfish families have recently penetrated. Except for gars, no North American family has reached beyond northern Guatemala. There are no non-ostariophysan primary fishes in the area.
In a phylogenetic analysis of the tribe Poeciliini, three of four subgenera of Poecilia (i.e., Limia, Pamphorichthys, and Poecilia) are recognized as genera based on the derived features of the gonopodium and its suspensorium. Based on the Hollister-foramen and a keel on the subdistal ventral side of ray 5 of the gonopodium, Limia, Pamphorichthys, and Poecilia comprise a monophyletic group. Xiphophorus is the sister taxon of the clade (Pamphorichthys, Poecilia, Limia). Neither Alfaro nor Priapella is known to share derived characters with the clade Xiphophorus (Limia, Pamphorichthys, and Poecilia). Falsification of the hypothesis of Priapella and Xiphophorus as sister taxa is discussed. /// En un análisis filogenético de la tribu Poeciliini, tres de los cuatro subgéneros de Poecilia (Limia, Pamphorichthys y Poecilia) son reconocidos como géneros debido a que comparten caracteres derivados en el gonopodio y sus suspensoria. Por la presencia del foramen de Hollister y de una quilla en el extremo subdistal ventral del radio 5 del gonopodio, se propone la hipótesis de que Limia, Pamphorichthys y Poecilia forman un grupo monofilético. Xiphophorus se propone como taxon hermano del clado (Limia, Pamphorichthys y Poecilia). No se encontró evidencia de que Alfaro y Priapella compartan caracteres derivados con el grupo monofilético Xiphophorus (Limia, Pamphorichthys y Poecilia. Se discute acerca de la falsación de la hipótesis de que Priapella y Xiphophorus son taxa hermanos.
The nature, composition, and evolution of Central American freshwater fish groups are discussed in relation to the history and derivation of the faunal elements. It is concluded that the entire area between the Isthmus of Tehuantepec and eastern Panamá was and always had been devoid of primary (obligatory) freshwater fishes prior to the very late Tertiary. Instead, secondary freshwater fishes evolved in this area during the Neogene and perhaps for a longer period, the Poeciliidae having probably had a longer history within the area than the Cichlidae. In the late Tertiary a very few North American immigrants entered the area from the north, and towards the end of the Pliocene the closing of the very ancient Panamá sea gap permitted an influx of South American primary types. Most of these have not yet gotten past Costa Rica, but a few aggressive characids have reached Guatemala or southern México and one has reached Texas. It follows that the rich South American primary freshwater fish fauna could not have been originally derived from or through Central or North America, and continental drift (not here discussed in detail) is suggested to explain South American-African similarities.
North America-Eurasia and South America-Africa were certainly joined in the classic reconstruction of Pangaea by Middle Triassic time. The line of collision and suture included the Appalachian Quachita-Marathon orogenic trend in the United States extending southwestward into what is now northeastern and southeastern Mexico and into Guatemala. Widespread continentality prevailed and there was no Gulf of Mexico or Caribbean Sea. In Late Triassic time and continuing into Early Jurassic time this construct began to founder by initial rifting between South America-Africa and North America. No oceanic crust was formed, however, thus Africa-South America were still completely connected by land or shallow sea to North America until mid-Jurassic time. During this same uppermost Triassic to Middle Jurassic period a largely continental magmatic arc was draped across the Pacific margin of southwestern North America and apparently continued unbroken into northwestern South America. Sometime in the Middle Jurassic oceanic crust began to form by seafloor spreading in the central Atlantic and Gulf of Mexico as separation of South America-Africa from North America accelerated. Once this dense crust began to form the trailing margins of the continents subsided below sea-level and construction of the Atlantic and Gulf coast continental shelves began. Evidence is quite conclusive that this ocean floor spreading did not reach the Pacific Ocean, but was transformed from the southwestern corner of the newly opened Gulf of Mexico northwestward across Mexico via a complex left-slip transform fault system that reached the Pacific margin near Los Angeles. In Early Cretaceous time spreading continued in the central Atlantic but extended southward into the southern Atlantic. As the main axis of spreading extended into the south Atlantic, spreading ceased in the Gulf of Mexico. The south Atlantic spreading initiated separation of South America from Africa, but they probably remained in partial contact via ridge-ridge transform faults until Late Cretaceous time. South America must have finally completely separated from North America in Early Cretaceous time, probably via a rift along the eastern edge of Yucatan and the Nicaraguan rise. By Late Jurassic time the Pacific continental margin arc had waned and was replaced by a complex, largely oceanic, magmatic arc whose position relative to southwestern North America and northwestern South America is not known. What we do know is that by Late Cretaceous-Early Tertiary time it had accreted against the Pacific margins of both. Connections between the continents are also not known but could have included a largely submarine magmatic arc, parts of which may have subsequently dispersed eastward as the Greater Antilles. Much of what is now Middle America is apparently underlain by oceanic crust at least as young as Late Cretaceous in age. By Late Cretaceous time the Greater Antilles magmatic arc seems to have fully formed and subsequently moved northeastward as a northeast-facing subduction system during Late Cretaceous-Early Tertiary Laramide time. The Greater Antilles arc-trench system ceased activity in Late Eocene time as it collided with Florida and the Bahama platform and as Laramide orogeny waned throughout western North America. This was followed by a major plate reorganization in the Caribbean-Middle America region nearly 40 m.y. B.P. which established the Caribbean plate more or less as we know it today. The principal change was initiation of the Lesser Antilles magmatic arc as an east-facing subduction system that began to consume Atlantic ocean floor. Also, a west-facing subduction system may have formed about this time along a proto-Central American western margin of the Caribbean plate. However, much of what is now Central America may have initially been off southern Mexico. The northern and southern margins of the Caribbean plate evolved into complex transform and transpressive systems as North and South America moved westward past a nearly stationary Caribbean plate. These motions significantly fragmented the Greater Antilles into their present array. There is no evidence for any complete land connection between North and South America via the Greater and/or Lesser Antilles throughout later Mesozoic or Tertiary time. Nor is there any evidence for complete land connection via Central America and the Isthmus of Panama before Neogene time.
Within the family Poeciliidae, a wide range of adaptations accompanying viviparity has evolved. The reproductive mechanisms of five representative species were examined and related to the habitats in which they are employed. Poecilia reticulata, the guppy, represents the majority of poeciliids which have a single stage of embryos in the ovary at a time. Most of the nutrients are prepack-aged in the eggs before fertilization; no specialized placental adaptations have evolved. The major variable among species utilizing this mechanism is in the yolk loading time; some eggs are mature and ready to be fertilized immediately after the birth of a clutch of embryos, others take a week or more. The mechanism may be thought of as a generalist-type, being employed throughout the range of poeciliids and in all varieties of habitats. Poeciliopsis monacha has embryos of two different ages occurring simultaneously in the ovary. Its large eggs provide the embryo's entire nutrient supply. Mature embryos weigh 47% less than mature eggs. This species lives in a harsh, montane environment with an unpredictable food supply; its reproductive mechanism is well suited to fluctuating resources. When conditions are favorable, a large clutch of eggs is loaded, but if food is in short supply, clutch sizes are small or only one stage is produced. During starvation conditions, no eggs are produced; but, with restoration of food supply, reproduction resumes quickly. Poeciliopsis lucida has medium-sized eggs and three stages of embryos. At birth, young weigh slightly more than mature ova. This weight gain plus the energy utilized for embryonic metabolism constitutes a significant maternal contribution during development. P. lucida is wide-spread in the three rivers that comprise its range but it does not enter the depauperate rocky arroyos occupied by P. monacha. P. lucida requires a stable food supply characteristic of the fertile and productive downstream regions. Poeciliopsis prolifica carries as many as five stages of embryos which are born at short brood intervals of two to eight days. Ova sizes are small and embryos receive almost all of their nutrients through a placenta. P. prolifica lives in a rich environment where food resources are stable. It is the smallest species in the genus and it produces the smallest young, yet its habitat seems precarious. Living on the steep slope between deep and shallow water it is wedged between deep and shallow water competitors, having to cope with large deep water fish predators as well. Poeciliopsis turneri is the largest of the five species studied and occupies a habitat somewhat unusual for poeciliids. Three stages of embryos are present in the ovary but brood sizes are usually small (ave. 3.6). The ova are small yet the mature embryos are large, weighing almost 19 times more than the ova. Brood sizes in neither P. prolifica nor P. turneri become larger as female size increases. P. turneri is adapted to life in deep swift water where large adults, large offspring and streamlining are important. The other four species can risk the swollen pregnant-look typical of poeciliids, whereas P. turneri cannot. Superfetation (multiple stages of embryos) is advantageous in that it avoids the surge of energy required to load a single large clutch of eggs. The energy for reproduction is sequentially divided among two to five small clutches. Reduction of ova size increases the space available for more stages of embryos. Although embryos with small yolk supplies place a nutrient drain directly on the mother, surges in demand are avoided since embryonic stages enter the growth phase at different times. A continuous food supply to the female is essential; otherwise, embryos will die and the reproductive effort to that point is lost.
— We studied sequence variation in 16S rDNA in 204 individuals from 37 populations of the land snail Candidula unifasciata (Poiret 1801) across the core species range in France, Switzerland, and Germany. Phylogeographic, nested clade, and coalescence analyses were used to elucidate the species evolutionary history. The study revealed the presence of two major evolutionary lineages that evolved in separate refuges in southeast France as result of previous fragmentation during the Pleistocene. Applying a recent extension of the nested clade analysis (Templeton 2001), we inferred that range expansions along river valleys in independent corridors to the north led eventually to a secondary contact zone of the major clades around the Geneva Basin. There is evidence supporting the idea that the formation of the secondary contact zone and the colonization of Germany might be postglacial events. The phylogeographic history inferred for C. unifasciata differs from general biogeographic patterns of postglacial colonization previously identified for other taxa, and it might represent a common model for species with restricted dispersal.
The predominant geophysical theory for the origin of Central America proposes that, in the Cretaceous-Paleocene, the Caribbean Plate migrated from the Eastern Pacific to the Western Atlantic. As it did so, it supposedly pushed the original Central American archipelago eastward to form the Antillean chain. This would have left an oceanic gap between the Americas that lasted some 60 million years. Palaeontological and neontological research now indicate that a variety of terrestrial and freshwater animals must have been able to disperse between North and South America during the time of the oceanic gap. The disharmonic composition and apparent later origin of the antillean faunas suggest that the Greater Antilles-Aves Ridge was not available as a dispersal corridor in the Cretaceous-Paleocene. Work on the Cretaceous marine bivalve fauna indicated the gradual development of a terrestrial Central American barrier during that Period. By the latest Cretaceous, the faunas of the eastern and western sides appear to have become well separated. This suggests an in situ formation of Central America, probably as the result of interaction between the Caribbean, Cocos, and Nazca plates. This theory is consistent with the evidence of terrestrial dispersals, marine bivalve separation, and the relatively old age of the Central American biota.
The galaxiid fishes exhibit a gondwanan distribution. We use mitochondrial DNA sequences to test conflicting vicariant and
dispersal biogeographic hypotheses regarding the Southern Hemisphere range of this freshwater group. Although phylogenetic
resolution of cytochrome b and 16S rRNA sequences is largely limited to more recent divergences, our data indicate that the radiation can be interpreted
as several relatively recent dispersal events superimposed on an ancient gondwanan radiation. Genetic relationships contradict
the findings of recent morphological analyses of galaxioid fishes. In particular, we examine several hypotheses regarding
phylogenetic placement of the enigmatic Lepidogalaxias. Although most workers consider Lepidogalaxias to be an unusual scaled member of the Southern Hemisphere galaxioids, it has also been suggested that this species is related
to the Northern Hemisphere esocoids. Our data strongly suggest that this species is not a galaxiid, and the alternative hypothesized
esocoid relationship cannot be rejected. The species-rich genus Galaxias is shown to be polyphyletic and the generic taxonomy of the Galaxiinae is reassessed in the light of phylogenetic relationships.
Juvenile saltwater-tolerance is phylogenetically distributed throughout the Galaxiinae, and the loss of this migratory phase
may be a major cause of speciation.
Phylogenetic relationships within the family Rivulidae (order Cyprinodontiformes) are investigated using 1972 aligned base pairs of mitochondrial DNA (mtDNA) for samples representing 66 species. Genes analyzed include those encoding the 12S ribosomal RNA; transfer RNAs for valine, glutamine, methionine, tryptophan, alanine, asparagine, cysteine, and tyrosine; complete NADH dehydrogenase subunit II; and part of cytochrome oxidase I. Parsimony analysis of the aligned mtDNA sequences results in a single most parsimonious tree. The phylogeny reveals two independent origins of developmental diapause within the family Rivulidae. It is unlikely that diapause evolved de novo in each group, suggesting that the presence or absence of diapause is the result of developmental switches between alternative stabilized pathways. Phylogeny of the family Rivulidae shows high concordance with predictions derived from the geological history of South America and Central America. Basal lineages in the rivulid phylogeny are distributed primarily on geologically old areas, whereas more nested lineages occur in geologically younger areas. However, there is little concordance between the molecular phylogeny and currently available morphological hypotheses and existing taxonomies. Based on the mtDNA phylogeny, the genera Pterolebias, Rivulus, Pituna, and Plesiolebias are considered nonmonophyletic and warrant taxonomic reassessment.
Evidence from morphology is used to infer the phylogeny of the superfamily Poecilioidea using other cyprinodontoid fishes as outgroups. The three equally most parsimonious trees resulting from the phylogenetic analysis support the monophyly of the families Anablepidae and Poeciliidae with respect to each other, but the previous taxonomy within the Poeciliinae is not consistent with the resultant phylogenetic trees. The Poeciliidae is recognized with three subfamilies: the Aplocheilichthyinae containing solely Aplocheilichthys spilauchen, the Procatopodinae containing Fluviphylax (Fluviphylacini) and the African lamp-eyed killifishes (Procatopodini), and the Poeciliinae. The inferred hierarchical relationships of included suprageneric taxa are: ((Oxyzygonectinae, Anablepinae) (Aplocheilichthyinae ((Fluviphylacini, Procatopodini) (Alfarini (Priapellini (Gambusini (Heterandrini (Cnesterodontini (Girardini, Poeciliini))))))))). The tribe Alfarini is resurrected and a new tribe, the Priapellini, is described. Tomeurus gracilis is not the most basal poeciliine, and facultative viviparity in Tomeurus is not a plesiomorphic intermediate condition of viviparity retained from the common ancestor of poeciliines. Facultative viviparity in Tomeurus is the result of an evolutionary loss of obligate viviparity. Tomeurus gracilis is recognized as a member of the tribe Cnesterodontini. Lamprichthys tanganicus and Micropanchax pelagicus are not sister taxa, and the pelagic lacustrine habits of these two species are inferred to have evolved independently. Based on the principles of vicariance biogeography, the origin of the Poecilioidea is inferred to have occurred before the separation of Africa and South America.
The combined use of mitochondrial DNA markers and polymerase chain reaction (PCR) techniques has greatly enhanced evolutionary studies. These techniques have also promoted the discovery of mitochondrial-like sequences in the nuclear genomes of many animals. While the nuclear sequences themselves are interesting, and capable of serving as valuable molecular tools, they can also confound phylogenetic and population genetic studies. Clearly, a better understanding of these phenomena and vigilance towards misleading data are needed.
"A dissertation submitted to the Graduate Faculty in Biology ... " Thesis (Ph. D.) -- City University of New York, 1988. Includes bibliographical references (leaves 291-305).
To test vicariant speciation hypotheses derived from geological evidence of the closing of the Tethys Sea, we reconstruct phylogenetic relationships of the predominantly fresh-water killifish genus Aphanius using 3263 aligned base pairs of mitochondrial DNA from samples representing 49 populations of 13 species. We use additional 11 cyprinodontid species as outgroup taxa. Genes analysed include those encoding the partial 12S and 16S ribosomal RNAs; transfer RNAs for valine, leucine, isoleucine, glutamine, methionine, tryptophan, alanine, asparagine, cysteine and tyrosine; and complete nicotinamide adenine dinucleotide dehydrogenase subunit I and II. Molecular substitution rate for this DNA region is estimated at of 8.6 ± 0.1 · 10)9 substitutions base pair)1 year)1, and is derived from a well dated transgression of the Red Sea into the Wadi Sirhan of Jordan 13 million years ago; an alternate substitution rate of 1.1 ± 0.2 · 10)8 substitutions base pair)1 year)1 is estimated from fossil evidence. Aphanius forms two major clades which correspond to the former eastern and western Tethys Sea. Within the eastern clade Oligocene divergence into a fresh-water clade inhabiting the Arabian Peninsula and an euhaline clade inhabiting coastal area from Pakistan to Somalia is observed. Within the western Tethys Sea clade we observe a middle Oligocene divergence into Iberian Peninsula and Atlas Mountains, and Turkey and Iran sections. Within Turkey we observe a large amount of genetic differentiation correlated with late Miocene orogenic events. Based on concordance of patterns of phylogenetic relationships and area relationships derived from geological and fossil data, as well as temporal congruence of these patterns, we support a predominantly vicariant-based speciation hypothesis for the genus Aphanius. An exception to this pattern forms the main clade of A. fasciatus, an euhaline circum-Mediterranean species, which shows little genetic differentiation or population structuring, thus providing no support for the hypothesis of vicariant differentiation associated with the Messinian Salinity Crisis. The two phylogenetically deepest events were also likely driven by ecological changes associated with the closing of the Tethys Sea.
DNA sequence evolution through nucleotide substitution may be assimilated to a stationary Markov process. The fundamental equations of the general model, with 12 independent substitution parameters, are used to obtain a formula which corrects the effect of multiple and parallel substitutions on the measure of evolutionary divergence between two homologous sequences. We show that only reversible models, with six independent parameters, allow the calculation of the substitution rates. Simulation experiments on DNA sequence evolution through nucleotide substitution call into question the effectiveness of the general model (and of any other more detailed description); nevertheless, the general model results are slightly superior to any of its particular cases.