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Mantel test. Relationship between Nei's genetic distance and geographical distance in km among populations of Abrothrix olivacea brachiotis (Mantel test of correlation, rxy = 0.386, p = 0.01). Full-size DOI: 10.7717/peerj.6955/fig-3
Source publication
The temperate rainforests of southern Chile, a recognized biodiversity hotspot, were significantly affected by Pleistocene glacial cycles in their southern portion and have been severely disrupted mainly due to recent human activities. Additionally, the landscape is characterized by a series of potential barriers to gene flow, such as the Chacao Ch...
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Context 1
... low sample size. The FST index calculated between all populations gave a majority of significant differences between populations with the exception of La Picada vs. the rest, but this may also be due to a low sampling size. Additionally, the Mantel correlation coefficient, the test for isolation by distance, was positive (Rxy = 0.386, p = 0.01; Fig. 3), giving a positive and significant correlation between genetic and geographic ...
Context 2
... low sample size. The FST index calculated between all populations gave a majority of significant differences between populations with the exception of La Picada vs. the rest, but this may also be due to a low sampling size. Additionally, the Mantel correlation coefficient, the test for isolation by distance, was positive (Rxy = 0.386, p = 0.01; Fig. 3), giving a positive and significant correlation between genetic and geographic ...
Citations
... This species ranges from southern Perú to the Patagonia of Chile and Argentina, and from sea level to elevations near to 2500 m [24,27]. Within Chile, A. olivacea is distributed between 18 and 54 • S, inhabiting contrasting landscapes in different ecosystems, including the Mediterranean ecoregion of central Chile [24,28]. A. olivacea is an omnivorous species feeding on a wide variety of food items including arthropods, shrub and herbaceous seeds, foliage, and fungi [29]. ...
... The home range of A. olivacea fluctuates between 730 and 2530 m 2 , which is considered near half the home range of one of the most vagile sigmodontine species occurring in south-central Chile, Oligoryzomys longicaudatus [31,32]. Phylogeographic evidence showed that A. olivacea is characterized by having a high intraspecific structure with seven subspecies [25,28], but [26] notes that A. olivacea subspecies are restricted to central Chile [25]. On the other hand, P. darwini (Darwin's leaf-eared mouse) is an endemic species of the Mediterranean ecoregion of central Chile, with a restricted distribution between 27 • and 36 • S [33], occurring from sea level up to approximately 2000 m. ...
Simple Summary
Two ecogeographic rules predict morphological changes along latitudinal clines based on thermoregulatory causes. To maintain corporal heat in cold environments (higher latitudes), larger body sizes and shorter appendages and limbs are predicted by Bergmann’s and Allen’s rules, respectively. Both rules may also apply to elevational gradients, due to the decrease in external temperature as elevation increases. We evaluated whether these ecogeographic rules were true in two rodent species across an elevational gradient in central Chile. The species studied were Abrothrix olivacea and Phyllotis darwini, which coexist across this altitudinal range. Our results showed a low support for these rules, as well as an opposite body size trend between both species. Other than morphology, physiological and behavioral strategies could be more critical to thermoregulating in high, montane environments, and new hypotheses should be tested to explain the morphological changes that we observed in this study.
Abstract
Bergmann’s and Allen’s rules are two classic ecogeographic rules concerning the physiological mechanisms employed by endotherm vertebrates for heat conservation in cold environments, which correlate with adaptive morphological changes. Thus, larger body sizes (Bergmann’s rule) and shorter appendages and limbs (Allen’s rule) are expected in mammals inhabiting cold environments (higher latitudes). Both rules may also apply to elevational gradients, due to the decrease in external temperature as elevation increases. In this study, we evaluated whether these patterns were true in two coexisting sigmodontine rodents across an elevational gradient in central Chile. We analyzed whether the size of the skull, body, and appendages of Abrothrix olivacea (n = 70) and Phyllotis darwini (n = 58) correlated with elevation, as predicted by these rules in a range between 154 and 2560 m. Our data revealed weak support for the Bergmann and Allen predictions. Moreover, we observed opposite patterns when expectations of Bergmann’s rules were evaluated, whereas Allen’s rule just fitted for ear size in both rodent species. Our results suggest that morphological changes (cranial, body, and appendage sizes) may play a minor role in the thermoregulation of these two species at high elevations, although behavioral strategies could be more critical. Other ecological and environmental variables could explain the morphological trends observed in our study. These hypotheses should be assessed in future studies to consider the relative contribution of morphology, behavior, and physiological mechanisms to the thermal adaptation of these two rodent species at high elevations.
... The mitochondrial genetic variation of Abrothrix olivacea has been examined in several studies (e.g., Pearson and Smith 1999;Smith et al. 2001;Palma et al. 2005;Rodriguez-Serrano et al. 2006, 2008Lessa et al. 2010;Zepeda et al. 2019), which have identified phylogeographic breaks and different patterns of genetic structuring among the phylogroups identified. However, these studies were performed based on restricted populational samples that come from small portions of the species' geographic range (e.g., Palma et al. 2005 andRodriguez-Serrano et al. 2006 Smith et al. 2001 andLessa et al. 2010 centered on Patagonian and Patagonian-Fuegian samples, respectively). ...
Although the mitochondrial diversity of Abrothrix olivacea has been widely studied, the phylogeographic structure and the historical demography of this species are still not fully comprehended. With the aim of better understanding these aspects, a 801 bp fragment of the Cytb gene sampled in 416 individuals (202 from Argentina and 214 from Chile) collected at 103 localities (46 from Argentina and 57 from Chile) was analyzed. This represents the most geographically and numerically widespread sampling used until now to study the mitochondrial variation of this species. The results obtained indicate that the mitochondrial diversity of A. olivacea is structured in four main phylogroups with barely overlapped geographic ranges that replace each other mostly latitudinally from northern Chile (ca. 18° S) to the Isla Grande of Tierra del Fuego (ca. 56° S). In turn, each mitochondrial phylogroup shows distinct crown ages and signals of asynchronous population expansions. Overall, the results obtained here improve the delimitation of the geographic ranges of the intraspecific mitochondrial lineages of this species and suggest that its subspecific taxonomy require an exhaustive revision. In addition, the pattern of genetic structure described here for the Patagonian-Fuegian populations differs from that evidenced by the characterization of nuclear variation. This mito-nuclear discordance could be associated with neutral demographic dynamics and the vagaries of allele sorting and suggest that the evolutionary history of this species could be more complex than that reconstructed from the isolated study of mitochondrial or nuclear variability.
... The algorithm identifies genetic discontinuities while estimating both the number and locations of populations without any a priori knowledge on the population units and limits (Zepeda et al., 2019). ...
en The Mesoamerican dry forests (MDF), rich in species and in endemic taxa, are distributed nearly continuously nearly continuously along the American Pacific slope from Mexico to Costa Rica; however, several of the bird species inhabiting the MDF show clear phenotypic differentiation recognized through the description of subspecies. There are two currently recognized species of magpie-jays of the genus Calocitta (Corvidae) distributed throughout the MDF: the monotypic black-throated magpie-jay (C. colliei) and the polytypic white-throated magpie-jay (C. formosa). These two species have sometimes been considered conspecific and have been reported to hybridize in sympatric areas, where birds with intermediate plumage characters are recorded. Using mitochondrial and nuclear DNA markers from individuals of the two species, we analyze the phylogeographic structure and the genetic diversity within Calocitta under an isolation with migration (IM) model. The results showed strong genetic structure, in which the two currently recognized species and some of the C. formosa subspecies grouped into four well-supported and reciprocally monophyletic clades. IM analyses suggested divergence dates for the split between C. colliei and C. formosa that were congruent with geological factors, as well as with the deep divergence of the three lineages within C. formosa. These factors likely led to a dynamic demographic history in all lineages. We also found strongly limited gene flow, null or near null migration values, and large genetic fixation and genetic distance values. We suggest that the strong genetic differentiation between lineages is the result of allopatric differentiation with later secondary contact, further supporting a highly dynamic biotic history in MDF.
Resumen
es Los bosques secos Mesoamericanos (MDF) son ricos en especies y están distribuidos casi de manera continua a lo largo de la vertiente pacífica de México hasta Costa Rica; sin embargo, varias de las especies de aves que los habitan muestran clara diferenciación fenotípica, lo que se ha reconocido a través de la descripción de subespecies. Existen dos especies actualmente reconocidas de urracas del género Calocitta (Corvidae) que se distribuyen en los MDF: la monotípica Urraca Hermosa Carinegra (C. colliei) y la politípica Urraca Hermosa Cariblanca (C. formosa). Estas dos especies a veces han sido consideradas conespecificas y se ha reportado que hibridizan en áreas de simpatría, donde se han registrados individuos con caracteres intermedios de plumaje. Usando marcadores de DNA mitocondrial y nuclear para individuos de ambas especies, analizamos la estructura filogeográfica y la diversidad genética dentro de Calocitta bajo un modelo de Aislamiento con Migración (IM). Los resultados muestran una fuerte estructura genética, en la cual las dos especies reconocidas y algunas de las subespecies de C. formosa se agrupan en cuatro clados bien soportados y recíprocamente monofiléticos. Los análisis de IM sugieren fechas de divergencia para la división entre C. colliei y C. formosa que son congruentes con factores geológicos, al igual que para las tres divergencias profundas entre los linajes dentro de C. formosa. Esos factores posiblemente llevaron a una historia demográfica dinámica en todos los linajes. También encontramos flujo génico muy limitado, valores de migración nulos o casi nulos, y valores altos de fijación y distancia genéticas. Sugerimos que esa fuerte diferenciación genética es el resultado de diferenciación alopátrica con posterior contacto secundario, apoyando aún más una historia biótica altamente dinámica en los MDF.
... Microsatellites, or simple sequence repeats (SSRs) are tandem repetitions of relatively short DNA motifs present in perfect (P-SSR), compound (C-SSR), and imperfect (I-SSR) forms in nearly all known genomes (Du et al., 2018;Du et al., 2020). Polymorphic microsatellites have been widely utilized as popular molecular markers for studying neutral genetic variation in diverse fields, including individual identification (Huang et al., 2015), population genetics (Zepeda et al., 2019), and other genetic studies (Highnam et al., 2012;Aristizábal et al., 2018). Recently, SSR instability in functional genes has been shown to be associated with many human diseases, such as neurological disorders (Rohilla and Gagnon, 2017) and colorectal cancers (Yamamoto and Imai, 2019). ...
Microsatellite or simple sequence repeat (SSR) instability within genes can induce genetic variation. The SSR signatures remain largely unknown in different clades within Euarchontoglires, one of the most successful mammalian radiations. Here, we conducted a genome-wide characterization of microsatellite distribution patterns at different taxonomic levels in 153 Euarchontoglires genomes. Our results showed that the abundance and density of the SSRs were significantly positively correlated with primate genome size, but no significant relationship with the genome size of rodents was found. Furthermore, a higher level of complexity for perfect SSR (P-SSR) attributes was observed in rodents than in primates. The most frequent type of P-SSR was the mononucleotide P-SSR in the genomes of primates, tree shrews, and colugos, while mononucleotide or dinucleotide motif types were dominant in the genomes of rodents and lagomorphs. Furthermore, (A)n was the most abundant motif in primate genomes, but (A)n, (AC)n, or (AG)n was the most abundant motif in rodent genomes which even varied within the same genus. The GC content and the repeat copy numbers of P-SSRs varied in different species when compared at different taxonomic levels, reflecting underlying differences in SSR mutation processes. Notably, the CDSs containing P-SSRs were categorized by functions and pathways using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes annotations, highlighting their roles in transcription regulation. Generally, this work will aid future studies of the functional roles of the taxonomic features of microsatellites during the evolution of mammals in Euarchontoglires.
... The other species, Abrothrix olivacea, the olive field mouse, has also an extense geographic distribution, encompassing from southern Perú southward to the Patagonia of Chile and Argentina. However, in that range at least seven geographic races are recognized of this rodent [29]. The higher geographic structure of A. olivacea would be consequence of its lower vagility and home range (730 to 2530 m [30]) when compared with O. longicaudatus. ...
Background:
Analysis of morphological variation in archipelagos has been essential to understand the evolution of terrestrial vertebrates. In particular, these natural scenarios allow to assess morphological changes experienced by insular fauna compared to their mainland counterparts. In mammals, morphological changes of insular forms have been observed in size and shape of body and cranial traits. The southern Patagonia of Chile represents a unique scenario to analyze morphological variation in two of the most widely distributed small rodents along western southern South America: Abrothrix olivacea and Oligoryzomys longicaudatus.
Methods:
We applied linear and three-dimensional geometric morphometric tools to analyze the variation in cranial morphology of A. olivacea ( N = 80) and O. longicaudatus ( N = 49). Sampled localities were distributed in the mainland and islands of the Fuegian archipelago in Chilean Patagonia. Standard multivariate methods, as Principal Components Analysis, and Logistic Regression models were carried out to evaluate differences in size and shape of crania.
Results:
We detected higher levels of morphological variation in the crania of A. olivacea if compared to O. longicaudatus. The variation was associated to cranial size instead of shape.
We observed significant differences between insular and mainland individuals in A. olivacea, being the cranium size of this species significantly bigger on islands. Indeed, specimens of A. olivacea from “Isla Wellington”, exhibited the higher increment in cranium size compared to any other mainland and insular site sampled for this species. In contrast, insular and mainland forms of O. longicaudatus did not show significant differences in cranial morphology.
Conclusions:
We suggest that the patterns of morphological variation observed in these two small rodents along Patagonia, could be explained in terms of the historical biogeography of the region, and the different ecological features of the studied species.
