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Google Earth imagery (Landsat/Copernicus) of Tucuruí Hydroelectric dam vicinity, before (left; December 1984) and after (right; December 2016) dam construction. Scale bar represents ~48.3 km (30 miles)
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While anthropogenic disturbances can have damaging effects on biodiversity, they also offer an opportunity to understand how species adapt to new environments and may even provide insights into the earliest stages of evolutionary diversification. With these topics in mind we explored the morphological changes that have occurred across several cichl...
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... changes in population abundance and composition, range, and diet type) in various taxonomic groups. These phenotypic changes can arise in response to environmental variations resulting from anthropogenic actions, such as climate change (Walsh et al. 2016, Millien et al. 2017, dam and reservoir construction (Gilbert et al. 2020), biological invasions (Geladi et al. 2019), and urbanization (Hüppi and Geiger 2022). However, such studies remain relatively scarce owing to the challenge of collecting and analysing sufficient long-term data (Lepetz et al. 2009). ...
Ecotypes constitute valuable markers for understanding the phenotypic responses influenced by evolutionary forces and environmental variations. Assessing the role of these processes in establishing and maintaining ecotype divergence is essential for anticipating evolutionary responses to future climate shifts. We studied the evolutionary dynamics of phenotypic population structure between Nacella concinna ecotypes through a morphometric and temporal analysis (2004–2021) in Antarctica. This approach enables the assessment of contemporary evolutionary dynamics in the presence of biotic and abiotic factors, facilitating the inference of interactions between the acting forces. Using generalized Procrustes analysis, ecotypes were successfully discriminated by their lateral shell traits consistently persisting over the analysed period. Multivariate linear and univariate mixed models revealed a significant temporal effect on shell phenotypic variation, surpassing the effect of inter-ecotype differences. However, according to phenotypic trajectory analysis, this temporal effect did not alter the direction of the phenotypic trajectory of ecotype shell shape, which evolved in parallel during the time series. Despite the environmental variation, the evidence of parallel evolution might indicate the incidence of natural selection in ecotype divergence rather than relying solely on phenotypic plasticity. This work enhances our understanding of ecotype temporal changes and microevolution, underscoring the importance of long-term phenotypic monitoring.
... Functional traits emerge in an organism through its performance (growth rate, survival, and reproduction) and the influence of ecological processes [2]. An organism's phenotype is determined by the species utilize a rich diversity of habitats and exhibit high differences in body morphology and functional traits due to community interactions (such as food type, predators, and competition) within habitat characteristics (current velocity, water depth, water chemistry, substrate type) [3,7]. Within a river system, individuals of a species population can freely move along the river network [8], allowing for ongoing gene flow among populations. ...
... While the lentic site presents a "natural" small lake habitat, lotic site 2 was a heavily "anthropogenically" degraded stream habitat because it was located in the Antalya city center (the population is 2.688,004) and was frequently exposed to industrial and domestic waste (water quality was classified as "very poor" according to HPI [21]). Fish can respond quickly to rapid natural or anthropogenic environmental changes [7]. The reason for the morphological difference between both populations might be due to the change in habitat type (lentic vs. lotic) and related environmental parameters. ...
Background Organisms with broad distribution ranges, such as fish, often exhibit local ecological specializations
based on their utilization of food and habitat. Populations of species that live in different habitat types (lotic vs.
lentic) show morphological variations. However, the phenotypic differences of endemic fish populations in a small
karst river basin under anthropogenic pressure are still not fully understood. In this study, the functional traits and
morphological variations of the populations of endemic Pseudophoxinus antalyae Bogutskaya, 1992, in the Düden
Stream basin, which is subjected to various anthropogenic disturbances and habitat types in southwestern Anatolia
of Türkiye, were examined using linear measurements and geometric morphometric analysis.
Results Differences have been identified in functional traits, particularly those related to food acquisition between
populations. Results of both univariate and multivariate analyses revealed significant differences in body shape and
size among populations living at sites along the stream with different habitat and environmental characteristics.
Conclusions The reason for these differences determined in the morphology and traits of the populations may
depend on habitat types, ecological, or environmental, and obstruction of gene flow. More detailed studies are
needed to explain the mechanisms (genetic and ecological) that cause these differences.
... The relationship between body shape and abiotic habitat variables offers a compelling functional explanation for the unequal morphological diversity observed in characiform fishes. Our results tend to support these functional predictions as well as previous studies that have shown similar phenotypic responses across the same environmental gradients in other groups of fishes (Foster et al., 2015;Gilbert et al., 2020;Hendry et al., 2002;Langerhans, 2008;McGuigan et al., 2003), including Characiformes (Langerhans et al., 2003) and Cypriniformes (Haas et al., 2010). ...
Understanding why some clades diversify greatly while others do not is a major goal of evolutionary biology. Both abiotic and biotic factors are important in driving unequal morphological diversity across the tree of life. However, few studies have quantified how abiotic habitat and community composition differences influence unequal morphological diversification in spatiotemporally diffuse radiations. We use geometric morphometrics, abiotic habitat data generated by Geographic Information Systems (GIS) analyses, evolutionary simulations, and phylogenetic comparative methods to determine whether random evolution, habitat variation, competition for niches, or a combination of factors influenced the unequal body shape diversity of a Gondwanan freshwater fish radiation. We find that Neotropical characiform lineages, which exhibit substantially more body shape diversity than their African counterparts, occupy significantly more slope and elevation habitats than African lineages. Differences in habitat occupation between the continental radiations occur through a combination of likely competition with cypriniform fishes in Africa restricting access to higher slope and elevation habitats and significantly more low-elevation and slope habitats available in the Neotropics. Our findings suggest that spatiotemporally widespread radiations, like Characiformes, do not diversify across homogenized habitats and biotic assemblages, with differences in community structure and physical habitat playing an important role in driving unequal morphological diversification.
... South European roaches with the deepest bodies were observed in site SET, which is an ancient reservoir/lentic environment, further suggesting that the hydrodynamic pattern, and in particular water velocity, might be the main driver determining morphological responses. Human alteration of freshwater environments was largely reported to induce changes in shape in fish populations, especially after construction of dams, with subsequent impoundments of rivers and creation of reservoirs (Franssen et al., 2013a;Perazzo et al., 2019;Gilbert et al., 2020). Our study confirmed that less drastic environmental changes, such as channelization and modifications of water velocity in streams, can also affect the phenotypic response of fish populations (Kelley et al., 2017;Kern & Langerhans, 2018). ...
The large number of cryptic species and extensive intraspecific phenotypic plasticity among freshwater fishes pose a challenge to the correct assessment of diversity within these taxa, which is crucial for their conservation. Recently, three different genetic lineages have been identified within the Italian endemic South European roach Sarmarutilus rubilio, a threatened species with a broad ecological niche. Using geometric morphometrics, we tested the existence of morphological differences associated with genetic common ancestry (i.e. between lineages) and/or environmental parameters. We observed streamlined body shapes in sites scarcely altered by human intervention and with fast water flow; on the contrary, we observed deeper body shapes in canals and in one reservoir with slow/still water flow. Our results suggest that morphological diversity in the South European roach is mainly a result of phenotypic plasticity in response to different environmental drivers (i.e. lotic vs. lentic hydrodynamic patterns) rather than different genetic backgrounds.
... Recent studies have documented rapid phenotypic evolution in organisms, detailing significant changes over time scales of a few generations rather than millions of years. Several studies have demonstrated rapid evolution in fishes, including color pattern selection based on predator presence over 15 generations in Trinidadian guppies (Endler, 1980), morphometric changes in South American cichlids within decades following river damming (Gilbert et al., 2020), and ecotype divergence in three-spine stickleback within a single generation (Laurentino et al., 2020). The sensory systems of organisms can evolve to match environmental conditions (Endler, 1980;Endler and Basolo, 1998) but it remains unclear how quickly sensory systems and their sensitivity to stimuli might adapt to changing conditions (Zakon, 2015;Dunlop et al., 2018) or may diverge between individuals within a population, resulting in speciation (Seehausen et al., 2008;Puechmaille et al., 2011;Tait et al., 2021). ...
Population divergence is often quantified using phenotypic variation. However, because sensory abilities are more difficult to discern, we have little information on the plasticity and rate of sensory change between different environments. The Mexican tetra (Astyanax mexicanus) is a fish distributed throughout Southern Texas and Northern Mexico and has evolved troglomorphic phenotypes, such as vestigial eyes and reduced pigmentation, when surface ancestors invaded caves in the past several hundred thousand years. In the early 1900s, surface A. mexicanus were introduced to the karstic Edwards-Trinity Aquifer in Texas. Subsequent cave colonization of subterranean environments resulted in fish with phenotypic and behavioral divergence from their surface counterparts, allowing examination of how new environments lead to sensory changes. We hypothesized that recently introduced cave populations would be more sensitive to light and sound when compared to their surface counterparts. We quantified divergence using auditory evoked potentials (AEPs) and particle acceleration levels (PALs) to measure differences in sound sensitivity, and electroretinography (ERGs) to measure light sensitivity. We also compared these results to measurements taken from native populations and lab-born individuals of the introduced populations. Honey Creek Cave fish were significantly more sensitive than proximate Honey Creek surface fish to sound pressure levels between 0.6 and 0.8 kHz and particle acceleration levels between 0.4 and 0.8 kHz. Pairwise differences were found between San Antonio Zoo surface and the facultative subterranean San Pedro Springs and Blue Hole populations, which exhibited more sensitivity to particle acceleration levels between 0.5 and 0.7 kHz. Electroretinography results indicate no significant differences between populations, although Honey Creek Cave fish may be trending toward reduced visual sensitivity. Auditory thresholds between wild-caught and lab-raised populations of recently invaded fish show significant differences in sensitivity, suggesting that these traits are plastic. Collectively, while these results may point to the rapid divergence of A. mexicanus in cave habitats, it also highlights the responsive plasticity of A. mexicanus auditory system to disparate environments.
... River damming is one of the primary anthropogenic disruptions to the Earth's natural water and matter cycles (Gilbert et al., 2020). Physical factors such as water level, flux, and velocity show notable changes after reservoir construction. ...
In recent decades, damming has become one of the most important anthropogenic activities for river regulation, and reservoirs have become hotspots for biogeochemical cycling. The construction of dams changes riverine hydrological conditions and alters the physical, chemical, and biological characteristics of rivers, eventually leading to significant variations in nutrient cycling. This review mainly explores the effects of river damming on nutrient transport and transformation, including i) nutrient (N, P, Si, and C) retention in reservoirs, ii) greenhouse gas (GHG) emissions, and iii) interactions between the nutrient stoichiometry ratio and the health of the reservoir ecosystem. The important drivers of nutrient transport and transformation, such as river connectivity, hydraulic residence time, hydropower development mode, microbial community variation, and anthropogenic pollution, have also been discussed. In addition, strategies to recover from the negative effects of damming on aquatic ecosystems are summarized and analyzed. To provide theoretical and scientific support for the ecological and environmental preservation of river-reservoir systems, future studies should focus on nutrient accumulation and GHG emissions in cascade reservoirs.
... Furthermore, the specimens analyzed come from dams on the principal course of the Grijalva River. Notably, there is evidence of environmental changes and reductions in gene flow being caused by dam construction, which may induce rapid morphological modifications in fish (Michel et al. 2008;Franssen 2011;Perazzo et al. 2019;Gilbert et al. 2020). Additionally, while the Grijalva and Usumacinta basins share some biological and ecological characteristics, each basin has an independent biogeographical history (Elías et al. 2021). ...
... This has also been found for other groups of fish for which the level of morphological variation among species is related to the level of dietary specialization Kentao and Jearranaiprepame 2021). Regarding cichlids, generalist species were found to have greater variation in body shape than specialists (Kassam et al. 2004;Gilbert et al. 2020). It is also known that changes in head size and eye position may be related to dietary conduct, especially in terms of size and diet type (Haas et al. 2010;Kentao and Jearranaiprepame 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.
... argyrostictus, G. gottwaldi, G. grammepareius, G. harreri, G. pyrineusi, and G. taeniopareius) have a more elongate body when compared with species in the G. surinamensis group (e.g., G. crocatus, G. abalios, G. winemilleri). The shallow body can be an ecomorphological adaptation to live in fast-flowing waters, while the deep-bodied species are best suited for slow-flowing waters of lowland rivers (see Gilbert et al., 2020). ...
Geophagus pyrineusi, new species, is described from the rio Teles Pires drainage, rio Tapajós basin, Brazil. The new species can be diagnosed from the majority of the congeners by presenting a complete infraorbital bar. Additionally, it differs from all other congeners by several coloration-related character states: flank bars 5 and 6-7 as dark as the infraorbital bar, and almost as dark as the midlateral spot; retention of dorsal melanophoric patch 6 as a distinct mark (not connected to any lateral melanophoric patch), and almost as dark as the midlateral spot in adults; retention of lateral melanophoric patch 1p and almost complete absence of dorsal-and caudal-fin color patterns in adults, among other characters.
Resumo Geophagus pyrineusi, espécie nova, é descrita da drenagem do rio Teles Pires, bacia do rio Tapajós, Brasil. A nova espécie pode ser diagnosticada da maioria das congêneres por apresentar uma barra infraorbital completa. Adicionalmente, ela difere de todas as outras congêneres por diversos caracteres relacionados à coloração: barras do flanco 5 e 6-7 tão escuras quanto a barra infraorbital e quase tão escura quanto a mancha médio-lateral; retenção da mancha melanofórica dorsal 6 como uma marca distinta (não conectada com nenhuma mancha melanofórica lateral) e quase tão escura quanto a mancha médio-lateral em adultos; retenção da mancha melanofórica lateral 1p e quase completa ausência de padrões de colorido nas nadadeiras dorsal e caudal em adultos, entre outros caracteres. Palavras-chave:
... To minimize detrimental effects of river regulation on the platypus and other species, new dams within the distribution of platypus need to be avoided in favour of other water saving strategies. Further research is needed to investigate the effects of dams on adaptive genetic variation to determine whether platypuses are able to respond to environmental change caused by dams, as other freshwater species including cichlid fishes (Gilbert, Akama, et al., 2020), Chinook salmon (Oncorhynchus tshawytscha; Waples et al., 2017) and Amazon river prawn (Macrobrachium amazonicum; Silva et al., 2020). ...
Thesis Abstract Genetic differentiation is a vital aspect of population genetics and is a direct consequence of evolutionary forces acting on genetic diversity. By interpreting patterns of genetic differentiation, we can detect, infer, and estimate the extent to which natural selection, genetic drift, and gene flow affect genetic diversity. In this thesis, estimation of genetic differentiation is used as a tool to answer the following questions, three mainly theoretical, and the other an applied study on platypus conservation.
... For instance, a selective advantage for increased dispersal ability for colonizing species has led to rapid evolution in morphology, including for wing size in birds (Berthouly-Salazar et al., 2012), foot size in rodents (Forsman et al., 2011), and bone structure and size in cane toad (Hudson et al., 2016). For fish, body shape changes in response to environmental transitions between stream and lake habitats have been observed in several taxa, although the general patterns of those changes are not always consistent (Akin & Geheber, 2020;Franssen, 2011;Gilbert et al., 2020). ...
... Rawlings et al. (2021) similarly reported patterns, with lake dwelling round gobies having deeper bodies; however, those authors found no differences in dorsal head shape when comparing individuals sampled among habitats. Morphological distinctions between lake a stream habitats have been similarly observed in other fish species, including the red shiner (Cyprinella lutrensis, Akin & Geheber, 2020;Franssen, 2011) and six cichlid species (Gilbert et al., 2020). The most common morphological change in those cases was a streamlining of body shape, as we observed with the reduction in body depth for CC round gobies; however, head shape from the dorsal perspective was not evaluated in any of the cited studies. ...
Geometric morphometrics provides a powerful means of evaluating differences in phenotypic traits among specimens. However, inferences of trait variability can be confounded when measurements are based on preserved samples. We evaluated effects of ethanol preservation on morphology over a 22-week time period for a Laurentian Great Lakes invasive fish, round goby (Neogobius melanostomus, Pallas 1814), using sets of 17 lateral and six dorsal landmarks. We tested whether ethanol preservation affected the magnitude of inter-population variation between individuals collected from lake and river habitats. Generalized least square regression determined that length did not significantly vary through the preservation time series for fish from either population, while mass decreased significantly. Body shape variation was summarized using principal component analysis, which revealed that most preservation-associated changes occurred in the first 14 days. The lateral shape experienced a large magnitude change during the first 24 hours in ethanol then only minor changes for the remainder of the study. The dorsal shape began to revert to pre-preservation measurements about 14 days following preservation. Additionally, differences in shape were apparent between the two populations throughout the experiment; however, the magnitude of differences between populations varied depending on whether dorsal or lateral landmarks were considered. Our study demonstrates that tissue responses to ethanol preservation can be more complex than a simple loss of mass, resulting in difficult to predict consequences for geometric morphometric analyses, including variable responses depending on the anatomical region being analyzed.
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