Jailed in the mountains: Genetic diversity and structure of an endemic newt species across the Pyrenees

Abstract

The Pyrenees represent a natural laboratory for biogeographic, evolutionary and ecological research of mountain fauna as a result of the high variety of habitats and the profound effect of the glacial and interglacial periods. There is a paucity of studies providing a detailed insight into genetic processes and better knowledge on the patterns of genetic diversity and how they are maintained under high altitude conditions. This is of particular interest when considering the course of past climate conditions and glaciations in a species which is considered site tenacious, with long generation times. Here we analyzed the genetic patterns of diversity and structure of the endemic Pyrenean brook newt (Calotriton asper) along its distribution range, with special emphasis on the distinct habitat types (caves, streams, and lakes), and the altitudinal and geographical ranges, using a total set of 900 individuals from 44 different localities across the Pyrenean mountain range genotyped for 19 microsatellite loci. We found evidence for a negative longitudinal and positive altitudinal gradient of genetic diversity in C. asper populations. The fact that genetic diversity was markedly higher westwards is in accordance with other Pyrenean species. However, the impact of altitudinal gradient on the genetic diversity seems to differ from other species, and mostly from other amphibians. We found that lower altitudes can act as a barrier probably because the lowlands do not provide a suitable habitat for C. asper. Regarding the distinct habitat types, caves had significantly lower values of genetic diversity compared to streams or lakes. The mean FST value was relatively high (0.304) with maximum values as high as 0.771, suggesting a highly structured total population. Indeed, populations were grouped into five subclusters, the eastern populations (cluster 1) remained grouped into two subclusters and the central-western Pyrenees (cluster 2) into three subclusters. The increase of isolation with geographical distance is consistent with the population structure detected. In conclusion, C. asper seems to be adapted to high altitude mountain habitats, and its genetic diversity is higher in the western Pyrenees. In terms of conservation priority, we consider more relevant the populations that represent a reservoir of genetic diversity.

Genomic data reveal deep genetic structure but no support for current taxonomic designation in a grasshopper species complex

“…In agreement with structure and faststructure results for K = 2, all phylogenetic analyses showed a basal split in two clades corresponding to populations located east and west of an imaginary line located around the Segre river (~1°E (Charrier et al, 2014;Valbuena-Ureña et al, 2018). Overall, these results are consistent with the transverse breaks proposed by Wallis et al (2016) for numerous alpine taxa and support the idea that the fragmentation of ancestral distributions during glacial periods and the presence of Pleistocene refugia along mountain ranges has played a key role on the diversification not only of lowland species but also of montane and alpine organisms.…”

“…In agreement with structure and faststructure results for K = 2, all phylogenetic analyses showed a basal split in two clades corresponding to populations located east and west of an imaginary line located around the Segre river (~1°E). Similar east–west genetic splits have been reported for many other plant and animal species from the Pyrenean region (e.g., Alvarez‐Presas, Mateos, Vila‐Farre, Sluys, & Riutort, ; Bidegaray‐Batista et al, ; Charrier, Dupont, Pornon, & Escaravage, ; Milá, Carranza, Guillaume, & Clobert, ; Valbuena‐Ureña et al, ). This east–west split might be well explained by detailed geological reconstructions documenting heavily glaciated areas in the central part of the range and the likely presence of ice‐free refugia at its longitudinal extremes (Ehlers, Gibbard, & Hugues, ) that might have allowed montane/alpine species to survive glaciations and recolonize high elevations during interglacial periods (Charrier et al, ; Valbuena‐Ureña et al, ).…”

“…Similar east–west genetic splits have been reported for many other plant and animal species from the Pyrenean region (e.g., Alvarez‐Presas, Mateos, Vila‐Farre, Sluys, & Riutort, ; Bidegaray‐Batista et al, ; Charrier, Dupont, Pornon, & Escaravage, ; Milá, Carranza, Guillaume, & Clobert, ; Valbuena‐Ureña et al, ). This east–west split might be well explained by detailed geological reconstructions documenting heavily glaciated areas in the central part of the range and the likely presence of ice‐free refugia at its longitudinal extremes (Ehlers, Gibbard, & Hugues, ) that might have allowed montane/alpine species to survive glaciations and recolonize high elevations during interglacial periods (Charrier et al, ; Valbuena‐Ureña et al, ). Overall, these results are consistent with the transverse breaks proposed by Wallis et al () for numerous alpine taxa and support the idea that the fragmentation of ancestral distributions during glacial periods and the presence of Pleistocene refugia along mountain ranges has played a key role on the diversification not only of lowland species but also of montane and alpine organisms.…”

Genetic diversity of maize landraces from the South-West of France

“…The geographical distribution of maize landraces in SWF could also be the result of a diversifying selection. The occurrence of a genetical longitudinal gradient along the Pyrenees area as observed in this study has been reported for several species (47)(48)(49)(50). Gradients, such as altitude or longitude, play an important role in the Pyrenees, as they shape the existing proportion of suitable habitats along the mountains (48,49).…”

“…Gradients, such as altitude or longitude, play an important role in the Pyrenees, as they shape the existing proportion of suitable habitats along the mountains (48,49). Valbuena-Ureña et al (50) emphasized that longitude is an important gradient to take into account in the Pyrenees, because the influence of the Atlantic ocean provides cooler and wetter climate westwards than in Eastern areas, which are more influenced by the Mediterranean climate.…”