Abstract
The identification of historic and contemporary barriers to dispersal is central to the conservation of endangered amphibians, but may be hindered by their complex life history and elusive nature. The complementary information generated by mitochondrial (mtDNA) and microsatellite markers generates a valuable tool in elucidating population structure and the impact of habitat fragmentation. We applied this approach to the study of an endangered montane newt, Euproctus platycephalus. Endemic to the Mediterranean island of Sardinia, it is threatened by anthropogenic activity, disease, and climate change. We have demonstrated a clear hierarchy of structure across genetically divergent and spatially distinct subpopulations. Divergence between three main mountain regions dominated genetic partitioning with both markers. Mitochondrial phylogeography revealed a deep division dating to ca. 1 million years ago (Mya), isolating the northern region, and further differentiation between the central and southern regions ca. 0.5 Mya, suggesting an association with Pleistocene severe glacial oscillations. Our findings are consistent with a model of southward range expansion during glacial periods, with postglacial range retraction to montane habitat and subsequent genetic isolation. Microsatellite markers revealed further strong population structure, demonstrating significant divergence within the central region, and partial differentiation within the south. The northern population showed reduced genetic diversity. Discordance between mitochondrial and microsatellite markers at this scale indicated a further complexity of population structure, in keeping with male‐biased dispersal and female philopatry. Our study underscores the need to elucidate cryptic population structure in the ecology and conservation strategies for endangered island‐restricted amphibians, especially in the context of disease and climate change.
Highlights
A global decline in amphibians has been in evidence for more than 25 years (Beebee & Griffiths, 2005)
The scenario of a sequential process underlying central intraregional divergence received the highest posterior support (Figures 6 and S4A), consistent with a model of southerly spread and subsequent loss of connectivity. This was endorsed by the comparison of scenarios incorporating admixture, the best-supported model showing a low level of admixture, between the northernmost central population (BP) and the geographically intermediate (SES), and Comparison of levels of significance for pairwise genetic distances between sites with mitochondrial DNA (mtDNA) and microsatellite markers, showing contrasting patterns of discrepancy between mitochondrial and microsatellite markers according to region. ns; nonsignificant (p > .05). *p < .05; **p < .01; ***p
We have demonstrated a clear hierarchy of structure between genetically divergent and spatially distinct subpopulations of the endangered E. platycephalus across its range of distribution
Summary
A global decline in amphibians has been in evidence for more than 25 years (Beebee & Griffiths, 2005). In contrast to mtDNA markers, microsatellites provide insight into more recent population genetic processes Their application generates more contemporary information at the level of the individual, allowing the identification of current populations and metapopulations, and the inference of connectivity (Allentoft & O’Brien, 2010) and of barriers to gene flow at a microgeographical scale (Jehle & Arntzen, 2002). Our results are consistent with both deep genetic divisions and contemporary barriers to gene flow, providing evidence that both historical and more recent factors underpin the current genetic structure These findings will be of value in the ongoing conservation management of this endangered amphibian, especially in the context of disease and climate change, with the potential of extrapolation to other island endemics
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