Abstract
The study of the European plethodontid salamander Hydromantes strinatii using allozyme and mitochondrial markers showed a strong geographical genetic structure. This was likely the outcome of different evolutionary mechanisms leaving their signature despite the effects of the genetic drift due to the low population size typical of this species. Two highly divergent clades were identified in the eastern and central-western part of the range, with further geographic sub-structure. Nuclear and mitochondrial markers substantially recovered the same population groups but were conflicting in reconstructing their relationships. This apparent incongruence highlighted the action of different mechanisms such as secondary contacts and incomplete lineage sorting in originating the observed genetic variation. The troglophilic habit of this species provided the opportunity to show the importance of caves as local refugia in maintaining the genetic diversity through the persistence of local populations. Accordingly, high nucleotide and haplotype diversity, strong geographic genetic structuring and lack of expansion were evidenced. This signature was found in the populations from the Ligurian and Maritime Alps, in agreement with the complex orography and paleoclimatic history of this Mediterranean hotspot.
Highlights
Cave species are considered fragile and endangered due to their strict ecological requirements, making them poorly able to face climatic variation
We examined the distribution of the number of differences between pairs of haplotypes by a mismatch analysis [49] and evaluating both the sum of square deviations (SSD) [50] and Harpending’s
The study of mt and nc markers in H. strinatii provided a complex picture, suggesting that the action of different evolutionary processes could be identified despite the low population size typical of this species enhancing the effects of the genetic drift and introducing some randomness in the general pattern of variation
Summary
Cave species are considered fragile and endangered due to their strict ecological requirements, making them poorly able to face climatic variation. Their strong association with underground retreats constrains their populations to low size and poor genetic diversity [1]. Some recent data started to overturn this view, especially for troglophilic animals that are able to exploit both subterranean and epigean habitats These features could make troglophilic species more resistant to climate changes than surface species since they have the possibility to draw back into local retreats under unfavourable external conditions and wait for better climate while sheltered. This hypothesis has been fuelled by recent case studies showing similar patterns of persistence in isolated troglophilic species [2] and in surface species linked to patchy and heterogeneous habitats, pointing out the relevance of localized
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