Pleistocene evolutionary history and conservation of mountain species within mediterranean peninsulas: insight from the alpine newt in the Apennine Chain
Author(s)
Chiocchio, Andrea
Date Issued
June 17, 2016
Type
Doctoral Thesis
Abstract
Mediterranean peninsulas are hotspots of intraspecific genetic diversity, and several studies on species genetic structure have investigated the evolutionary processes involved in generating such richness. However, despite Mediterranean peninsulas are mainly mountainous regions, most studies were focused on temperate species, whereas the evolutionary dynamics involving mountain species remain underinvestigated. Here I investigated the genetic structure and the evolutionary history of the mountain amphibian Ichthyosaura alpestris within the Apennine peninsula, using both mitochondrial and nuclear genetic markers, coupled with Bayesian phylogeographic analyses and species distribution models. I found a deep and ancient genetic structure, with three distinct genetic lineages whose divergence dates back to the Early and Middle Pleistocene. Two of these lineages form a secondary contact zone in the Ligurian Apennine, which corresponds to the area where populations showed the highest levels of genetic diversity. These results confirm the role of Mediterranean peninsulas as multiple refugia during the Pleistocene for mountain species as well, and suggest that repeated cycles of fragmentation and allopatric isolation, followed by secondary admixture, may have been a common process in forming hotspots of intraspecific diversity within these peninsulas. Moreover, to evaluate if population genetic diversity of I. alpestris could be affected by some on-going erosive processes, I tested for presence of Chytrid fungus, an emerging infectious disease which is strongly affecting amphibians worldwide, especially in mountain habitats. I found a wide distribution of the pathogen along peninsula, but low prevalence within populations. However, I also found an interesting correlation between the absence of the pathogen and the high levels of population genetic diversity. Such result might suggest a role of genetic diversity in protecting populations, as already observed in other species, and provide useful information for conservation strategies. This research highlights the necessity to better understand the processes generating genetic diversity, in order to evaluate how the evolutionary potential of populations could favour their long term persistence, in the face of global change.
Additional information
Dottorato di ricerca in Ecologia e gestione delle risorse biologiche
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