Frammentazione geografica, ibridazione introgressiva e nascita dell'hotspot di diversità genetica in Italia meridionale
Author(s)
Caputo, Francesco Paolo
Date Issued
March 20, 2012
Type
Doctoral Thesis
Abstract
Glacial refugia are often hotspots of intraspecific diversity. In order to shed more light on the
causative processes underling this pattern, I investigated the geographic patterns of genetic diversity
among populations of the Italian endemic newt Lissotriton italicus. Exceptionally high levels of
diversity were found among and within populations of L.italicus. Two main evolutionary lineages
were identified, one restricted to the Calabrian peninsula, the other spanning the rest of the species
range. Among them, I found evidence of at least two cycles of geographical isolation and secondary
contact. Bayesian analyses of historical and contemporary gene flow indicated that the most ancient
event of secondary contact would have lead to extensive introgression among lineages, while for the
most recent event no evidence of gene exchange were found. Since no extrinsic barriers to gene
flow exists, these data suggest the presence of intrinsic ones, and the occurrence of two cryptic
species within L. italicus. Evidence of allopatric fragmentation and secondary admixture were also
inferred in various areas of the ranges of both lineages. Overall, the diffuse pattern of high genetic
diversity within L.italicus populations appears best explained by multiple events of allopatric
divergence and secondary admixture. I discuss the main eco-evolutionary and conservation
implications of these findings for L. italicus and for the Italian hotspot of Mediterranean
biodiversity as a whole.
Additional information
Dottorato di ricerca in Ecologia e gestione delle risorse biologiche
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