Phylogeography of two newts sub-endemic to the italian peninsula : lissotriton vulgaris meridionalis and triturus carnifex (amphibia, salamandridae)

Abstract

In the western Palaearctic region phylogeographic patterns of temperate species have been investigated intensively. Nevertheless, as more phylogeographic studies become available, a high variability of temperate species responses to Pleistocene climatic oscillations continue to emerge. In this thesis, I investigated population genetic structure, phylogeography and demographic history of two newts subendemic of the Italian Peninsula, Triturus carnifex and Lissotriton vulgaris meridionalis. Triturus carnifex showed three main parapatric and ancient mtDNA lineages distributed in three separated geographic districts, namely the Italian Peninsula, northern Italy and western Croatia/Slovenia. Multiple evidences indicate that these three main lineages have had independent evolutionary histories trough Pleistocene and that they have showed different responses to Pleistocene climatic oscillations encompassing multiple refugia along the Apennine chain, lowland refugia in large peri-coastal plains, and a ‘cryptic’ northern refugium. On the other hand, Lissotriton vulgaris meridionalis showed ten allo-parapatric mtDNA lineages, likely of Middle Pleistocene origin, distributed in distinct geographic compartments across the Italian Peninsula and north Italy. The phylogeographic structure observed, time estimates of common ancestors and geographic distribution of each lineage suggested that L. v. meridionalis survived last glacial-interglacial cycles in several refugia, many of them located in north Italy and likely in peri-Alpine and peri-northern Apennines areas. Thus, for this species, a scenario of glacial survival of northern lineages at foothills of water-donating mountains would likely explain such a pattern of ‘northern richness’ observed. When comparing the evolutionary histories of these newts with those of co-distributed temperate species, while the pattern of ‘northern richness’ showed by L. v. meridionalis is unprecedented, T. carnifex exemplified in one species most of the responses to Pleisotcene climatic cycles previously observed in temperate species from Italy. Interestingly, both species showed glacial survival in north of Italy, and together with previous evidences from phylogeographic and palaeo-environmental studies indicated that this area allowed long-term persistence of temperate species during Pleistocene glacial-interglacial cycles. This study gave a contribution to unravelling the complex scenario of temperate species’ responses to Plio-Pleistocene climatic oscillations, in the regional context of Italy. Moreover, the north of Italy has been identified as a key area to focus future investigation and to evaluate the role of peri-mountains and coastal refugia for the evolution of the Italian biota