Phylogeography and historical demography of the Italian treefrog,Hyla intermedia,reveals multiple refugia, population expansions and secondary contacts within peninsular Italy

Abstract

We investigated the geographical patterns of genetic diversity in the Italian treefrog through sequence analysis of a mitochondrial cytochrome b gene fragment. Three main mitochondrial lineages were identified, distributed in northern, central and southern Italy, respectively. Their divergence appears indicative of a split time largely predating Late Pleistocene climatic oscillations, and syntopy between them was only observed in the geographically intermediate populations. The historical demographic reconstructions suggest that in both northern and central Italy, an expansion occurred during the last major glacial phase, when a vast widening of the lowland habitats followed the glaciation-induced fall of the sea level. Instead, in southern Italy an expansion event likely followed the end of the last glaciation, although the inference of expansion appears less reliable for the southern clade than for the others. Within this geographical area, a sharp phylogeographic discontinuity separated peninsular from Sicilian populations, and the overall pattern of diversity suggests that the latter derived from a recent colonization of the island, probably through a Late Pleistocene land bridge. Phylogenetic, phylogeographic and historical demographic analyses thus concur in delineating a scenario of multiple refugia, with four groups of populations which survived the last glacial-interglacial cycles in at least three distinct refugia arranged along peninsular Italy, and have recently come into contact following range expansions. Therefore, these results support the hypothesis that a plethora of microevolutionary processes, rather than the prolonged stability of populations, were mainly responsible for shaping the patterns of diversity within this major biodiversity hotspot.

A combination of long term fragmentation and glacial persistence drove the evolutionary history of the Italian wall lizard Podarcis siculus

“…Indeed, this area acted as a dispersion barrier during the repeated Plio-Pleistocene marine transgressions separating the Italian Peninsula from the Calabrian and Sicilian paleo-archipelagos [64, 65]. This main vicariance event has also been observed in other detailed works on different vertebrate taxa, confirming this region as one of the most important in driving long-term allopatric differentiation in southern Italy [25, 66–69]. …”

Mitochondrial phylogeography of the edible dormouse (Glis glis) in the western Palearctic region

“…3). These results suggest possible refugia within refugia in Italy, and several studies (Canestrelli et al 2006(Canestrelli et al , 2007Podnar et al 2005;Santucci et al 1996;Ursenbacher et al 2006) have shed light on possible multiple glacial refugia in the Italian peninsula. One example involves the beech tree (Fagus sylvatica- Magri et al 2006), which is a dominant species in several dormouse habitats and particularly important to G. glis.…”

What triggers the rising of an intraspecific biodiversity hotspot? Hints from the agile frog

“…Although not unusual, it may be difficult to reconcile the discordance between nuclear and mitochondrial data to infer the history of populations, given the diversity of microevolutionary processes that are potentially involved36. However, while the northern Apennine is a well known suture zone between both intra- and interspecific lineages2737383940, a contact zone in the area close to our sites 17–19 would not have any analogues in the phylogeographic literature of co-distributed temperate species. In addition, no environmental features (present or past) were present that could explain the observed pattern.…”