Multiple lines of evidence for demographic and range expansion of a temperate species (Hyla sarda) during the last glaciation

Abstract

Many temperate species experienced demographic and range contractions in response to climatic changes during Pleistocene glaciations. In this study, we investigate the evolutionary history of the Tyrrhenian tree frog Hyla sarda, a species inhabiting the Corsica-Sardinia island system (Western Mediterranean basin). We used sequence analysis of two mitochondrial (overall 1229 bp) and three nuclear (overall 1692 bp) gene fragments to assess the phylogeography and demographic history of this species, and species distribution modelling (SDM) to predict its range variation over time. Phylogeographic, historical demographic and SDM analyses consistently indicate that H. sarda does not conform to the scenario generally expected for temperate species but rather underwent demographic and range expansion mostly during the last glacial phase. Palaeogeographic data and SDM analyses suggest that such expansion was driven by the glaciation-induced increase in lowland areas during marine regression. This unusual scenario suggests that at least some temperate species may not have suffered the adverse effects of glacial climate on their population size and range extent, owing to the mitigating effects of other glaciations-induced palaeoenvironmental changes. We discuss previous clues for the occurrence of such a scenario in other species and some possible challenges with its identification. Early phylogeographic literature suggested that responses to the Pleistocene glacial-interglacial cycles were expected to vary among species and regions. Our results point out that such variation may have been greater than previously thought.

Mammal endemism In Italy: A review

“…Older species result to be the soricomorph Sorex samniticus and Talpa romana, and the two insular endemics: the bat Plecotus sardus and the soricomorph Crocidura sicula. It should be considered that the southernmost part of Italy, including Sicily and Sardinia, constitute for some xerophilic species a particular favorable area not only during interglacials but even during glacial maxima when a strong sea level decrease occurred (as much as 120-135 m) leading to the increase of the Mediterranean coastal plains and favoring the formation of new suitable habitats with consequent population expansions (Bisconti et al 2011;Senczuk et al 2017). This could have allowed the survival of some old mammal endemic species as well as for other paleoendemic vertebrates across different climatic oscillations in those southern areas of the country.…”

Digging up the roots of an insular hotspot of genetic diversity: decoupled mito-nuclear histories in the evolution of the Corsican-Sardinian endemic lizard Podarcis tiliguerta

“…Further connections between them occurred during the Messinian Salinity Crisis (5.7–5.3 mya) [16, 101] and repeatedly in the Pleistocene at each ice age, from 2.58 mya up to 12 thousands years ago (12 kya) [18, 19]. Especially during the Pleistocene glaciations, faunal exchange between the two Islands has been intense, as documented in the other endemic lizards of Corsica and Sardinia, Archaeolacerta bedriagae [12, 27] and Algyroides fitzingeri [31], but also in other thermophilic endemic taxa ( Hyla sarda [30]; Euleptes europaea (Salvi et al unpublished data); see also preliminary data on Discoglossus sardus in [11]). Palaeogeographic data and results from SDM analyses (Fig.…”

“…A significant realization of these studies is that the current patterns of genetic structure and diversity of these endemic species have been historically shaped by an unexpectedly diverse array of evolutionary and demographic processes acting across unrelated spatial and temporal scales [20]. In fact, essentially each phylogeographical reconstruction carried out so far on Corsican-Sardinian species suggested an idiosyncratic scenario for the evolution of the current geographical patterns of intraspecific genetic diversity [12, 19, 20, 30, 31]. This suggests that we are still far from either an exhaustive inventory or a deep understanding of the evolutionary processes underlying the origins and diversity of this biodiversity hotspot.…”

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

“…These new perspectives suggest that some temperate species could have undergone attenuated or even reverse responses to glacial population contractions, with the absence of a post-LGM (re)colonization pattern [13, 14]. This scenario appears plausible considering the strong sea level decrease (as much as 120–135 m) during the LGM, leading to the increase of Mediterranean coastal plains and favoring the formation of new suitable habitats with consequent population expansions.…”