Grass snakes are widely distributed across the Western Palearctic. Recent phylogeographic studies provided evidence that three distinct parapatric species exist. Two of these occur in Italy, Natrix helvetica and N. natrix, and a contact zone between both taxa has been suggested for north‐eastern Italy. Moreover, previous investigations revealed for the Italian Peninsula a complex phylogeographic structure. Using mtDNA sequences and microsatellite loci, we examined the situation for mainland Italy, Sicily, Sardinia, and Corsica. Our study confirmed the occurrence of N. natrix in north‐eastern Italy. Cline analyses revealed limited gene flow between N. helvetica and N. natrix across a narrow hybrid zone. Within N. helvetica, conflicting patterns of mitochondrial and nuclear genomic differentiation were revealed. Three nuclear genomic clusters were found; one of them corresponded to no fewer than five distinct and, in part, deeply divergent and ancient mitochondrial lineages from mainland Italy and Sicily. This cluster was paraphyletic with respect to the two remaining mitochondrial lineages, each of which matched with another nuclear genomic cluster (one from Corsica plus Sardinia and another one from western Europe north of the Alps). This unexpected pattern most likely results from mainly male‐mediated gene flow and female philopatry combined with population‐density‐dependent processes such as ‘high‐density blocking’. With respect to taxonomy, we propose to synonymize N. h. lanzai Kramer, 1970 with N. h. sicula (Cuvier, 1829), acknowledging their lacking nuclear genomic differentiation. The studied hybrid zone of N. h. helvetica and N. h. sicula in Italy is wide, with a smooth cline for nuclear markers, supporting their subspecies status. We found no evidence for the distinctiveness of the two subspecies from Corsica (N. h. corsa) and Sardinia (N. h. cetti), suggesting their synonymy, but refrain from taxonomic conclusions because of small sample sizes and the endangered status of the Sardinian taxon.
Two distinctive patterns of adhesive toepad are found in the Gekkotaterminal leaf-like pads situated at the distal ends of the digits, and basal pads that encroach more proximally along the digits, are proportionally larger and are associated with more than just the ungual and distal portion of the penultimate phalanges. Although these two configurations have long been recognized, there has been no explanation of whether or not they are functionally different. A small offshore island provided a potential arena for testing the possibility of differential functionality of these two patterns. Euleptes europaea, a leaf-padded taxon, is widespread on Giraglia Island (Corsica), whereas Tarentola mauritanica, a basally padded recent colonizer, has remained restricted to its one concrete building. Challenges to adhesion occur on dusty surfaces, and the self-cleaning mechanism of gecko setal fields can be rendered ineffective if the dust is ubiquitous. Giraglia is composed of prasinite, an inherently friable and dusty schist. The leaf-like terminal pads of E. europaea can be withdrawn from close contact with dusty surfaces, leaving the claws alone to provide traction. The digits of T. mauritanica more fully integrate the claws and adhesive pad, with full-digit hyperextension rendering the claws alone incapable of gripping the surface. Colonization of Giraglia by T. mauritanica has failed because its adhesive system is incompatible with the island's rocky terrain. This has permitted the relictual E. europaea to persist in the face of potentially intense competition. Our findings shed light on the previously noted association of leaf-like pads with rupicolous habits, and indicate that an enhanced understanding of particular surfaces that leaf-padded geckos exploit may further clarify how definitive these associations are.
Background Podarcis tiliguerta is a wall lizard endemic to the Mediterranean islands of Corsica and Sardinia. Previous findings of high mtDNA and morphological diversity have led to the suggestion that it may represent a species complex. Here, we analysed mitochondrial and nuclear markers (mtDNA, 3110 bp; 6 nDNA loci, 3961 bp) in P. tiliguerta sampled from thirty-two localities across Corsica and Sardinia.ResultsWe find much greater intraspecific genetic divergence than between sister species of other Mediterranean island Podarcis, i.e., between P. lilfordi and P. pityusensis. We detected three mtDNA clusters in Corsica (North, South-East and South-West) and either two or three in Sardinia (North vs. South) depending on the clustering method. Only one or two nDNA groups were identified within each main island (again, depending on the method). A Bayesian time-calibrated multispecies coalescent tree was obtained from mtDNA and provided statistical support for a Miocene origin of the species (13.87 Ma, 95% HPD: 18.30–10.77 Ma). The posterior mean divergence time for the Corsican and Sardinian lineages was 12.75 Ma ago (95% HPD: 16.94–9.04 Ma).ConclusionThe results support the evolutionary distinctiveness of Corsican and Sardinian populations and also indicate a lack of post-divergence migration despite periods of contact being possible. Further to this, species delimitation analyses of Corsican and Sardinian lineages provided statistical support for their recognition as distinct (sister) taxa. Our results provide new insights into the biogeography of the Mediterranean biodiversity hotspot, and contribute important findings relevant to the systematics and evolution of this speciose lizard genus.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-016-0860-4) contains supplementary material, which is available to authorized users.
A new occurence of geographic variation in a micro-insular population of Phyllodactylus europaeus confirms the intraspecific variability of this Gekkonid lizard, first demonstrated by Delaugerre & Dubois (1985). The adult European leaf-toed geckos of the Sperduto Grande islet are larger-sized (especially the males) and they display several chromatic and pattern variations. This is the first record of a population where sexual size difference of adults lacks. The structure and density of this population are also discussed in this paper.
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