Phylogeography of the smooth snakeCoronella austriaca(Serpentes: Colubridae): evidence for a reduced gene pool and a genetic discontinuity in Central Europe

Abstract

The present study considers the genetic structure and phylogeography of the smooth snake (Coronella austriaca) in Central Europe, as analyzed on the basis of 14 microsatellite markers and a 284-bp fragment of cytochrome b. We found deep divergence between western and south-eastern Poland, suggesting at least two different colonization routes for Central Europe, originating in at least two different refugia. The west/south-east divide was reflected in the haplotype distribution and topology of phylogenetic trees as defined by mitochondrial DNA, and in population structuring seen in the admixture analysis of microsatellite data. The well supported western European clade suggests that another refugium might have existed. We also note the isolation-by-distance and moderate-topronounced structuring in the examined geographical demes. Our data fit the assumption of the recently suggested sex-biased dispersal, in that we found a strong divide in the maternal line, as well as evidence for a small but existent gene flow based on biparentally inherited microsatellite markers. All studied populations were very similar in respect of allelic richness, observed and expected heterozygosities, and inbreeding coefficients. However, some genetic characteristics were different from those expected compared to a similar fine-scale study of C. austriaca from Great Britain. In the present study, we observed heterozygosity deficit, high inbreeding, and low GarzaWilliamson indices, suggesting a reduction in population size.

Evolutionary divergence of the smooth snake (Serpentes, Colubridae): The role of the Balkans and Anatolia

“…Previous research in C . austriaca based on mtDNA markers indicated that specimens from Poland grouped with specimens from Slovakia and Greece, supporting also the hypothesis that the colonization of Poland took place quite recently and rapidly (Sztencel‐Jabłonka et al, 2015). In addition, Galarza et al (2015) showed that the central lineage originating in the Balkans was the only lineage that reached Scandinavia.…”

“…The 'Central Europe clade' with populations from Austria, Croatia, Bosnia and Herzegovina, Czech Republic, Slovenia, Slovakia, Italy, Norway and Sweden (Figure 1) is sister clade to the Balkan clades. Previous research in C. austriaca based on mtDNA markers indicated that specimens from Poland grouped with specimens from Slovakia and Greece, supporting also the hypothesis that the colonization of Poland took place quite recently and rapidly (Sztencel-Jabłonka et al, 2015). In addition, Galarza et al (2015) showed that the central lineage originating in the Balkans was the only lineage that reached Scandinavia.…”

“…To date, only very few studies have included sequences describing relationships among the smooth snake's populations of the Eastern Mediterranean in relation to the Central and Western European populations. These studies included one or two mitochondrial markers (Galarza et al, 2015;Jablonski et al, 2019;Sztencel-Jabłonka et al, 2015). One study (Jablonski et al, 2019) presented the whole-range phylogeographic hypothesis with 14 distict phylogenetic clades of C. austriaca based on cytochrome b.…”

“…For the clades from the western Europe ('Italy', 'West Europe', 'Iberian' [only in mtDNA trees], 'Sicily-North Iberian', 'West Iberian'), the phylogenetic status remains unchanged. Previously published data (Jablonski et al, 2019;Sztencel-Jabłonka et al, 2015) have shown that the specimens and populations from Western Europe form a group that includes all specimens of western origin, except the Iberian ones. This lineage (Western 1 clade in Jablonski et al ( 2019)) probably originated from the Apennine and colonized a big part of Europe (Austria, France, Germany and United Kingdom).…”

“…Currently, only a few molecular studies involving the geographically restricted interest have been carried out for C. austriaca (e.g. United Kingdom (Bond et al, 2005;Pernetta et al, 2011), Finland, the northern end of its distribution (Galarza et al, 2015), Iberian Peninsula (Llorente et al, 2012;Santos et al, 2008) and Poland (Sztencel-Jabłonka et al, 2015)), showing the existence of three main colonization routes across Europe arising from the south with an increased diversity in the Iberian Peninsula with three mitochondrial DNA lineages that may have originated during the Messinian Salinity Crisis (MSC; ~5.59-5.33 Mya) (Krijgsman et al, 1999).…”