In both directions: Expansions of European land snails to the north and south from glacial refugia

Abstract

Aim: Were postglacial recolonizations facilitated by persistence close to the colonized areas rather than by dispersal ability allowing for colonization from distant sources? This question is particularly relevant for organisms with low active dispersal abilities and lacking specialized propagules. Here we identified glacial refugia of four Central European land snail species, including one for which a northern glacial refugium in the region was indicated by indirectly dated fossils.Location: Central Europe and the Balkans.Taxon: Pulmonate land snails: Monachoides incarnatus (Hygromiidae) and Helix pomatia, Helix thessalica and Caucasotachea vindobonensis (Helicidae). Methods:We used continuous phylogeographic analysis of mitochondrial sequence data to trace the origin of postglacially expanding lineages. We assessed the credibility of results from our focal species, M. incarnatus, by comparison to three other broadly sympatric land snail species. In addition, we performed direct radiocarbon dating of fossil shells to verify the presumed glacial presence of M. incarnatus on the territories of Czechia and Slovakia and to test the reliability of the available fossil data. Results:In three of the four species, the molecular data supported refugia located south of the Pannonian Basin, from the south-eastern Alps to the south-western Carpathians, but not more northerly. The direct radiocarbon dating resulted in younger dates than previously assumed. However, the molecular data also revealed unexpected, yet substantial postglacial southward expansions of M. incarnatus and C. vindobonensis into the Balkans.Main Conclusions: Neither the phylogeographic analyses nor the direct radiocarbon dating provided evidence for the glacial survival of studied land snail species in Central Europe. The refugia located adjacent to the Pannonian Basin were the most important source of postglacial expansions to Central Europe, but were also the source of the expansion southwards. Both climatic factors and biological interactions might explain why such southward expansions seem rather rare in Europe.

Taxonomic revision and dissolution of the genus Monachoides (Gastropoda, Stylommatophora)

“…There is a substantial intraspecific diversity of relatively deeply divergent mitochondrial lineages in M. incarnatus (Figure 2; intraspecific p-distance in the cox1 fragment reaching 16%). The distribution of these lineages (Figure 5) has been detailed by Korábek et al (2023), who inferred that the glacial refugia from which the present distributions derived were located mainly in northern Croatia and Slovenia. However, there was another refugium inferred in northwestern Italy ("M. incarnatus armatus").…”

“…southwest of Gospić. Its range lies completely within the range of M. incarnatus, but it is distributed southwest of the glacial refugia of M. incarnatus inferred by Korábek et al (2023). Based on the material analysed so far, the Croatian clade has a very shallow intraspecific variation in the mitochondrial markers (pdistance in cox1 under 2%).…”

“…All sequences were deposited in GenBank, and accession numbers are listed in Appendix S1. Most of the mitochondrial data from M. incarnatus were already reported in Korábek et al (2023).…”

Holocene transformation of natural steppe into an agricultural landscape in the Polabí and Pojizeří Lowlands, Czech Republic, based on mollusc evidence

“…The glacial refugia of these four thermophilic species are still unknown, with the exception of C. vindobonensis , which originates from the Western Balkans. From there it gradually spread to Central Europe, and we have its oldest occurrence here from the Slovenian Karst from the very beginning of the Middle Holocene (Korábek et al, 2023). In Polabí, where this species has its northwestern temperature-dependent limit of distribution, it is strictly bound to the steppe, although it inhabits a wider range of biotopes further southwest.…”

Journal of Biogeography Innovation Awards, 2023

“…Thus, we are delighted to introduce a new Virtual Issue that does all these things, collating papers submitted in response to the announcement of the JBI Innovation Awards , a venue for manuscripts first‐authored by early career researchers that encourages new ideas and perspectives in the discipline. The virtual issue begins with the inaugural (Carvalho et al, 2023; Vasconcelos et al, 2023; Windsor et al, 2023) and most recent (Korábek et al, 2022; Schrader et al, 2023) papers and will continue to grow each year. The manuscripts were considered using JBI's standard editorial and peer review processes and were additionally ranked in terms of the originality of their ideas, identification of a gap in knowledge, and impact of findings.…”