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Free keywords:
Amphibia; Rana temporaria; Rana dalmatina; genetic variation;
phylogeography; palearctic
Abstract:
We reconstruct range–wide phylogeographies of two widespread and largely co-occurring Western Palearctic
frogs, Rana temporaria and R. dalmatina. Based on tissue or saliva samples of over 1000 individuals,
we compare a variety of genetic marker systems, including mitochondrial DNA, single-copy protein-coding
nuclear genes, microsatellite loci, and single nucleotide polymorphisms (SNPs) of transcriptomes of
both species. The two focal species differ radically in their phylogeographic structure, with R. temporaria
being strongly variable among and within populations, and R. dalmatina homogeneous across Europe
with a single strongly differentiated population in southern Italy. These differences were observed across
the various markers studied, including microsatellites and SNP density, but especially in protein-coding
nuclear genes where R. dalmatina had extremely low heterozygosity values across its range, including
potential refugial areas. On the contrary, R. temporaria had comparably high range-wide values, including
many areas of probable postglacial colonization. A phylogeny of R. temporaria based on various concatenated
mtDNA genes revealed that two haplotype clades endemic to Iberia form a paraphyletic group at
the base of the cladogram, and all other haplotypes form a monophyletic group, in agreement with an
Iberian origin of the species. Demographic analysis suggests that R. temporaria and R. dalmatina have
genealogies of roughly the same time to coalescence (TMRCA 3.5 mya for both species), but R. temporaria
might have been characterized by larger ancestral and current effective population sizes than R. dalmatina.
The high genetic variation in R. temporaria can therefore be explained by its early range expansion
out of Iberia, with subsequent cycles of differentiation in cryptic glacial refugial areas followed by admixture,
while the range expansion of R. dalmatina into central Europe is a probably more recent event.
