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Keywords:

  • Divergence time;
  • eastern Mediterranean;
  • genetic diversity;
  • geology;
  • molecular clock;
  • mtDNA;
  • Pelophylax (Rana);
  • phylogeography;
  • speciation;
  • water frogs

Abstract

Aim  Our aims were to assess the phylogeographic patterns of genetic diversity in eastern Mediterranean water frogs and to estimate divergence times using different geological scenarios. We relate divergence times to past geological events and discuss the relevance of our data for the systematics of eastern Mediterranean water frogs.

Location  The eastern Mediterranean region.

Methods  Genetic diversity and divergence were calculated using sequences of two protein-coding mitochondrial (mt) genes: ND2 (1038 bp, 119 sequences) and ND3 (340 bp, 612 sequences). Divergence times were estimated in a Bayesian framework under four geological scenarios representing alternative possible geological histories for the eastern Mediterranean. We then compared the different scenarios using Bayes factors and additional geological data.

Results  The extensive genetic diversity in mtDNA divides eastern Mediterranean water frogs into six main haplogroups (MHGs). Three MHGs were identified on the Anatolian mainland; the most widespread MHG with the highest diversity is distributed from western Anatolia to the northern shore of the Caspian Sea, and includes the type locality of Pelophylax ridibundus. The other two Anatolian MHGs are restricted to south-eastern Turkey, occupying localities west and east of the Amanos mountain range. One of the remaining three MHGs is restricted to Cyprus; the second, to the Levant; and the third was found in the distribution area of European lake frogs (P. ridibundus group), including the Balkans.

Main conclusions  Based on geological evidence and estimates of genetic divergence we hypothesize that the water frogs of Cyprus have been isolated from the Anatolian mainland populations since the end of the Messinian salinity crisis (MSC), that is, since c. 5.5–5.3 Ma, while our divergence time estimates indicate that the isolation of Crete from the mainland populations (Peloponnese, Anatolia) probably pre-dates the MSC. The observed rates of divergence imply a time window of c. 1.6–1.1 million years for diversification of the largest Anatolian MHG; divergence between the two other Anatolian MHGs may have begun about 3.0 Ma, apparently as a result of the uplift of the Amanos Mountains. Our mtDNA data suggest that the Anatolian water frogs and frogs from Cyprus represent several undescribed species.