Phylogeography and taxonomy of the Psorodonotus caucasicus (Orthoptera, Tettigoniidae) group: independent double invasion of the Balkans from the Caucasus

High mountain ranges within and around Anatolia have played an important role in the biogeography of mountainous organisms, which are threatened by climate change. Using the Psorodonotus caucasicus species group (PCG), whose range is the Caucasus, Anatolia and the Balkans, as a model group, this study aims to determine the importance of Anatolian mountain ranges and to estimate possible future effects of global warming on such lineages by establishing an analogy between interglacial dynamics and global warming. Twenty populations, representing all extant species of the PCG, were studied. Sequences of four mitochondrial loci and three nuclear loci were obtained and used in phylogenetic, time estimation and phylogeographic analyses of PCG members. Additionally, ecological modelling analyses were conducted to estimate the range of PCG members at present and during the last glacial maximum and the last interglacial, with the aim of determining the roles of altitudes and glacial cycles in shaping the distribution of the PCG. Phylogenetic analyses supported the monophyly of the PCG as a whole and each individual species with the exception of P. suphani. The radiation of the PCG started approximately 3 Ma, according to beast. Species distribution models suggested a wider range during the last glacial maximum than during the last interglacial and at present, but these models also suggested that present conditions represent a substantial range loss. The PCG dispersed to the Balkans through two independent corridors from the Caucasus. The following conclusions were reached based on the results: (i) the uplift of the Pontic and East Anatolian Blocks during the mid‐Pliocene and the closing of the Mediterranean and the Paratethys connection in the Plio–Pleistocene and the mid‐Pleistocene Transition are the main events that triggered the radiation of the PCG; (ii) the PCG radiated from a Caucasian origin and invaded the Balkans twice, first through Northern Anatolia and second via the ‘Taurus Way’ dispersal corridor; (iii) lowlands are a barrier to the dispersal of PCG members; (iv) the last four intense glacial periods had little effect on the radiation of the PCG; (v) the range of the PCG has receded substantially from its original southern margin, and P. salmani and P. anatolicus have become extinct since the 1950s, possibly because of global warming; and (vi) automatic species delimitation tests supported species status of the morphospecies P. caucasicus, P. macedonicus, P. fieberi, P. illyricus and P. ebneri, but not that of P. suphani, thus, P. suphani Taylan & Sirin, 2014 syn.n. synonymized with P. caucasicus (Fischer von Waldheim, 1846).