Phylogeography of Rock Nuthatches: An Integrated Approach

Abstract

In this study, morphological and genetic variations of Eastern Rock Nuthatch (Sitta tephronota Sharpe, 1872) and Western Rock Nuthatch (Sitta neumayer Michahelles, 1830) were evaluated. To this end, historical biogeography of the species has been discussed using phylogeography and ecological niche modeling. Climatic fluctuations in the Quaternary have caused many species to shift their ranges across Palearctic ecosystem. In the Last Glacial Maximum some species have expanded their distribution areas. A large part of the species, on the other hand, had to narrow their distribution areas. The impact of the Last Integlacial period is rarely studied in this respect. Moreover, how bird species distributed across southern latitudes known as refugial areas have historically changed their distributional areas have not been a popular subject. It is possible to test these changes in the distribution areas of species with ecological niche models and phylogenetic analyzes. In this thesis, morphological variation, genetic diversity and distributional patterns of these two bird species have been examined in detail. The genetic diversity patterns of the species and therefore phylogenetic inferences about species were done by using ND2 and ND3 regions of the mitochondrial DNA (mtDNA). As a result of the phylogenetic evaluation of the genetic diversity patterns revealed by these two gene regions, cryptic genetic diversity patterns were found for both species. Accordingly, Balkan, Anatolian and Zagros (Iran) population of S. neumayer formed a monophyletic group. The same pattern was also found for S. tephronota as Zagros and eastern population of the species formed a monophyletic group. Phylogenetic results were highly consistent with morphological results. With the use of species specific occurrence data and the maximum entrophy machine learning algorithm (MAXENT),an ecological niche model is developed to predict the geographic distribution of these nuthatch species under reconstructed past (the Last Interglacial, ~ 130000 to 116000 years ago and the Last Glacial Maximum, 22000 years ago) and present (1960 to 1990) bioclimatic conditions. Co-evaluation of the results of the ecological niche model and phylogeography reveals reliable conclusions about the evolutionary history of species. Ecological niche model results for both species showed that they had narrower distributions in the Last Interglacial Period when compared to the Present and the Last Glacial Maximum distributions. When the results obtained are evaluated altogether and combined with previous taxonomic studies; Sitta n. tschitscherini, which has been previously proposed in the Zagros region for Sitta neumayer, and Sitta t. dresseri which has been proposed for Sitta tephronota in the same region, should be examined as species rather than subspecies.