Skull variation of the genus Apodemus Kaup, 1829 (Mammalia: Rodentia) distributed in the Northern Anatolia region including three Turkish Islands, with evolutionary insight

In this study, skull variations of 134 genetically identified (mtDNA cyt b and mtDNA control region) Apodemus specimens from 39 localities from Northern Anatolia, Thrace, Gökçeada Island, Bozcaada Island and Marmara Island were analyzed based on skull morphology. The limits of variation of five Apodemus species (A. flavicollis, A. witherbyi, A. sylvaticus, A. uralensis, A. mystacinus) distributed in Turkey were determined. These species, which live in similar habitats and thus have a complex taxonomic situation, were genetically identified to determine location-specific variations and standard characters. It was determined whether geographical barriers such as the Marmara Sea, Istanbul and Çanakkale straits, Melet River and Çoruh River separate the populations of the species from each other. These inferences were discussed in terms of paleogeographic reasons. The Kızılırmak River or ecological constriction were found to separate A. mystacinus to west and east parts. Also, the İstanbul strait was found to cause a possible separation of A. flavicollis specimens. The Melet River and the Çoruh River were not found to cause a distinction within the species. Differences between island populations and mainland populations were determined in Apodemus slyvaticus and A. witherbyi distributed in the islands. Differences in the East–West transition in Northern Anatolia were identified within species and related to habitat. Phylogenetic trees suggested that A. sylvaticus is nearly related to A. flavicollis. Differences were observed among Apodemus species in the palatine bone, and this diversity was also detected between geographic regions.