Skull shape in the genus Apodemus: phylogenetic conservatism and-or adaptation to local conditions

We studied morphological variation among western Palaearctic species of woodmice (genusApodemus). Twenty one dental and skull variables were measured and evaluated using multivariate statistical approaches. A total of 501 specimens of the following 9 species of wood mice were examined:A. hermonensis, A. hyrcanicus, A. uralensis (=microps),A. flavicollis, A. sylvaticus, A. epimelas, A. mystacinus, A. peninsulae, A. agrarius. Species occupying large geographic areas were represented by two or three geographically distant populations. The analyses, based both on original and size adjusted data, revealed congruence between morphological evolution and phylogenetic relationships. The integrity of major clades was supported by morphometric trees. Conspecific samples showed a clear tendency to cluster together regardless of ecological differences and geographical distances. This finding may suggest that studied traits exhibit evolutionary conservatism, and therefore are not fully determined by actual selective pressures. Besides this, we demonstrated that morphological differentiation of taxa belonging to the subgenus Sylvaemus was more pronounced in Central Europe than in the Near East. This observed phenomenon could be of adaptive nature.