Coupled Chronographic Variation of Morphofunctional Traits in Cenopopulations of Two Sympatric Rodent Species

— Methods of geometric morphometrics have been used to assess chronographic variation of morphofunctional traits in the same cenopopulations of the bank vole ( Clethrionomys glareolus ) and pigmy wood mouse ( Sylvaemus uralensis ) in Orenburg oblast. Changes in the mandible size and shape and in morphofunctional mandibular indices that occurred over 30 years (1986–2016) have been evaluated. As a result, directional shifts in morphogenesis of the mandible and its morphofunctional transformations related to change in trophic preferences have been revealed in both voles and mice. The mandible shape has changed toward specialization for food gnawing and crushing in C. glareolus cenopopulation and for transverse food grinding in S. uralensis cenopopulation. Sexual dimorphism in the mandible centroid size (CS) in both species has increased over the 30-year period, whereas the parameter of morphological disparity ( MNND ) has decreased significantly, providing indirect evidence for an increase in developmental stability. Despite a shift in climatic regime and associated changes in vegetation, parallelism of chronographic variation has been revealed in the two taxonomically distant species, reflecting a high and positive coevolutionary potential, i.e., similar morphogenetic responses to changes in environmental conditions in different years. These results show that rapid directional modifications of morphogenesis actually occur in cenopopulations of sympatric rodent species under climate change.