The Ratio between Chronographic and Geographic Variation in the Morphofunctional Features of Bank Vole (Clethrionomys glareolus Shreb.) in the South of Its Range

Abstract

A simultaneous analysis of the chronographic variation of the mandible of bank vole (Clethrionomys glareolus Shreb.) in three longitudinally distant populations that inhabit floodplain forests of Sakmara and Samara rivers in the south of the species range (Orenburg oblast) has revealed significant morphogenetic and morphofunctional changes in each of these populations over 33 years. Changes in the shape of the mandible in allochronous vole samples (1983 and 2015) have been detected using methods of geometric morphometrics. Morphofunctional rearrangements have been assessed based on mandibular indices, which characterize differences in the structure of the mandible resulting from changes in functional loads after a shift in diet. Significant changes in the mandible shape and in the values of these indices have occurred in all allochronous populations. Chronographic variation in the mandible shape in all populations has similar direction in the morphospace; its range exceeds that of geographic variation and reflects a significant historical rearrangement of morphogenesis. The authors discuss the probable relationship of rapid morphogenetic and morphofunctional changes in vole mandibles to the transformation of local trophic conditions caused by different directions of plant successions, which, in turn, are related to local trends of climate changes.