Coupled variation of red-backed vole species in biotopes disturbed by windfall and fire in the Visim State Nature Reserve (the Middle Urals)

The use of morphogenetic characteristics and functionally important morphological structures in monitoring natural populations and communities is one of the modern directions in developing approaches to eco-morphology and functional synecology. New approaches make it possible to test the hypothesis of a similar spectrum of morphogenetic modifications of sympatric species during their development in disturbed biotopes. In this study, the coupled variability of the size and shape of the mandible was studied for the first time using geometric morphometrics to assess the resistance of the rodent community to two natural catastrophic phenomena (windfall and wildfire) for three sympatric red-backed vole species in the Visim State Nature Reserve (Middle Urals). Samples of Clethrionomys glareolus, Clethrionomys rutilus and Craseomys rufocanus young-of-the-years were studied in two biotopes modified by windfall and fire impacts under different weather conditions (2003 vs. 2004). It was found that Clethrionomys glareolus preferred the overgrown fire-damaged site, Craseomys rufocanus the windfall zone, and Clethrionomys rutilus did not express a pronounced preference. Interannual and biotopic differences in the variation of the size and shape of the mandible have been revealed for all species. Weather conditions affected the species variability more than biotopic ones. Based on functional mandibular indices, it was found that the shape of the mandible of the species, as a biological tool for foraging and its primary processing, depends more on weather factors than on the biotope characteristics. A similar morphofunctional reaction of sympatric species populations to similar biotopes was expressed. This fact reflects the parallelism of modifications of the morphogenesis of mandibles of the studied species in disturbed biotopes, confirming the hypothesis. In particular, in the fire-damaged site, the tendency to longitudinal grinding of feed was revealed for all species, while in the windfall zone, the tendency to gnawing of forage objects (possibly, seeds of coniferous plants) was revealed. It is assumed that weather factors indirectly affect the morphogenesis of species through the change of plant communities, which, in turn, changes the diet of animals and the mechanics of the load on the musculoskeletal apparatus of mandibles. The within-group morphological disparity (MNND), which reflects the measure of destabilisation of development, was small in Clethrionomys glareolus, indicating the stability of its morphogenesis in both biotopes; the development of Craseomys rufocanus was stable only on the windfall site; in Clethrionomys rutilus, MNND was unstable in both biotopes. The MNND development stability estimates are consistent with the species abundance. They are recommended for monitoring the population status of sympatric species of the red-backed voles and other rodents in Protected Areas.