ON THE PATTERNS AND CAUSES OF CHRONOGRAPHIC VARIABILITY OF MORPHOLOGICAL CHARACTERISTICS IN SOME MAMMALS: THE ORDERS RODENTIA AND CARNIVORA

Abstract

Chronographic variations in some craniological features in the Spotted ground squirrel, the Red fox and the Wolf in the middle of the 20th to early 21st centuries have been established. They represent their temporary deviations from the average size towards an increase which, after several generations, is replaced by a return to the original values. The influence of trophic and climatic factors, parasites, diseases and population densities during the development of young individuals is considered. Chronographic changes in the condylobasal length and zygomatic width of the skull are established as temporary and reversible, increases in their values being replaced by their decreases. Increases in the size of the skull of the Spotted ground squirrel and the Red fox occur “suddenly” in individuals of one generation, and their return to the initial values occurs gradually in individuals of several subsequent generations. Chronographic variations in the size of the skull of the Spotted ground squirrel and the Red fox correlate with changes in reproduction rates and some other varying factors. They correspond to certain phases of population abundance. Increased sizes of the Red fox and Wolf skulls are observed in the phases of quitting a depression to the beginning of a population growth. The probable causes of chronographic changes lie in somatic heterosis, caused in natural habitats by the alternation of the prevailing mating types (inbreeding or outbreeding), these being due to massive rearrangements of individuals as a result of deep population reductions from natural or anthropogenic impacts.