The Patterns and Reason for Chronographic Variability of Morphological Traits in Some Mammalian Species: Orders Rodentia and Carnivora

Chronographic changes in some craniological measurements were established in the speckled ground squirrel, fox, and wolf in the middle of the 20th and beginning of the 21st centuries. These changes represent their temporary deviations from the average sizes towards an increase. After several generations, there is a return to the initial values. The skull sizes of the speckled ground squirrel and fox increase “jumpily” in individuals of the same generation, and their return to the initial values occurs gradually in individuals of the next several generations. Chronographic changes in the skull sizes in the speckled ground squirrel and fox correlate with changes in the reproduction indices and number. The skull dimensions correspond to certain population phases. Increased skull sizes in the fox and wolf are observed at the phases of recovery of the number from depression and beginning of its growth. A somatic heterosis, caused in natural habitats by an alternation of predominant types of mating (outbreeding and inbreeding), is a likely reason for chronographic changes. They are a result of massive regroupings of individuals with deep reductions in the number due to natural or anthropogenic effects.