[The multifariousness of the gene differentiation of taxa at the species and genus levels and the biological heterogeneity of mammalian orders].

Correlation analysis revealed close relationships between genetic differentiation (measured by percent of fixed gene differences of species and genera) and some biological indexes reflecting the peculiarities of ontogenesis, age, fecundity, body size, and taxonomic structure at the level of order. The most strong relationships were found between paleontological age of order, polytypic character of genera, linear body size, and duration of ontogenesis. The least significant were correlations of genetic differentiation with fecundity as well as with biological age of orders. The factors determining decrease in genetic differentiation among species and genera in large mammals, are 1) the young age of orders which determines the ranks of lower taxa; 2) the overestimation of taxonomic rank of orders of larger mammals in comparison with smaller ones.