GENETIC DIFFERENTIATION OF MAMMAL TAXA - ESTIMATION BASED ON BIOCHEMICAL-GENETIC MARKERS

A review of data on genetic differentiation of mammalian taxa has been made on the basis of estimating the percent of fixed gene differences (PFD). The results substantiate the existence of evident differences in the scale of genetic divergence between taxa in different mammalian orders. Among smaller mammals (marsupials, insectivores, chiropterans , myomorph and sciuromorph rodents, african mole rats, and elephant sh rews) interspecific differences within a genus involve the average of 25-40% of investigated loci. At the genetic level the value is 50-60%, whereas at the familial level the differences, are beyond the resolut ion capacity of the method (PFD = 60-80%). Orders of larger mammals ca n be divided into two subgroups. One of them that includes carnivores, artiodactylans, and hystricomorph rodents is characterised by PFD val ues of 10-14%, 30-50%, and 69-70% at respective levels. The other subg roup composed of proboscideans, primates, pinnipeds, and toothed whale s, has a low level of genetic divergence expressed by PFD values of 0- 3%, 7-36%, and 50-60% at species, generic and familial levels, respect ively. Insufficiency of data on ballen whales and perissodacytls does not allow to cluster them ultimately with any of these groups. There a re three possible, but not necessarily alternative, causes for the obs erved differences in genetic divergence: 1) overranking of genera in l arger mammals; 2) different palaenthological age of orders; 3) unequal rates of molecular evolution.