Speciation in allopatric species of hamster subfamily Cricetinae (Rodentia, Cricetidae)
aA.N. Severtsov Institute of Ecology and Evolution, RAS, 119071 Moscow, Leninsky pr., 33, Russia
#e-mail: Feoktistovanyu@gmail.com
According to the Dobzhansky-Muller model (Dobzhansky, 1937; Muller, 1942), in the absence of genes flow, conspecific populations can become reproductively isolated, and postzigotic isolation should increase in proportion to the square of the time elapsed since their divergence. Using as an example four pairs of allopatric species of subfamily Cricetinae, characterized by different level of divergence, the extent of reproductive barriers formation is established by behavioral and physiological methods. The potential prezigotic isolation was assessed by the results of behavioral experiments with the exhibition of male olfactory stimuli to females. To detect postzigotic isolation, a crossbreeding analysis was performed. The time of divergence was determined by molecular genetic methods. It was shown that complete reproductive isolation has formed in a pair of allopatric species of the genus Phodopus (P. roborovskii and P. sungorus) for about 5 million years. Sterility of F1 males, conspecific preferences with slight differences in morphology of chromosomes has formed in hamsters (P. sungorus and P. campbelli) for 0.8–1.0 million years. In a pair of species belonging to genus Allocricetulus, which have diverged only 0.3–0.4 million years ago, postzigotic isolation mechanisms and conspecific preferences, for a number of traits, are already partially formed along with differences in the structure and number of chromosomes, although in the laboratory conditions it is possible to obtain fertile hybrids (F1 and F2). In the species (chromosomal forms) of the superspecies Cricetullus barabensis sensu lato, which have diverged later than a pair of species of the genus Allocricetulus (0.16–0.2 million years ago), reproductive barriers are less pronounced. Thus, the example of closly related species of Cricetinae shows that reproductive barriers can develop in allopatry, and are more pronounced in species staying longer in isolation. At that, prezygotic barriers in allopatry can develop as fast as postzigotic ones, which makes the mechanism of “reinforcement” suggested by F.G. Dobrzhanskynot so actual (in case of secondary contact zones).
