Experimental Analysis of the Reproductive Potential of House Mice (Mus musculus sensu lato, Rodentia, Muridae) in Transcaucasia and Other Regions

Abstract

The fecundity, fertility, and fitness of house mice from Transcaucasian populations have been investigated in laboratory conditions. We interpret our data in accordance with Milishnikov’s hypothesis (2004) that the ancestral form might have come from Transcaucasia. It is genetically close to Mus musculus s. str. and has kept a relict gene pool. The already differentiated M. musculus and M. domesticus have been introduced into this region as well. All three forms have crossed with one another, resulting in a very complicated hybrid zone formed in Transcaucasia. In our experiment, house mice from Moscow and Moscow oblast and from the hybrid zone of Transcaucasia were characterized by a similar reproduction rate. Reproduction indices weren’t significantly differ in different variants of crossings of mice from Transcaucasia with M. musculus as well as in hybrids from direct and back crosses and in backcrosses. Nevertheless, these rates differed significantly from those in M. musculus and Transcaucasian mice. In some cases, the mortality of the young was relatively high. The data obtained disagree with the presumed reduced fitness of house mice in Transcaucasia. No serious evidence has been obtained for the presence of postcopulative isolating mechanisms contributing to separation of mice from Transcaucasia from M. musculus. The results of these studies are consistent with the assumed kinship of house mouse populations of Transcaucasia and M. musculus.