GENOTYPIC VARIABILITY IN POPULATIONS OF MOUNDBUILDER MICE MUS-SPICILEGUS PET., 1882, AT DIFFERENT LIFE-CYCLE STAGES

Genotypic variability in two Moldovian populations of moundbuilder mic e Mus spicilegus Pet. was examined at different stages of their life c ycle - at the beginning of overwintering in mounds and in the middle o f summer in agrocenoses. Thirty allozymes were assayed. Significant di fferences in allele frequencies and heterozygosity between overwintere d and mice born in the year of the experiment were recorded only for I dh-1. This fact was related to the presence of differential mortality among overwintered mice in the populations by the middle of summer. Th e increase in heterozygosity for Idh-1 in the populations occurred bec ause of ''old'' mice that lived until the middle of summer, at which p oint they still have not contributed to the gene pool of the populatio n. The generic effect of the annual separation of generations of mound builder mice due to their overwintering in mounds is analyzed. Overwin tering has a bottleneck effect on the population The relatively low ge netic variability in moundbuilder-mice populations is considered with regard to their biological and ecological features. Based on obtained data, a conclusion on the high genetic stability of moundbuilder-mice populations during their entire life cycle is made.