GENETIC-VARIATION IN A FLUCTUATING POPULATION OF THE YELLOW-NECKED MOUSE APODEMUS-FLAVICOLLIS

Protein polymorphism in 767 yellow-necked mice Apodemus flavicollis (Melchior, 1834), was studied in spring and autumn during five years in the Bialowieza National Park, Eastern Poland. Two peaks and two declines of population number were observed, and population density varied from 3 to 63 inds/ha. Twenty three loci of proteins were studied, 4 of them were polymorphic; and mean heterozygosity of the studied population was H = 0.057. The greatest variability was observed in the transferrin locus and 4 alleles (Trf(a), Trf(b), Trf(c), and Trf(d)) were described. The frequency of the Trf(a) allele and Trf(a)/Trf(a) homozygotes was negatively correlated with population density in autumn, whereas the frequency of the Trf(c) allele and Trf(a)/Trf(c) heterozygotes was positively correlated with population density in autumn. The frequency of heterozygotes was higher than the frequency of homozygotes during each spring. Significant excess of Trf(a)/Trf(c) heterozygotes, compared to the values expected from the Hardy-Weinberg ratio, was observed in autumn 1983 and spring 1984, 1986, and 1987. Natural selection may be an important force in maintenance of the transferrin polymorphism in A. flavicollis. It is suggested that heterozygotes survive better than homozygotes during winter and at high population densities. It is also supposed that non-selective forces influence on the Trf allele frequency changes in the studied population of A. flavicollis.