Breeding structure in two field vole populations.

Abstract

The breeding structure of the field vole (Microtus agrestis L.) was studied in two populations in the south of Sweden by the use of enzyme electrophoresis. The sampling sites were closely situated but sufficiently separated to make it unlikely for animals to move from one site to the other. The populations were Sampled in two different ways: from the first population, 62 animals were collected over a 17-month period, while at the other site 103 animals were captured within a time-span of less than two weeks. of 21 enzymes studied. 3 were informative about genetic variation at a single locus each (LDH, ME and PGM). The distribution of genotypes for the three polymorphic loci showed no significant deviation from the expected Hardy-Weinberg proportions in any of the populations. When the genotype proportions were calculated for different inbreeding coefficients, the most likely value for the inbreeding coefficient in these populations was well below 0.10. A high degree of inbreeding has earlier been reported to occur in the field vole, but in the present investigation no such evidence was found. Nor was there any variation in allele frequencies between the two populations, which—if present—could lead to a Wahlund effect under a less stringent sampling scheme.