Genetic and selected demographic aspects of natural populations of Mus in corn cribs of southwestern Ontario.

Mechanisms responsible for the maintenance of genetic variation in natural populations remain unclear. To provide additional insight, mice (Mus domesticus) were collected from 198 corn cribs in southwestern Ontario from 1984-89. Analyses involved: (1) selected population demographics, (2) autosomal and X-linked genetic variability, (3) releases of mice with autosomal (Alb-1$\sp{\rm c})$ or X-linked (Pgk-1$\sp{\rm l})$ marker alleles, (4) fluorescent dye tracking of mice, and (5) mitochondrial DNA RFLP. Concurrent studies included: comparisons of the sensitivity of 1D and 2D SDS-PAGE and the development of a computer program (REDI) to assist in the choice of restriction enzymes. Selected population demographics included: mouse densities, sex ratios and pregnancy data. Changing farming practices appeared to be the main factor responsible for the reduction in the densities observed over the study period. Allelic frequencies of the most common alleles at five autosomal loci examined were relatively stable. Some heterogeneity based on $F\sb{ST}$ values and the distribution of rare alleles did exist. Genetic marker studies suggested that gene flow between adjacent populations was high (0.40 to 0.77), but no data were available on gene flow between distant populations. Powder-tracking indicated that mice moved considerable distances in short time-frames, even over expanses of less than optimal habitats, suggesting the potential for significant gene flow. Four X-linked enzymatic loci surveyed and the 2D SDS-PAGE analysis on mouse blood proteins showed no detectable X-linked variability. Purifying selection was proposed as the factor responsible. Of 21 restriction endonucleases employed, only one (Hinf I) detected mitochondrial DNA RFLP and more than 80% of the populations possessed two lineages. The simplest hypothesis to explain these data involved neutrality and founder population sizes of about three females. In summary, gene flow alone could explain most, if not all of the similarities in the variability observed among these mouse populations, and the total lack of variability apparent in some systems could be best explained by directional selection.Dept. of Biological Sciences. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1991 .S233. Source: Dissertation Abstracts International, Volume: 53-01, Section: B, page: 0076. Chairman: M. L. Petras. Thesis (Ph.D.)--University of Windsor (Canada), 1991