Phenotypic and Genotypic Variation in Odontometric Traits of the House Mouse

Abstract

A comparison of the phenotypic variation in molar width was made among 15 populations of the house mouse including a total of 873 specimens. The populations were divided into wild, randombred, inbred and hybrid types. The squared coefficient of variation was used as the measure of variation. The overall pattern of relative variation was in reasonable agreement with expectation based on the different genetic and environmental histories of the groups. The inbred strains were more variable than their hybrids and frequently not significantly less variable than the randombreds or the wild populations. An estimate of the degree of genetic determination was calculated from the mean squared co- efficients and the environmental component of the total variation was partitioned into wild and laboratory fractions. Intrapopulational varia- tion was the greatest in the M3 and the pattern of interpopulational vari- ation was the most erratic in this tooth. However, the magnitude of the genetic component was approximately the same as for the two anterior teeth. The coefficients of correlation of the molar widths were also cal- culated for each population.