Morphometric Studies in Inbred and Hybrid House Mice. V. Directional and Fluctuating Asymmetry

Directional and fluctuating asymmetry were assessed for 10 paired osteometric traits in inbred and hybrid house mice primarily in order to test five separate hypotheses. Hypothesis (1) stated that directional asymmetry (DA) would be relatively low for these characters, especially those directly involved in locomotion. The DA for most characters was nonsignificant or negligible in importance, including that for the posterior limb bones most used in locomotion. Hypothesis (2), that the heritability of DA would be low, was confirmed, averaging only 2% in inbreds and 4% in hybrids. Hypothesis (3) was that fluctuating asymmetry (FA) would be moderate in magnitude. The average contribution of FA to the total variance was in fact considerable, 18% across populations and characters. Hypothesis (4) proposed that the inbreds should show more FA than hybrids, particularly for those characters with high heritabilities. FA did exhibit statistical significance for heterosis, and there was a significant positive association of heterosis with the magnitude of heritability of each trait. Hypothesis (5) stated that there should be a populationwide association of FA values among the characters (a "population asymmetry parameter"), and Kendall's coefficient of concordance suggested that this was the case.