Morphological integration of fluctuating asymmetry in the mouse mandible

Morphological integration of fluctuating asymmetry (FA) was assessed for nine mandibular characters in random-bred house mice to test the hypothesis that there should be a significant integration or concordance of FAs at the population level, but not at the individual level. FA estimates for each of the nine characters were made for each of 16 subpopulations (two replicates each for mice varying in sex and age) and their correlations indicated a moderate level of integration (index of integration = 0.42). A matrix permutation test of the differences of the correlations within two (‘incisor’ and ‘muscle’) developmentally different character groups versus correlations between groups was significant, indicating the presence of morphological integration. Kendall's coefficient of concordance also indicated a significant population asymmetry parameter for FAs within the two character groups. Correlations among individual FA estimates were generally lower than those calculated from subpopulations, the index of integration being 0.21. The matrix permutation test failed to show significant morphological integration among individual FAs, but Kendall's coefficient of concordance was significant, indicating the presence of an ‘individual asymmetry parameter’ among the nine characters. Principal components analysis and canonical correlation analysis confirmed the overall higher level of integration of FAs among the subpopulations and within the two character groupings.