Independence between developmental stability and canalization in the skull of the house mouse.

The relationship between the two components of developmental homeostasis, that is canalization and developmental stability (DS), is currently debated. To appraise this relationship, the levels and morphological patterns of interindividual variation and fluctuating asymmetry were assessed using a geometric morphometric approach applied to the skulls of laboratory samples of the house mouse. These three samples correspond to two random-bred strains of the two European subspecies of the house mouse and their F1 hybrids. The inter- and intraindividual variation levels were found to be smaller in the hybrid group compared to the parental ones, suggesting a common heterotic effect on skull canalization and DS. Both buffering mechanisms might then depend on the same genetic condition, i.e. the level of heterozygosity. However, related morphological patterns did not exhibit any congruence. In contradiction with previous studies on insect wing traits, we therefore suggest that canalization and DS may not act on the same morphological characters. The fact that this discrepancy could be related to the functional importance of the symmetry of the characters under consideration is discussed in the light of our knowledge of the genetic bases of both components of developmental homeostasis.