Quantitative Genetics and Modularity in Cranial and Mandibular Morphology of Calomys expulsus

Patterns of genetic covariance between char- acters (represented by the covariance matrix G) play an important role in morphological evolution, since they interact with the evolutionary forces acting over popula- tions. They are also expected to influence the patterns expressed in their phenotypic counterparts ðPÞ, because of limits imposed by multiple developmental and functional restrictions on the genotype/phenotype map. We have investigated genetic covariances in the skull and mandible of the vesper mouse (Calomys expulsus) in order to esti- mate the degree of similarity between genetic and pheno- typic covariances and its potential roots on developmental and functional factors shaping those integration patterns. We use a classic ad hoc analysis of morphological inte- gration based on current state of art of developmental/ functional factors during mammalian ontogeny and also applied a novel methodology that makes use of simulated evolutionary responses. We have obtained P and G that are strongly similar, for both skull and mandible; their simi- larity is achieved through the spatial and temporal organization of developmental and functional interactions, which are consistently recognized as hypothesis of trait associations in both matrices.