Meeting Abstract

15.3  Thursday, Jan. 3  Morphological integration and the role of pleiotropy in the evolution of primate hands and feet ROLIAN, Campbell; Harvard University rolian@fas.harvard.edu

Morphological integration is an emergent property of complex organisms whereby certain phenotypic traits covary more strongly than others because of shared functions and/or developmental phenomena such as pleiotropy. The digits of vertebrate hands and feet are serially homologous elements that share most of their developmental architecture in common. Accordingly, these elements should be more prone to the effects of pleiotropy, and should covary more strongly than other skeletal traits. Pleiotropy could in fact play potentially conflicting roles in the evolution of hand and foot digit morphology: when digits evolve to perform similar functions, pleiotropy should facilitate correlated changes in morphology. However, when hands and feet are selected to perform different functions, then pleiotropy may impose a constraint on their independent morphological evolution. I tested this hypothesis by comparing patterns of phenotypic covariation in the autopods of 11 haplorhine primates representing a broad range of locomotor specializations and phylogenetic relatedness. Linear distance data were collected in the autopods and proximal limb bones using standard morphometric techniques, and covariation patterns were compared using matrix correlations, eigenanalysis and partial correlations. Results indicate that some aspects of autopod morphology, including the length and proportion of homologous digits, covary more strongly than other traits in the appendicular skeleton. However, the comparative data also suggest that selection for independent functional specialization in each autopod leads to reduced levels of covariation between them. Thus, although pleiotropy may cause homologous digits to covary, its effects do not significantly impact on the capacity for independent evolution of digital morphology in primates.