6 Morphology and Behavior: Are They Coupled at the Genome Level?

Abstract

In all organisms, behavior and morphology are inextricably coupled. Morphology constrains the range of behavioral patterns, and behavior regulates and modifies morphological function. Over centuries, this constraint has been recognized in the selective breeding of dogs to perform specific tasks. Here, we explore the genetic coupling of morphology and behavior in a fox model system: the heritable morphological variation that has accompanied selection for tame and aggressive behavioral traits in the silver fox.

In what follows, we demonstrate that similar functional trade-offs in morphology are found in both foxes and dogs and that this morphological variation may be concomitant with behavioral variation. Finally, we describe preliminary results from experiments designed to test whether these two phenotypes are related at the genetic level (thus co-selected) or have become associated serendipitously as a result of random genetic drift and founder effects.

The red fox, Vulpes vulpes, of which the silver fox is a subspecies, is the out-group for modern canids. Its phylogenetic lineage has been separated from Canis familiaris for about 10 million years (Wayne 1993). V. vulpes has the largest natural geographic distribution of any terrestrial mammal other than humans. It occupies habitats ranging from mixed forest to alpine tundra, from sand dunes to urban outskirts (Nowak and Paradiso 1991; Sheldon 1992). Associated with this diversity of habitats is a wide range of anatomical configurations and a behavioral plasticity that makes the red fox the bane of chicken farmers, the favorite of hunting sportsmen, and a mythic symbol of crafty intelligence...