Geographic Variation in Ontogeny of the Fox Sparrow

Kevin J. Burns
1993 The Condor  
Ontogeny of two morphologically differentiated populations of Fox Sparrows (PassereNa iliaca) was compared to reveal the developmental bases of adult morphological differences. Growth of tarsus, wing, bill, and tail length relative to body mass was compared between the two populations to determine if geographic variation in adults results from different relative growth rates or different relative timings of onset and offset of growth. Differences in adult morphologies between populations result
more » ... populations result from both changes in allometric growth rates and changes in starting points along the same allometric trajectory. Sexual dimorphism in bill length is mostly the result of differences in growth rate occurring late in ontogeny. Differences between populations greatly exceed those between sexes. Factors underlying growth are complex and probably result from many different genetic and environmental factors.
doi:10.2307/1369608 fatcat:6jnj3edvwzdl5o5pnwydrck4qu