COMPETITION AMONG BODY PARTS IN THE DEVELOPMENT AND EVOLUTION OF INSECT MORPHOLOGY

Changes in form during ontogeny and evolution depend in large measure on changes in the relative growth of the various parts of the body, Th e current consensus In developmental biology Is that the final size of appendages and internal organs Is regulated autonomously, within the structure itself, Size regulation of body parts typically requires no external control and is thought to be relatively Insensitive to signal s from the developmental environment, We show in two very different sy stems, butterfly wings and beetle horns, that experimentally induced c hanges In the allocation of developmental resources to one trait produ ces compensatory changes in the relative sizes of other traits, These findings illustrate that interaction among body parts in development i s part of the mechanism of size regulation of those parts, Furthermore , in the case of beetle horns, we show that the tradeoff in size is ma nifest as a significant negative genetic correlation among the involve d body parts and, therefore, constitutes a developmental source of gen etic constraint on the evolution of body form.