Meeting Abstract
Allometry, the proportional growth of the body and body parts, gives rise to the characteristic forms of species. Most studies concerned with allometry have focused on its role as a developmental constraint, neglecting the possibility that alternative scaling relationships emerge from differing growth conditions. The study of reaction norms, the effect of environmental factors on growth, size and shape, has neglected allometry for this same reason. A few studies in insects have surveyed the effect of different growth conditions on allometry, and they have demonstrated that scaling relationships are greatly influenced by environmental factors such as nutrition, population density, and temperature. We argue that allometric scaling relationships can be viewed as reaction norms, whereby the relative size of body parts is influenced by both the growth of the body and the environment. We show how environmental factors influence the proportional growth of wings in the tobacco hornworm Manduca sexta. We demonstrate that 1) the growth of the body and the wings are influenced by external developmental conditions, 2) the slope of the population wing-body scaling relationship changes when larvae are reared under different growth conditions such as temperature and nutrition, and 3) these differences are caused by changes in the relative duration of the growth of the wings. We will use a new allometry equation to deduce and predict how different growth conditions influence wing-body scaling.
