Meeting Abstract

37.4  Jan. 5  Stress, stability and size: capturing process variation in the development of multicellular organisms BABBITT, G.A.; Arizona State University babbitts@gmail.com

Definitions of developmental instability (DI) and its most common estimator, fluctuating asymmetry (FA), have often assumed that the variation in FA is caused by the organism�s ability to buffer additive effects of independent perturbations during the process of development, leading to a subsequent normal distribution in FA. Recent opinion and empirical research has questioned this view of the basis of FA. Because FA is generated during growth, it is best viewed as a specific type of process variation or error that includes both the propogation of multiplicative errors (geometric Brownian motion) during growth in geometrically expanding cell populations, as well normal error in the timing of the termination of growth. In addition this generative process is probably also under simple regulatory control (e.g. via a Rashevsky-Turing process). In this paper, I present a tissue level model of FA with these generative and regulatory aspects. The model is used to simulate variation of FA in large populations exposed to various levels of environmental stress and genetic relatedness. Results are compared to large samples of wild trapped, inbred and isogenic lines of Drosophila. The simulation demonstrates that mean FA decreases with growth rate (i.e. increasing with environmental stress) and that FA decreases with relatedness among the population. Inbreeding also increases leptokurtosis in the distribution of FA in both the simulation and in Drosophila lines. The simulation also reveals Pertoldi�s theorem; that phenotypic variance and FA are correlated under environmental stress in clonal populations. The potential application of the statistical model in studies of environmental and genetic stress and the behavior of cancer tissue are discussed.