BABBITT, Gregory A; University of Florida: Population-level power-law distribution of developmental stability is associated with genetic homogeneity

The interpretation of elevated fluctuating asymmetry(FA)in the context of environmental stress and evolutionary processes has served as a major source of discord. Yet, the molecular and statistical mechanics that underlie the basis of the noise component of FA remains largely undetermined. In the last several years, research has demonstrated that many if not all aspects of cellular organization exhibit a scale-invariant (scale-free) topology or structure. Scale-free structure has been demonstrated to lend error tolerance or robustness to the dynamical processes within cellular systems. In addition, cluster size distribution and spatial patterning of multiple cell aggregations often exhibits scale-free behavior. Because FA must mechanically result from the dynamics of signaling and supply at the cellular level, we hypothesize that it may also exhibit a scale-invariant or power law distribution within a genetically identical population. Furthermore, we hypothesize that individual genetic variation may act to normalize these distributions in genetically diverse populations. Because, power law distributions have fatter tail regions, we think this process may explain why mean FA generally increases in more homozygous populations. We tested this idea by asking whether genetic relatedness within populations/taxa altered the fit of FA distribution to best-fitting normal and powerlaw (i.e. pareto) distributions. We find that our general hypothesis is supported across 5 insect taxa. We conclude that the process we propose would eliminate the need for the nebulous concept of �genetic stress�, and it may also serve as a potential source of high variability of FA in sexually selected traits as well.