BABBITT, G.A.*; KILTIE, R.; BOLKER, B.; Univ. of Florida; Florida Fish and Wildlife Conservation Commission; Univ. of Florida: Are fluctuating asymmetry studies adequately sampled? Implications of a new model for size distribution

Previous work on fluctuating asymmetry (FA), a measure of developmental instability, has highlighted its controversial relationship with environmental stress and genetic architecture. While size-based measures of FA have long been assumed to be half-normally distributed within populations, recent studies that model developmental mechanisms have suggested other plausible distributions for FA. We investigated the distribution of FA in large empirical datasets of wing shape and wing size asymmetry from three species of insects (cotton aphid, Aphis gossipyi Glover, honeybee, Apis mellifera, and long-legged flies, Chrysosoma crinitus). Regardless of method of measurement, FA was best described by a double Pareto lognormal distribution (DPLN), or one of its limiting functional forms. To investigate convergence of mean sample FA to the population mean at various sample sizes, we sampled repeatedly under a DPLN using parameter values that best fit our data. Sample variances are much larger, and hence convergence is slowed considerably, with univariate or multivariate size-based measures of FA in contrast to a multivariate shape-based measure of FA. We suggest that much of the past work in FA may be under-sampled and we recommend using multivariate shape-based approaches or collecting larger datasets in future studies. We also discuss the implications of the DPLN distribution for understanding the developmental mechanisms underlying FA.