Fluctuating asymmetry, mating success, body size and heterozygosity in Coenagrion scitulum (Rambur) (Odonata: Coenagrionidae)

For decades fluctuating asymmetry (FA) has been considered a good descriptor of developmental stability. Correlations have been shown between FA and several fitness components, including mating success and heterozygosity level. However, some doubts have been expressed about the generalization of these results, perhaps because of bias towards positive results and a poor critical approach in the first phase of FA studies. Studies on Odonata are scarce and are concentrated on the Coenagrionidae family, with contrasting results in the relationships between FA and mating success, size and other fitness components. We investigated the relationships between FA expressed as right - left wing length (R - L), body size expressed as (R+L)/2, multilocus and single locus heterozygosity assessed by allozyme electrophoresis and short-term mating success (SMS) assessed from the status (mated or not) of the males at the moment of collection. We collected 260 males from a breeding population. The data were analysed by both univariate and multifactorial statistical methods. After excluding a correlation between FA and body size, we checked the presence of a true FA by using tests for normality, directional asymmetry, antisymmetry and difference from the interindividual variations. The results showed no correlation between FA (either signed or absolute) and heterozygosity, body size and SMS, while heterozygosity was clearly positively correlated with body size and with SMS. Our data suggest an effect of the presence of some particular alleles on SMS, instead of an effect of the multilocus heterozygosity, even if the presence of only three polymorphic loci weakens the conclusions. Finally, no correlation was found between body size and SMS. (C) 2001 The Association for the Study of Animal Behaviour