Condition dependence and the origins of elevated fluctuating asymmetry in quality signals

Abstract

Developmental stability is the ability of organisms to buffer development against perturbations. Different classes of traits typically have different levels of fluctuating asymmetry (FA), a measure of developmental instability. In particular, elevated FA in sexually selected quality signals has attracted a great deal of attention. There are 3 main hypotheses to explain elevated developmental instability in quality signals. Developmental instability may be related to the cost of trait production, a trait’s condition dependence, or the levels of interindividual trait variation. Here we test these 3 hypotheses by comparing FA in structural traits, nonsignaling color traits, and 2 signaling color traits: a condition-dependent quality signal in Polistes dominulus wasps and noncondition-dependent identity signals in P. fuscatus wasps. Overall, color traits have higher FA than structural traits, though FA differs among the 3 classes of color traits. The clypeal identity signal in P. fuscatus has the highest interindividual trait variation, yet shows relatively low FA, indicating that interindividual trait variation does not explain heightened FA. The quality signal in P. dominulus has the highest FA, though it is not costly to produce. Therefore, the elevated FA in quality signals cannot be attributed to costs of signal production. The quality signal in P. dominulus is condition dependent, however, so our results indicate that increased developmental instability in quality signaling traits can be attributed to their condition-dependent development. A link between developmental stability and condition dependence provides a mechanism through which quality signals may integrate information about overall condition in the absence of costly trait development. Key words: badge of status, condition dependence, fluctuating asymmetry, identity signal, Polistes, quality signal, sexual selection. [Behav Ecol]