Sex ratio adjustment in thirteen species of Panamanian fig wasps

A general model for predicting optimal brood sex ratios under varying intensities of local mate competition and varying levels of inbreeding is presented. The model predicts that the proportion of male offspring should increase with increasing numbers of foundress mothers contributing to common broods. The model also predicts that more inbred species should have more female-biased broods given the same number of foundresses. The specific quantitative predictions of brood sex ratios are compared with data collected from thirteen species of fig pollinating wasps occurring in the vicinity of the Panama Canal. The data show broad qualitative agreement with both predictions. Analyses of the deviations of observed brood sex ratios from predicted show that the sex ratio responses of the species tend to agree most closely with theoretical optima for the situations that the species naturally encounter most frequently. Further, the demonstrated ability of the species to adjust sex ratio to situations with different numbers of foundresses tend to be correlated positively with increasingly variable selective regimes, with species that rarely encounter variation in the foundress situations showing the least capacity for shifting sex ratios to different situations. I interpret these results as demonstrating variable degrees of adaptive behavioral plasticity in the different fig wasp species correlated with the variability of their selective regimes.