SEX-RATIO, SEXUAL DIMORPHISM AND MATING STRUCTURE IN BETHYLID WASPS

Sexual dimorphism has been linked to parasitoid mating structure by se veral authors. In turn mating structure has an important influence on predicted sex ratio optima. Here we test the relationship between sexu al dimorphism and sex ratio using data from 19 species of bethylid was ps. Using phylogenetically based comparative methods we confirm the fi ndings of a previous cross-species analysis that sex ratio (proportion of males) is strongly and negatively correlated with clutch size. Usi ng cross-species comparisons we show an additional positive correlatio n of sex ratio and relative male size, as predicted. The relationship however is not significant when using phylogenetically based methods. The cross-species result is largely due to differences between two bet hylid sub-families: the Epyrinae have relatively large males and relat ively high sex ratios, whereas the Bethylinae have relatively small ma les and lower sex ratios. Our study illustrates the benefits and drawb acks of using cross-species versus phylogenetically based comparisons.