Male morphological variation and the determinants of body size in two Otiteselline fig wasps

Abstract

The chalcid wasps (Hymenoptera) that develop in fig tree inflorescences (Ficus: Moraceae) have often been used to study alternative reproductive behaviors. However, recent work suggests that such behaviors are more complex than previously thought. We investigated this in Otitesella longicauda and O. rotunda. In addition to known dimorphisms in the two species (each have "religiosa" males that use their mandibles to fight for mates in the fig, and "digitata" males that disperse from the fig to mate), we found that religiosa males below species-specific body size switch points have relatively larger mandibles and are less sclerotized than those above. Thus, they are actually trimorphic. We suggest that the religiosa morph variation is linked to fighter/nonfighter alternative mating behaviors, with small (nonfighting) males having relatively larger mandibles because they also use them to pull females out of their galls before mating. Also, we investigated the determinants of wasp body size, and whether females (foundresses) adjust their offspring allocation strategies according to expected offspring size. We found that wasp size is larger in ovaries near the center of the fig, and more females and fewer religiosa males are laid in such ovaries than in those further away. This probably indicates that foundresses lay females when they are expected to be large because their fitness is more body size-dependent than that of religiosa males. We then discuss the implications of our findings for the study of alternative reproductive behaviors and foundress offspring allocation strategies.