DIFFERENTIAL FLOWER HERBIVORY AND GALL FORMATION ON MALES AND FEMALESOF NEEA PSYCHOTRIOIDES, A DIOECIOUS TREE

The goal of this study was to determine whether there exists intersexu al differences in the degree of herbivore attack on a tropical, dioeci ous tree. Neea psychotrioides is a Costa Rican tree that experiences a t least two types of attack on its reproductive structures: flower her bivory and gall formation on inflorescences. Although female trees wer e more common than males in the two study populations (overall sex rat io = 1.5 females/male), male flowers were more likely to be eaten by l epidopteran larvae. Similarly, inflorescence-borne, fly-induced galls were more frequent on males. Ten families of insects from three orders (Diptera, Hymenoptera, Lepidoptera) occupied the gals with varying le vels of parasitism and hyperparasitism occurring within. Although the sexes were not significantly different in vegetative size, males had l arger flora displays (more inflorescences and larger flowers) that may have acted as attractants to herbivores and gall makers. The results are consistent with the hypothesis that flower damage and the energeti c costs of producing gals exert a greater expense to males, ultimately resulting in death, and over rime, a skewing of the sex ratio.