Seed predation in the legume Crotalaria

Abstract

Correlates of individual plant escape from seed predation were investigated for an East African population of the shrub Crotalaria pallida (Papilionaceae) in which seed mortality due to chewing insects is high and varies among neighboring individuals. Several plant properties expected to influence phytophagous insect host choice or fitness were measured simultaneously and their contribution to variance in predation examined with multiple regression analysis. Microhabitat, seed pyrrolizidine alkaloid concentration, and parasitoid load on the seed predators are the best predictors of predation intensity; plant size, distance from conspecifics, and infructescence characteristics do not appear to affect predation probabilities. However, predictions of the direction of microhabitat effects were only partially successful, and contrary to expectation, plants with higher seed alkaloid levels experienced greater seed predation; several hypotheses are advanced to account for these results. Higher parasitoid loads are associated with lower predation intensity, probably due in part to interference between lepidopteran larvae and the less voracious hymenopteran seed predators or their parasitoids.