The Ecology of a Prairie Legume (Baptisia leucantha) and an Associated Curculionid Seed Predator (Apion rostrum)

Abstract

The ecology of seed-eating insects and the plants they attack remains, for the most part, unexplored. It has been hypothesized that the interacting characteristics of certain insect-plant associations result in a concentration of the insect in dense host-plant populations. Baptisia leucantha (White Wild Indigo) and Apion rostrum (weevil) provide a system which can he tested with this hypothesis. Apion rostrum frequently infests the seed pods of the prairie legume Baptisia leucantha. The rate of this infestation was compared to plant density in Baptisia populations located in the southeastern Lake Michigan region. Infestation rate was also compared with the degree to which the plant communities which accompanied the Baptisia populations resembled Baptisia’s indigenous plant community, the prairie. The theory that Apion infestation increases the germination rate of Baptisia seeds by acting as a vector for a seed-coat-scarifying fungus was also tested. Results imply that: l)the Apion - Baptisia association is not density dependent, 2) infestation is not influenced by the degree to which the accompanying plant community resembles a prairie community, 3) Apion may serve as a vector for the introduction of a seed-cost-scarifying fungus into Baptisia pods.