CLUTCH SIZE MANIPULATIONS IN 2 SEED BEETLES - CONSEQUENCES FOR PROGENY FITNESS

Seed beetles (Coleoptera: Bruchidae) lay their eggs on discrete resour ce patches, such that competition among larvae for food is an importan t component of their biology. Most seed beetles, including Stator limb atus, lay eggs singly on individual seeds and avoid superparasitism ex cept when seeds are limiting. In contrast, S. beali, a closely related congener, lays eggs in clutches on a single seed. We tested the hypot hesis that natural selection on larval life history characters favors small clutches (selection against large clutches) in S. limbatus, but that selection against large clutches is relaxed in S. beali because o f the large size of its host's seeds. We manipulated clutch size and e xamined its relationship to offspring fitness. Clutch size affected th e survivorship of S. limbatus larvae (r(2)=0.14), but had no detectabl e effect on the survivorship of S. beali larvae (r(2)=0.04). Also, clu tch size had a large effect on development time and body weight of S. limbatus, but not of S. beali. We discuss the implications of this res ult for the evolution of clutch size in S. limbatus and S. beali.