Selective Pressures on Fruit Seediness: Differential Predation of Fly Larvae on the Fruits of Berberis Hispanica

Abstract

single in fruits (0.688) than when two (0.379) or more (0.120) are together in the same berry. With increasing fruit seediness, larval food increases and larval mortality decreases. Differential predation on differently-seeded fruits apparently results from higher larval survival in multi-seed fruits, which in turn has selected for differential oviposition among fruit classes by female flies. The proportions of differently-seeded fruits are linearly correlated with the estimated number of surviving seeds per mass unit of pulp expenditure, suggesting that B. hispanica plants are probably adjusting the distribution of seeds among fruit classes to maximize absolute number of surviving seeds through accounting simultaneously for predation risk and pulp costs. Mean number of seeds per fruit was found to be greater in a population which did not suffer fly attack, but no difference existed with regard to average pre-abortion seed number per fruit. Fly predation on fruits and seeds of B. hispanica seems therefore to influence fruit seediness through seed abortion-mediated plant responses.