Cumulative effects of plant-animal interactions on seed production by Bauhinia ungulata, a neotropical legume [Costa Rica]

Seed production was studied in Bauhinia ungulata, a neotropical, perennial legume. Our goals were to identify the biotic factors influencing seed output, the magnitude and variability of their effects, and whether these effects were density dependent. We measured predispersal reproductive success in five stands, ranging in size from 18 to 175 ramets. Pollination success and flower herbivory were evaluated for 1375 flowers. Other sources decreasing seed output were observed by examining 1714 seedpoints. Six factors led to reduction in potential seed-set. In order of the magnitude of their effects, these factors were lack of pollination, incomplete development of ovules in flowers that formed seedpods, herbivores that damaged flowers that could have been pollinated, bruchids that destroyed developing seeds, herbivores that damaged pistils, and herbivores that ate developing pods. Density dependence was observed for three of the factors: level of pollination success, seed predation, and herbivory on developing seedpods. There was significant variation among stands for the six factors that were measured in all stands. Key factor analysis was used to estimate the influence of these factors on variation among stands in seed-set. Seed predators and pollinators accounted for most of the observed variation. We conclude that pollinators and predators on seeds are potentially important to the population dynamics of this plant.