Pollen Deposition Is More Important than Species Richness for Seed Set in Luffa Gourd

In the context of global biodiversity decline, it is imperative to understand the different aspects of bee communities for sustaining the vital ecosystem service of pollination. Bee species can be assigned to functional groups (average difference among species in functionally related traits) on the basis of complementarity (trait variations exhibited by individual organisms) in their behavior but is not yet known which functional group trait is most important for seed set. In this study, first, the functional groups of bees were made based on their five selected traits (pollen deposition, visitation rate, stay time, visiting time of the day, body size) and then related to the seed set of obligate cross-pollinated Luffa gourd (Luffa aegyptiaca). We found that bee diversity and abundance differed significantly among the studied plots, but only the bee species richness was positively related to the seed set. Functional group diversity in terms of pollen deposition explained even more of the variance in seed set (r = 0.74) than did the species richness (r = 0.53) making it the most important trait of bee species for predicting the crop reproductive success.