Community Structure of Neotropical Flower Visiting Bees and Wasps: Diversity and Phenology

Abstract

This study examines the species richness of bees and flower visiting wasps in seasonal neotropical habitats in Costa Rica. A total of 9231 individuals were netted at flowers. These represented 192 species of bees and 138 species of wasps. Over 50% of the bee individuals were eusocial Apidae, but there were only 12% of the bee species. There was less dominance among the wasp families. Most of the species in both groups were uncommon: 50% of the bee species were represented by fewer than 8 individuals, and over 50% of the wasp species had only 1 or 2 individuals. Previous comparisons of the species richness of bees in tropical and temperature areas have been complicated by different sample sizes and a lack of distinguishing within— and between—habitat diversity components. Here, comparisons are made of within—habitat species richness for structurally similar habitats. The within—habitat species richness of bees was higher in tropical forests than in the temperate forests previously described. The tropical grassland had lower bee species richness, and it is postulated that the coevolutionary history of a habitat is an important component of bee diversity. The higher species richness of tropical forests was correlated with the abundance and diversity of animal—pollinated plants. Tropical bees were not more temporally specialized despite the longer flowering seasons, so diversity and temporal specialization were not correlated. The average flight season of tropical species was 3 times longer than that reported for bees in most temperate areas, and the turnover in species was also similar. Seasonality was correlated with the degree of species' sociality: eusocial bees were essentially aseasonal. Most seasonal bee species were encountered in the dry season. Flower visiting wasps were much more diverse in the tropical habitats than reported for temperate habitats, and they overlap with bees in resource use. Many other taxa also fed at flowers, and such diversity among competitors may be a factor in limiting bee diversity in the tropics.