Diversidade de vespas sociais (Hymenoptera: Vespidae) e utilização de recursos florais em uma área de caatinga na Bahia

Abstract

The insect fauna of the caatinga floral visitors in general, has been little studied, and among the most important groups of insects in the study community are the Hymenoptera, in particular social wasps. Although studies of insect visitors to flowers focus on one or a few species, a perspective of community is important to point out ways to understand the partition and competition for resources and their effects on community structure. As a result, this study aimed to characterize the community structure of social wasps visitors to flowers of the savanna, identifying plant species and mode of use of those resources. Fieldwork was conducted from October 2005 to September 2006, and collected monthly consist of two days of activities, totaling up to 10 hours of work / day. On each sampling day, two collectors traveled a pre-existing track along which were inspected flowering plants, which were collected species of social wasps visiting the inflorescences with entomological net. The community of social wasps was characterized by means of different indices: relative frequency, consistency and diversity (H ') and the patterns of use of floral resources by these insects were investigated by comparing the amplitude of trophic niches. We recorded 172 individuals of social wasps, distributed in eight species. The abundance of the monthly number of individuals of wasps showed a significant variation (χ 2 = 169.16, p <0.0001) and diversity obtained in the present study was to H '= 0.66, this value was smaller than the range obtained in other studies with wasps in different localities. This difference is due to the savanna biome is subject to wide seasonal variation. The wasps visiting flowers of 26 species of these, 11 (42%) were visited by one or two subjects and 16 (61%) were visited by only one or two species. The wasp Polybia ignobilis (Haliday, 1836) visited 21 plant species, with the broader trophic niche (4,64). Already species Mischocyttarus cearensis Richards, 1945 and Brachygastra lecheguana (Latreille, 1824), showed narrower niches (0.76 and 0.67, respectively). The variation in the values of niche breadth for species of wasps can be related to some factors that influence the foraging activity, such as differences in biomass of some species, which shows the ability of these insects foraging and population size, which together with the need energy supply of the colony, determines the level of resource consumption, which interferes with foraging range of these species. The plasticity of these species using numerous floral sources reveals the importance of these insects in the collection of nectar from different plant species of the caatinga, demonstrating the need for more accurate studies aimed at evaluating the effectiveness of social wasps in pollination of plants.