Partição do nicho alimentar de Xylocopa (Neoxylocopa) frontalis (Olivier) e Xylocopa (Neoxylocopa) grisescens Lepeletier (Apidae, Xylocopini)

Abstract

The ecological niche of the species is composed of all the biotic and abiotic conditions that exert influence on species survival and reproduction. Sympatric species overlap the temporal and spatial axis, and for this reason they can compete for food resources. One way to avoid food competition is to partition the food axis and this separation may be interspecific or intraspecific. Factors such seasonality and fragmentation may affect the availability of food resources. In the tropics, seasonality has an effect more related to the number of flowers available throughout the annual cycle. The fragmentation of the natural areas is recognized as the main factor that influences the bees decline, being even more intense when it comes to solitary species. Xylocopa frontalis (Olivier) and Xylocopa grisescensLepeletier (Apidae, Xylocopini) are solitary generalist and sympatric species that occur in the Brazilian savanna. They are important pollinators of native and cultivable plant species. Have similar body size and nesting behavior, which use preexisting cavities as nests. Through the nests-traps it is possible to collect and analyze the pollen content of the larval food, in which the identification and quantification of the pollen types allows to analyze the food preferences of each specie. Intraspecific and interspecific behavioral variations can lead to differences in the use of food resources by individuals or populations. Thus, the general objective of this dissertation was to evaluate the use of food resources by bees of the genus Xylocopa at both the individual and the population level. For this, we divide it into two chapters. Chapter 1: Partition of the food niche between two species of sympatric bees: Xylocopa frontalis (Olivier) and Xylocopa grisescensLepeletier (Apidae, Xylocopini); Chapter 2: Networks of Xylocopa individual-resource interactions: generalist species, specialist individuals?The objective of the first chapter was to evaluate the niche partition of the two bee species in an agricultural area and a nature reserve area. The results demonstrate the occurrence of food niche partition between the two species in greater proportion in the environment with larger natural area. Which, X. frontalis preferably used pollen from plants with poricidal dehiscence anthers, while X. grisescens used pollen from plants with non-poricidal anthers. The richness of pollen types was higher at preserved area for both species. The objective of the second chapter was to evaluate the individual specialization of X. frontalis and X. grisescens using network metrics. The results demonstrate that both X. frontalis and X. grisescens individuals presented low connectivity value and high degree of specialization, indicating a partition of the resource within the population.However, X. frontalis individuals used a single preferred food resource, and X. grisescens individuals split into subgroups using resources similar to each other but different from other sets of individuals. Thus, although these species have similarities in body size, nesting habit and foraging period, a partition of the food niche between populations has been demonstrated, and individuals have individual specializations regarding the collection of pollen sources.