Efeitos bottom-up e top-down na regulação da abundância em comunidades de cupins (Insecta: Isoptera)

• Autor(a) principal: Araújo, Fernanda Sguizzatto de
• Data de Publicação: 2010
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/880
• topic: Recursos; Predação; Forrageamento; Resources; Predation; Foraging; CNPQ::CIENCIAS BIOLOGICAS::ECOLOGIA::ECOLOGIA TEORICA

The general objective of this thesis was to analyze how resources and predation (bottom-up and top-down) regulate the communities of termites, determining the possible factors modulating these forces. Initially, it was rated as the bottom-up effects, quantity and quality of the resource in uence the presence of galleries of termites on trees. The amount of the resource was estimated by the diameter of the trees and their condition (dead or alive). The quality of trees was measured by the presence of latex, and taxonomical identity. It was found that termites selected trees with more amount of resources not being importante tree's quality. The proportion of galleries of termites was more frequently in large trees compared to small trees and more frequently in dead trees compared to live ones. Thus, it can assume that termites are foraging selectively and not randomly. In a later study, besides the quality and quantity of resources, predation risk was assessed in communities of termites in different stages of forest succession. It was hypothesized that the abundance of termites is higher in intermediate levels of forest succession due to the prevalence of bottom-up effects in early stages and top-down in later stages of succession. The results confirmed the hypothesis of peak abundance at intermediate levels of succession, but not exactly as expected. The mechanisms proposed to explain the pattern was different. The bottom-up effects were instrumental in the change of termites throughout the succession and there was no top-down effect. The amount of resource (biomass of litter) was important for termites, but quality (C / N of litter) did not affect termites. Accumulated litter can have affected the foraging behavior of termites and therefore having regulate the abundance of them. Besides, when termites dealing with litter accumulation may occur differences in habitat structure that generates: i) refuge for termites and to their predators and ii) physical impairments that limit both escape as the capture of prey. These effects were seen in laboratory and field experiments and proved that the risk of predation of termites was lower in more structured habitat (serapilheira/m2), but the ants were able to get around when their search effort was increased. Thus, this study demonstrates the role of bottom-up and top-down e ects in the regulation of termite communities, and concludes that bottom-up effects can be more important than top-down.