Influence of architectural complexicity of vegetative branches on the richness and abundance of spiders and other arthropods

Author(s)

Suzana Diniz

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
• Defense date: 2011-02-21

Examining board members

João Vasconcellos Neto; Claudia Maria Jacobi; Flavio Antonio Maës dos Santos

• Advisor: Gustavo Quevedo Romero; João Vasconcellos Neto

Abstract

Habitat structure has been a recurrent subject in literature and there have been several researches that correlated a greater structural complexity of habitat to the richness and abundance of diverse taxa. However, this represents a subject of hard generalization and experimental approaches are still rare. Vegetation is an element that provides structural complexity to habitat due to diverse architectural organization of their modules. Many researches demonstrated that arthropods associated to plants are one of the most affected groups by the vegetation architecture, especially the spiders. Thus, the objective of present research was to evaluate possible effects of vegetation architecture on the richness and abundance of arthropod guilds, with special emphasis on spider community. The research was divided in two parts: (1) a survey research, whose objective was to correlate diverse architectural traits of plants with the arthropod community, this in order to assess whether certain groups of the arthropod community are more or less abundant in certain plant architectural configurations; (2) an experimental research, whose objective was to manipulate plant architecture by grouping and spacing the vegetative branches in order to evaluate the effects of plant density on the arthropod community. A total of 17 plant species and eight architectural traits was used in survey research, whereas the experiment was performed in three plant species and repeated in two seasons (dry and wet) for evaluation of seasonal effects on the arthropod community response to manipulation of the plant architecture. All data referring to arthropod abundance and richness were given per unit of plant biomass and the prey availability for predators (i.e., all arthropods except the group of predators being studied) was set as a covariate. The abundance patterns of spider community were strongly correlated to the plant architecture, both in experimental and in survey research. Nevertheless, the other arthropod guilds, with some exceptions, were weakly affected by vegetation architecture. Some phytophagous guilds had consistent patterns of distribution on plant with different architectural traits. These patterns, by the way, occurred as in survey as in experimental research. The abundance of parasitoids and predators (except spiders) was more explained by the prey availability than by the plant architecture per se. Patterns of spider distribution on plants can be quite explained by the advantages that some plant architectures provide to the foraging habits of each guild. Abundance patterns of phytophagous guilds on plants with different architectural traits, nevertheless, were probably due to modulation of predation rates, since the plant architecture could determine refuge availability (AU)