Insetos engenheiros de ecossistemas em plantas e seus efeitos indiretos na comunidade de artrópodes

Abstract

Ecossystem engineers are organisms that directly or indirectly control resource availability to other organisms, by physical changes in biotic and abiotic factors. By their activities, ecosystem engineers modify, maintain, or create new habitats. It is recognized now that many plant-herbivore systems can be understood as the interactions between organisms and the physical environment are evaluated and integrated to the ecology of ecosystems the concept of insects as environmental modifiers or ecosystem engineers. This study approaches, both qualitatively and quantitatively, the subject insects by ecosystem engineering in two chapters. The first chapter consists of a qualitative review of the role of leaf shelters builders insect as ecosystem engineers and quantitative analysis of the role of leaf shelters in the richness local patterns and diversity of arthropods based on data published in 12 studies. The objective of this chapter was to evaluate the role of insects as ecosystem engineers, and specifically as physical structures created by insects have the potential to improve abiotic conditions and biotic processes such as predation and parasitism. It was also evaluated the consequences of ecosystem engineering can affect the structure and composition of communities with effects on local biodiversity through a quantitative analysis of the effects of shelters built by insects on secondary colonization by arthropods. The second chapter consist of an experimental study to evaluate the role of Pandemis spp. (Lepidoptera, Tortricidae) - a leaf-rolling caterpillar in plant Trigonia rotundifolia (Trigoniaceae) - on arthropod community. Our objectives were to determine whether (i) the presence of leaf shelters increases the frequency of occurrence, the richness and diversity of arthropods in plants, (ii) the type of shelter - natural or artificial - interfere with the colonization of arthropods, and (iii) plants with leaf present shelters have a lower rate of leaf herbivory. In the first experiment we conducted a survey of arthropods in two plant groups: 1) control (absent shelters) and 2) plants with two artificial leaf shelters added. Each sample group was evaluated in three fortnightly censuses. In this experiment found higher abundance and richness of arthropods in plants with artificial leaf shelters. In the second experiment carried out the survey of arthropods in plant groups 1) control, 2) plants with an artificial shelter and 3) plants with a natural shelter. Plants in each sample group were evaluated in three fortnightly censuses. In this experiment, it was observed that only the richness of arthropods differ among treatments. In order to evaluate whether the herbivore rate on Trigonia varies according to the number of leaf shelter per plant was calculate the average percentage of leaf area removed. Plants with two cylinders shown a larger leaf removal rate compared plants that did not have shelters.It was also conducted to compare the similarity analysis of the composition guild arthropods and herbivores in plants with and without leaf shelters. It was observed that in both experiments, there was no significant difference in the species composition of arthropods in plants with and without shelters. Our results demonstrated that the arthropod community in plants can be indirectly affected by leaf-rolling caterpillar, revealing their role as ecosystem engineers in Brazilian Cerrado.