Fatores ambientais e espaciais associados à diversidade de térmitas na floresta amazônica brasileira

Abstract

The Amazon is the largest and most diverse tropical forest in the world, with about a quarter of the planet's biodiversity. Although many studies have been conducted over the years in this ecoregion, there are still significant gaps related to the spatial distribution of sampling and taxa studied. Termites, especially in the Amazon, exhibit high diversity, endemism, and biomass but are under-sampled. Therefore, our objective was to expand termite inventories in the Brazilian Amazon and investigate the main spatial and environmental variables influencing the distribution patterns of the group and the conspicuous nests density. Thus, we evaluated the effects of environmental and spatial variables on species richness, composition, and beta diversity of termite communities, and the wood- and soil-feeders groups, in seven areas of the Brazilian Amazon Forest (Chapter 1). Additionally, we evaluated the communities of conspicuous nest-building termites in terms of species richness, composition, and density per hectare, in 11 areas (Chapter 2). In each area, a rapid diversity and a nest density protocols were applied, consisting of six transects with 65x2m and 65x20m, respectively. Different types of regression analyses (GLM, RDA, MRM) were performed to assess the relationship of predictor variables with response variables. In Chapter 1, 177 species were recorded in 1056 encounters. Species richness was positively and significantly influenced by vegetation height and soil sodium. Only soil pH influenced community composition, and similarity between communities decreased as the environmental distance of variables such as temperature, thermal amplitude, pH, and soil potassium, and geographical distance increased. Furthermore, the relationships varied according to the feeding group, with wood-feeders termites being more influenced by space than soil-feeders. In Chapter 2, 40 nest-building species were found, and the average density of constructions ranged from 30.8 to 109.0 active nests per hectare. The influence of environmental variables on nest density differed between epigeal and arboreal nests, but both were mainly influenced by climatic variables (annual temperature, thermal amplitude, and precipitation seasonality) and resource availability. The species richness of nest builders was not significantly influenced by any evaluated variable, and changes in composition were primarily associated with precipitation seasonality and temperature range. This study contributes to elucidating the ecological patterns of termites in the Amazon, allowing a better understanding of how space and environment can influence overall diversity and "subgroups" within Isoptera, whether they are feeding groups or conspicuous nest-building species. Thus, it becomes possible to identify processes operating on a broad spatial scale, capturing important environmental gradients. Moreover, understanding how environmental variables influence termite communities gives us insights into how they might be affected by environmental changes, whether caused by climate change or more direct anthropogenic impacts.