Padrões de montagem de comunidades : investigando a estrutura funcional e filogenética para inferir processos em comunidades naturais

Abstract

Community ecology aims to disentangle the relative influence of the drivers of community assembly. My thesis is composed of four chapters with different focus on the drivers of assembly in natural and simulated communities. In the first chapter we studied stream aquatic insects over 600 km extension. We found that the phylogenetic structure of communities had a spatial signature, suggesting dispersal limitation. We found that large insects, with high flight capacity and with univoltine life cycles were the most affected by spatial distance. We suggest that the number of generation per year and hence the number of dispersal events is a strong factor for the distribution of aquatic insects. In the second chapter we studied the assembly of stream insects over a smaller scale in the Itanhaém river basin. We were interested on the influence of competition and environmental filtering on the functional and phylogenetic structure of insects. If environmental filtering was strong, traits of respiration type and pollution sensitivity should be more similar than expected by chance, while if competition was strong we should find less similarity in feeding strategies among co-occurring taxa. We found evidence of environmental filtering but not of strong competition. Additionally, we found common co-occurrence of ancient clades of aquatic insect orders, likely due to the stability of stream habitats along evolutionary scale. In the third chapter we also investigated competition and environmental filtering, but we used odonates, a group with aggressive behavior against visually similar species. This happen because it cannot properly identify if a similar individual is a mate competitor or not. Even in this case, we found more evidence of environmental filtering, likely because related odonates have similar reproductive strategies linked to specific riverine characteristics, forcing these related species to co-occur. In the fourth chapter we were interested again on the signatures of competition, however we used computational simulations to generate communities assembled by competition. We aimed to identify if the observational approach could indeed identify competitive exclusion. Simulated communities were generally composed of similar species, because species with small competitive difference do not exclude each other. Strikingly, we commonly found random patterns owing to the relaxed competition diluted among multiple species. In conclusion, we found that the assembling of natural and simulated communities is influenced by dispersal and history on the regional scale, and by environmental filtering on the local scale. The influence of competition is still open to questioning given the lack of reliability of the traditional observational approach.