Colonização de ilhas artificiais de herbáceas aquáticas por peixes no Lago Catalão, Amazonas, Brasil

Abstract

Explaining the processes responsible for structuring biological communities remains a challenge. In this study, we aimed to verify if the process of fish assembly in aquatic herbaceous banks is predictable in a floodplain environment in the Amazon. Using artificial islands of aquatic herbaceous plants, we evaluated the colonization by fish over time, during the period of high waters in the Catalão, a floodplain area in Central Amazon. Three treatments (time intervals) were employed: 5, 15 and 30 days of colonization. Through analysis of variance (ANOVA), we compared how the abundance, richness and diversity of species (Shannon’s H') varied over time. The species composition was analyzed through similarity analyzes (ANOSIM), performed between treatments and environments (artificial islands and samples from natural banks of aquatic herbaceous plants), and visualized by means of a Principal Coordinate Analysis (PCoA). With the use of null models (C-Score), we evaluated the co-occurrence of species in the artificial islands. No statistical differences were detected in the abundance, richness and diversity of species and the species composition was similar among the treatments. Among the environments, there was a significant difference in composition, but the overlapping of observed points indicates that the combinations of species observed in the artificial islands also occur in the natural banks. Thus, the ichthyofauna of artificial islands is a subset of natural banks, that is, a nested pattern. The results of the species co-occurrence analysis indicated randomness in the colonization process, suggesting that biotic interactions such as competition and predation are not determining factors in the assembly of fish assemblages in the new habitats available during high water periods. However, the nested pattern and the dominance of some species on artificial islands are deterministic factors in our study. Therefore, we still do not understand the relative importance of these processes in community assembly in natural habitats, such as aquatic herbaceous banks.