Diversity of ostracod communities (Crustacea, Ostracoda) across hierarchical spatial levels in a tropical floodplain

Assessing and evaluating the mechanism and patterns of species distribution across multiple hierarchical spatial levels, such as in floodplains, are important for understanding the factors that influence the structure of communities. The species composition may vary at these spatial levels or between the spatial levels along the hierarchical scale. Thus, using the additive partitioning in species richness, Shannon index, and Simpson coefficient, we tested the hypothesis that the alpha and beta components of ostracod diversity are unevenly distributed along the hierarchical spatial levels in the Upper Parana River floodplain (Brazil). The results obtained by PCoA and diversity partitioning allowed us to conclude that dispersal is efficient, and that at higher spatial levels (floodplain, systems, and environments), the establishment of a new population of ostracods depends on both abiotic and biotic factors. However, at lower levels, spatial factors such as plants architecture and other biotic factors, e.g., competition, may have greater influence on community structure

Association of body size and behavior of freshwater ostracods (Crustacea, Ostracoda) with aquatic macrophytes

In aquatic systems, macrophytes play an important role in habitat structuring and can be relevant for the establishment and/or mobility of the organisms and might thus influence species composition. This study evaluates the influence of the structural complexity of aquatic plants on the community composition of Ostracoda in the upper Parana River floodplain. We tested the hypothesis that non-swimming and small-sized species have a higher association with more complex plants by a threshold indicator taxa analysis. Some small and non-swimming ostracod species had a significant affinity for macrophytes with higher complexity, especially Eichhornia crassipes. However, most species did not show an association with the structure of aquatic macrophytes, and there was only a slightly distinction among the communities of different plants. The results show that structural complexity is in some cases an important determining factor for the community composition of Ostracoda, but other factors may interact with and even override the effects of complexity. It can thus be concluded that the relation between habitat complexity and the Ostracoda community composition is complex and not always responds to general predictions