Is the littoral zone taxonomically and functionally more diverse? Investigating the rotifer community of a tropical shallow lake

Abstract

We investigated the taxonomic and functional diversity of rotifers in the littoral, intermediate, and pelagic zones of a tropical lake. Rotifers were collected at 10 sampling stations located in the three distinct zones. Taxonomic diversity was determined by species richness, abundance, and Shannon–Wiener diversity, while functional diversity was calculated using functional richness (FRic), functional evenness (FEve), and the community-weighted mean of functional traits (CWM). Redundancy analysis (RDA) were applied to ordinate the taxonomic and functional composition between the zones of the lake. The taxonomic diversity, represented by the abundance of organisms, was higher in the ecotone (i.e., intermediate zone). The RDA showed a difference between the three zones, with the occurrence of epiphytic rotifers in the littoral zone and semi-planktonic and planktonic species in the intermediate and pelagic zones. Regarding functional diversity, values of FRic and FEve did not differ between the zones. In contrast, CWM showed a distinct response between the zones of the lake. Illoricate species with raptorial characteristics, virgate trophi, and corona of the Asplanchna-type dominated in the littoral zone. In turn, microphagous rotifers, loricate species with spines, malleate trophi, and corona of the Brachionus/Euchlanis-type occurred in the intermediate and pelagic zones of the lake. The ecotone (intermediate zone) was taxonomically more diverse for the abundance of organisms compared to other two zones of the lake. For functional diversity, the three zones of the lake presented distinct functional traits.