Biological traits of diatoms in the characterization of a reservoir and a stream in a subtropical region

Abstract

The structure of epiphytic diatom communities in a reservoir and a stream were studied with regard to different taxonomic levels (species, genera, and families) and biological traits (strategies of attachment to the substrate). We expected that strongly attached diatoms would abound in the stream, and those employing a loosely attached strategy should predominate in the reservoir due to the lentic flow condition. The congruence of high taxonomic levels and biological traits of the species was assessed and tested against an equal pattern of distribution. Our hypothesis was that taxonomic levels and biological traits have high congruence with species community. As periphytic diatoms have specialized structures to colonize substrates, we believed biological trait groups would show greater congruence with the species than groups formed by taxonomic levels. In fact, we observed the prevalence of strongly attached strategies in the lotic environment and stalked, prostrate, motile, and planktonic strategies predominated in the reservoir. The congruence between species and biological traits was stronger in both environments than that with different taxonomic levels. These results suggest that the strategies of attachment represent a key factor to the occurrence and distribution of species. The attached strategy showed greater competitive advantages under unstable environmental conditions than the loosely attached strategy, which predominated under stable conditions. Our results demonstrated a strong association of the diatom community with environmental conditions and suggest that biological traits may be an additional alternative for characterizing environments.