Taxonomic and functional diversity of rotifers, what do they tell us about community assembly?

Community assembly depends on dispersal, environmental parameters, and species interactions. Here, we compared rotifer communities from two environmentally distinct, but connected basins of Lake Tovel for five years, with biweekly (2002) and monthly (2003-2006) sampling. We applied taxonomic and functional diversity-based multivariate analyses (principal components analysis, redundancy analysis) to compare rotifer communities in both basins. For functional diversity, we focused separately on defence and feeding traits that were inferred from rotifer morphology. Taxonomic and functional diversity were generally higher in the deep compared to the shallow basin. In multivariate analyses, water residence time and surface water temperature were important environmental predictors for both taxonomic and functional diversity while the importance of competitors and predators varied according to defence or feeding traits used. The difference between basins showed a gradient from taxonomic (marked difference) to functional diversity, indicating that the processes that regulate feeding traits were similar in both basins while those regulating defence traits were different. The distinction of different aspects of rotifer life (i.e. feeding and predation) outlined different important drivers that would have been neglected by focusing solely on species abundance. Furthermore, we outlined the status quo of trait research in rotifer ecology including its challenges and difficulties.