Patterns of abundance and co-occurrence in aquatic plant communities

Aquatic plants are well suited as subjects for studies on the distribution and abundance of co-occurring species, especially due to the simple structure of their communities, well defined toposequences and relatively easily measurable environmental factors. Here we show that underwater plants occurring in semi-natural lakes form stable communities, where species interactions dominate over dispersal dynamics to form a modular community structure with a high degree of zonation (turnover) and low within-module species richness. In turn, human-induced disturbance largely destroyed the modular structure. Our results indicate that (1) species abundance distributions (SADs) of underwater plant communities are well described by the lognormal model; (2) environmental characters did not significantly influence the SADs of underwater plant communities; (3) log-series SADs do not indicate specific types of community organization; (4) in our lake communities only few satellites (tourists) occur; (5) the co-occurrence of species is highly dependent on the turnover across lakes and water depth zones; and (6) species zonation is a function of lake properties.