Body size as key trait determining aquatic metacommunity assemblies in benthonic and planktonic habitats of Dongting Lake, China

Abstract

• Aquatic community diversity decreased with increasing body size. • Body size affected distance-decay relationship of benthonic communities. • Higher effects of body size on benthonic community assembly than planktonic one. • Biotic interactions between microbial species were mediated by their body sizes. Body size play a key role in driving bioecological patterns by affecting community assembly processes at the organism level. However, the extent to which the relative influences of ecological processes operating community assembly with different body sizes at different habitat types in freshwater ecosystem is still unclear. Here, we conducted a comprehensive biodiversity survey on bacterial, fungal and invertebrate communities in planktonic and benthonic habitats of Dongting Lake, China, and evaluated the biogeographic distribution pattern and community assembly processes of distinct organism groups with different body sizes. Significant negative relationships between body size and community diversity indexes were observed in two habitats, and significant relationship between body size and distance-decay relationship was only observed in benthonic habitat. Body size showed stronger correlations with the ecological processes and ecological interactions of distinct organisms in benthonic habitat. Specifically, body size showed significantly positive correlation with the relative influence of deterministic processes which controlled the microbial community assembly processes, whereas body size was significantly positively correlated with stochastic processes in zoobenthos community. Molecular ecological network analyses also found that the average clustering coefficients and among-module connectivity were significantly negatively and positively correlated with their corresponding body size, respectively. Slops of correlations between body size and these parameters (including the null deviation value, dispersal rate, niche breadth and among-module connectivity) were steeper in benthonic habitat than that in planktonic habitat. Our findings suggested that body size operated the aquatic organism community assembly to affect their biogeographic distribution pattern, and the effect was stronger in benthonic habitat than in planktonic habitat. This study provides a better understanding of the mechanisms supporting the aquatic biodiversity on the sight of organism life-history trait.