Trait-mediated species niche and fitness differences that link ecological and competitive differences to coexistence have been increasingly applied to infer mechanisms driving community assembly. While spatial partitioning has long been considered to play a critical role in species coexistence, much of the recent research into the role of species differences for assembly mechanisms has not fully incorporated spatial patterns based on the individual-based species distributions. Here, we predict that functional similar species tend to occupy disjoint areas and reveal spatial segregation via limiting similarity, while the spatially clustered functional pattern might be either caused by environmental filtering or competitive exclusion of inferior competitors.
We used a fully mapped 50-ha subtropical forest plot in South China to explore how species spatial associations were associated with absolute and hierarchical trait distances, which refer to niche and fitness differences respectively, in order to gain insight into coexistence mechanisms. We assessed pairwise spatial associations by two summary statistics of spatial point pattern analysis at different spatial scales and compared the effects of absolute and hierarchical trait distances on spatial patterns.
Results/Conclusions
We found that absolute trait distances were generally negatively correlated with interspecific spatial associations, revealing no support for limiting similarity. We further found that the hierarchical trait distances provided at least comparable explanatory power to the spatial associations with the absolute trait distances.
The spatially clustered functional pattern found in our study, which was generally interpreted as an effect of environmental filtering with a progressive sorting of species best adapted to the local abiotic conditions with some certain functional traits in previous work, might alternately reflect the combined effects of the environment and local competition, which selects species with traits conferring greater competitive and resource-acquisition ability.