Reduced historical contingency in communities with higher functional and phylogenetic diversity
Ecological communities often exhibit historical contingencies, and one important goal of community assembly research is to understand mechanisms regulating the importance of assembly history in shaping the assembled communities. The ecological similarity of species in the regional species pool has been thought to influence community assembly, but direct experimental tests of this idea are rare. In addition, few assembly studies have linked patterns of community assembly to contemporary species coexistence theory that distinguishes species niche and fitness differences. We performed a laboratory microcosm experiment, with bacterivorous protists as model organisms, to examine how species’ ecological differences in the species pool, characterized by functional and phylogenetic diversity, influence community assembly.
Our results showed that β-diversity among communities with different assembly histories decreased with both functional and phylogenetic diversity, whereas α-diversity of the assembled communities increased with both functional and phylogenetic diversity. Mechanistically, species niche differences increased with functional/phylogenetic diversity, facilitating coexistence and reducing the strength of priority effects. Species fitness differences, which explained little variation in α- and β-diversity, were less important. Our study also supported the utility of the combined use of functional and phylogenetic diversity in identifying important functional traits. These results advocate the use of functional and phylogenetic knowledge for better understanding the mechanisms underlying community assembly.