Print PageBiological invasions that carry broad ecosystem impacts have received much attention from ecologists. However, phylogenetic approaches have rarely been used to explain community invasibility, and the roles of phylogenetic diversity (PD) of resident communities, and phylogenetic relatedness (PR) between residents and invaders in regulating invasibility are poorly understood. Since PD may be a good proxy of the spectrum of resource utilization by resident communities and PR can indicate the niche similarity and competition intensity between residents and invaders if species niches are phylogenetically conserved, we suggest that both PD and PR can be used to predict invasion success. Specifically, we hypothesized that communities with higher PD and PR exhibit strong resistance to invasion. Here we present a laboratory microcosm experiment testing this hypothesis. We used 22 strains of bacteria isolated from Lake Clara Meer, Atlanta, GA to establish resident communities, and used an alien bacterium Serratia marcescens as the invader. We independently manipulated PD and PR in a 3×3 factorial design based on the phylogenetic analyses of 16s RNA sequences, and challenged resident communities with invaders after they attained steady states.
Results/Conclusions
Our results showed that PR significantly affected community invasibility indexed by the invader density, resulting in a strong negative relationship between PR and invasibility. However, PD had no effect on invasibility. We calculated the functional diversity (FD) and the functional relatedness (FR) based on sixty bacterial traits, most of which were not phylogenetically conserved. Accordingly, we found that both FD and FR were negatively related with invasibility, but the relationships were relatively weak. In conclusion, our experiment suggests that phylogenetic relatedness between residents and invaders is the best indicator of community invasibility.
