Search

One of the oldest ideas in invasion biology, known as Darwin's naturalization hypothesis, suggests that introduced species are more successful in communities in which their close relatives are absent. We conducted the first experimental test of this hypothesis in laboratory bacterial communities varying in phylogenetic relatedness between resident and invading species with and without a protist bacterivore. As predicted, invasion success increased with phylogenetic distance between the invading and the resident bacterial species in both the presence and the absence of protistan bacterivory. The frequency of successful invader establishment was best explained by average phylogenetic distance between the invader and all resident species, possibly indicating limitation by the availability of the unexploited niche (i.e., organic substances in the medium capable of supporting the invader growth); invader abundance was best explained by phylogenetic distance between the invader and its nearest resident relative, possibly indicating limitation by the availability of the unexploited optimal niche (i.e., the subset of organic substances supporting the best invader growth). These results were largely driven by one resident bacterium (a subspecies of Serratia marcescens) posting the strongest resistance to the alien bacterium (another subspecies of S. marcescens). Overall, our findings support phylogenetic relatedness as a useful predictor of species invasion success. [ABSTRACT FROM AUTHOR]

The question of how species diversity affects ecological stability has long interested ecologists and yet remains largely unresolved. Historically, attempts to answer this question have been hampered by the presence of multiple potentially confounding stability concepts, confusion over responses at different levels of ecological organization, discrepancy between theoretical predictions, and, particularly, the paucity of empirical studies. Here we used meta-analyses to synthesize results of empirical studies published primarily in the past 2 decades on the relationship between species diversity and temporal stability. We show that the overall effect of increasing diversity was positive for community-level temporal stability but neutral for population-level temporal stability. There were, however, striking differences in the diversity-stability relationship between single- and multitrophic systems, with diversity stabilizing both population and community dynamics in multitrophic but not single-trophic communities. These patterns were broadly equivalent across experimental and observational studies as well as across terrestrial and aquatic studies. We discuss possible mechanisms for population stability to increase with diversity in multitrophic systems and for diversity to influence community-level stability in general. Overall, our results indicate that diversity can affect temporal stability, but the effects may critically depend on trophic complexity. [ABSTRACT FROM AUTHOR]