Contrasting effects of invader-natives phylogenetic relatedness on invader success and impact: A meta-analysis of Darwin’s naturalization hypothesis

Background/Question/Methods

A major goal of invasion ecology is to identify potentially successful invaders and communities vulnerable to biological invasions. A conundrum proposed by Darwin, which considers those two aspects together, has recently gained renewed interest. On the one hand, Darwin proposed that alien species more distantly related to native communities would be more likely to invade, as they would suffer weaker biotic resistance from native species that share similar niches with them. On the other hand, Darwin also suggested that alien species closely related to native species might be favored during invasion, as they tend to share necessary adaptations to the local environments to which their native relatives already adapt. Recent studies of these ideas, across numerous taxa and ecosystems, often produced mixed results, as they focused on different conceptual frameworks, spatial scales and invasion stages. Here, by using meta-analysis to synthesize results of 95 empirical studies published in the last two decades, we explored how phylogenetic relatedness between invaders and native communities affects invader success and impact at different spatial scales.

Results/Conclusions

Our results showed that invader-natives phylogenetic relatedness had contrasting effects on invader success and impact. Specifically, invaders more closely related to natives were less successful at the local scale, but not at the regional scale. In contrast, alien species more closely related to natives were more likely to be invasive and have stronger impacts on native communities at the local scale, but show weaker impacts at the regional scale. These patterns were broadly equivalent across terrestrial and aquatic ecosystems as well as across plant and animal assemblages. These findings suggested that the two sides of Darwin’s naturalization conundrum may apply to different invasion stages at different spatial scales, highlighting the necessary to consider different scales, different invasion stages, and species evolutionary relationships in invasion ecology.