Species but not genotype diversity strongly impacts the establishment of rare colonisers

1. Understanding species coexistence and regulation of biodiversity are major research challenges, yet there is no consensus on the effects of diversity on diversity, including their mediation through plant–plant interactions.
2. We examined how the diversity of recipient communities impacted on the establishment of colonising species. We ran a greenhouse-based community experiment, creating artificial arable crop communities with varying levels of barley genotype and weed species diversity, analysed with structural equation modelling of responses across trophic levels.
3. Colonising arable weed species establishment was significantly reduced when the recipient communities’ weed species richness, but not barley genotype richness, increased. Recipient plant communities with higher species richness occupied more total niche space and showed stronger competition with colonising species. In contrast, recipient plant communities with higher genotype richness, even though they had slightly ...