Estimates of community stability using the invasion criterion are robust across levels of invader species richness

A key feature of natural communities is that the species within them stably coexist. A common metric used to test community stability is measuring the ability of each species to recover from rare. Here, each species is assumed to have negative frequency dependent fitness and have a greater fitness relative to the other community members. A conceptual issue with measurements of relative invader fitness is that single species are invaded from rare. In natural communities, multiple species would likely decline following perpetuations e.g. antibiotic application, global warming, natural disasters. In our study, we compare previous estimates of community stability in a five species microbial community to experimental results in which multiple species are invaded from rare. Our results showed that single species invasions were broadly predictive of whole community stability when multiple species are invaded simultaneously. Precise values of relative invader fitness were less comparable, however being non-significantly different in most comparisons in 3/5 species. This work provides the first experimental test of the robustness of relative invader fitness metrics under multi-species invasion scenarios.