Weighted species richness outperforms species richness as predictor of biotic resistance
2016 (English)In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 97, no 1, 262-271 p.Article in journal (Refereed) Published
The species richness hypothesis, which predicts that species-rich communities should be better at resisting invasions than species-poor communities, has been empirically tested many times and often poorly supported. In this paper we contrast the species richness hypothesis with four alternative hypotheses with the aim of finding better descriptors of invasion resistance. These alternative hypotheses state that resistance to invasions is determined by abiotic conditions, community saturation (i.e., the number of resident species relative to the maximum number of species that can be supported), presence/absence of key species, or weighted species richness. Weighted species richness is a weighted sum of the number of species, where each species' weight describes its contribution to resistance. We tested these hypotheses using data on the success of 571 introductions of four freshwater fish species into lakes throughout Sweden (i.e., Arctic char (Salvelinus alpinus), tench (Tinca tinca), zander (Sander lucioperca), and whitefish (Coregonus lavaretus)). We found that the weighted species richness best predicted invasion success. The weights describing the contribution of each resident species to community resistance varied considerably in both strength and sign. Positive resistance weights, which indicate that species repel invaders, were as common as negative resistance weights, which indicate facilitative interactions. This result can be contrasted with the implicit assumption of the original species richness hypothesis, that all resident species have negative effects on invader success. We argue that this assumption is unlikely to be true in natural communities, and thus that we expect that weighted species richness is a better predictor of invader success than the actual number of resident species.
Place, publisher, year, edition, pages
2016. Vol. 97, no 1, 262-271 p.
biotic resistance, freshwater fish, species identity, species richness, saturation, weighted species richness
IdentifiersURN: urn:nbn:se:umu:diva-110249DOI: 10.1890/15-0463.1ISI: 000369852600027OAI: oai:DiVA.org:umu-110249DiVA: diva2:861759