Publication Details

Category Text Publication
Reference Category Journals
DOI 10.1016/j.ppees.2020.125565
Licence creative commons licence
Title (Primary) Natural enemies do not contribute to negative frequency-dependence in native and exotic grassland plants
Author Schmidt, R.; Deising, H.B.; Hensen, I.; Schädler, M.; Auge, H.
Journal Perspectives in Plant Ecology, Evolution and Systematics
Year 2020
Department BZF; iDiv
Volume 46
Page From art. 125565
Language englisch
Keywords Enemy release hypothesis; equalizing and stabilizing mechanisms; exotic species; negative frequency-dependence; productivity; species diversity; biodiversity; biological invasions; coexistence; community assembly; grasslands; insects; pathogens; plant communities; species interactions

Species’ responses to antagonists, such as fungal pathogens and insect herbivores, are part of a species’ niche and are thought to contribute to species coexistence. In theory, coexistence is supposed to be maintained by the effects of equalizing mechanisms that reduce fitness differences among species, and stabilizing mechanisms that are the result of niche differences. The presence of stabilizing niche differences is hallmarked by negative frequency-dependent per capita rates of increase. However, rigorous experimental testing of how insect herbivores and fungal pathogens contribute to negative frequency dependence among co-occurring plant species, in particular in the context of biological invasions, is scarce. We present an experimental study in a grassland in central Germany, in which we established native and exotic-dominated communities on 1 m²-plots, and reduced above- and belowground fungal pathogens and insect herbivores by applying pesticides. We manipulated the frequencies of six native and six exotic focal species, in order to assemble one dominant and five rare species per community. We quantified productivity and diversity for each community, and recorded data on per capita rates of increase and other fitness components for two native and two exotic focal species over three years. We found that native and exotic-dominated communities did not differ in their productivity and diversity. Reduction of fungi and insects increased productivity but the effect was similar for both species origins, suggesting that effects of enemy release are transitory or not existent. Negative frequency-dependence was common in our species, but could not be linked to interactions with antagonists. Although focal species responded to the reduction of antagonists, these effects were only present at low frequency, suggesting a greater importance of intraspecific competition, e.g. for resources, in explaining the observed stabilizing niche differences. Offsetting responses of the two exotic focal species to both antagonist groups highlight the significance of equalizing mechanisms among native and exotic species at the community level. Our study demonstrates the importance of both equalizing and stabilizing mechanisms in the context of biological invasions and differential contributions of antagonistic interactions to these mechanisms.

Persistent UFZ Identifier
Schmidt, R., Deising, H.B., Hensen, I., Schädler, M., Auge, H. (2020):
Natural enemies do not contribute to negative frequency-dependence in native and exotic grassland plants
Perspect. Plant Ecol. Evol. Syst. 46 , art. 125565