Even though studies of invasive species are at root studies of species with different evolutionary histories sharing a common community, few studies or theories of invasive species acknowledge the impacts of evolutionary history on interactions within a mixed-origin community. Here I use an experimental study to determine how species origin and taxonomic relatedness impact interactions among plants and herbivores. The study followed a grassland plant community over four years in the presence and absence of both an exotic herbivore and disturbance. The study system had plant species originating from five continents, no native herbivore, and an exotic herbivore, European rabbits (Oryctolagus cuniculus). This community composition allowed separation of effects of origin and taxonomic relatedness on experimental response from those of evolutionary naiveté, and naiveté to the invaded community, and allowed careful examination of factors beyond species nativity.
Results/Conclusions
Surprisingly, overall effects of plant species to impacts of rabbits were negligible regardless of plant origin and despite strong evidence of herbivory. However, exotic plants regardless of origin were positively affected by disturbance, while native and endemic plants were negatively affected by disturbance even when native plants had congeners from the native range of the herbivore, or had conspecifics in the native range of non-rabbit herbivores. The demonstrated strong response to disturbance suggests that change in disturbance regime may be the strongest facilitation factor for many invasive species, and that herbivory itself may not be as strongly causal for community change as the disturbance some herbivores cause.
