Print PageIn the relatively short history of invasion biology, multiple hypotheses have been proposed to explain the success or failure of exotic species, such as the enemy release, biotic resistance, and facilitation hypotheses. We tested different factors that correspond to different general hypotheses to understand the factors controlling invasion by Pinaceae on Isla Victoria, Nahuel Huapi National park. On this area 80 years ago more than 130 species of exotic trees were planted in large quantities, and most of the plantations still remain. The analyzed factors were seed predation (corresponding to the biotic resistance hypothesis), facilitation by mycorrhizal fungi (faciliation hypothesis), herbivory by exotic deer (enemy release), propagule pressure (stochastic factors), and species traits (intrinsic invasiveness) with field and greenhouse experiments and with field surveys.
Results/Conclusions
We found that intense seed predation and the lack of proper mycorrhizal fungi may be impeding the invasion of exotics, while deer herbivory appears to have a positive effect on the invasion. Propagule pressure and species traits appear to play a minor role in explaining these invasions. These results show that multiple hypotheses collectively help to explain plant invasions, and that multiple factors are involved in the success or failure of biological invasions.
