Intra and interspecific competition via allelopathy among native and non-native plants

Abstract

Invasive non- native species success often is attributed to their competitive superiority, potentially through allelochemical inhibition (allelopathy) of native species, as suggested by the novel weapons hypothesis. However, it is also possible that non- native species are able to be successful through decreased intraspecific competition. Decreased intraspecific competition could be attributed to a lack of genetic variation creating less variable allelopathic effects. I predict that if non- native species follow the novel weapons hypothesis, their allelochemicals will restrict more biomass and give them a competitive edge compared to native species. Additionally, I predict that if non- native species have lower intraspecific genetic variation, non- native species will have less variation of allelopathic effects than natives. Furthermore, if non- native plant invasion is driven by allelopathy, I expect greater inhibitory effects of non- native than native plants. I conducted a greenhouse experiment to compare the competitive allelopathy of the non- native and native plants. This experiment involved assessing the restricted growth of non- native and native plant pairs (shrub or tree) in both intra- and inter-specific competition, with allelochemical extracts applied. Additionally, I conducted a laboratory bioassay experiment to evaluate the variability of allelopathic effects on model seed germination and growth using field- collected non- native and native leaf samples. My results showed little evidence that non- native invasive plants in Western New York possess particular novel or stronger allelopathic effects compared to native plants. Allelopathic effects did not vary based on invasive status, and non- native allelochemicals did not inhibit model seeds more than native allelochemicals. These findings suggest that native allelochemicals could be just as prominent as those from non- native species