Impact of alien species: Negative and positive, direct and indirect
Invasive species are considered one of the greatest threats to biodiversity worldwide. However, invasive species could simultaneously have negative and positive effects on native species. Effects of invaders on natives can be direct (e.g., through consumption or competition for abiotic resources) or indirect (e.g., supporting populations of pollinators or making natives less apparent to herbivores or pollinators). Indirect effects could be mediated through interactions with other invasive or other native species. Furthermore, abiotic conditions, which are in flux due to ongoing climate change, could modify these indirect and direct effects, changing their magnitudes. While invasive species are nearly universally considered in planning plant conservation and restoration, without tackling the complex ways that invasive species may interact with each other and with multiple native species to determine the impact on focal natives, it is likely that control of invasive species will not be implemented in the most efficient and productive way. A better understanding of the positive and negative effects of invaders is of general importance in a world of greatly elevated anthropogenic species introductions. There are many anecdotal examples where invaders have not driven native species extinct. My research aims to help drive conservation decisions by developing a framework to determine a priori if the net impacts of invaders are likely to be negative or not in order to direct limited management resources as efficiently as possible. We need to identify traits that govern the balance of positive and negative effects of invaders on natives, so we can anticipate, without detailed study, which natives will be strongly impacted. Through my research, I work to understand mechanistically how different invaders and climate directly and indirectly affect populations of native plants that differ in key traits and model how these interactions impact native plant populations into the future.
Invasive species have been traditionally viewed as detrimental and potentially disastrous for native plants and there are many obvious ways invaders can have negative effects through competition for resources. However, there are several mechanisms by which alien species could also have positive effects on native plants. Alien plants could shelter natives from extreme abiotic conditions, improve soil for native plants by fixing nitrogen or adding organic matter, and provide associational resistance against native or introduced herbivores. Alien herbivores could reduce native plant competition with native or alien neighboring plants. Alien plants could also increase pollinator visitation to native plants, by attracting them to areas with native plants or by providing resources that increase pollinator population. To understand the complete impact of invasive species on native plants, it is essential to consider these potentially beneficial interactions as well as the negative effects of invaders.
Invasive species have been traditionally viewed as detrimental and potentially disastrous for native plants and there are many obvious ways invaders can have negative effects through competition for resources. However, there are several mechanisms by which alien species could also have positive effects on native plants. Alien plants could shelter natives from extreme abiotic conditions, improve soil for native plants by fixing nitrogen or adding organic matter, and provide associational resistance against native or introduced herbivores. Alien herbivores could reduce native plant competition with native or alien neighboring plants. Alien plants could also increase pollinator visitation to native plants, by attracting them to areas with native plants or by providing resources that increase pollinator population. To understand the complete impact of invasive species on native plants, it is essential to consider these potentially beneficial interactions as well as the negative effects of invaders.