Resident species and genotype composition impact invasibility in experimental mesocosms

Kelsey Lyberger and Matthew Kim, Evolution and Ecology, University of California, Davis, Davis, CA, Amelia Munson, Animal Behavior, University of California, Davis, Davis, CA

Background/Question/Methods
Understanding what factors increase the likelihood of invasion is critical for improving conservation efforts. Previous studies suggest a successful invasion is likely to depend on the biodiversity and composition of the invaded community. In theory, more diverse communities are more resistant to invasion, due to fewer open ecological niches. For similar reasons, communities that are more genetically similar to the invader should also be more resistant. This study tested whether the composition of an invaded (i.e., resident) community affected invasion success. We used a genotype of the water flea, Daphnia, to serve as the invader into aquatic mesocosms. We invaded three types of resident communities: (1) a second Daphnia genotype, (2) a zooplankton community without Daphnia, and (3) a second Daphnia genotype plus zooplankton community. We expected that invasion success into resident communities that contained the second Daphnia genotype would be lowest because genotypes of the same species would share similar ecological niches. Whereas we expected invasion success into resident communities without Daphnia would be highest.
Results/Conclusions
Interestingly, our findings indicate that invading Daphnia were not able to establish in the resident community of other zooplankton but were able to establish in the resident communities that included the second Daphnia genotype. One possible reason for this result is the abundance of the strong competitor Simocephalus. Overall, our research suggests that the species and genotype composition of the resident community are important drivers of invasion success.