Biodiversity includes geographic variation in species interactions and underlying species traits. Effects of such variation can be particularly important for the resistance of resident communities to the impacts of invasive species. Resistance of communities to exotic invaders affects their composition and richness, which are other expressions of biodiversity. We tested the hypothesis that allopatry or sympatry of the resident mosquito Aedes aegypti with the invasive Aedes albopictus results from variation in the inherent competitive ability of A. aegypti, and the role of variation in fecundity-size relationship in population-level outcome of competition with A. albopictus. We compared competitive abilities of eight North American populations of A. aegypti, four populations sympatric to A. albopictus, and four populations allopatric of A. albopictus. Competition among larvae from each A. aegypti population and a single A. albopictus population was tested in laboratory microcosms in a response-surface design.

Results/Conclusions

We found origin of A. aegypti influences its competitive response to competition from A. albopictus and effect on A. albopictus. Aedes aegypti from allopatric sites was superior in competition with A. albopictus than A. aegypti from sympatric sites by having stronger effect on A. albopictus. Miami had the strongest effect and best response of all populations but effect and response slopes of all populations was uncorrelated, indicating inconsistent ranking of A. aegypti in competitive effect and response. Although A. albopictus is generally a superior competitor than A. aegypti, stronger competitive effect of particular A. aegypti populations against invading A. albopictus may help resist the spread of the invasive. These results suggest that inherent interpopulation variation in the competitive ability of A. aegypti may explain the exclusion of A. albopictus in some areas of the southeastern United States and offers evidence of biotic resistance by an inferior competitor.