Larval competition between the invasive <i>Aedes aegypti</i> (Diptera: Culicidae) and the Caribbean endemic <i>Aedes mediovittatus</i> (Diptera: Culicidae) from Puerto Rico, USA

Competition between mosquito species during the larval phase is a well-established mechanism structuring container mosquito communities, with invasive species often outperforming natives. We assessed the competitive outcome between 2 species that occur on the island of Puerto Rico, the historic invasive Aedes aegypti (L.) and the endemic Aedes mediovittatus (Coquillett) (Diptera: Culicidae). Trials were conducted under intra- and interspecific densities crossed with 2 amounts of 4 different leaf types serving as detrital resources for developing larvae; leaf types were representative of either urban or rural locations. Response variables included survival, male and female mass and development time, and a composite index of population growth (λ'). We also measured tannin levels in detrital environments, a secondary metabolite that can negatively influence mosquito development and survival. The co-occurrence of Ae. aegypti and Ae. mediovittatus generally did not affect survival or population growth of Ae. mediovittatus, however the converse was not true. Specifically, Ae. aegypti suffered lower survival and lower population growth in the presence of Ae. mediovittatus compared to when it was alone. Tannin concentrations did not correspond to competitive outcomes, as the highest tannin levels occurred under the detrital conditions where mosquitoes had highest growth and survival, with no evidence of differences between urban or rural leaf types. This is the first study to quantify the competitive outcomes between these species, both of which are part of the dengue transmission cycle on the island, and our findings suggest that Ae. mediovittatus is capable of outcompeting Ae. aegypti under some resource environments.