The distribution of mosquitoes across an altitudinal gradient in the Galapagos Islands

An avian malaria parasite (genus Plasmodium) has been detected consistently in the Galapagos Penguin (Spheniscus mendiculus) and less frequently in some passerines. We sampled three resident mosquito species (Aedes taeniorhynchus, Culex quinquefasciatus, and Aedes aegypti) using CDC light and gravid traps on three islands in 2012, 2013, and 2014. We sampled along altitudinal gradients to ask whether there are mosquito-free refugia at higher elevations as there are in Hawaii. We captured both Ae. taeniorhynchus and Cx. quinquefasciatus at all sites. However, abundances differed across islands and years and declined significantly with elevation. Aedes aegypti were scarce and limited to areas of human inhabitation. These results were corroborated by two negative binomial regression models which found altitude, year, trap type, and island as categorized by human inhabitation to be significant factors influencing the distributions of both Ae. taeniorhynchus and Cx. quinquefasciatus. Annual differences at the highest altitudes in Isabela and Santa Cruz indicate the lack of a stable highland refuge if either species is found to be a major vector of a parasite, such as avian malaria in Galapagos. Further work is needed to confirm the vector potential of both species to understand the disease dynamics of avian malaria in Galapagos.