Two species of Aedes show altitudinal variation in temperature preference in the islands of the Gulf of Guinea

BackgroundTemperature choice is a vector trait that influences microhabitat selection and can have important implications for vector species, as it may affect how often vectors encounter hosts. Aedes aegypti and Ae. albopictus are disease vectors whose geographic ranges continue to expand each year. One aspect that remains largely understudied is the altitudinal range of these species and the extent of differences in thermal behavior between lowland and highland populations. MethodsI collected Ae. aegypti and Ae. albopictus on the islands of Bioko and Sao Tome. I compared the distribution of the two species along an altitudinal cline spanning 2,000 m of elevation. I then used live specimens to test temperature preference for both species in a laboratory thermocline. ResultsI report the distribution of these two species on the island of Bioko and show that the abundance of immature stages of both species follows a negative exponential decay with altitude. I compare this distribution with that observed on the neighboring island of Sao Tome, also in the Gulf of Guinea. Overall, the distribution patterns of the two species are similar, but models indicate a higher abundance at sea level in Sao Tome than in Bioko. I used specimens from this survey to study temperature preference under controlled conditions. I found no significant differences between species or between sexes; however, I detected an altitudinal cline in temperature preference, with high-elevation populations preferring cooler temperatures on both islands. ConclusionsThese results indicate the presence of phenotypic variation in a key trait--temperature choice--that may alter the likelihood of contact between these vectors and humans.