The research, published in the open-access journal Parasites & Vectors, was conducted by Daniel R. Matute of the Department of Biology at the University of North Carolina at Chapel Hill. Its central question is deceptively simple: do these mosquitoes behave the same way everywhere they live, or do populations that have colonized different thermal environments also differ in the temperatures they seek out? The distinction matters because temperature preference is not a trivial trait. It shapes microhabitat selection, which in turn influences how often a vector encounters the hosts it feeds on, including humans. A mosquito that chooses where to rest, seek blood, and deposit eggs on the basis of temperature is a mosquito whose biting risk is spatially structured by thermal behavior.

Aedes aegypti and Aedes albopictus are among the most intensively studied vectors on the planet, yet the study argues that one dimension of their ecology remains strikingly understudied: their altitudinal range, and the extent to which thermal behavior differs between lowland and highland populations. Both species are continuing to expand their geographic ranges year after year, driven by trade, urbanization, and a changing climate. Aedes aegypti is the primary vector of yellow fever, dengue, Zika, and chikungunya viruses, while Aedes albopictus, the Asian tiger mosquito, is a capable secondary vector of several of the same pathogens. Where these insects can live, and where they choose to live within the landscapes they occupy, directly determines which human communities sit in the path of transmission.

The fieldwork took place on Bioko and São Tomé, two islands that form a natural laboratory for questions of range and adaptation. Bioko, belonging to Equatorial Guinea, sits off the coast of Cameroon near the mouth of the Gulf of Guinea, while São Tomé lies farther southwest as part of the nation of São Tomé and Príncipe. Both are volcanic in origin, rising steeply from the ocean floor and offering compressed environmental gradients in which lowland rainforest transitions to montane habitat over a horizontal distance of only tens of kilometers. On such islands, a researcher can sample a 2000-meter elevation span that on a continental landmass might require journeys of hundreds of kilometers, all while holding insular context, isolation, and broad biogeographic history roughly constant.

The first stage of the study was distributional. Matute collected both Aedes species across the altitudinal cline on Bioko and mapped how the abundance of immature stages, the larvae and pupae found in aquatic containers, changed with elevation. The statistical picture that emerged was consistent: abundance follows a negative exponential decay with altitude. In practical terms, this means that most immature mosquitoes are concentrated near sea level, and populations thin rapidly as elevation increases, with a long tail of sparse occurrences reaching up the mountainsides. This functional form is more punishing than a linear decline; it implies that each additional increment of elevation removes a proportionally large share of the remaining mosquito population, rather than a fixed amount.

Comparison with neighboring São Tomé added an instructive wrinkle. The overall distribution patterns of the two species were similar across the two islands, suggesting that the same altitudinal filtering operates in both places. But the models indicated a higher abundance at sea level on São Tomé than on Bioko. Islands that look superficially similar, sharing volcanic origin, tropical latitude, and the same two invasive mosquito species, apparently differ in how many mosquitoes their coastal zones support. Whether that difference stems from ecology, history of colonization, availability of breeding containers, or other local factors is a question the distribution data raise but do not settle. What the comparison establishes is that the pattern is repeatable in shape while remaining variable in magnitude, a combination that invites hypothesis-driven follow-up work.

The second stage of the study moved from the field to the laboratory, and this is where the results become most provocative. Using live specimens collected during the survey, Matute tested temperature preference in a laboratory thermocline, an apparatus that presents an insect with a continuous gradient of temperatures and records where it settles. With such a device, preference can be measured under controlled conditions, free from the confounds of field sampling, where differences in abundance might reflect survival or reproduction rather than choice. The critical comparison was between mosquitoes whose ancestors came from different elevations, tested side by side under identical conditions.

Two results stand out. First, there were no significant differences in temperature preference between the two species. Aedes aegypti and Aedes albopictus, despite their distinct evolutionary origins and invasion histories, did not differ detectably in the temperatures they chose. Second, and more strikingly, the study detected an altitudinal cline in temperature preference: high-elevation populations preferred cooler temperatures on both islands. In other words, the trait varies with elevation rather than with species identity. This is the signature of phenotypic variation organized along an environmental gradient, the kind of pattern that classic ecological genetics has long used to identify locally adapted traits. Because the preference difference appears on two separate islands, it is unlikely to be a one-off idiosyncrasy of a single population; it looks like a systematic relationship between where mosquitoes live and what temperatures they favor.

The conclusion the author draws from this is carefully framed: the 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. The word “may” carries real weight here. The study measures preference under controlled conditions and abundance along elevation; it does not demonstrate that highland mosquitoes bite people less often, nor that the preference difference is genetically based rather than plastic. Mosquito behavior can be shaped by developmental temperature, and laboratory-reared or field-collected adults may carry the imprint of the conditions in which they matured. Distinguishing heritable adaptation from environmental carryover would require common-garden or breeding experiments that the present study does not include. These are not weaknesses so much as the natural boundaries of a first, foundational survey, and the author’s framing respects them.

Even within those boundaries, the public health implications are worth spelling out. If temperature preference varies clinally with altitude, then models that assume a single, uniform thermal behavior for Aedes aegypti or Aedes albopictus may misestimate where human exposure actually occurs. Elevational gradients are also where climate change is expected to reshuffle vector distributions most visibly: as temperatures rise, thermal conditions once found only at low elevations move upslope, and the upper limits of vector ranges shift with them. A population of mosquitoes already preferring cooler temperatures at altitude could be positioned differently in that reshuffling than models predict. Conversely, the steep exponential decay of abundance suggests that highland communities currently enjoy a substantial buffer, with far fewer immature mosquitoes than coastal settlements on the same island. Whether that buffer will hold, and whether temperature preference itself will evolve or shift as the climate warms, are now empirically tractable questions. What this study provides is the baseline: two disease vectors, two islands, one clear altitudinal pattern of abundance, and a measured behavioral cline in the temperatures these insects choose. For a trait as consequential as thermal preference, establishing that the variation exists is the essential first step toward understanding what it will mean for the human communities living along these mountainsides.

Subject of Research: Altitudinal variation in temperature preference of Aedes aegypti and Aedes albopictus mosquitoes on the Gulf of Guinea islands of Bioko and São Tomé

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

Article References: Matute, D. R. (2026). Two species of Aedes show altitudinal variation in temperature preference in the islands of the Gulf of Guinea. Parasites & Vectors. https://doi.org/10.1186/s13071-026-07662-0

Image Credits: AI Generated

DOI: 10.1186/s13071-026-07662-0

Keywords: Aedes aegypti, Aedes albopictus, temperature preference, altitudinal cline, Bioko, São Tomé, Gulf of Guinea, disease vectors, mosquito ecology, thermocline, vector-borne disease, phenotypic variation