Warming Alters Mosquito Morphology, Not Transmission Risk Uniformly

A systematic review of 24 sources finds that warmer developmental conditions generally produce smaller adult body or wing dimensions in mosquitoes, but the effect varies substantially among species, populations and nutritional environments. The analysis, published in Frontiers in Veterinary Science, includes 12 primary empirical studies and 12 contextual or methodological sources. Its central conclusion is that climate-associated morphological change is biologically plausible, yet the resulting impact on pathogen transmission cannot be reduced to a single prediction: biting frequency, vector competence, survival, pathogen development and local ecology can move in different directions. The review therefore treats morphology as one component of vectorial capacity rather than as a stand-alone indicator of disease risk.

The authors searched PubMed/MEDLINE, Embase, the Web of Science Core Collection and CAB Direct for English-language studies published from 2000 through the search dates in July 2026. The search produced 95 records. Removal of 34 duplicates left 61 unique records for title and abstract screening, of which 37 proceeded to full-text assessment. Thirteen full texts were excluded, including eight non-peer-reviewed, preprint or conference records and five whose authorship or publication provenance could not be independently verified. The final synthesis comprised 24 sources. Searches were designed around a Population, Exposure, Comparator, Outcome framework covering mosquitoes of public-health importance, elevated or experimentally varied developmental temperatures, lower or control temperatures, and outcomes that included morphology, life history, vector competence, adaptation, distribution and transmission.

Across the primary evidence, the clearest pattern was a reduction in adult body or wing size under warmer developmental conditions. In a laboratory study of Aedes aegypti from central India, mosquitoes reared at 32 °C had wing centroid sizes approximately 18% lower in females and 15% lower in males than those reared at 20 °C, with the comparison reported as statistically significant. Experiments involving Nyssorhynchus darlingi across four Brazilian biomes found that mosquitoes raised at 28 °C were approximately 11–17% smaller than those raised at 20 °C, with the magnitude varying by population. These observations are consistent with a temperature-size pattern in ectotherms, whose development and physiology are temperature-dependent, but the review emphasizes that a common response does not imply identical performance in every population.

Geographic and biological differences complicate that general pattern. Populations of N. darlingi from different Brazilian biomes differed in their developmental responses to warming, suggesting that population-specific genetic backgrounds and thermal histories can modify morphological plasticity. In A. aegypti, one population from a humid subtropical region in central India produced smaller wings at higher temperatures, but its authors cautioned against extending the result to populations in arid or coastal parts of India. A geometric-morphometric study of Aedes albopictus in Thailand also showed contrasting curves: a laboratory strain declined in wing area as temperature rose, whereas a field-derived strain reached its largest wings at an intermediate temperature. Such findings mean that models applying one universal thermal-performance curve could misrepresent morphology and population performance in locally adapted areas.

Temperature does not act independently of larval resources. Experimental work across Aedes species found that the thermal response of adult morphology and population fitness depended on resource availability, with estimates differing by approximately 12–20% under resource limitation. Controlled laboratory studies often standardize diet to isolate the effect of temperature, whereas mosquitoes in nature encounter nutritional stress that may vary with habitat, water availability and interactions with other organisms. The review consequently treats nutritional condition as a source of uncertainty rather than a minor background factor. A thermal exposure associated with a particular wing or body phenotype in the laboratory may not produce the same phenotype where larvae develop under fluctuating food supplies.

Most of the observed size response is consistent with developmental or phenotypic plasticity, in which the same genotype produces different phenotypes under different environmental conditions. A plastic response can occur within one generation and may be reversible; it does not by itself demonstrate evolutionary adaptation. The review found separate evidence that heritable adaptation can also occur. Common-garden experiments in A. aegypti showed population-specific thermal performance that persisted under shared conditions, with divergence of roughly 9–14% in selected comparisons. Genomic observations in Panamanian field populations also found differentiation associated with local climatic conditions, about 6–10% in key contrasts. These studies support adaptive potential, but the relative contributions of plasticity and inherited adaptation have not been quantified together across successive generations.

Morphological change affects several separate components of vectorial capacity, and the components do not necessarily point in the same direction. Smaller mosquitoes may have reduced energy reserves and compensate by feeding more frequently, increasing host contact per unit time. Conversely, larger mosquitoes have shown greater competence, susceptibility or dissemination in some experiments. One study of A. aegypti and A. albopictus found approximately 1.7-fold higher odds of dengue dissemination in the larger size class, while the review also cites evidence that moderate warming can shorten the gonotrophic cycle, potentially allowing more frequent blood-feeding. These observations are not contradictory: feeding frequency affects how often a mosquito encounters hosts, whereas competence describes the probability that an infectious bite leads to pathogen acquisition or transmission. Body size alone therefore cannot establish whether transmission will rise or fall.

Adult survival and the extrinsic incubation period further complicate the relationship between temperature and transmission. The extrinsic incubation period is the time between a mosquito taking an infectious blood meal and becoming able to transmit the pathogen. Both this interval and daily survival respond non-linearly to temperature, creating a trade-off: conditions that accelerate pathogen development may also shorten the mosquito’s life. Mechanistic models summarized in the review found transmission maximized within limited thermal ranges for dengue, Zika and chikungunya, rather than increasing continuously with warmth. In the central Indian A. aegypti experiments, survival and fecundity peaked near 26 °C, whereas smaller wings were evident at 32 °C. The temperature that produces the most favorable development, survival and transmission may therefore differ from the temperature associated with a particular body form.

Geographic expansion adds another layer. Models included in the review indicate poleward and altitudinal movement in the ranges of A. aegypti and A. albopictus, with potential expansion into Europe and North America by mid-century under the scenarios considered. A synthesis of malaria-vector records from 1898 to 2016 reported an average altitudinal increase of 6.5 metres per year and a poleward shift of 4.7 kilometres per year. These are model and historical-synthesis findings, not direct evidence that changing mosquito body size has caused range shifts. The review instead identifies an unresolved interaction: new thermal environments may alter the morphology of invading mosquitoes, but it remains untested whether morphological plasticity facilitates expansion or merely follows it. Direct longitudinal work combining morphometrics, population genetics and field dispersal measurements is needed to distinguish those possibilities.

The review’s main limitation is that most primary evidence comes from controlled laboratory experiments, often under constant temperatures, with mosquitoes derived from a small number of founders and maintained without predators, interspecific competition or the full variability of larval habitats. Such experiments offer strong internal control but limited external validity. Four of the 12 primary studies were assessed as having low overall risk of bias, while eight had some concerns, most often because outcome assessors could not be blinded to exposure. No study was classified as having high overall risk of bias, yet the findings reduce confidence in exact effect sizes and in extrapolation to field populations. Direct evidence is also concentrated in A. aegypti and, to a lesser extent, N. darlingi, with comparatively little information on major African malaria vectors and Culex species involved in West Nile virus transmission. Few studies measured morphology, biting activity, vector competence and pathogen incubation together across the same temperature gradient, leaving the net effect on transmission uncertain.

The findings support adding wing geometric morphometrics to mosquito surveillance as a supplementary measure, provided it is validated locally, rather than using it as a universal proxy for transmission risk. For future research, the review identifies a need for multi-generational selection experiments, field studies under fluctuating temperatures and variable nutrition, and models that incorporate morphology alongside development, survival and biting behavior. The central result is therefore more qualified than a simple climate-to-disease warning: warming usually shrinks mosquitoes, but how that change translates into biting, pathogen competence, survival and transmission depends on the species, population, environment and temperature regime. Climate-associated morphology is best understood as one measurable part of a larger, nonlinear system, not as a stand-alone forecast of mosquito-borne disease.

Subject of Research: Systematic review of climate-associated mosquito morphology and its implications for vector competence, distribution and disease transmission

Article Title: Climate-driven morphological change in mosquito vectors: implications for vector competence, distribution and disease transmission—a systematic review

Article References: Ekeleme, U. G., Dozie, U. W., Omire, J. C., Nnadozie, E. C., Chinemerem, O. M., Iwuala, C. C., Chikaodi, N. O., Okereke, C. C. A., & Chukwuocha, U. M. (2026). Climate-driven morphological change in mosquito vectors: implications for vector competence, distribution and disease transmission—a systematic review. Frontiers in Veterinary Science, 13, Article 1956293. https://doi.org/10.3389/fvets.2026.1956293

Image Credits: AI Generated

DOI: 10.3389/fvets.2026.1956293

Keywords: climate change, mosquito morphology, vector competence, vectorial capacity, wing morphometrics, phenotypic plasticity, thermal adaptation, disease transmission, mosquito surveillance, Climate-driven, morphological, change