The potential for adaptive evolution to enable species persistence under a changing climate is one of the most important questions for understanding impacts of future climate change. Climate adaptation may be particularly likely for short-lived ectotherms, including many pest, pathogen, and vector species. For these taxa, estimating climate adaptive potential is critical for accurate predictive modeling and public health preparedness. Here, we demonstrate how a simple theoretical framework used in conservation biology—evolutionary rescue models—can be used to investigate the potential for climate adaptation in these taxa, using mosquito thermal adaptation as a focal case. Synthesizing current evidence, we find that short mosquito generation times, high population growth rates, and strong temperature-imposed selection favor thermal adaptation. However, knowledge gaps about the extent of phenotypic and genotypic variation in thermal tolerance within mosquito populations, the environmental sensitivity of selection, and the role of phenotypic plasticity constrain our ability to make more precise estimates. We describe how common garden and selection experiments can be used to fill these data gaps. Lastly, we investigate the consequences of mosquito climate adaptation on disease transmission using Aedes aegypti-transmitted dengue virus in Northern Brazil as a case study. The approach outlined here can be applied to any disease vector or pest species and type of environmental change.

Accurately predicting and mitigating the effects of climate change on species ranges and interactions is a critical challenge. In particular, mosquito-borne diseases like malaria and dengue are poised to shift with climate change. Understanding this impact hinges on a key open question: How will mosquitoes adapt to climate change? Here we adapt a simple framework widely used in conservation biology—evolutionary rescue models—to investigate the potential for mosquito climate adaptation, and we synthesize current evidence, focusing on adaptation to rising temperatures. Short mosquito generation times, high population growth rates, and strong temperature-imposed selection favor mosquito thermal adaptation. However, knowledge gaps about the extent of phenotypic and genotypic variation in thermal tolerance within mosquito populations, the environmental sensitivity of selection, and the role of phenotypic plasticity constrain our ability to make more precise estimates. Future research efforts should prioritize filling these data gaps. Specifically, we outline how common garden and selection experiments can be used to this end. Collecting and incorporating these data into an evolutionary rescue framework will improve estimates of mosquito adaptive potential and of changes in mosquito-borne disease transmission under climate change, and this approach can be applied more broadly to pests as well as species of conservation concern.

Whether mosquitoes can adapt apace with rapid climate warming will have a large impact on their future distributions, and consequently those of mosquito-borne diseases, but remains unknown for most species. We investigated the adaptive potential of a wide-ranging mosquito species, Aedessierrensis, by conducting a common garden experiment measuring mosquito fitness and its component life history traits. Although field-collected populations originated from vastly different thermal environments that spanned over 1,200 km, we found that populations varied in maximum fitness, but not in the thermal performance of fitness, with upper thermal limits varying by <1°C across the species range. However, for one life history trait – pupal development rate – we found clear evidence of local thermal adaptation. The upper thermal limits of pupal development rate varied between populations by 1.6°C – five times greater than the average variation in ectotherm upper limits across the same latitudinal extent – and was significantly associated with source temperatures. Despite this evidence of local thermal adaptation, we found that for all populations, temperatures in the source environment already frequently exceed their estimated upper thermal limits, suggesting high vulnerability to additional warming. This was particularly true at the adult life stage, which had the lowest upper thermal limits across traits (31.6°C), the largest impact on mosquito fitness, and occurs during the warmest part of the year. Our results suggest that evolutionary adaptation alone may be insufficient to sustain mosquito populations, and that behavioral thermoregulation and temporary coping strategies are likely important for mosquito persistence under ongoing climate warming.

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Climate change will alter interactions between parasites and their hosts. Warming may affect patterns of local adaptation, shifting the environment to favor the parasite or host and thus changing the prevalence of disease. We assessed local adaptation in the facultative ciliate parasite Lambornella clarki, which infects the western tree hole mosquito Aedes sierrensis. We conducted laboratory infection experiments with mosquito larvae and parasites collected from across a climate gradient, pairing sympatric or allopatric populations across three temperatures that were either matched or mismatched to the source environment. L. clarki parasites were locally adapted to their hosts, with 2.6x higher infection rates on sympatric compared to allopatric populations, but were not locally adapted to temperature. Infection peaked at the intermediate temperature of 13C. Our results highlight the importance of host selective pressure on parasites, despite the impact of temperature on infection success.