COS 35-1 - Limited variation in thermal tolerance across the range of a widespread mosquito species

Abstract: 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, Aedes sierrensis, 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 and spanned over 1,200 km, we found 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. For one life history trait—pupal development rates—between-population variation in upper thermal limits and optima was substantial and positively associated with the source thermal environment, providing clear, although limited, evidence of local thermal adaptation. Further we found that for all populations, temperatures at their source environment 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) and the largest impact on mosquito fitness. 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.