Heritability and adaptive phenotypic plasticity of adult body size in the mosquito Aedes aegypti with implications for dengue vector competence.

Adaptive phenotypic plasticity is particularly important to organisms with developmental cycles that undergo ontogenetic niche shifts that differentially subject individual life stages to heterogeneous and often stressful environmental conditions. The yellow fever and dengue fever vector mosquito, Aedes aegypti, typically breeds in small water-filled containers that expose the developing aquatic larvae to competition for resources with conspecifics and high probabilities for habitat drying. Here we investigated the heritability (h(2)) and phenotypic plasticity among A. aegypti laboratory populations and field populations from Trinidad, West Indies. Heritability for body size was moderate or completely eroded among the laboratory populations, while field populations contained high genetic variation among both males and females. Norms of reactions based on optimum vs. deficient larval conditions for artificial sibling families representing Trinidad field populations suggested significant gene × environment interactions influence body size and that there may be sex specific differences in allocation of resources. Individuals reared under optimum laboratory conditions were significantly larger and showed much less variability in body size plasticity than their field reared cohorts, suggesting that exposure to environmental stress may be common for A. aegypti larval development and would undoubtedly impact other traits, including arbovirus vector competence among adult females, in a similar fashion. Broad genetic variance in body size and other characters is likely maintained by balancing selection. Our results also suggest the need for caution in translating conclusions from experiments with laboratory colonies to natural populations. These would likely be more informative to expected phenotypes under natural conditions if conducted over a range of conditions that simulate environmental stress.