Interspecific Larval Competition Differentially Impacts Adult Survival in Dengue Vectors.

Mosquitoes often experience intraspecific and interspecific competition among larvae attributable to high densities and nutrient limitation, especially container mosquitoes including Aedes aegypti (L.) and Aedes albopictus (Skuse). Density-dependent effects on larvae impact adult production and adult traits that influence transmission of arboviruses. To improve our understanding of the mechanisms by which density-dependence influences transmission and identify species-specific traits, we tested the hypotheses: 1) Competitive asymmetry in favor of Ae. albopictus over Ae. aegypti translates to altered adult female survival, and 2) Ae. aegypti adult females are more resistant to life-shortening effects of low-humidity conditions than Ae. albopictus. We gauged the relative impact of inter- and intraspecific larval competition on adult survival in high- and low-humidity regimes (77 and 44% relative humidity, respectively). For Ae. albopictus, intraspecific but not interspecific competition usually reduced adult survival under both humidity regimes. For Ae. aegypti, both intraspecific and interspecific competition reduced adult survival. Ae. albopictus adult survival was minimally influenced by interspecific competition with Ae. aegypti, consistent with observations that Ae. albopictus is the superior competitor. A species comparison indicated that Ae. aegypti exhibited a survival advantage relative to Ae. albopictus under both low- and high-humidity conditions. However, similar survival of these Aedes species was observed in some cases depending on conditions experienced in both the aquatic and terrestrial environments. These results demonstrate plasticity in survival rates of dengue and chikungunya vectors and the significance of considering the influence of biological interactions during the immature stages and abiotic conditions during the adult stage.