Influence of resource levels, organic compounds and laboratory colonization on interspecific competition between the Asian tiger mosquito Aedes albopictus (Stegomyia albopicta) and the southern house mosquito Culex quinquefasciatus.

The mosquitoes Aedes albopictus (Stegomyia albopicta) (Skuse) and Culex quinquefasciatus (Say) (Diptera: Culicidae) are common inhabitants of tyres and other artificial containers, which constitute important peridomestic mosquito breeding habitats. We tested the hypotheses that interspecific resource competition between the larvae of these species is asymmetrical, that the concentration of chemicals associated with decomposing detritus affects the competitive outcomes of these species, and that wild and colonized strains of Cx. quinquefasciatus are affected differently by competition with Ae. albopictus. We conducted two laboratory competition experiments wherein we measured survivorship and estimated population growth (λ') in both species under multiple mixed-species densities. Under varying resource levels, competition was asymmetrical: Ae. albopictus caused competitive reductions or exclusions of Cx. quinquefasciatus under conditions of limited resources. In a second experiment, which used both wild and colonized strains of Cx. quinquefasciatus, organic chemical compounds associated with decomposing detritus did not affect the competitive outcome. The colonized strain of Cx. quinquefasciatus had greater survivorship and adult mass, and faster development times than the wild strain, but both strains were similarly affected by competition with Ae. albopictus. Competition between these species may have important consequences for vector population dynamics, especially in areas in which tyres and artificial containers constitute the majority of mosquito breeding habitats.

Constitutive differences between natural and artificial container mosquito habitats: vector communities, resources, microorganisms, and habitat parameters.

Aquatic containers, including tree holes and vehicle tires, harbor a diverse assemblage of mosquitoes capable of vectoring important diseases. Many studies have examined containers as a mosquito breeding site, although no data exist that have simultaneously compared mosquito communities between tree holes and tires, and few have quantified differences in environmental factors or food resources that may be important for explaining population or community differences. At two times (early and late summer 2009) we sampled two tire and two tree hole sites in south-central Mississippi, and for each container we enumerated mosquito larvae and measured several environmental parameters (canopy cover, water volume, and detritus), and biomass and productivity of fungi and bacteria, and species richness and abundance of protozoans. Tree holes held less water but were more shaded compared with tires; however, after correcting for volume differences, tree holes contained more detritus and were higher in some microorganism measures (protozoan richness, bacterial productivity in the water column). Based on community dissimilarity analysis of mosquitoes, strong differences existed between container types and sampling period; Aedes albopictus (Skuse) and Culex quinquefasciatus (Say) were dominant in tires, whereas Ae. triseriatus (Say) and Orthopodomyia signifera (Coquillett) were dominant in tree holes. This study also reports the use of tires by the invasive mosquito Cx. coronator (Dyar and Knab). Tree holes supported a higher density of larvae but fewer species than tires, though there was variation across time. Our work illustrates that detrital inputs and some microorganisms differ in fundamental ways between tires and tree holes, and because of compositional differences in mosquito communities, these small aquatic habitats cannot be considered to be homogeneous mosquito habitats.