Larval mosquito communities in discarded vehicle tires in a forested and unforested site: detritus type, amount, and water nutrient differences

Abstract

Discarded tires are an important habitat for larvae of multiple species of disease-transmitting mosquitoes. Although tire locations likely influence composition and abundance of vectors, there are few data linking vector populations to the characteristics of the aquatic tire environment. We sampled water-filled tires at three times at a forested and an unforested site to evaluate how differences in detritus inputs or nutrients in these two macrohabitats may be associated with composition of mosquito-dominated invertebrate communities. The forested site had significantly greater inputs of leaves, twigs, seeds, and fine detritus at the first sampling, but subsequent sampling indicated no differences in inputs of any detritus type. Total phosphorous levels were significantly greater in the forested site, but there was no difference in total nitrogen or total ion concentrations during any sampling. Chlorophyll a levels were not different between sites, even though light levels were greater and canopy cover was less at the unforested site. Culex restuans dominated at the unforested site, and Ochlerotatus triseriatus, Anopheles barberi, and Orthopodomyia signifera were found primarily in the forest. Tires at the forested site had significantly more species but not more individuals than at the unforested site. Leaf amount was a good predictor of densities of Oc. triseriatus and overall abundance of mosquitoes in the forest, whereas the amount of seeds was a good predictor of overall invertebrate richness and of Oc. triseriatus numbers in the unforested site. Differences in mosquito assemblage composition between forested and unforested locations may be explained by greater inputs of plant-based detritus and some nutrients, but other factors, such as macrohabitat or host preferences of adult mosquitoes, also may be important.

Figure 1

Mean abundance (± 1 SE) per tire of invertebrate species collected across dates at a forested and unforested site. Bars represent the mean of 6–10 tires at each site per sampling date. Species associated with principal component (PC) axes which were important in explaining differences in invertebrate communities (Table 3) between sites are presented along the x-axis. Species abbreviations are: Cx. restuans (Cxrest), Oc. triseriatus (Octris), An. barberi (Anbarb), Culicoides sp. (Culic), Or. signifera (Orsig), Ostracoda (Ostra), Telmatoscopus sp. (Telma), Chironomidae sp. A (ChirA), Chironomidae sp. B (ChirB), Mallota posticata (Mallot), and Helodes sp. (Helod).