Effects of elevated CO2 and shade on the decomposition of senesced tree foliage: impacts on the growth and survival of treehole mosquitoes

We tested the hypothesis that growth, survival, and reproductive capacity of treehole mosquitoes can be affected by alterations of forest sunlight and CO2 levels. Larval Aedes triseriatus were fed naturally senesced , abscised foliage from red oak (Quercus rubra) and paper birch (Betula papyrifera) seedlings grown in ambient and elevated CO2 atmospheres. Oak seedlings were grown in full sunlight. Birch were grown in full sun and partial shade. Females fed birch leaves grown in elevated CO2 were larger than those fed birch grown in ambient CO2. However, fewer females emerged from microcosms containing birch foliage grown in elevated CO2, which significantly lowered estimates of microcosm total egg production. Elevated CO2 did not affect the performance of mosquitoes reared on leaves of either species grown in full sunlight. Shading birch foliage led to the production of more mosquitoes of both sexes. Males fed shaded foliage were larger and survivorship was higher for males and females, which led to a significantly higher estimate of microcosm egg potential. Birch diets produced larger females and a larger quantity of smaller males than did diets of oak. Mosquitoes of both sexes took significantly longer to develop on birch. Our results indicate that A. triseriatus larvae are more sensitive to forest light intensity and tree species composition than they would be to a doubling of atmospheric CO2 elevation.