Leaf detritus of native and invasive plants alters microbial resource diversity in aquatic habitats and performance of container-breeding mosquitoes
The enhancement of animal fitness by resource diversity is a well-documented phenomenon in many ecosystems. In communities fueled by plant-based detritus, a major source of resource diversity is mixing of leaf litter species. These may include leaves of invasive plant species whose potential impacts on the higher trophic levels (i.e. microbial flora and higher order consumers) are understood incompletely. Our laboratory experiments tested three hypotheses regarding the effect of leaf litter inputs from native and invasive shrubs in the aquatic habitat on a container-breeding mosquito, Culex pipiens. We hypothesized 1) leaf detritus of two native and two invasive shrubs yields different mosquito emergence and development rates; 2) mixtures of leaves from subsets of these plants synergistically affect these life history traits; and 3) the mechanism for this effect is variation in the microbial flora that form in container habitats as leaf litter breaks down, the direct food source for larvae.
Among single leaf species, leaf infusion of an invasive bush honeysuckle (Lonicera maackii) yielded the highest adult mosquito emergence rates, while native blackberry infusion (Rubus allegheniensis) yielded no emergence. Mixtures of three or four leaf species yielded higher emergence rates than predicted based on mosquito performance in single leaf species treatments, indicating a synergistic effect of resource diversity on mosquito development. A trial in which microbes were filtered from leaf infusion and replaced with a uniform diet across all leaf mixtures demonstrated no treatment-dependent variation in mosquito performance, suggesting the importance of microbial flora to emergence rates. Finally, our ongoing research seeks to identify microbial community characteristics (e.g. alpha and beta diversity) and indicator species correlated to mosquito performance.