Assessing the effects of native and alien plant ash on mosquito abundance

Plant invasions have been linked to displacement of native vegetation and altering of fire regimes and might influence vector mosquito populations by altering habitats or nutrient inputs. Whereas wildfire effects on terrestrial ecosystems are relatively well-studied, ash depositions into aquatic ecosystems and effects on semi-aquatic taxa such as mosquitoes have remained overlooked. Here, we investigated mosquito colonization in water treated with ash from native plants [quinine tree (Rauvolfia caffra), Transvaal milk plum (Englerophytum magalismontanum), apple leaf (Philenoptera violacea)] and invasive alien plants [i.e., lantana (Lantana camara), guava (Psidium guajava), red river gum (Eucalyptus camaldulensis)] in containers at two ash concentrations (i.e., 1, 2 g/L). Overall, there was no statistically clear difference in colonization between ash from native and alien species. We recorded colonization by two mosquito genera (Culex spp. and Anopheles spp.), with Culex generally much more abundant than Anopheles. Few differences were identified among the plants, with statistically clear effects of ash type and concentration on larval and pupal stages. High Culex egg and larval abundances were shown in lantana and apple leaf treatments compared to controls, and milkplum versus controls for pupae of both genera. Further research is required to elucidate the influence of nutrient inputs from different ash species on vector mosquito population dynamics.