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 g L-1, 2
g L-1). 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.