Anthropogenic environmental changes, such as deforestation, agriculture, and introduced exotic species, have often coincided with an increase in mortality and morbidity from mosquito-borne diseases worldwide. Deforestation and agricultural development are likely to regulate immature mosquito populations through the addition of nutrients from livestock waste, decreased shade resulting in increased insolation (solar radiation), and the proliferation of artificial container habitats. We conducted a field experiment in Waikanae, New Zealand, to tease apart the relative effects of shade and nutrient levels on aquatic immature populations of two generalist mosquito species. Container habitats were subjected to five levels of detrital input (0–500-g sheep manure/liter of water) and three shade treatments (open, artificial shade, and forest canopy) in a factorial design. The native species Culex pervigilans constituted 98.9% of all late-instar larvae; the remainder being the exotic Ochlerotatus notoscriptus. We observed higher overall immature mosquito abundance and pupal productivity in open containers with medium detrital loads (5 g/L). Exotic mosquito abundance was low in all treatments and was excluded from containers in unshaded, or deforested, areas. No native or exotic mosquito abundance was observed in containers with extremely high detrital loads (500 g/L). As many exotic species thrive in similar high nutrient conditions, these containers and other larval habitats of similarly high nutrient levels represent potentially vacant niches for exotic mosquito invasion. These results indicate the importance of shade and nutrient level as central determinants of mosquito productivity in temperate climates, such as New Zealand, as well as show that anthropogenic environmental change can have flow-on effects on the ecology of disease-vector mosquitoes.
|Publication status||Published - 2004|