Association between habitat size, brushtail possum density, and the mosquito fauna of native forests in the Auckland region, New Zealand.

Human activities have been causing dramatic and unprecedented changes to the Earth's ecosystems, and are a primary factor associated with biological invasions. Disturbed and fragmented habitats allow some vector mosquitoes to thrive. The New Zealand landscape has been extensively modified since the arrival of humans, and there is accumulating evidence that the distribution of mosquitoes is being altered as a result of anthropogenic environmental changes. This study aimed to assess whether forest habitat size affected the community composition of mosquitoes, and whether the density of the introduced brushtail possum would benefit exotic mosquito species that feed primarily on mammal hosts. Extensive sampling of the mosquito community was carried out using dry ice-baited light traps, oviposition traps, and larval surveys. The results provided the first experimental evidence in New Zealand that changes in forest habitat size affect the indigenous and introduced mosquito fauna differently. The proportion of native species making up the mosquito community appears to be steadily reduced as native forest habitats become smaller. In contrast, the opposite pattern appears to occur for the introduced vector Aedes notoscriptus. Although there was a trend indicating that possums may have a negative impact on a native species (Culex pervigilans), the impact of these animals on the mosquito fauna remains unclear. The evidence suggests that the conservation of large pristine forest ecosystems in New Zealand could have human health implications.