Association Between Habitat Size, Brushtail Possum Density, and the Mosquito Fauna of Native Forests in the Auckland Region, New Zealand

Abstract

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.

Mosquito Communities and Avian Malaria Prevalence in Silvereyes (Zosterops lateralis) Within Forest Edge and Interior Habitats in a New Zealand Regional Park

“…The ecological findings of this study also support data from previous work on mosquitoes in the Auckland region, as A. antipodeus was also the most abundant native species recorded in other tracts of native forest (Derraik et al 2005b;Derraik 2009a). This species breeds in temporary ground pools in areas with partial or dense shade (Belkin 1968), and our results and previous findings (Derraik et al 2005a;Derraik 2009a) suggest that relatively pristine mature forests provide greater availability of suitable larval habitats.…”

“…Our results corroborate previous findings showing that forest fragmentation in the Auckland region favours introduced mosquito species, which were nearly absent from large tracts of native forest (Derraik et al 2005a;Derraik 2009a). Given both C. quinquefasciatus and A. notoscriptus are vectors of human and animal disease (Derraik 2004), this study adds further evidence that anthropogenic environmental change is associated with an increased transmission risk of vector-borne diseases, particularly in the more densely populated Auckland region.…”

“…This species breeds in temporary ground pools in areas with partial or dense shade (Belkin 1968), and our results and previous findings (Derraik et al 2005a;Derraik 2009a) suggest that relatively pristine mature forests provide greater availability of suitable larval habitats.…”

“…This type of trap was chosen for its relatively high capture efficiency across a wide range of mosquito species (Silver 2008), and similar CO 2 -light traps have been successfully used in previous studies on mosquitoes in New Zealand (e.g. Derraik et al 2005a, b;Derraik 2009a). Since most of the mosquito species present in the North Island of New Zealand appear to be crepuscular and/or nocturnal feeders (Derraik et al 2005a), the traps were set approximately 2 h before sunset (*19:00) and emptied approximately 2 h after sunrise (*07:00) for a total of 12 trapping hours per sampling bout.…”

Chikungunya Virus: A Novel and Potentially Serious Threat to New Zealand and the South Pacific Islands

“…20 Furthermore, the species appears to be favored by anthropogenic environmental change and it is therefore likely to continue to spread into previously unoccupied habitats such as human-modified native forests. 24 Aedes notoscriptus mosquitoes are not only highly anthropophilic but also a vector of Alphavirus in Australia, where they are believed to be important vectors of Ross River virus (RRV) in urban areas. 25 A recent laboratory study found Ae.…”