Do remnants of native vegetation on farmland provide a refuge for native mosquito species or a source to maintain introduced invasives? 

Mary McIntyre *1

1 University of Otago Wellington, 23a Mein St, Wellington, 6242, New Zealand

Land development for farming has created new ecological  scenarios for many nuisance and disease organisms as well as for native diversity.  The Manawatu rural floodplain was formerly extensive swamp and coastal forest, now converted to livestock farming & fodder cropping  with only small fragments of native land cover remaining. This report investigates the occurrence of native and exotic mosquitoes on farmland and in  remnants of native vegetation  in the lower floodplain  area  as a basis to consider future climate and land use scenarios for nuisance and potential disease vector species.  Adult mosquitoes were sampled at 2-week intervals Jan-April  at three farm locations in 2008-10,  and in 2010 also in three remnant forest and three wetland locations.  CO2-baited light traps were set out  late afternoon-dawn, using 12 traps/night on a rotating schedule to a total of 420 trap-nights. Breeding habitats were identified by standardized dipping for larvae in available water bodies.  Data were analysed with regard to species counts, meterological measures and  habitat type.  The size and shape of remnant native areas and degree of native character was also considered.Two introduced species, and a common native species  were present at all locations. Three further native species were found in forest sites.  An expectation that one or both of  two other native species might be found at wetland sites was not supported. Seasonal dynamics and the response of one species to severe drought, as occurred in 2008, and the possible role of native remnants in maintaining populations of native and introduced species are examined.

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