POPULATION AND COMMUNITY ECOLOGY Evidence for Reduction of Native Mosquitoes With Increased Expansion of Invasive Ochlerotatus japonicus japonicus (Diptera: Culicidae) in the Northeastern United States

Ochlerotatus japonicus japonicus (Theobald) is an invasive mosquito native to Japan, Korea, and easternChina. The species was Þrst detected in the northeasternUnited States in 1998 and has rapidly spread throughout much of eastern North America. In addition to used tire casings, Oc. j. japonicus develops in a wide variety of artiÞcial and natural container habitats, especially rock pools along stream beds. In an effort to evaluate the invasion success and impact of Oc. j. japonicus on populations of native containerdwelling species,waste tiredisposal sites andnatural rockpool habitats were sampled for mosquito larvae throughout Connecticut in 2005, and data were compared with results from prior surveys made in 1987 and 1999. Oc. j. japonicus was the predominant species collected at the waste tire disposal sites regardless of surrounding landscape features, accounting for 55.9% of all larvae. A comparison with collections from prior surveys revealed a 90% reduction in the relative abundanceof larval populationsofOc. triseriatus(Say)and signiÞcant reductions among larval populations of Oc. atropalpus (Coquillett) and Culex restuans Theobald. Oc. j. japonicus was also the most abundant mosquito collected in rock pool habitats, accounting for nearly 80% of all collected larvae, except where water temperatures exceeded 30 C. This was concomitant with signiÞcant declines in the relative abundance ofOc. atropalpus andCx. restuans.We conclude thatOc. j. japonicus is a potentially effective competitor in rock pool and tire environments and may be responsible for reducing populations of several native species occupying these habitats through interspeciÞc competition for limited resources. The exclusion ofOc. j. japonicus fromwarmwater pools further suggests that a temperature barrier may exist for Oc. j. japonicus and that populations may not be able to colonize southern regions of the United States with relatively high summer temperatures.