POPULATION AND COMMUNITY ECOLOGY The Effects of Resource Type and Ratio on Competition With Aedes albopictus and Culex pipiens (Diptera: Culicidae) K. S. COSTANZO, 1,2 E. J. MUTURI, 1 R. L. LAMPMAN, 1 AND B. W. ALTO 1,3 J. Med. Entomol. 48(1): 29Ð38 (2011); DOI: 10.1603/ME10085 ABSTRACT The introduction of Aedes albopictus (Skuse) in the United States has been associated with declines in abundance of resident mosquito species, presumably because of resource competition, as larvae of Ae. albopictus have been illustrated as superior competitors under certain resource conditions. We evaluated the hypothesis that varying the type and ratio of two food resources (Foxtail grass: American elm) alters the competitive outcome of Ae. albopictus and Culex pipiens (L.). We measured survivorship, development time, size, and adult longevity, and estimated the population growth index (') of populations raised both alone and in equal number with the interspeciÞc competitor, across Þve ratios of the two food resources. Competition was asymmetric with Ae. albopictus, the superior competitor across all resource treatments; however, the competitive advantage Ae. albopictus had over Cx. pipiens was reduced as grass became the predominant resource. With elm as the predominant resource, the population growth index (') for both Ae. albopictus and Cx. pipiens was lower in intraspeciÞc and interspeciÞc competition treatments, respectively. The treatments also impacted adult life history, as life spans of both Ae. albopictus and Cx. pipiens varied when they emerged from larval conditions with different resource and competition treatments. We discuss the possible differences in the two speciesÕ efÞciencies in exploiting the two resource types. Despite some resource conditions alleviating the competitive effects of Ae. albopictus on Cx. pipiens, competition remained asymmetric; thus, additional mechanisms are likely operating under Þeld conditions when the two species coexist. KEY WORDS Aedes albopictus, competition, Culex pipiens, detritus, resource ratios Invasive species provide a unique opportunity to in- vestigate the ecological processes that shape their es- tablishment and distribution among the communities they invade (Elton 1958, Williamson 1996, Shigesada and Kawasaki 1997). If the dynamics of an invasive species are observed from its early introduction, they can offer insight into various mechanisms that either promote or impede the success of an invader. The relative importance of biotic and abiotic variables on the interaction of introduced and native species is typically evaluated under controlled Þeld and labora- tory studies to develop predictive models of how an invader may exclude, coexist, or be suppressed by resident species in the communities it invades. The invasive mosquito, Aedes albopictus (Skuse), the Asian Tiger mosquito, has been extensively stud- ied, particularly its interactions with resident mosqui- toes in the United States (Lounibos 2002, Juliano and Lounibos 2005, Benedict et al. 2007, Alto et al. 2009). This particular species has been of high interest be- cause its invasion is both ecologically and medically important (Lounibos 2002, Juliano and Lounibos 2005). The introduction and dispersal of Ae. albopictus could have epidemiological implications for the trans- mission of numerous human and zoonotic arboviruses. Additionally, this species has offered itself as a model system for invasion biology as the introduction of Ae. albopictus has been associated with declines in abun- dance of the resident mosquito, Aedes aegypti (L.), most likely because of competitive displacement (re- viewed by Juliano and Lounibos 2005, Juliano 2009). Although many studies indicate Ae. albopictus as a superior competitor to other mosquito species, in some cases competition between Ae. albopictus and resident mosquitoes is condition speciÞc, in which abiotic and biotic factors may alter or reverse the competitive outcome and foster coexistence (Daugh- erty et al. 2000, Juliano et al. 2002, Costanzo et al. 2005a, Bevins 2007, Yee et al. 2007, Murrell and Juliano 2008). The larval stages of Ae. albopictus reside in natural and artiÞcial container habitats such as tree- holes and tires, and feed by Þltering or browsing the microorganisms that grow on nutrients from leaf de- tritus or invertebrate carcasses that fall into these habitats (Merritt et al. 1992). In these container com- munities, the type of resource input (leaf or animal detritus) can affect mosquito growth, population per- 1 University of Illinois, Illinois Natural History Survey, 1816 S. Oak Street, Champaign, IL 61820. 2 Corresponding author, current address: Department of Biology, Canisius College, 2001 Main Street, Buffalo, NY 14208 (e-mail: kscosta@gmail.com). 3 Current address: Florida Medical Entomology Laboratory, Uni- versity of Florida, 200 9th St. S. E., Vero Beach, FL 32962. 0022-2585/11/0029Ð0038$04.00/0  2011 Entomological Society of America Downloaded from https://academic.oup.com/jme/article/48/1/29/905107 by guest on 16 July 2022