The coexistence of species that seemingly utilize similar resources has been an intriguing area of inquiry for ecologists. Indeed, mechanisms by which species escape competition was classically highlighted by G.E. Hutchinson in 1961 to explain the 'paradox of the plankton' - the paradox being that numerous species of planktonic algae frequently coexist in simple environments with little apparent scope for niche differentiation. The invasion of North America of the mosquito Aedes albopictus and its interaction with Aedes agyepti provides an ideal opportunity to investigate the coexistence of a species with a superior resource competitor. Both species are also important vectors of a number of human diseases and pose significant public health risks worldwide. The spread of invasive A. albopictus throughout much of southern North America is associated with a decline, often to local extinction, of A. aegypti. Most field and laboratory studies have shown that North American A. albopictus are superior in competition for resources with A. aegypti. Despite an apparent competitive advantage for A. albopictus, A. aegypti remains dominant in some areas in the southern USA.
Geographic variation in competitive effect and
competitive response of Aedes albopictus
Prior studies have yet to evaluate the role of inter-population variation in the competitive ability of A. albopictus, thus the role of geographic variation in the outcome of A. albopictus invasion remains unknown. I compared the competitive ability of 9 populations of A. albopictus from different parts of North America where the population history of invasion and coexistence with A. aegypti is known. Three populations of A. albopictus represented each of three site types: extinction of A. aegypti following A. albopictus invasion, coexistence of both species, and A. albopictus allopatric to A. aegypti. Varying ratios of newly hatched larvae from each A. albopictus population and a single A. aegypti population were added to laboratory microcosms provisioned with plant detritus as a resource to create a response surface design.
Results so far are presented in a poster I recently
presented at the 91st Annual Meeting for The Ecological Society of America
Metapopulation dynamics of A. albopictus and A. aegypti in urban
Tampa, FL
In collaboration with Dr. Steven Juliano, Dr. Sabine S. Loew, and Kavitha Damal, I am examining the role of spatial and temporal mechanisms in fostering the coexistence of A. albopictus with A. aegypti in an urban landscape. My current research incorporates concepts and methods from competition ecology, evolutionary biology, and phylogeography, to examine metapopulation dynamics of Aedes in Tampa, FL. It is primarily funded by a Illinois State University Internal Research Grant.
Geographic variation in the survival and reproduction tactics of A. albopictus
Across latitude
Climate differences across latitude can result in seasonal constraints and selection on life-history characters. Since A. albopictus invaded North America in the mid-1980s, it has spread across a range of »14º latitude and populations in the north experience complete adult mortality due to cold winter temperatures that are absent in the south. Life-table experiments were conducted to test for differences in the survival and reproductive schedules of Ae. albopictus of two populations from the northern (Bloomington, IN (BL) and Manassas, VA (VA); »39°N) and southern (Tampa, FL and Fort Myers, FL; »27-28°N) extremes of the species distribution in North America. Regardless of population origin, age-specific hazard rate increased with reproductive output and decreased with number of bloodmeals. Larger females took fewer bloodmeals and had greater hazard rates than did smaller females. There were no consistent differences between northern vs. southern populations in resource allocation between reproduction and maintenance, reproduction over time, and reproductive investment among offspring, suggesting that latitudinal variation in climate is probably not the main selective factor impinging on adult mortality and reproductive schedules. One possible effect of climate on geographic differences in life-history was detected. BL had lower survivorship, lower lifetime reproductive output, and lower reproductive rate than did all other populations. This result may be an indirect result of lower egg survivorship due to the severity of winter in BL compared to other populations, including VA at approximately the same latitude. Such a scenario may make the BL population more prone to extinction, irregularly recolonized from more favorable sites, and thus more susceptible to founder effect, genetic drift, and inbreeding, resulting in lower mean values of fitness-related traits.
Other studies I am working on include:
Geographic variation in life-history trade-offs between female body size and fecundity of A. albopictus and A. aegypti
Geographic variation in competitive effect and competitive response of A. aegypti