Spatio-temporal distribution of container breeding mosquito species across a socioeconomic gradient in Baltimore, MD
Ecological theory and empirical data indicate that with one limiting factor in a constant environment, interspecific competition should result in competitive exclusion. However, many competitors appear to escape local extinction and coexist. In urban environments, a variety of mosquito species utilize water-holding containers during their developmental stages (eggs and larvae). Despite their competitive disadvantage, competitively inferior species often co-occur with superior competitors across city landscapes. Understanding the mechanisms behind species coexistence can provide insight into processes governing species distributions and guide public health management efforts. Several medically important species of mosquitoes coexist across neighborhoods that vary in socio-economic status in southwest Baltimore, Maryland. These include the ecologically similar resident species Culex pipiens and Culex restuans, and the competitively superior invasive Aedes albopictus, all of which are competent West Nile virus vectors. We tested predictions of temporal and spatial habitat segregation that foster coexistence of these species. Standard oviposition cups were deployed every three weeks in four socio-economically disparate but adjoining neighborhoods in Baltimore City during the mosquito developmental season (May – November) in 2014.
A total of 61,534 mosquito larvae were collected during the study. Aedes albopictus, C. restuans, and C. pipiens constituted 80.4%, 10.9%, and 7.9% of total larvae, respectively. Of the 627 ovicups deployed, 19.9% showed the coexistence of two or more species. Aedes albopictus and C. pipiens abundances peaked in late summer, whereas C. restuans abundances were highest during early summer. The highest abundances of both A. albopictus and C. restuans were found in the same neighborhood (Union Square) whereas the highest C. pipiens abundances were found in a different neighborhood (Franklin Square). Aedes albopictus abundances in the highest socioeconomic neighborhood (Bolton Hill) were on average approximately half that of the other three neighborhoods, while C. pipiens abundances varied little among neighborhoods. C. restuans abundances in the two higher socioeconomic neighborhoods were approximately twice that of the two lower income neighborhoods. These results suggest that both spatial and temporal habitat segregation may foster coexistence of Culex spp. with A. albopictus in southwest Baltimore, but the specific type varies between species, even though they are ecologically quite similar. These results also suggest that socioeconomic status may affect A. albopictus abundances, presumably through changes in larval habitat types.