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A tale of two mosquitoes. The effect of leaf type on competitive interaction of mosquitoes.
Gunawardene, Eshani*,1, Juliano, Steven1, 1 Illinois State University, Normal, IL, USA
ABSTRACT- Previous experiments have investigated competition between Aedes aegypti and the recently introduced Aedes albopictus. Often, when leaves are used as a substrate for the microorganisms on which these Aedes feed, A. albopictus seems to be the better competitor. Although several single species studies have investigated the effects of leaf type on population performance of each species, there have been no experiments investigating whether different leaf substrates can alter the outcome of competition between A. aegypti and A. albopictus. We conducted such an experiment. Different leaf types (scotch pine needles, live oak leaves, foxtail grass clippings) were placed into water-filled containers with different combinations of A. aegypti+A. albopictus: 10+0; 20+0; 10+10; 20+20; 0+20; 0+10. For each species in each container, we recorded median development time and mean dry mass of males and females, and survivorship to adulthood. We incorporated these fitness components into the ' index, which is commonly used as an estimate of finite rate of increase in such cohort studies. There was no effect of treatment or leaf substrate on survivorship. Development time for females was significantly affected by the treatment-leaf interaction, with treatments producing significant differences for oak and pine, but not for grass. Body mass of females of A. aegypti was significantly affected by treatments, but body mass of females of A. albopictus was not, suggesting competitive asymmetry, with A. albopictus the superior competitor. Thus, analysis of these fitness components individually results in heterogeneous conclusions about whether leaf type alters competitive interactions. Analysis of the synthetic variable ' resolves this heterogeneity, and suggests that leaf type does affect the outcome of competition. In order to understand the interaction of these competitors, we must have further studies of how the interaction varies with important environmental variables.
Key words: interspecific competition, aquatic insect, Aedes aegypti, Aedes albopictus