Document: STE-3-71-3

Invasion biology of Asian tiger mosquito, Aedes albopictus: Competitive effects on a resident species at multiple sites in Florida.

JULIANO, S.A.* ¹, L.P.LOUNIBOS ² and G.F.O'MEARA ²

Illinois State University, Normal, IL 61790 USA ¹
University of Florida, Vero Beach, FL USA ²

Abstract:
Introduction and spread of the container dwelling mosquito Aedes albopictus in Florida have been accompanied by declines in resident Aedes aegypti at some sites. Prior experiments show that when larvae compete, A. albopictus is the superior competitor. In this experiment, we test the hypothesis that competition among larvae is important at ambient densities at sites where A. aegypti has gone extinct and at sites where it survives. Vases were placed at 3 cemeteries in south Florida where A. aegypti went extinct after invasion by A. albopictus, and at 3 cemeteries where A. aegypti now coexists with A. albopictus. In June, we counted and removed Aedes larvae and pupae, removed eggs, returned water and detritus, and added hatchling A. aegypti and A. albopictus larvae in three treatments: CONTROL - 15 or 20 larvae of each species, depending on the cemetery; REMOVAL - A. aegypti at the same density as in CONTROL and no A. albopictus; INCREASED - A. aegypti at the same density as in CONTROL and twice that number of A. albopictus. After 10 days, we collected larvae, pupae, and adults, and determined survivorship and mean instar (an index of development rate) of A. aegypti. Mean instar was significantly less for INCREASED (4.580.08) vs. CONTROL (4.900.07), or REMOVAL (5.200.08). CONTROL and REMOVAL also differed significantly. Site type effect (aegypti survives vs. aegypti extinct) and interaction were not significant. Survivorship was significantly lower at sites where A. aegypti has gone extinct (367%) vs. sites where it survives (637%). Despite a significant effect of treatment on survivorship, there were no significant pairwise differences in survivorship among CONTROL (452%), REMOVAL (512%), and INCREASED (532%) treatments. Interaction was not significant. Thus, competition among larvae has detectable effects on development rate at approximately ambient densities. Effects of competition do not differ between sites now with or without A. aegypti (no interaction). However, the site effect on survival suggests that sites where A. aegypti has gone extinct are lower quality sites for A. aegypti, even when A. albopictus is removed.

Keywords: Interspecific competition; Water-filled container communities; Aedes; Mosquitoes; Introduced species

This abstract is being presented at: 10:45 AM in session:
Oral Session #55: Invertebrates in Streams: Foodwebs.