Tropical Mosquito Assemblages Demonstrate ‘Textbook’ Annual Cycles

• Published in: PloS one 2009-12, Vol.4 (12), p.e8296-e8296
• Main Authors: Franklin, Donald C, Whelan, Peter I
• Format: Article
• Language: English
• Subjects: 21st century; Abundance; Animals; Annual cycles; annual rhythms; Aquatic insects; Aquatic organisms; Australia; Biodiversity; Carbon dioxide; Community ecology; Creeks & streams; Culicidae; Culicidae - physiology; Data collection; Datasets; Ecology/Community Ecology and Biodiversity; Ecology/Marine and Freshwater Ecology; Ecology/Population Ecology; Estuaries; insect ecology; monsoon season; Monsoons; Mosquitoes; Multivariate analysis; Ordination; Periodicity; population density; Population Dynamics; population ecology; Rain; Rainfall; Rainfall forecasting; Rainfall frequency; Rainy season; Rhythm; seasonal variation; Seasonal variations; Seasons; Species diversity; Species richness; Suction; Textbooks; Tropical Climate; Tropical environments; tropics; wet season; Wind
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0008296

Background: Annual biological rhythms are often depicted as predictably cyclic, but quantitative evaluations are few and rarely both cyclic and constant among years. In the monsoon tropics, the intense seasonality of rainfall frequently drives fluctuations in the populations of short-lived aquatic organisms. However, it is unclear how predictably assemblage composition will fluctuate because the intensity, onset and cessation of the wet season varies greatly among years. Methodology/Principal Findings: Adult mosquitoes were sampled using EVS suction traps baited with carbon dioxide around swamplands adjacent to the city of Darwin in northern Australia. Eleven sites were sampled weekly for five years, and one site weekly for 24 years, the sample of c. 1.4 million mosquitoes yielding 63 species. Mosquito abundance, species richness and diversity fluctuated seasonally, species richness being highly predictable. Ordination of assemblage composition demonstrated striking annual cycles that varied little from year to year. The mosquito assemblage was temporally structured by a succession of species peaks in abundance. Conclusion/Significance: Ordination provided strong visual representation of annual rhythms in assemblage composition and the means to evaluate variability among years. Because most mosquitoes breed in shallow freshwater which fluctuates with rainfall, we did not anticipate such repeatability; we conclude that mosquito assemblage composition appears adapted to predictable elements of the rainfall.