Environmental and Regional Determinants of Anopheles (Diptera: Culicidae) Larval Distribution in Belize, Central America

摘要

Surveys of Anopheles larval habitats in northern Belize were carried out during September 1990 and April 1991. At each site, larvae were collected and the physical and chemical characteristics of water and species composition of aquatic vegetation were measured or estimated. Data on presence or absence of four species, Anopheles albimanus Wiedemann, A. crucians Wiedemann, A. pseudopunctipennis Theobald, and A. argyritarsis Robineau-Desvoidy, were used for analysis of associations with environmental factors, habitat types, and regions. Using significantly contributing environmental variables, discriminant functions (DF) were constructed for the Anopheles species, except for A. argyritarsis whose distribution could be predicted solely by altitude. The stability of DFs was checked by cross-validation runs. The DF for A. pseudopunctipennis was 93% accurate in predicting positive habitats. Predictions based on DFs for A. albimanus and A. crucians. were 74 and 80% accurate, respectively. Of the four Anopheles species present in the study area, A. albimanus was the most common. Together with A. crucians, it occurred mostly on the coastal plain, and both species were present in both wet and dry seasons. Anopheles albimanus was positively associated with cyanobacterial mats and submersed-periphyton habitat types and negatively associated with the filamentous algae habitat type. A. crucians was positively associated with Eleocharis-periphyton habitat type. A. pseudopunctipennis and A. argyritarsis were common only during the dry season and their distribution was limited to the Karst and Mountain Pine Ridge regions. Both species were positively associated with the filamentous algae habitat type, and A. argyritarsis was also positively associated with the rock pools habitat type. Physical factors (e.g., water depth, water temperature, and oxygen content) were usually marginally correlated with larval occurrence.