Nicholas C. Manoukis, Jeffrey R. Powell, Mahamoudou B. Touré, Adama Sacko, Frances E. Edillo, Mamadou B. Coulibaly, Sekou F. Traoré, Charles E. Taylor, Nora J. Besansky
The role of chromosomal inversions in speciation has long been of interest to evolutionists. Recent quantitative modeling has stimulated reconsideration of previous conceptual models for chromosomal speciation. Anopheles gambiae, the most important vector of human malaria, carries abundant chromosomal inversion polymorphism nonrandomly associated with ecotypes that mate assortatively. Here, we consider the potential role of paracentric inversions in promoting speciation in A. gambiae via "ecotypification," a term that refers to differentiation arising from local adaptation. In particular, we focus on the Bamako form, an ecotype characterized by low inversion polymorphism and fixation of an inversion, 2Rj, that is very rare or absent in all other forms of A. gambiae. The Bamako form has a restricted distribution by the upper Niger River and its tributaries that is associated with a distinctive type of larval habitat, laterite rock pools, hypothesized to be its optimal breeding site. We first present computer simulations to investigate whether the population dynamics of A. gambiae are consistent with chromosomal speciation by ecotypification. The models are parameterized using field observations on the various forms of A. gambiae that exist in Mali, West Africa. We then report on the distribution of larvae of this species collected from rock pools and more characteristic breeding sites nearby. Both the simulations and field observations support the thesis that speciation by ecotypification is occurring, or has occurred, prompting consideration of Bamako as an independent species. © 2008 by The National Academy of Sciences of the USA.
Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA 90095, United States; Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06520, United States; Malaria Research and Training Center, University of Bamako, Bamako, Mali; Department of Biology, University of San Carlos, Cebu City, 6000, Philippines; Center for Global Health and Infectious Diseases, Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, United States; Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, United States
