ARTICLE Spatial and Habitat Distribution of Anopheles gambiae and Anopheles arabiensis (Diptera: Culicidae) in Banambani Village, Mali FRANCES E. EDILLO, 1 YEYA T. TOURE ´ , 2 GREGORY C. LANZARO, 3 GUIMOGO DOLO, 2 AND CHARLES E. TAYLOR 1 J. Med. Entomol. 39(1): 70Ð77 (2002) ABSTRACT We studied the larval distribution and composition of Anopheles arabiensis Patton, An. gambiae s.s. Giles, and its forms, among local habitats; and their association with the adults between these habitats in Banambani village, Mali during the mid-rainy seasons of 1997Ð1999. For species and form identiÞcation we used polymerase chain reaction (PCR) and PCR-restriction fragment-length polymorphism(RFLP).Differencesamongspeciesinthedistributionoflarvaewereobservedin1998, but not in 1997 or 1999, although they were on the borderline of statistical signiÞcance. Differences among the M and S molecular forms were statistically signiÞcant in 1999 when rainfall was high, but not in the two prior, drier sampling periods. Combining all information into the Fisher multiple comparisons test, there were statistically signiÞcant differences between species and molecular forms during the 3-yr study period. Hybrid larvae between the M and S forms were observed (0.57%), the Þrst such observation to our knowledge. In spite of differences among larval distribution, no differ- ences of adult species composition were observed among habitats. Factors that inßuence the distri- butions of An. gambiae larval populations are discussed. KEY WORDS Anopheles gambiae, Anopheles arabiensis, Anopheles gambiae s.s.,MoptiandSavannah, habitat differences, hybrid Anopheles gambiae s.s. Giles and An. arabiensis Patton, sibling species in the An. gambiae Giles complex, are found together through much of their home ranges. Macrogeographic trends are marked, with An. ara- biensis tendingtobemorefrequentwhereitishotand dry (Coluzzi et al. 1979; Toure ´ et al. 1998). On a microgeographic scale the trends are less clear. White (1974) reports that in East Africa An. arabiensis tends to be more zoophilic whereas An. gambiae s.s. is an- thropophilic,thoughinMali,WestAfricabothspecies seem to be, for all practical purposes, completely an- thropophilic (Toure ´ 1985, Toure ´ et al. 1986). Further, in mark-release-recapture (MRR) studies conducted over several years at Banambani, Mali, Toure ´ et al. (1998a) found no difference in distribution or dis- persal pattern between adults of the two species. Ac- cordingly, if the species do occupy different niches when sympatric, then we would expect to Þnd differ- ences between them during other parts of the life cycle, possibly the larval stages. In early investigations of this possibility, Service (1970) and White and Rosen (1973) searched for, but were unable to discern, any microgeographic differ- ence in larval distributions at study sites in Kenya and in Nigeria. Because larvae are morphologically indis- tinguishable, the accuracy of these studies was nec- essarily limited (Gillies and De Meillon 1968, Gillies and Coetzee 1987). Since that time, much better methods for discriminating the larvae have been de- veloped, most notably a PCR-based diagnostic test published by Scott et al. (1993). Using this probe, Charlwood and Edoh (1996) observed microgeo- graphic differences in the distribution of larvae around the town of Ifakara, Tanzania. The differences appeared to be linked to location rather than types of breeding substrate. In that region An. arabiensis was much more zoophilic than was An. gambiae s.s., and larvae of An. arabiensis were relatively more common inpoolsclosetocattle.Theyattributedthedifferences in distribution of immatures to distance from adult feeding sources. Similarly, Minakawa et al. (1999) sampled larvae from different sites throughout the Suba District in Kenya. They, too, found signiÞcant spatialheterogeneityinspeciescomposition,butwere unable to identify the key environmental factors that determined species occurrence and abundance. We inquired whether such differences in micro- geographic distribution occur at our focal study site, Banambani Village, in Mali, West Africa. Here both species are almost entirely anthropophilic (Toure ´ 1979,1985),sotheexplanationputforthbyCharlwood and Edoh (1996) seems unlikely. In addition to dif- ferences between species, we also inquired about the 1 Department of Organismic Biology, Ecology and Evolution, Uni- versity of California at Los Angles, CA 90095Ð1606. 2 Malaria Research and Training Center, De ´ partement dÕ Epide ´ - miologie des Affections Parasitaires, Ecole Nationale de Me ´ decine de Pharmacie et dÕ Odonto-Stomatologie, Bamako, B.P. 1805, Mali. 3 Department of Pathology and Center for Tropical Diseases, Uni- versity of Texas Medical Branch, Galveston, TX 77555Ð0609. Downloaded from https://academic.oup.com/jme/article/39/1/70/878747 by guest on 14 December 2021