title: Species and populations of the Anopheles gambiae complex in Cameroon with special emphasis on chromosomal and molecular forms of Anopheles gambiae s.s.
abstract: We studied the geographical distribution of species, chromosomal, and molecular forms of the Anopheles gambiae Giles (Diptera: Culicidae) complex in 23 sites in Cameroon, Central Africa. Almost all the specimens collected in the four northern-most arid sites were Anopheles arabiensis. Anopheles melas was found in a rural locality surrounded by mangrove swamps, on the Atlantic Coast. In total, 1,525 An. gambiae s.s. females were identified down to their molecular form, and inversion polymorphisms on polytene chromosomes were scored from 186 half-gravid females. The Forest chromosomal form, with standard arrangements almost fixed on both arms of chromosome-2, was the only one observed in the southern, more humid localities. Karyotypes typical of Savanna and Mopti were recorded northwards, in the humid savannas of the Adamawa Province. The molecular forms M and S were widespread throughout Cameroon, and assort independently from the chromosomal forms. S-form populations were characterized by karyotypes typical of Forest and Savanna chromosomal forms, and M-form populations were characterized by karyotypes typical of Forest, Savanna, and Mopti. No M/S hybrid patterns were detected, although M and S mosquitoes were sympatric in 15 sites, providing further evidence for positive assortative mating within molecular forms. The observed ecogeographical distribution of M and S was peculiar: the ecological parameters involved in this distribution still need to be clarified as well as the possible role of competitive exclusion between chromosomally homosequential molecular forms. No difference was observed in host preference or in Plasmodium falciparum infection rates between sympatric M and S populations.
authors.affiliation: Organisation de Coordination pour lalutte contre les Endémies en Afrique Centrale, Yaoundé, Cameroon. c.s.wondji@liverpool.ac.uk
authors.forename: Charles
authors.initials: C
authors.lastname: Wondji
authors.forename: Simard
authors.initials: S
authors.lastname: Frédéric
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Petrarca
authors.forename: Josiane
authors.initials: J
authors.lastname: Etang
authors.forename: Federica
authors.initials: F
authors.lastname: Santolamazza
authors.forename: Alessandra
authors.initials: A
authors.lastname: Della Torre
authors.forename: Didier
authors.initials: D
authors.lastname: Fontenille
mesh_terms: D000818:Animals; D000852:Anopheles / Q000145:classification* / Q000235:genetics*; D002163:Cameroon; D002417:Cattle; D002875:Chromosomes / Q000235:genetics; D002980:Climate; D004463:Ecology; D005260:Female; D006790:Host-Parasite Interactions; D006801:Humans; D007303:Insect Vectors / Q000145:classification* / Q000235:genetics*; D007621:Karyotyping; D008288:Malaria / Q000635:transmission; D011110:Polymorphism, Genetic; D011153:Population; D011891:Rain; D013045:Species Specificity; D013997:Time Factors