Population genetic structure of the malaria mosquito Anopheles arabiensis across Nigeria suggests range expansion

Abstract

Ten microsatellite loci, four located within and six outside chromosome inversions, were employed to study the genetic structure of Anopheles arabiensis across the ecological zones of Nigeria (arid savannah in the north gradually turns into humid forest in the south). Regardless of location within or outside inversions, genetic variability at all loci was characterized by a reduction in both the number of alleles per locus and heterozygosity from savannah to forest. Across all loci, all but one allele in the forest also occurred in the savannah, whereas at least 78 alleles in the savannah were missing in the forest. Genetic differentiation increased with geographical distance; consequently, genetic distances between zones exceeded those within zones. The largest genetic distances were between localities at the extremes of the transect (range F(ST) = 0.196-0.258 and R(ST) = 0.183-0.468) and were as large as those between A. arabiensis and Anopheles gambiae s.s. Gene flow across the country was very low, so that Nm between the extremes of the transect was < 1. These data suggest that A. arabiensis has extended its range from the savannah into the forest during which it experienced a reduction in effective population size due to sequential founder effects. Gene flow post range expansion appears too restricted by geographical distance to homogenize the gene pool of A. arabiensis across Nigeria.

Identification and expression of odorant-binding proteins of the malaria-carrying mosquitoesAnopheles gambiae andAnopheles arabiensis

“…gambiae s.s. Giles and An. arabiensis Patton, are the most widely distributed and are amongst the most efficient vectors of human malaria known anywhere in the world (White, 1974;Coetzee et al, 2000;Onyabe and Conn, 2001). An.…”

Population Genetic Structure of <I>Anopheles gambiae</I> and <I>Anopheles arabiensis</I> in Niger

“…In particular, Matthews et al (2007) recently conÞrmed the expansion of An. arabiensis populations within Nigeria, which had been suggested earlier (Onyabe and Conn 2001), and observed a stronger expansion signature in northern localities. These sites are situated in the Sudan savanna zone, near the south border of Niger and not far from our sampling sites.…”

“…arabiensis West African populations. A study conducted in Nigeria (Onyabe and Conn 2001) showed signiÞcant differentiation both within and between ecological zones, although F ST values for between zones comparisons were far greater. These results suggesting low gene ßow contrast with the data presented in this study.…”

“…Twelve microsatellite loci with dinucleotide repeats were selected on the basis of physical and linkage maps (Zheng et al 1996), previous studies that showed polymorphism (Wang et al 1999, Donnelly and Townson 2000, Onyabe and Conn 2001, Wondji et al 2002, Kayondo et al 2005, and preliminary tests for reliable ampliÞcation and polymorphism on both species samples from Niger. Eleven of these loci were used for both An.…”

A Simple Key for Identifying the Sibling Species of the Malaria Vector Anopheles gambiae (Giles) Complex by Polytene Chromosome Cytogenetics

“…comorensis Brunhes, le Goff and Geoffroy (Gillies and DeMeillon, 1968;White, 1974 and1985;Hunt et al, 1998;Harbach, 2003;Coetzee et al, 2013). Amongst these sibling species, A. gambiae and A. Arabiensis are the two major malaria vectors in Africa (Gillies and De Meillon 1968), particularly in Nigeria (Boreham et al, 1979;Onyabe and Conn, 2001;Obembe and Awopetu, 2014). There are strains of A. gambiae complex sibling species in which the parasite cannot complete its life cycle; such strains are said to be refractory (Collins et al, 1986;Chris et al, 2011;Obembe and Awopetu, 2014).…”