Present address: Malaria Entomology Research Unit, Faculty of Health Sciences, University of Witwatersrand, Johannesburg, South Africa.
Evidence for X-linked introgression between molecular forms of Anopheles gambiae from Angola
Version of Record online: 20 SEP 2011
© 2011 The Authors. Medical and Veterinary Entomology © 2011 The Royal Entomological Society
Medical and Veterinary Entomology
Volume 26, Issue 2, pages 218–227, June 2012
How to Cite
CHOI, K. S. and TOWNSON, H. (2012), Evidence for X-linked introgression between molecular forms of Anopheles gambiae from Angola. Medical and Veterinary Entomology, 26: 218–227. doi: 10.1111/j.1365-2915.2011.00977.x
- Issue online: 3 MAY 2012
- Version of Record online: 20 SEP 2011
- Accepted 13 June 2011
- Anopheles gambiae;
- M and S forms;
- X chromosome;
The M and S molecular forms of the African malaria vector Anopheles gambiae (Diptera: Culicidae) are morphologically identical incipient species in which reproductive isolation is incomplete, enabling low-level gene flow between forms. In an attempt to find differences between the M and S forms, sequence variation was studied at loci along the X chromosome in adult female An. gambiae from Angola. A high proportion of M form specimens from Angola (79% of the 456 X chromosomes sampled) were found to contain a 16-bp insertion in intron 4 of the X-linked GPRCCK1 locus, relative to the AgamP3 release of the An. gambiae PEST genome sequence. The insertion was in Hardy–Weinberg equilibrium in Angolan M form populations. The same insertion was found in all S form specimens examined, regardless of where in Africa they were sampled, but was absent from a sample of M form specimens collected in Ghana, Bioko and Mali. In M form specimens from Angola, there was an association between alleles at the GPRCCK1 locus and those at a microsatellite locus, AGXH678, close to the centromere of the X chromosome, with significant linkage disequilibrium between loci separated by 0.472 Mbp (P < 0.033). We show that the insertion results from introgression from the S form into the M form, rather than from the retention of an ancestral character. Gene flow from the S to M form could allow genes of adaptive value to be transferred, including those conferring insecticide resistance and others influencing ecology and behaviour, and thus malaria transmission and control. We discuss factors that may have led to this introgression event.