Genetic Structure, Snp Establishment, and Cloning the 2la-Inversion Distal Breakpoint in the Malaria Vector Anopheles Gambiae

Alternative means of malaria control are urgently needed. Vector targeted malaria control campaigns require good grasp of the biology and population structure. Use of insecticide treated nets has been recommended and control by genetic manipulation of the vectors considered.Evaluating the effectiveness of measures that involve genetic manipulation of vector populations will be facilitated by identifying small, genetically isolated vector populations. The study was designed to recover Anopheles.gambiae 2La inversion distal breakpoint structure and to establish SNPs and use variation in both SNPs and microsatellite markers to look at genetic structure across 4 lake Victoria islands and 2 surrounding mainland populations and for evidence of any restriction to free gene flow. Four Islands (from 20-50 km apart) and two surrounding mainland populations (96 km apart) were studied. Samples of indoor resting adult mosquitoes collected over two consecutive years were genotyped at marker loci distributed broadly throughout the genome and analyzed for general population structure and for marker comparisons. Effective population size (Ne) estimates showed island populations to consist of smaller demes compared to the main-land ones. Most populations were significantly differentiated geographically, and from one year to the other. Average geographic pair-wise FST ranged from 0.014-0.105, and several pairs of populations had Ne m < 3. The loci showed broad heterogeneity at capturing or estimating population differences. SNPs confirmed microsatellite population structure though at lesser resolution. These islands are significantly genetically differentiated; with real differences that reoccurred over the study period, from the two mainland populations and from some of each other. This appears to be the product of their separation across water, dynamics of small populations and local adaptation. With further characterisation these islands could become possible sites for applying measures evaluating effectiveness of control by genetic manipulation. The 2La breakpoint was successfully cloned, found monophyletic across A. gambiae siblings' inverted karyotypes and a diagnostic PCR based molecular karyotyping assay developed. The PCR based 2La molecular diagnostic will greatly facilitate study of inversion biology in natural populations.