Genetic diversity and population structure of malaria vector mosquitoes Anopheles peditaeniatus, An. subpictus and An. vagus (Diptera: Culicidae) in five districts of Sri Lanka

Abstract

Anopheles subpictus is the secondary vector and An. peditaeniatus and An. vagus are potential vectors of malaria in Sri Lanka. Understanding population structure of vectors is vital in implementing successful vector control programmes to face the threat of re-emergence of malaria in Sri Lanka. This study reports the genetic diversity and the population structure of An. peditaeniatus, An. subpictus and An. vagus in five geographical locations in Sri Lanka using their mitochondrial gene, Cytochrome oxidase subunit I (COI). Adults were collected from Ampara, Badulla, Batticoloa, Jaffna and Kurunegala districts and the COI sequences were obtained from morphologically identified species using Polymerase Chain Reaction (PCR) assay. Statistical analyses were conducted using Dnasp 5.10.01 and Arlequin 3.11. An. peditaeniatus, An. subpictus and An. vagus had 8, 15 and 10 haplotypes respectively. All the three species had high genetic diversities. An. subpictus had the highest nucleotide diversity (0.025 ± 0.011) while An. peditaeniatus had the lowest (0.007 ± 0.002). According to neutrality tests, there is no positive selection driven in any of these species. No significant pairwise differences or genetic structure variations among An. peditaenatus or An. vagus populations which shows that random mating occurs among different populations of each species. A significant pairwise difference was observed between Jaffna (northern province) and Kurunegala (northwestern province) An. subpictus populations (FST= 0.965,). This strongly supports the previous reports on the presence of two different sibling species of An. subpictus in these two provinces. Analysis of Molecular Variance (AMOVA) results showed 82.21% significant genetic structure variation between An. subpictus populations (FCT= 0.822) compared to a smaller 17.79% variation within populations (FSC= 1.000), suggesting the existence of different An. subpictus sibling species in different geographical areas. The present study shows that geographic distance between populations has no effect on the population structures of An. peditaeniatus and An. vagus but affects the population structure of An. subpictus. Application of control measures against An. subpictus must be done with close monitoring since similar control measures may not be effective for all the populations and the high genetic variation can give rise to the population’s resistant to control measures.