title: Genetic population structure of the malaria vector Anopheles baimaii in north-east India using mitochondrial DNA.
abstract: BACKGROUND
  Anopheles baimaii is a primary vector of human malaria in the forest settings of Southeast Asia including the north-eastern region of India. Here, the genetic population structure and the basic population genetic parameters of An. baimaii in north-east India were estimated using DNA sequences of the mitochondrial cytochrome oxidase sub unit II (COII) gene.
  
  
  METHODS
  Anopheles baimaii were collected from 26 geo-referenced locations across the seven north-east Indian states and the COII gene was sequenced from 176 individuals across these sites. Fifty-seven COII sequences of An. baimaii from six locations in Bangladesh, Myanmar and Thailand from a previous study were added to this dataset. Altogether, 233 sequences were grouped into eight population groups, to facilitate analyses of genetic diversity, population structure and population history.
  
  
  RESULTS
  A star-shaped median joining haplotype network, unimodal mismatch distribution and significantly negative neutrality tests indicated population expansion in An. baimaii with the start of expansion estimated to be ~0.243 million years before present (MYBP) in north-east India. The populations of An. baimaii from north-east India had the highest haplotype and nucleotide diversity with all other populations having a subset of this diversity, likely as the result of range expansion from north-east India. The north-east Indian populations were genetically distinct from those in Bangladesh, Myanmar and Thailand, indicating that mountains, such as the Arakan mountain range between north-east India and Myanmar, are a significant barrier to gene flow. Within north-east India, there was no genetic differentiation among populations with the exception of the Central 2 population in the Barail hills area that was significantly differentiated from other populations.
  
  
  CONCLUSIONS
  The high genetic distinctiveness of the Central 2 population in the Barail hills area of the north-east India should be confirmed and its epidemiological significance further investigated. The lack of genetic population structure in the other north-east Indian populations likely reflects large population sizes of An. baimaii that, historically, were able to disperse through continuous forest habitats in the north-east India. Additional markers and analytical approaches are required to determine if recent deforestation is now preventing ongoing gene flow. Until such information is acquired, An. baimaii in north-east India should be treated as a single unit for the implementation of vector control measures.
authors.affiliation: Regional Medical Research Centre, NE (ICMR), Dibrugarh-786001, Assam, India.
authors.forename: Devojit K
authors.initials: DK
authors.lastname: Sarma
authors.forename: Anil
authors.initials: A
authors.lastname: Prakash
authors.forename: Samantha M
authors.initials: SM
authors.lastname: O'Loughlin
authors.forename: Dibya R
authors.initials: DR
authors.lastname: Bhattacharyya
authors.forename: Pradumnya K
authors.initials: PK
authors.lastname: Mohapatra
authors.forename: Kanta
authors.initials: K
authors.lastname: Bhattacharjee
authors.forename: Kanika
authors.initials: K
authors.lastname: Das
authors.forename: Sweta
authors.initials: S
authors.lastname: Singh
authors.forename: Nilanju P
authors.initials: NP
authors.lastname: Sarma
authors.forename: Gias U
authors.initials: GU
authors.lastname: Ahmed
authors.forename: Catherine
authors.initials: C
authors.lastname: Walton
authors.forename: Jagadish
authors.initials: J
authors.lastname: Mahanta
mesh_terms: D000818:Animals; D000852:Anopheles / Q000145:classification / Q000235:genetics*; D004272:DNA, Mitochondrial / Q000235:genetics*; D003576:Electron Transport Complex IV / Q000235:genetics; D014644:Genetic Variation; D005828:Genetics, Population; D006239:Haplotypes; D007194:India; D007303:Insect Vectors / Q000145:classification / Q000235:genetics*; D008969:Molecular Sequence Data
chemical_list: D004272:DNA, Mitochondrial; D003576:Electron Transport Complex IV