title: Limited genomic divergence between intraspecific forms of Culex pipiens under different ecological pressures.
abstract: BACKGROUND
  Divergent selection can be a major driver of ecological speciation. In insects of medical importance, understanding the speciation process is both of academic interest and public health importance. In the West Nile virus vector Culex pipiens, intraspecific pipiens and molestus forms vary in ecological and physiological traits. Populations of each form appear to share recent common ancestry but patterns of genetic differentiation across the genome remain unknown. Here, we undertook an AFLP genome scan on samples collected from both sympatric and allopatric populations from Europe and the USA to quantify the extent of genomic differentiation between the two forms.
  
  
  RESULTS
  The forms were clearly differentiated but each exhibited major population sub-structuring between continents. Divergence between pipiens and molestus forms from USA was higher than in both inter- and intra-continental comparisons with European samples. The proportion of outlier loci between pipiens and molestus (≈3 %) was low but consistent in both continents, and similar to those observed between sibling species of other mosquito species which exhibit contemporary gene flow. Only two of the outlier loci were shared between inter-form comparisons made within Europe and USA.
  
  
  CONCLUSIONS
  This study supports the molestus and pipiens status as distinct evolutionary entities with low genomic divergence. The low number of shared divergent loci between continents suggests a relatively limited number of genomic regions determining key typological traits likely to be driving incipient speciation and/or adaptation of molestus to anthropogenic habitats.
authors.affiliation: Global Health & Tropical Medicine, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Rua da Junqueira 100, 1349-008, Lisbon, Portugal. Bruno.GomesdaSilva@lstmed.ac.uk.|Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK. Bruno.GomesdaSilva@lstmed.ac.uk.
authors.forename: Bruno
authors.initials: B
authors.lastname: Gomes
authors.affiliation: Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK. C.S.Wilding@ljmu.ac.uk.|School of Natural Sciences and Psychology, Liverpool John Moores University, Liverpool, L3 3AF, UK. C.S.Wilding@ljmu.ac.uk.
authors.forename: Craig S
authors.initials: CS
authors.lastname: Wilding
authors.affiliation: Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK. david.weetman@lstmed.ac.uk.
authors.forename: David
authors.initials: D
authors.lastname: Weetman
authors.affiliation: Global Health & Tropical Medicine, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Rua da Junqueira 100, 1349-008, Lisbon, Portugal. CASousa@ihmt.unl.pt.
authors.forename: Carla A
authors.initials: CA
authors.lastname: Sousa
authors.affiliation: Global Health & Tropical Medicine, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Rua da Junqueira 100, 1349-008, Lisbon, Portugal. TeNovo@ihmt.unl.pt.
authors.forename: Maria T
authors.initials: MT
authors.lastname: Novo
authors.affiliation: Centers for Disease Control and Prevention, 3156 Rampart Road, Fort Collins, CO, 80521, USA. hms1@cdc.gov.
authors.forename: Harry M
authors.initials: HM
authors.lastname: Savage
authors.affiliation: Global Health & Tropical Medicine, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Rua da Junqueira 100, 1349-008, Lisbon, Portugal. PAlmeida@ihmt.unl.pt.
authors.forename: António P G
authors.initials: AP
authors.lastname: Almeida
authors.affiliation: Global Health & Tropical Medicine, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Rua da Junqueira 100, 1349-008, Lisbon, Portugal. jpinto@ihmt.unl.pt.
authors.forename: João
authors.initials: J
authors.lastname: Pinto
authors.affiliation: Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK. Martin.Donnelly@lstmed.ac.uk.
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Donnelly
mesh_terms: D000818:Animals; D016000:Cluster Analysis; D003465:Culex / Q000145:classification* / Q000235:genetics*; D017753:Ecosystem; D005060:Europe; D051456:Gene Flow; D040961:Genetic Drift; D049810:Genetic Speciation; D007303:Insect Vectors / Q000145:classification / Q000235:genetics / Q000821:virology; D018895:Microsatellite Repeats; D061350:Sympatry; D014481:United States; D014901:West Nile Fever / Q000635:transmission