title: Does extreme asymmetric dominance promote hybridization between Anopheles coluzzii and Anopheles gambiae s.s. in seasonal malaria mosquito communities of West Africa?
abstract: BACKGROUND
  Anopheles gambiae s.s. and An. coluzzii are two of the most important malaria vector species in sub-Saharan Africa. These recently-diverged sibling species do not exhibit intrinsic post-zygotic barriers to reproduction and are thought to be separated by strong assortative mating combined with selection against hybrids. At present, little is known about the ecological conditions that determine hybridization and introgression between these cryptic taxa.
  
  
  METHODS
  Swarm segregation and assortative mating were studied in Western Burkina Faso in the villages of Vallée du Kou (VK7) and Soumousso which differed in terms of which sibling species was much rarer than the other, and in Bana where both occurred in similar proportions. Swarms and pairs in copula were collected and genotyped, the proportion of intra and interspecific mating determined, and interspecific sperm transfer checked genetically. Females were collected through larval and adult indoor collections and genotyped or sexed-and-genotyped via a novel multiplex PCR.
  
  
  RESULTS
  A total of 3,687 males and 220 females were collected and genotyped from 109 swarms. Only 3 swarms were composed of males from both species, and these were from the village of VK7 where An. gambiae s.s. was comparatively rare. Mixed-species pairs captured in copula were only detected in that area and made for 3.62 % and 100 % of mating pairs involving An. coluzzii and An. gambiae s.s. individuals, respectively. The high An. gambiae s.s. cross-mating rate was mirrored by high rates of hybridizations estimated from female larvae and adults indoor collections. This contrasted with Soumousso, where despite being much less common than An. gambiae s.s., An. coluzzii males did not form mixed swarms, females were not found in interspecific swarms or copula and hybridization rates were low in both sibling species.
  
  
  CONCLUSIONS
  These data suggest that ecological conditions leading to rare An. gambiae s.s. in populations dominated by An. coluzzii may promote a breakdown of spatial swarm segregation and assortative mating between the two species. The lower overall hybridization rates observed at the larval and adult indoor stages compared to cross-mating rates support the idea that post-mating selection processes acting against hybrids may occur mostly prior to and/or at the early larval stages.
authors.affiliation: Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso. bband79@yahoo.fr.
authors.forename: Abdoulaye
authors.initials: A
authors.lastname: Niang
authors.affiliation: Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso. epopastef@yahoo.fr.
authors.forename: Patric S
authors.initials: PS
authors.lastname: Epopa
authors.affiliation: Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso. sawsimp2005@yahoo.fr.
authors.forename: Simon P
authors.initials: SP
authors.lastname: Sawadogo
authors.affiliation: Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso. maigahamid@yahoo.fr.
authors.forename: Hamidou
authors.initials: H
authors.lastname: Maïga
authors.affiliation: Laboratoire d'Ecologie Vectorielle et Parasitaire, Faculté des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Senegal. konatela@yahoo.fr.
authors.forename: Lassana
authors.initials: L
authors.lastname: Konaté
authors.affiliation: Laboratoire d'Ecologie Vectorielle et Parasitaire, Faculté des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Senegal. ousmane.faye@ucad.edu.sn.
authors.forename: Ousmane
authors.initials: O
authors.lastname: Faye
authors.affiliation: Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso. dabire_roch@hotmail.com.
authors.forename: Roch K
authors.initials: RK
authors.lastname: Dabiré
authors.affiliation: Centre for Applied Entomology and Parasitology, School of Life Sciences, Keele University, Staffordshire, UK. f.tripet@keele.ac.uk.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Tripet
authors.affiliation: Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso. a_diabate@hotmail.com.
authors.forename: Abdoulaye
authors.initials: A
authors.lastname: Diabaté
mesh_terms: D000818:Animals; D000852:Anopheles / Q000235:genetics / Q000502:physiology*; D002050:Burkina Faso / Q000453:epidemiology; D004777:Environment; D005260:Female; D005838:Genotype; D006801:Humans; D006824:Hybridization, Genetic; D007303:Insect Vectors / Q000235:genetics / Q000502:physiology*; D008288:Malaria / Q000635:transmission*; D008297:Male; D052586:Mating Preference, Animal; D012621:Seasons