title: Genetic structure, nestmate recognition and behaviour of two cryptic species of the invasive big-headed ant Pheidole megacephala.
abstract: BACKGROUND
  Biological invasions are recognized as a major cause of biodiversity decline and have considerable impact on the economy and human health. The African big-headed ant Pheidole megacephala is considered one of the world's most harmful invasive species.
  
  
  RESULTS
  To better understand its ecological and demographic features, we combined behavioural (aggression tests), chemical (quantitative and qualitative analyses of cuticular lipids) and genetic (mitochondrial divergence and polymorphism of DNA microsatellite markers) data obtained for eight populations in Cameroon. Molecular data revealed two cryptic species of P. megacephala, one inhabiting urban areas and the other rainforests. Urban populations belong to the same phylogenetic group than those introduced in Australia and in other parts of the world. Behavioural analyses show that the eight populations sampled make up four mutually aggressive supercolonies. The maximum distance between nests from the same supercolony was 49 km and the closest distance between two nests belonging to two different supercolonies was 46 m. The genetic data and chemical analyses confirmed the behavioural tests as all of the nests were correctly assigned to their supercolony. Genetic diversity appears significantly greater in Africa than in introduced populations in Australia; by contrast, urban and Australian populations are characterized by a higher chemical diversity than rainforest ones.
  
  
  CONCLUSIONS
  Overall, our study shows that populations of P. megacephala in Cameroon adopt a unicolonial social structure, like invasive populations in Australia. However, the size of the supercolonies appears several orders of magnitude smaller in Africa. This implies competition between African supercolonies and explains why they persist over evolutionary time scales.
authors.affiliation: Evolutionary Biology and Ecology, Université Libre de Bruxelles, Brussels, Belgium. Denis.Fournier@ulb.ac.be
authors.forename: Denis
authors.initials: D
authors.lastname: Fournier
authors.forename: Maurice
authors.initials: M
authors.lastname: Tindo
authors.forename: Martin
authors.initials: M
authors.lastname: Kenne
authors.forename: Paul Serge
authors.initials: PS
authors.lastname: Mbenoun Masse
authors.forename: Vanessa
authors.initials: V
authors.lastname: Van Bossche
authors.forename: Eliane
authors.initials: E
authors.lastname: De Coninck
authors.forename: Serge
authors.initials: S
authors.lastname: Aron
mesh_terms: D000374:Aggression; D000825:Animal Structures / Q000378:metabolism / Q000648:ultrastructure; D000818:Animals; D001000:Ants / Q000145:classification / Q000235:genetics* / Q000502:physiology*; D001499:Bayes Theorem; D002163:Cameroon; D016000:Cluster Analysis; D058893:DNA Barcoding, Taxonomic; D003576:Electron Transport Complex IV / Q000235:genetics; D014644:Genetic Variation; D005843:Geography; D006838:Hydrocarbons / Q000378:metabolism; D058865:Introduced Species; D018895:Microsatellite Repeats / Q000235:genetics; D008855:Microscopy, Electron, Scanning; D009425:Nesting Behavior / Q000502:physiology*; D010802:Phylogeny; D021641:Recognition, Psychology; D013045:Species Specificity
chemical_list: D006838:Hydrocarbons; D003576:Electron Transport Complex IV