title: The population genetics of wild chimpanzees in Cameroon and Nigeria suggests a positive role for selection in the evolution of chimpanzee subspecies.
abstract: BACKGROUND
  Chimpanzees (Pan troglodytes) can be divided into four subspecies. Substantial phylogenetic evidence suggests that these subspecies can be grouped into two distinct lineages: a western African group that includes P. t. verus and P. t. ellioti and a central/eastern African group that includes P. t. troglodytes and P. t. schweinfurthii. The geographic division of these two lineages occurs in Cameroon, where the rages of P. t. ellioti and P. t. troglodytes appear to converge at the Sanaga River. Remarkably, few population genetic studies have included wild chimpanzees from this region.
  
  
  RESULTS
  We analyzed microsatellite genotypes of 187 wild, unrelated chimpanzees, and mitochondrial control region sequencing data from 604 chimpanzees. We found that chimpanzees in Cameroon and eastern Nigeria comprise at least two, and likely three populations. Both the mtDNA and microsatellite data suggest that there is a primary separation of P. t. troglodytes in southern Cameroon from P. t. ellioti north and west of the Sanaga River. These two populations split ~200-250 thousand years ago (kya), but have exchanged one migrant per generation since separating. In addition, P. t. ellioti consists of two populations that split from one another ~4 kya. One population is located in the rainforests of western Cameroon and eastern Nigeria, whereas the second population appears to be confined to a savannah-woodland mosaic in central Cameroon.
  
  
  CONCLUSIONS
  Our findings suggest that there are as many as three genetically distinct populations of chimpanzees in Cameroon and eastern Nigeria. P. t. troglodytes in southern Cameroon comprises one population that is separated from two populations of P. t. ellioti in western and central Cameroon, respectively. P. t. ellioti and P. t. troglodytes appear to be characterized by a pattern of isolation-with-migration, and thus, we propose that neutral processes alone can not explain the differentiation of P. t. ellioti and P. t. troglodytes.
authors.forename: Matthew W
authors.initials: MW
authors.lastname: Mitchell
authors.forename: Sabrina
authors.initials: S
authors.lastname: Locatelli
authors.forename: Lora
authors.initials: L
authors.lastname: Ghobrial
authors.forename: Amy A
authors.initials: AA
authors.lastname: Pokempner
authors.forename: Paul R
authors.initials: PR
authors.lastname: Sesink Clee
authors.forename: Ekwoge E
authors.initials: EE
authors.lastname: Abwe
authors.forename: Aaron
authors.initials: A
authors.lastname: Nicholas
authors.forename: Louis
authors.initials: L
authors.lastname: Nkembi
authors.forename: Nicola M
authors.initials: NM
authors.lastname: Anthony
authors.forename: Bethan J
authors.initials: BJ
authors.lastname: Morgan
authors.forename: Roger
authors.initials: R
authors.lastname: Fotso
authors.forename: Martine
authors.initials: M
authors.lastname: Peeters
authors.forename: Beatrice H
authors.initials: BH
authors.lastname: Hahn
authors.affiliation: Department of Biology, Drexel University, Philadelphia 19104, Pennsylvania, USA. gonder@drexel.edu.
authors.forename: Mary Katherine
authors.initials: MK
authors.lastname: Gonder
mesh_terms: D000818:Animals; D005075:Biological Evolution; D002163:Cameroon; D004272:DNA, Mitochondrial / Q000235:genetics; D005828:Genetics, Population; D018895:Microsatellite Repeats; D009549:Nigeria; D002679:Pan troglodytes / Q000145:classification* / Q000235:genetics*; D010802:Phylogeny
chemical_list: D004272:DNA, Mitochondrial