title: Environmental variation and rivers govern the structure of chimpanzee genetic diversity in a biodiversity hotspot.
abstract: BACKGROUND
  The mechanisms that underlie the diversification of tropical animals remain poorly understood, but new approaches that combine geo-spatial modeling with spatially explicit genetic data are providing fresh insights on this topic. Data about the diversification of tropical mammals remain particularly sparse, and vanishingly few opportunities exist to study endangered large mammals that increasingly exist only in isolated pockets. The chimpanzees of Cameroon represent a unique opportunity to examine the mechanisms that promote genetic differentiation in tropical mammals because the region is home to two chimpanzee subspecies: Pan troglodytes ellioti and P. t. trogolodytes. Their ranges converge in central Cameroon, which is a geographically, climatically and environmentally complex region that presents an unparalleled opportunity to examine the roles of rivers and/or environmental variation in influencing the evolution of chimpanzee populations.
  
  
  RESULTS
  We analyzed microsatellite genotypes and mtDNA HVRI sequencing data from wild chimpanzees sampled at a fine geographic scale across Cameroon and eastern Nigeria using a spatially explicit approach based upon Generalized Dissimilarity Modeling. Both the Sanaga River and environmental variation were found to contribute to driving separation of the subspecies. The importance of environmental variation differed among subspecies. Gene-environment associations were weak in P. t. troglodytes, whereas environmental variation was found to play a much larger role in shaping patterns of genetic differentiation in P. t. ellioti.
  
  
  CONCLUSIONS
  We found that both the Sanaga River and environmental variation likely play a role in shaping patterns of chimpanzee genetic diversity. Future studies using single nucleotide polymorphism (SNP) data are necessary to further understand how rivers and environmental variation contribute to shaping patterns of genetic variation in chimpanzees.
authors.affiliation: Department of Biology, Drexel University, Philadelphia 19104, Pennsylvania, USA. mwmitchell@drexel.edu.
authors.forename: Matthew W
authors.initials: MW
authors.lastname: Mitchell
authors.forename: Sabrina
authors.initials: S
authors.lastname: Locatelli
authors.forename: Paul R
authors.initials: PR
authors.lastname: Sesink Clee
authors.forename: Henri A
authors.initials: HA
authors.lastname: Thomassen
authors.forename: Mary Katherine
authors.initials: MK
authors.lastname: Gonder
mesh_terms: D000349:Africa; D000818:Animals; D044822:Biodiversity; D005075:Biological Evolution; D004272:DNA, Mitochondrial / Q000235:genetics; D059647:Gene-Environment Interaction; D014644:Genetic Variation; D005828:Genetics, Population; D015186:Hominidae / Q000235:genetics; D018895:Microsatellite Repeats; D002679:Pan troglodytes / Q000145:classification / Q000235:genetics*; D045483:Rivers
chemical_list: D004272:DNA, Mitochondrial