title: Explosive diversification following a benthic to pelagic shift in freshwater fishes.
abstract: BACKGROUND
  Interspecific divergence along a benthic to pelagic habitat axis is ubiquitous in freshwater fishes inhabiting lentic environments. In this study, we examined the influence of this habitat axis on the macroevolution of a diverse, lotic radiation using mtDNA and nDNA phylogenies for eastern North America's most species-rich freshwater fish clade, the open posterior myodome (OPM) cyprinids. We used ancestral state reconstruction to identify the earliest benthic to pelagic transition in this group and generated fossil-calibrated estimates of when this shift occurred. This transition could have represented evolution into a novel adaptive zone, and therefore, we tested for a period of accelerated lineage accumulation after this historical habitat shift.
  
  
  RESULTS
  Ancestral state reconstructions inferred a similar and concordant region of our mtDNA and nDNA based gene trees as representing the shift from benthic to pelagic habitats in the OPM clade. Two independent tests conducted on each gene tree suggested an increased diversification rate after this inferred habitat transition. Furthermore, lineage through time analyses indicated rapid early cladogenesis in the clade arising after the benthic to pelagic shift.
  
  
  CONCLUSIONS
  A burst of diversification followed the earliest benthic to pelagic transition during the radiation of OPM cyprinids in eastern North America. As such, the benthic/pelagic habitat axis has likely influenced the generation of biodiversity across disparate freshwater ecosystems.
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Tennessee, 569 Dabney Hall, Knoxville, TN 37996, USA. phollin1@utk.edu.
authors.forename: Phillip R
authors.initials: PR
authors.lastname: Hollingsworth
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Simons
authors.forename: James A
authors.initials: JA
authors.lastname: Fordyce
authors.forename: C Darrin
authors.initials: CD
authors.lastname: Hulsey
mesh_terms: D000818:Animals; D044822:Biodiversity; D005075:Biological Evolution; D004272:DNA, Mitochondrial / Q000235:genetics; D017753:Ecosystem; D005399:Fishes / Q000145:classification* / Q000235:genetics*; D005618:Fresh Water; D049810:Genetic Speciation; D008928:Mitochondria / Q000235:genetics; D008969:Molecular Sequence Data; D009656:North America; D010802:Phylogeny
chemical_list: D004272:DNA, Mitochondrial