title: Diversification and the evolution of dispersal ability in the tribe Brassiceae (Brassicaceae).
abstract: OBJECTIVE
  Dispersal and establishment ability can influence evolutionary processes such as geographic isolation, adaptive divergence and extinction probability. Through these population-level dynamics, dispersal ability may also influence macro-evolutionary processes such as species distributions and diversification. This study examined patterns of evolution of dispersal-related fruit traits, and how the evolution of these traits is correlated with shifts in geographic range size, habitat and diversification rates in the tribe Brassiceae (Brassicaceae).
  
  
  METHODS
  The phylogenetic analysis included 72 taxa sampled from across the Brassiceae and included both nuclear and chloroplast markers. Dispersal-related fruit characters were scored and climate information for each taxon was retrieved from a database. Correlations between fruit traits, seed characters, habitat, range and climate were determined, together with trait-dependent diversification rates.
  
  
  RESULTS
  It was found that the evolution of traits associated with limited dispersal evolved only in association with compensatory traits that increase dispersal ability. The evolution of increased dispersal ability occurred in multiple ways through the correlated evolution of different combinations of fruit traits. The evolution of traits that increase dispersal ability was in turn associated with larger seed size, increased geographic range size and higher diversification rates.
  
  
  CONCLUSIONS
  This study provides evidence that the evolution of increased dispersal ability and larger seed size, which may increase establishment ability, can also influence macro-evolutionary processes, possibly by increasing the propensity for long-distance dispersal. In particular, it may increase speciation and consequent diversification rates by increasing the likelihood of geographic and thereby reproductive isolation.
authors.affiliation: Department of Biology, Duke University, Box 90338, Durham, NC 27708, USA charleswillis@fas.harvard.edu.
authors.forename: C G
authors.initials: CG
authors.lastname: Willis
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Alberta, T6G 2E9, Canada.
authors.forename: J C
authors.initials: JC
authors.lastname: Hall
authors.affiliation: Departamento de Ecología, Facultad de Ciencias, Universidad de Granada, Granada, 18071, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Rubio de Casas
authors.affiliation: Duke University School of Medicine, Duke University, DUMC 3710, Durham, NC 27710, USA.
authors.forename: T Y
authors.initials: TY
authors.lastname: Wang
authors.affiliation: Department of Biology, Duke University, Box 90338, Durham, NC 27708, USA.
authors.forename: K
authors.initials: K
authors.lastname: Donohue
mesh_terms: D001499:Bayes Theorem; D044822:Biodiversity; D005075:Biological Evolution; D019607:Brassicaceae / Q000502:physiology*; D002980:Climate; D005638:Fruit / Q000502:physiology; D010802:Phylogeny; D019655:Quantitative Trait, Heritable; D058614:Seed Dispersal / Q000502:physiology*; D012639:Seeds / Q000502:physiology
keywords: Brassica; Brassicaceae; Cakile; extinction; fruit traits; heteroarthrocarpy; limited dispersal; long-distance dispersal; range size; speciation; species diversification