title: Convergent evolution of a complex fruit structure in the tribe Brassiceae (Brassicaceae).
abstract: OBJECTIVE
  Many angiosperms have fruit morphologies that result in seeds from the same plant having different dispersal capabilities. A prime example is found in the Brassiceae (Brassicaceae), which has many members with segmented or heteroarthrocarpic fruits. Since only 40% of the genera are heteroarthrocarpic, this tribe provides an opportunity to study the evolution of an ecologically significant novelty and its variants.
  
  
  METHODS
  We analyzed nuclear (PHYA) and plastid (matK) sequences from 66 accessions using maximum parsimony, maximum likelihood, and Bayesian inference approaches. The evolution of heteroarthrocarpy and its variants was evaluated using maximum parsimony and maximum likelihood ancestral state reconstructions.
  
  
  RESULTS
  Although nuclear and plastid phylogenies are incongruent with each other, the following findings are consistent: (1) Cakile, Crambe, Vella, and Zilla lineages are monophyletic; (2) the Nigra lineage is not monophyletic; and (3) within the Cakile clade, Cakile, Didesmus, and Erucaria are paraphyletic. Despite differences in the matK and PHYA topologies at both deep and shallow nodes, similar patterns of morphological evolution emerge. Heteroarthrocarpy, a complex morphological trait, has evolved multiple times across the tribe. Moreover, there are convergent transitions in dehiscence capabilities and fruit disarticulation across the tribe.
  
  
  CONCLUSIONS
  We present the first explicit analysis of fruit evolution within the Brassiceae, which exemplifies evolutionary lability. The repeated loss and gain of segment dehiscence and disarticulation suggests conservation in the genetic pathway controlling abscission with differential expression across taxa. This study provides a strong foundation for future studies of mechanisms underlying variation in dispersal capabilities of Brassiceae.
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Canada. jocelyn.hall@ualberta.ca
authors.forename: Jocelyn C
authors.initials: JC
authors.lastname: Hall
authors.forename: Tracy E
authors.initials: TE
authors.lastname: Tisdale
authors.forename: Kathleen
authors.initials: K
authors.lastname: Donohue
authors.forename: Andrew
authors.initials: A
authors.lastname: Wheeler
authors.forename: Mohammed A
authors.initials: MA
authors.lastname: Al-Yahya
authors.forename: Elena M
authors.initials: EM
authors.lastname: Kramer
mesh_terms: D001483:Base Sequence; D001499:Bayes Theorem; D005075:Biological Evolution; D019607:Brassicaceae / Q000033:anatomy & histology* / Q000235:genetics*; D004722:Endoribonucleases / Q000235:genetics; D005638:Fruit / Q000033:anatomy & histology* / Q000235:genetics* / Q000254:growth & development; D017343:Genes, Plant / Q000235:genetics; D016013:Likelihood Functions; D009713:Nucleotidyltransferases / Q000235:genetics; D010802:Phylogeny; D051942:Phytochrome A / Q000235:genetics; D058614:Seed Dispersal / Q000235:genetics
chemical_list: D051942:Phytochrome A; D009713:Nucleotidyltransferases; C034038:mRNA maturase; D004722:Endoribonucleases