title: Phylogenetic evidence for cladogenetic polyploidization in land plants.
abstract: Polyploidization is a common and recurring phenomenon in plants and is often thought to be a mechanism of "instant speciation". Whether polyploidization is associated with the formation of new species (cladogenesis) or simply occurs over time within a lineage (anagenesis), however, has never been assessed systematically.
  
  
  
  We tested this hypothesis using phylogenetic and karyotypic information from 235 plant genera (mostly angiosperms). We first constructed a large database of combined sequence and chromosome number data sets using an automated procedure. We then applied likelihood models (ClaSSE) that estimate the degree of synchronization between polyploidization and speciation events in maximum likelihood and Bayesian frameworks.
  
  
  
  Our maximum likelihood analysis indicated that 35 genera supported a model that includes cladogenetic transitions over a model with only anagenetic transitions, whereas three genera supported a model that incorporates anagenetic transitions over one with only cladogenetic transitions. Furthermore, the Bayesian analysis supported a preponderance of cladogenetic change in four genera but did not support a preponderance of anagenetic change in any genus.
  
  
  
  Overall, these phylogenetic analyses provide the first broad confirmation that polyploidization is temporally associated with speciation events, suggesting that it is indeed a major speciation mechanism in plants, at least in some genera.
authors.affiliation: Department of Zoology, 4200-6270 University Boulevard, University of British Columbia, Vancouver, British Columbia V6T 1Z4 Canada.
authors.forename: Shing H
authors.initials: SH
authors.lastname: Zhan
authors.affiliation: Department of Molecular Biology and Ecology of Plants, George S. Wise Faculty of Life Sciences, Tel Aviv University, P. O. Box 39040, Tel Aviv 69978, Israel.
authors.forename: Michal
authors.initials: M
authors.lastname: Drori
authors.affiliation: Department of Ecology, Evolution, & Behavior, University of Minnesota, 140 Gortner Laboratory, 1479 Gortner Avenue, St. Paul, Minnesota 55108 USA.
authors.forename: Emma E
authors.initials: EE
authors.lastname: Goldberg
authors.affiliation: Department of Zoology, 4200-6270 University Boulevard, University of British Columbia, Vancouver, British Columbia V6T 1Z4 Canada.
authors.forename: Sarah P
authors.initials: SP
authors.lastname: Otto
authors.affiliation: Department of Molecular Biology and Ecology of Plants, George S. Wise Faculty of Life Sciences, Tel Aviv University, P. O. Box 39040, Tel Aviv 69978, Israel itaymay@post.tau.ac.il.
authors.forename: Itay
authors.initials: I
authors.lastname: Mayrose
mesh_terms: D001499:Bayes Theorem; D019669:Embryophyta / Q000235:genetics*; D049810:Genetic Speciation; D018745:Genome, Plant / Q000235:genetics*; D016013:Likelihood Functions; D019684:Magnoliopsida / Q000235:genetics; D010802:Phylogeny; D011123:Polyploidy
keywords: ClaSSE; anagenesis; cladogenesis; polyploidy; speciation