title: Polyploidy and sexual system in angiosperms: Is there an association?
abstract: Flowering plants display a variety of sexual systems, ranging from complete cosexuality (hermaphroditism) to separate-sexed individuals (dioecy). While dioecy is relatively rare, it has evolved many times and is present in many plant families. Transitions in sexual systems are hypothesized to be affected by large genomic events such as whole-genome duplication, or polyploidy, and several models have been proposed to explain the observed patterns of association.
  
  
  
  In this study, we assessed the association between ploidy and sexual system (separate or combined sexes). To this end, we assembled a database of ploidy levels and sexual systems for ∼1000 species, spanning 18 genera and 15 families. We applied several phylogenetic comparative approaches, including Pagel's coevolutionary framework and sister clade analyses, for detecting correlations between ploidy level and sexual system.
  
  
  
  Our results indicate a broad association between polyploidy and sexual system dimorphism, with low evolutionary stability of the diploid-dioecious condition observed in several clades. A detailed examination of the clades exhibiting this correlation reveals that it is underlain by various patterns of transition rate asymmetry.
  
  
  
  We conclude that the long-hypothesized connection between ploidy and sexual system holds in some clades, although it may well be affected by factors that differ from clade to clade. Our results further demonstrate that to better understand the evolutionary processes involved, more sophisticated methods and extensive and detailed data sets are required for both broad and focused inquiry.
authors.affiliation: Department of Molecular Biology and Ecology of Plants, Tel Aviv University, Tel Aviv, Israel.
authors.forename: Lior
authors.initials: L
authors.lastname: Glick
authors.affiliation: Department of Molecular Biology and Ecology of Plants, Tel Aviv University, Tel Aviv, Israel.
authors.forename: Niv
authors.initials: N
authors.lastname: Sabath
authors.affiliation: Department of Biological Sciences University of Pittsburgh, Pittsburgh, Pennsylvania 15260 USA.
authors.forename: Tia-Lynn
authors.initials: TL
authors.lastname: Ashman
authors.affiliation: Department of Ecology, Evolution and Behavior, University of Minnesota, St. Paul, Minnesota 55108-6097 USA.
authors.forename: Emma
authors.initials: E
authors.lastname: Goldberg
authors.affiliation: Department of Molecular Biology and Ecology of Plants, Tel Aviv University, Tel Aviv, Israel itaymay@post.tau.ac.il.
authors.forename: Itay
authors.initials: I
authors.lastname: Mayrose
mesh_terms: D005075:Biological Evolution; D004171:Diploidy; D018745:Genome, Plant / Q000235:genetics*; D019684:Magnoliopsida / Q000235:genetics*; D008957:Models, Genetic; D010802:Phylogeny; D011123:Polyploidy; D012098:Reproduction / Q000235:genetics
keywords: correlated evolution; dioecy; hermaphroditism; polyploidy; sexual dimorphism; sexual system; whole-genome duplication