title: Macroevolutionary synthesis of flowering plant sexual systems.
abstract: Sexual system is a key determinant of genetic variation and reproductive success, affecting evolution within populations and within clades. Much research in plants has focused on evolutionary transitions away from the most common state of hermaphroditism and toward the rare state of dioecy (separate sexes). Rather than transitions predominantly toward greater sexual differentiation, however, evolution may proceed in the direction of lesser sexual differentiation. We analyzed the macroevolutionary dynamics of sexual system in angiosperm genera that contain both dioecious and nondioecious species. Our phylogenetic analyses encompass a total of 2145 species from 40 genera. Overall, we found little evidence that rates of sexual system transitions are greater in any direction. Counting the number of inferred state changes revealed a mild prevalence of transitions away from hermaphroditism and away from dioecy, toward states of intermediate sexual differentiation. We identify genera in which future studies of sexual system evolution might be especially productive, and we discuss how integrating genetic or population-level studies of sexual system could improve the power of phylogenetic comparative analyses. Our work adds to the evidence that different selective pressures and constraints act in different groups, helping maintain the variety of sexual systems observed among plants.
authors.affiliation: Department of Ecology, Evolution, and Behavior, University of Minnesota, Saint Paul, Minnesota, 55108.
authors.forename: Emma E
authors.initials: EE
authors.lastname: Goldberg
authors.affiliation: Department of Zoology, University of British Columbia, Vancouver, BC, V6J 3S7, Canada.
authors.forename: Sarah P
authors.initials: SP
authors.lastname: Otto
authors.affiliation: Department of Biological Sciences, University of Calgary, Calgary, AB, T2N 1N4, Canada.
authors.forename: Jana C
authors.initials: JC
authors.lastname: Vamosi
authors.affiliation: Department of Molecular Biology and Ecology of Plants, Tel Aviv University, Tel Aviv 69978, Israel.
authors.forename: Itay
authors.initials: I
authors.lastname: Mayrose
authors.affiliation: Department of Molecular Biology and Ecology of Plants, Tel Aviv University, Tel Aviv 69978, Israel.
authors.forename: Niv
authors.initials: N
authors.lastname: Sabath
authors.affiliation: FAFU and UIUC-SIB Joint Center for Genomics and Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian, 350002, China.|Department of Plant Biology, University of Illinois, Urbana, Illinois, 61801.
authors.forename: Ray
authors.initials: R
authors.lastname: Ming
authors.affiliation: Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, 15260.
authors.forename: Tia-Lynn
authors.initials: TL
authors.lastname: Ashman
mesh_terms: D005075:Biological Evolution; D014644:Genetic Variation; D019684:Magnoliopsida / Q000235:genetics / Q000502:physiology*; D010802:Phylogeny; D012098:Reproduction
keywords: Dioecy; hermaphroditism; phylogenetic comparative analysis; plant sexual system