title: Non-equilibrium dynamics and floral trait interactions shape extant angiosperm diversity.
abstract: Why are some traits and trait combinations exceptionally common across the tree of life, whereas others are vanishingly rare? The distribution of trait diversity across a clade at any time depends on the ancestral state of the clade, the rate at which new phenotypes evolve, the differences in speciation and extinction rates across lineages, and whether an equilibrium has been reached. Here we examine the role of transition rates, differential diversification (speciation minus extinction) and non-equilibrium dynamics on the evolutionary history of angiosperms, a clade well known for the abundance of some trait combinations and the rarity of others. Our analysis reveals that three character states (corolla present, bilateral symmetry, reduced stamen number) act synergistically as a key innovation, doubling diversification rates for lineages in which this combination occurs. However, this combination is currently less common than predicted at equilibrium because the individual characters evolve infrequently. Simulations suggest that angiosperms will remain far from the equilibrium frequencies of character states well into the future. Such non-equilibrium dynamics may be common when major innovations evolve rarely, allowing lineages with ancestral forms to persist, and even outnumber those with diversification-enhancing states, for tens of millions of years.
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN 37996, USA bomeara@utk.edu.
authors.forename: Brian C
authors.initials: BC
authors.lastname: O'Meara
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309, USA stacey.d.smith@colorado.edu.
authors.forename: Stacey D
authors.initials: SD
authors.lastname: Smith
authors.affiliation: School of Biological Sciences, University of Portsmouth, Portsmouth PO1 2DY, UK Institute of Arctic Biology, University of Alaska, Fairbanks, AK 99775, USA Department of Biology, Norwegian University of Science and Technology, 7491 Trondheim, Norway.
authors.forename: W Scott
authors.initials: WS
authors.lastname: Armbruster
authors.affiliation: Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada T2N 1N4.
authors.forename: Lawrence D
authors.initials: LD
authors.lastname: Harder
authors.affiliation: Biology Department, Millersville University, Millersville, PA 17551, USA.
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Hardy
authors.affiliation: Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045, USA.
authors.forename: Lena C
authors.initials: LC
authors.lastname: Hileman
authors.affiliation: School of Biological Sciences, Washington State University, Pullman, WA 99164, USA.
authors.forename: Larry
authors.initials: L
authors.lastname: Hufford
authors.affiliation: Department of Botany and Plant Sciences, University of California, Riverside, CA 92521, USA The New York Botanical Garden, Bronx, NY 10459, USA.
authors.forename: Amy
authors.initials: A
authors.lastname: Litt
authors.affiliation: Instituto de Biología, Universidad Nacional Autónoma de México, México DF 04510, México.
authors.forename: Susana
authors.initials: S
authors.lastname: Magallón
authors.affiliation: Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109, USA.
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Smith
authors.affiliation: Missouri Botanical Garden, St Louis, MO 63166, USA.
authors.forename: Peter F
authors.initials: PF
authors.lastname: Stevens
authors.affiliation: Department of Biology and Microbiology, South Dakota State University, Brookings, SD 57007, USA.
authors.forename: Charles B
authors.initials: CB
authors.lastname: Fenster
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT 06269-3043, USA.
authors.forename: Pamela K
authors.initials: PK
authors.lastname: Diggle
mesh_terms: D044822:Biodiversity; D005075:Biological Evolution; D035264:Flowers / Q000033:anatomy & histology* / Q000502:physiology*; D019684:Magnoliopsida / Q000502:physiology*; D008954:Models, Biological; D010802:Phylogeny; D019655:Quantitative Trait, Heritable; D013269:Stochastic Processes
keywords: diversification; floral evolution; flower symmetry; macroevolution; non-equilibrium; pollination