title: Gradual vs. abrupt reduction of carpels in syncarpous gynoecia: A case study from Polyscias subg. Arthrophyllum (Araliaceae: Apiales).
abstract: OBJECTIVE
  Revealing the relative roles of gradual and abrupt transformations of morphological characters is an important topic of evolutionary biology. Gynoecia apparently consisting of one carpel have evolved from pluricarpellate syncarpous gynoecia in several angiosperm clades. The process of reduction can involve intermediate stages, with one fertile and one or more sterile carpels (pseudomonomery). The possible origin of monomery directly via an abrupt change of gynoecium merism has been a matter of dispute. We explore the nature of gynoecium reduction in a clade of Araliaceae.
  
  
  METHODS
  The anatomy and development of unilocular gynoecia are investigated using light and scanning electron microscopy in two members of Polyscias subg. Arthrophyllum. Gynoecium diversity in the genus is discussed in a phylogenetic framework.
  
  
  RESULTS
  Unilocular gynoecia with one fertile ovule have evolved at least four times in Polyscias, including one newly discovered case. The two unilocular taxa investigated are unicarpellate, without any traces of reduced sterile carpels. Carpel orientation is unstable, and the ovary roof and style contain numerous vascular bundles without clearly recognizable dorsals or ventrals. In contrast to pluricarpellate Araliaceae and Apiaceae, the cross zone is apparently oblique in the unicarpellate species.
  
  
  CONCLUSIONS
  No support was found for gradual gynoecium reduction via pseudomonomery. The abrupt origin of monomery via direct change of gynoecium merism and the unstable carpel orientation observed are related to the general lability of the flower groundplan in Polyscias. The apparent occurrence of the unusual oblique cross zone in unicarpellate Araliaceae can be explained by developmental constraints.
authors.affiliation: Biological Faculty, M.V. Lomonosov Moscow State University, 119234 Moscow, Russia.
authors.forename: Polina V
authors.initials: PV
authors.lastname: Karpunina
authors.affiliation: Department of Botany and Plant Biotechnology, University of Johannesburg, P.O. Box 524, Auckland Park 2006, Johannesburg, South Africa.|Botanical Museum, V.L. Komarov Botanical Institute, Prof. Popov 2, 197376 St. Petersburg, Russia.
authors.forename: Alexei A
authors.initials: AA
authors.lastname: Oskolski
authors.affiliation: Biological Faculty, M.V. Lomonosov Moscow State University, 119234 Moscow, Russia.
authors.forename: Maxim S
authors.initials: MS
authors.lastname: Nuraliev
authors.affiliation: Africa & Madagascar Department, Missouri Botanical Garden, P.O. Box 299, St. Louis, Missouri 63166-0299 USA.|Institut de Systématique, Évolution, et Biodiversité (ISYEB), Unité Mixte de Recherche 7205, Centre National de la Recherche Scientifique/Muséum National d'Histoire Naturelle/École Pratique des Hautes Études/Université Pierre et Marie Curie, Sorbonne Universités, CP 39, 57 rue Cuvier 75231 Paris CEDEX 05, France.
authors.forename: Porter P
authors.initials: PP
authors.lastname: Lowry
authors.affiliation: Biological Faculty, M.V. Lomonosov Moscow State University, 119234 Moscow, Russia.
authors.forename: Galina V
authors.initials: GV
authors.lastname: Degtjareva
authors.affiliation: Department of Evolutionary Biochemistry, A.N. Belozersky Institute of Physicochemical Biology, M.V. Lomonosov Moscow State University 119234 Moscow, Russia.
authors.forename: Tahir H
authors.initials: TH
authors.lastname: Samigullin
authors.affiliation: Department of Evolutionary Biochemistry, A.N. Belozersky Institute of Physicochemical Biology, M.V. Lomonosov Moscow State University 119234 Moscow, Russia.
authors.forename: Carmen M
authors.initials: CM
authors.lastname: Valiejo-Roman
authors.affiliation: Biological Faculty, M.V. Lomonosov Moscow State University, 119234 Moscow, Russia sokoloff-v@yandex.ru.
authors.forename: Dmitry D
authors.initials: DD
authors.lastname: Sokoloff
mesh_terms: D027481:Araliaceae / Q000235:genetics / Q000254:growth & development / Q000648:ultrastructure*; D005075:Biological Evolution; D035264:Flowers / Q000235:genetics / Q000254:growth & development / Q000648:ultrastructure*; D008853:Microscopy; D008855:Microscopy, Electron, Scanning; D056771:Ovule / Q000235:genetics / Q000254:growth & development / Q000648:ultrastructure; D010802:Phylogeny; D012639:Seeds / Q000235:genetics / Q000254:growth & development / Q000648:ultrastructure; D017422:Sequence Analysis, DNA
keywords: anatomy; developmental constraints; evolution; flower; gynoecium; monomery; phylogeny; pseudomonomery; saltation; vasculature