title: Evolution of leaf anatomy and photosynthetic pathways in Portulacaceae.
abstract: OBJECTIVE
  Portulacaceae is a family with a remarkable diversity in photosynthetic pathways. This lineage not only has species with different C4 biochemistry (NADP-ME and NAD-ME types) and C3-C4 intermediacy, but also displays different leaf anatomical configurations. Here we addressed the evolutionary history of leaf anatomy and photosynthetic pathways in Portulacaceae.
  
  
  METHODS
  Photosynthetic pathways were assessed based on leaf anatomy and carbon isotope ratios. Information on the NADP-ME and NAD-ME C4 variants was obtained from the literature. The evolutionary relationships and trait evolution were estimated under a Bayesian framework, and divergence times were calibrated using the ages obtained in a previous study.
  
  
  RESULTS
  C4 photosynthesis is the main pathway in Portulacaceae. One clade (Cryptopetala), however, includes species that have non-Kranz anatomy and C3 type isotope values, two of which are C3-C4 intermediates. The ancestral leaf anatomy for the family is uncertain. The analysis showed one origin of the C4 pathway, which was lost in the Cryptopetala clade. Nevertheless, when a second analysis was performed taking into account the limited number of species with NAD-ME and NADP-ME data, a secondary gain of the C4 pathway from a C3-C4 intermediate was inferred.
  
  
  CONCLUSIONS
  The C4 pathway evolved ca. 23 Myr in the Portulacaceae. The number of times that the pathway evolved in the family is uncertain. The diversity of leaf anatomical types and C4 biochemical variants suggest multiple independent origins of C4 photosynthesis. Evidence for a switch from C4 to C3-C4 intermediacy supports the hypothesis that intermediates represent a distinct successful strategy.
authors.affiliation: Rancho Santa Ana Botanic Garden and Claremont Graduate University, 1500 North College Avenue, Claremont, California 91711 USA.
authors.forename: Gilberto
authors.initials: G
authors.lastname: Ocampo
authors.forename: Nuria K
authors.initials: NK
authors.lastname: Koteyeva
authors.forename: Elena V
authors.initials: EV
authors.lastname: Voznesenskaya
authors.forename: Gerald E
authors.initials: GE
authors.lastname: Edwards
authors.forename: Tammy L
authors.initials: TL
authors.lastname: Sage
authors.forename: Rowan F
authors.initials: RF
authors.lastname: Sage
authors.forename: J Travis
authors.initials: JT
authors.lastname: Columbus
mesh_terms: D001499:Bayes Theorem; D005075:Biological Evolution; D002244:Carbon / Q000378:metabolism*; D057486:Carbon Cycle; D002247:Carbon Isotopes / Q000378:metabolism; D008293:Malates / Q000378:metabolism; D009243:NAD / Q000235:genetics / Q000378:metabolism; D009249:NADP / Q000235:genetics / Q000378:metabolism; D010788:Photosynthesis / Q000235:genetics*; D010802:Phylogeny; D018515:Plant Leaves / Q000033:anatomy & histology / Q000502:physiology; D029622:Portulacaceae / Q000033:anatomy & histology / Q000235:genetics* / Q000502:physiology
chemical_list: D002247:Carbon Isotopes; D008293:Malates; D009243:NAD; D009249:NADP; D002244:Carbon; C030298:malic acid
keywords: C3-C4 intermediacy; C4 photosynthesis; Cactineae; Kranz anatomy; Portulaca; Portulacaceae; Portulacineae; leaf anatomy