title: Gisekia (Gisekiaceae): phylogenetic relationships, biogeography, and ecophysiology of a poorly known C₄ lineage in the Caryophyllales.
abstract: OBJECTIVE
  Gisekiaceae are a monogeneric family of the core Caryophyllales distributed in arid regions of Africa and Asia. The only widespread species of the genus, Gisekia pharnaceoides, performs C4 photosynthesis based on CO2 compensation point measurements. This study investigates the C4 syndrome and its evolution in Gisekia. The infrageneric relationships, distribution and bioclimatic preferences of Gisekia are also investigated.
  
  
  METHODS
  Leaf gas exchange characteristics, activity of Rubisco and major C4 cycle enzymes, and ultrastructural characteristics of mesophyll and bundle sheath cells are studied for Gisekia pharnaceoides. δ(13)C values and leaf anatomy are analyzed for all species. A dated molecular phylogeny of 39 accessions representing all species of Gisekiaceae and 14 representatives of closely related core Caryophyllales families is generated using four cp markers and ITS. The precise current distribution and bioclimatic niche of Gisekia is assessed on the basis of 520 georeferenced specimen localities.
  
  
  RESULTS
  All traditionally recognized species of Gisekia are C4 plants with atriplicoid Kranz anatomy. Gisekia pharnaceoides uses the NAD-ME biochemical type. The molecular phylogeny demonstrated two East African clades nested within South African clades, demonstrating migration along the arid areas of eastern Africa during the Late Miocene/Pliocene Epochs. Most traditionally defined species are polyphyletic.
  
  
  CONCLUSIONS
  Gisekia represents an isolated C4 lineage within core Caryophyllales dating back to the Miocene Epoch and probably spread along the African arid corridor from a South African center of origin. The seven currently recognized species should be treated as one polymorphic species or species complex, Gisekia pharnaceoides agg.
authors.affiliation: Institut für Allgemeine und Spezielle Botanik, Anselm-Franz-von Bentzel weg 9a, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Bissinger
authors.forename: Roxanne
authors.initials: R
authors.lastname: Khoshravesh
authors.forename: Jan Peter
authors.initials: JP
authors.lastname: Kotrade
authors.forename: Jason
authors.initials: J
authors.lastname: Oakley
authors.forename: Tammy L
authors.initials: TL
authors.lastname: Sage
authors.forename: Rowan F
authors.initials: RF
authors.lastname: Sage
authors.forename: Heidrun E K
authors.initials: HE
authors.lastname: Hartmann
authors.forename: Gudrun
authors.initials: G
authors.lastname: Kadereit
mesh_terms: D000349:Africa; D005075:Biological Evolution; D057486:Carbon Cycle; D002247:Carbon Isotopes / Q000032:analysis; D018744:DNA, Plant / Q000737:chemistry / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000737:chemistry / Q000235:genetics; D017753:Ecosystem; D019684:Magnoliopsida / Q000033:anatomy & histology / Q000145:classification / Q000235:genetics / Q000502:physiology*; D010788:Photosynthesis; D010802:Phylogeny; D058974:Phylogeography; D018515:Plant Leaves / Q000033:anatomy & histology / Q000145:classification / Q000235:genetics / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018526:Plant Transpiration / Q000502:physiology; D012273:Ribulose-Bisphosphate Carboxylase / Q000235:genetics / Q000378:metabolism*
chemical_list: D002247:Carbon Isotopes; D018744:DNA, Plant; D021903:DNA, Ribosomal Spacer; D010940:Plant Proteins; D012273:Ribulose-Bisphosphate Carboxylase
keywords: Africa; C4 photosynthesis; Gisekia; Gisekiaceae; Kranz anatomy; arid corridor; carbon isotope values; phylogeny