title: Unique expression of a sporophytic character on the gametophytes of notholaenid ferns (Pteridaceae).
abstract: OBJECTIVE
  Not all ferns grow in moist, shaded habitats; some lineages thrive in exposed, seasonally dry environments. Notholaenids are a clade of xeric-adapted ferns commonly characterized by the presence of a waxy exudate, called farina, on the undersides of their leaves. Although some other lineages of cheilanthoid ferns also have farinose sporophytes, previous studies suggested that notholaenids are unique in also producing farina on their gametophytes. For this reason, consistent farina expression across life cycle phases has been proposed as a potential synapomorphy for the genus Notholaena. Recent phylogenetic studies have shown two species with nonfarinose sporophytes to be nested within Notholaena, with a third nonfarinose species well supported as sister to all other notholaenids. This finding raises the question: are the gametophytes of these three species farinose like those of their close relatives, or are they glabrous, consistent with their sporophytes?
  
  
  METHODS
  We sowed spores of a diversity of cheilanthoid ferns onto culture media to observe and document whether their gametophytes produced farina. To place these species within a phylogenetic context, we extracted genomic DNA, then amplified and sequenced three plastid loci. The aligned data were analyzed using maximum likelihood to generate a phylogenetic tree.
  
  
  RESULTS
  Here we show that notholaenids lacking sporophytic farina also lack farina in the gametophytic phase, and notholaenids with sporophytic farina always display gametophytic farina (with a single exception). Outgroup taxa never displayed gametophytic farina, regardless of whether they displayed farina on their sporophytes.
  
  
  CONCLUSIONS
  Notholaenids are unique among ferns in consistently expressing farina across both phases of the life cycle.
authors.affiliation: Department of Biology, Duke University, Durham, North Carolina 27708 USA.
authors.forename: Anne K
authors.initials: AK
authors.lastname: Johnson
authors.forename: Carl J
authors.initials: CJ
authors.lastname: Rothfels
authors.forename: Michael D
authors.initials: MD
authors.lastname: Windham
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Pryer
mesh_terms: D021901:DNA, Intergenic / Q000235:genetics; D018744:DNA, Plant / Q000737:chemistry / Q000235:genetics; D029624:Ferns / Q000145:classification / Q000235:genetics* / Q000254:growth & development; D017343:Genes, Plant / Q000235:genetics*; D014644:Genetic Variation; D055993:Germ Cells, Plant / Q000254:growth & development / Q000378:metabolism*; D008969:Molecular Sequence Data; D010802:Phylogeny; D018087:Plastids / Q000235:genetics; D006180:Proton-Translocating ATPases / Q000235:genetics; D012347:RNA, Transfer, Arg / Q000235:genetics; D012353:RNA, Transfer, Gly / Q000235:genetics; D012273:Ribulose-Bisphosphate Carboxylase / Q000235:genetics; D017422:Sequence Analysis, DNA; D013045:Species Specificity
chemical_list: D021901:DNA, Intergenic; D018744:DNA, Plant; D012347:RNA, Transfer, Arg; D012353:RNA, Transfer, Gly; D006180:Proton-Translocating ATPases; C101625:RbcL protein, plastid; D012273:Ribulose-Bisphosphate Carboxylase