title: Unraveling the origin of the Appalachian gametophyte, Vittaria appalachiana.
abstract: Ferns and lycophytes are distinct among plants in producing two free-living life stages: a long-lived sporophyte phase and a (usually) short-lived gametophyte phase. Notably, however, some species have perennial, vegetatively reproducing gametophytes. Vittaria appalachiana is one of just three species in which mature sporophytes are unknown. It has a wide range throughout the Appalachian Mountains and Plateau, where it reproduces asexually via gemmae. The origin of V. appalachiana, however, has long been a mystery, with most previous studies suggesting it may have resulted from hybridization of two closely related Vittaria species (V. graminifolia and V. lineata).
  
  
  
  A four-gene plastid data set including 32 samples of six Vittaria species, plus samples of five outgroup species, was analyzed to uncover phylogenetic relationships. Additional analyses of nuclear DET1 gene sequences allowed for the examination of hypotheses involving a hybrid origin for V. appalachiana.
  
  
  
  In the plastid phylogeny, V. appalachiana is well supported as monophyletic, but is embedded within V. graminifolia. With the exception of a single aberrant allele, this result is mirrored in the nuclear tree.
  
  
  
  Through analyses of plastid and nuclear data sets, this study demonstrates that a hybrid origin for V. appalachiana is unlikely. Instead, it appears that this species emerged from within the V. graminifolia lineage. Further work is needed to fully elucidate the genetic structure within this group.
authors.affiliation: Department of Biology, University of Florida, Gainesville, Florida 32611-8525 USA jbp4166@ufl.edu.
authors.forename: Jerald B
authors.initials: JB
authors.lastname: Pinson
authors.affiliation: Department of Botany, Smithsonian Institution, MRC 166 PO Box 37012 Washington, District of Columbia 20013-7012 USA.
authors.forename: Eric
authors.initials: E
authors.lastname: Schuettpelz
mesh_terms: D001499:Bayes Theorem; D002467:Cell Nucleus / Q000235:genetics; D029624:Ferns / Q000502:physiology*; D005843:Geography; D055993:Germ Cells, Plant / Q000502:physiology*; D010802:Phylogeny; D018087:Plastids / Q000235:genetics
keywords: Appalachian Mountains; Pteridaceae; hybridization; independent gametophytes; leptosporangiate ferns; nuclear DET1; plastid genes; polyploidy