title: Pollinator shifts and the evolution of spur length in the moth-pollinated orchid Platanthera bifolia.
abstract: OBJECTIVE
  Plant-pollinator interactions are thought to have shaped much of floral evolution. Yet the relative importance of pollinator shifts and coevolutionary interactions for among-population variation in floral traits in animal-pollinated species is poorly known. This study examined the adaptive significance of spur length in the moth-pollinated orchid Platanthera bifolia.
  
  
  METHODS
  Geographical variation in the length of the floral spur of P. bifolia was documented in relation to variation in the pollinator fauna across Scandinavia, and a reciprocal translocation experiment was conducted in south-east Sweden between a long-spurred woodland population and a short-spurred grassland population.
  
  
  RESULTS
  Spur length and pollinator fauna varied among regions and habitats, and spur length was positively correlated with the proboscis length of local pollinators. In the reciprocal translocation experiment, long-spurred woodland plants had higher pollination success than short-spurred grassland plants at the woodland site, while no significant difference was observed at the grassland site.
  
  
  CONCLUSIONS
  The results are consistent with the hypothesis that optimal floral phenotype varies with the morphology of the local pollinators, and that the evolution of spur length in P. bifolia has been largely driven by pollinator shifts.
authors.affiliation: Department of Plant Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-752 36 Uppsala, Sweden.
authors.forename: Elin
authors.initials: E
authors.lastname: Boberg
authors.forename: Ronny
authors.initials: R
authors.lastname: Alexandersson
authors.forename: Magdalena
authors.initials: M
authors.lastname: Jonsson
authors.forename: Johanne
authors.initials: J
authors.lastname: Maad
authors.forename: Jon
authors.initials: J
authors.lastname: Ågren
authors.forename: L Anders
authors.initials: LA
authors.lastname: Nilsson
mesh_terms: D000825:Animal Structures / Q000033:anatomy & histology; D000818:Animals; D005075:Biological Evolution; D017753:Ecosystem; D035264:Flowers / Q000033:anatomy & histology* / Q000502:physiology; D009036:Moths / Q000502:physiology*; D029595:Orchidaceae / Q000033:anatomy & histology* / Q000502:physiology*; D009929:Organ Size; D054817:Pollination / Q000502:physiology*; D025341:Principal Component Analysis; D013045:Species Specificity
keywords: Ecotype; Platanthera bifolia; evolution of floral traits; moth pollination; pollination ecotypes; pollination success; pollinator shift; population differentiation; proboscis length; speciation; spur length