Pollinator shifts and the evolution of spur length in the moth-pollinated orchid Platanthera bifolia.
BACKGROUND AND AIMS
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.


KEY 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.
['Boberg|Elin|E|', 'Alexandersson|Ronny|R|', 'Jonsson|Magdalena|M|', 'Maad|Johanne|J|', 'Ågren|Jon|J|', 'Nilsson|L Anders|LA|']
D000825:Animal Structures D000818:Animals D005075:Biological Evolution D017753:Ecosystem D035264:Flowers D009036:Moths D029595:Orchidaceae D009929:Organ Size D054817:Pollination D025341:Principal Component Analysis D013045:Species Specificity
pollinator shift spur length Platanthera bifolia proboscis length pollination success Ecotype evolution of floral traits moth pollination pollination ecotypes population differentiation speciation