1 Separating selection by diurnal and nocturnal pollinators on floral display and spur length 2 in Gymnadenia conopsea 3 4 Nina Sletvold1,2, Judith Trunschke1,3, Carolina Wimmergren1, Jon Ågren1 5 6 1Plant Ecology and Evolution, Department of Ecology and Genetics, Evolutionary Biology 7 Centre, Uppsala University, Norbyvägen 18 D, SE-752 36 Uppsala, Sweden 8 E-mail:
[email protected] 9 Phone: +46 18 471 28 71, Fax: +46 18 55 34 19 10 11 2Norwegian University of Science and Technology, Museum of Natural History and 12 Archaeology, N-7491 Trondheim, Norway 13 14 3Present address: Institute of Systematic Botany, University of Zurich, Zollikerstrasse 107, 15 CH-8008 Zürich, Switzerland 16 1 17 Abstract 18 Most plants attract multiple flower visitors that may vary widely in their effectiveness as 19 pollinators. Floral evolution is expected to reflect interactions with the most important 20 pollinators, but few studies have quantified the contribution of different pollinators to current 21 selection on floral traits. To compare selection mediated by diurnal and nocturnal pollinators on 22 floral display and spur length in the rewarding orchid Gymnadenia conopsea, we manipulated 23 the environment by conducting supplemental hand-pollinations and selective pollinator 24 exclusions in two populations in central Norway. In both populations, the exclusion of diurnal 25 pollinators significantly reduced seed production compared to open-pollination, whereas the 26 exclusion of nocturnal pollinators did not. There was significant selection on traits expected to 27 influence pollinator attraction and pollination efficiency in both the diurnal and nocturnal 28 pollination treatment. The relative strength of selection among plants exposed to diurnal and 29 nocturnal visitors varied among traits and populations, but the direction of selection was 30 consistent.