title: Strong pollinator-mediated selection for increased flower brightness and contrast in a deceptive orchid.
abstract: Contrasting flower color patterns that putatively attract or direct pollinators toward a reward are common among angiosperms. In the deceptive orchid Anacamptis morio, the lower petal, which makes up most of the floral display, has a light central patch with dark markings. Within populations, there is pronounced variation in petal brightness, patch size, amount of dark markings, and contrast between patch and petal margin. We tested whether pollinators mediate selection on these color traits and on morphology (plant height, number of flowers, corolla size, spur length), and whether selection is consistent with facilitated or negative frequency-dependent pollination. Pollinators mediated strong selection for increased petal brightness (Δβpoll = 0.42) and contrast (Δβpoll = 0.51). Pollinators also tended to mediate stabilizing selection on brightness (Δγpoll = -0.27, n.s.) favoring the most common phenotype in the population. Selection for reduced petal brightness among hand-pollinated plants indicated a fitness cost associated with brightness. The results demonstrate that flower color traits influence pollination success and seed production in A. morio, indicating that they affect attractiveness to pollinators, efficiency of pollen transfer, or both. The documented selection is consistent with facilitated pollination and selection for color convergence toward cooccurring rewarding species.
authors.affiliation: Department of Plant Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18 D, SE-752 36, Uppsala, Sweden. nina.sletvold@ebc.uu.se.
authors.forename: Nina
authors.initials: N
authors.lastname: Sletvold
authors.affiliation: Department of Plant Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18 D, SE-752 36, Uppsala, Sweden.
authors.forename: Judith
authors.initials: J
authors.lastname: Trunschke
authors.affiliation: Department of Plant Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18 D, SE-752 36, Uppsala, Sweden.
authors.forename: Mart
authors.initials: M
authors.lastname: Smit
authors.affiliation: Department of Plant Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18 D, SE-752 36, Uppsala, Sweden.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Verbeek
authors.affiliation: Department of Plant Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18 D, SE-752 36, Uppsala, Sweden.
authors.forename: Jon
authors.initials: J
authors.lastname: Ågren
mesh_terms: D000818:Animals; D001516:Bees / Q000502:physiology*; D003116:Color; D035264:Flowers / Q000033:anatomy & histology* / Q000502:physiology*; D029595:Orchidaceae / Q000033:anatomy & histology* / Q000502:physiology*; D011058:Pollen; D054817:Pollination
keywords: Anacamptis morio; facilitation; floral evolution; flower color; natural selection; plant-animal interactions; pollination by deceit