title: Quantifying hummingbird preference for floral trait combinations: The role of selection on trait interactions in the evolution of pollination syndromes.
abstract: Darwin recognized the flower's importance for the study of adaptation and emphasized that the flower's functionality reflects the coordinated action of multiple traits. Here we use a multitrait manipulative approach to quantify the potential role of selection acting on floral trait combinations underlying the divergence and maintenance of three related North American species of Silene (Caryophyllaceae). We artificially generated 48 plant phenotypes corresponding to all combinations of key attractive traits differing among the three Silene species (color, height, inflorescence architecture, flower orientation, and corolla-tube width). We quantified main and interaction effects of trait manipulation on hummingbird visitation preference using experimental arrays. The main effects of floral display height and floral orientation strongly influenced hummingbird visitation, with hummingbirds preferring flowers held high above the ground and vertically to the sky. Hummingbirds also prefer traits in a nonadditive manner as multiple two-way and higher order interaction effects were important predictors of hummingbird visitation. Contemporary trait combinations found in hummingbird pollinated S. virginica are mostly preferred. Our study demonstrates the likelihood of pollination syndromes evolving due to selection on trait combinations and highlights the importance of trait interactions in understanding the evolution of complex adaptations.
authors.affiliation: Department of Biology, University of Maryland, College Park, College Park, Maryland, 20742. cfenster@umd.edu.|Mountain Lake Biological Station, 240 Salt Pond Road, Pembroke, Virginia, 24136. cfenster@umd.edu.
authors.forename: Charles B
authors.initials: CB
authors.lastname: Fenster
authors.affiliation: Department of Biology, University of Maryland, College Park, College Park, Maryland, 20742.|Mountain Lake Biological Station, 240 Salt Pond Road, Pembroke, Virginia, 24136.|Division of Clinical Immunology and Rheumatology, Department of Medicine, University of Alabama at Birmingham.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Reynolds
authors.affiliation: Mountain Lake Biological Station, 240 Salt Pond Road, Pembroke, Virginia, 24136.|Frostburg State University, Frostburg, Maryland, 21502.|National Institutes of Health, NIDDK, Bethesda, Maryland, 20892.
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Williams
authors.affiliation: Phoenix, Arizona, 85086.
authors.forename: Robert
authors.initials: R
authors.lastname: Makowsky
authors.affiliation: Department of Biology, University of Maryland, College Park, College Park, Maryland, 20742.|Mountain Lake Biological Station, 240 Salt Pond Road, Pembroke, Virginia, 24136.
authors.forename: Michele R
authors.initials: MR
authors.lastname: Dudash
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D001717:Birds / Q000235:genetics* / Q000502:physiology; D019143:Evolution, Molecular; D035264:Flowers / Q000235:genetics; D010641:Phenotype; D054817:Pollination; D019655:Quantitative Trait, Heritable; D012641:Selection, Genetic; D029751:Silene / Q000235:genetics* / Q000502:physiology
keywords: Correlational selection; floral evolution; pollination syndromes; trait interaction