Phenotypic selection to increase floral scent emission, but not flower size or colour in bee-pollinated Penstemon digitalis.
Fragrance is a putatively important character in the evolution of flowering plants, but natural selection on scent is rarely studied and thus poorly understood. We characterized floral scent composition and emission in a common garden of Penstemon digitalis from three nearby source populations. We measured phenotypic selection on scent as well as floral traits more frequently examined, such as floral phenology, display size, corolla pigment, and inflorescence height. Scent differed among populations in a common garden, underscoring the potential for scent to be shaped by differential selection pressures. Phenotypic selection on flower number and display size was strong. However, selection favoured scent rather than flower size or colour, suggesting that smelling stronger benefits reproductive success in P. digitalis. Linalool was a direct target of selection and its high frequency in floral-scent bouquets suggests that further studies of both pollinator- and antagonist-mediated selection on this compound would further our understanding of scent evolution. Our results indicate that chemical dimensions of floral display are just as likely as other components to experience selective pressure in a nonspecialized flowering herb. Therefore, studies that integrate visual and chemical floral traits should better reflect the true nature of floral evolutionary ecology.
Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853, USA.|Present address: Plant Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, Uppsala 752 36, Sweden.
Amy L
AL
Parachnowitsch
Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA.
Robert A
RA
Raguso
Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853, USA.
André
A
Kessler
D000080462:Acyclic Monoterpenes; D000818:Animals; D001516:Bees / Q000502:physiology*; D005075:Biological Evolution; D003116:Color; D035264:Flowers / Q000737:chemistry* / Q000502:physiology; D008401:Gas Chromatography-Mass Spectrometry; D039821:Monoterpenes / Q000737:chemistry; D009812:Odorants; D032263:Penstemon / Q000737:chemistry* / Q000502:physiology; D010641:Phenotype; D054817:Pollination; D012098:Reproduction; D012641:Selection, Genetic; D055549:Volatile Organic Compounds / Q000737:chemistry
D000080462:Acyclic Monoterpenes; D039821:Monoterpenes; D055549:Volatile Organic Compounds; C018584:linalool