Majetic, Cassie , Raguso, Robert A. , Levin, Donald A. .
All in the family: assessing floral pigment-floral scent associations in the genus Phlox.
Floral color and floral scent are two characteristics used by plants to attract pollinators. Until recently, biologists have assumed that color and scent evolved separately to match pollinator preference. However, some scent compounds (benzenoids and phenylpropanoids) are produced by branches of the same biochemical pathways that produce anthocyanin floral pigments, suggesting the potential for pleiotropic associations between them. Other scent compounds, such as terpenes, have no direct biochemical linkage to anthocyanin synthesis and should not co-vary with pigment. We studied six species from the genus Phlox (Polemoniaceae) and a related outgroup species (Polemonium caeruleum), examining floral scent composition and emission rates from pigmented vs. white (no visible anthocyanin) cultivars for each species. Specifically, we predicted that white and pigmented cultivars should differ significantly in benzenoid/phenylpropanoid production regardless of species, while the production of terpenoids and other scent compounds should show no specific pattern related to color. Our results suggest mixed support for this hypothesis. We do find substantial qualitative and quantitative differences between conspecific color morphs for most species. Relative abundance of such benzenoid/phenylpropanoid compounds as methyl salicylate and 3-hydroxy-4-phenyl-2-butanone account for some of the differences in scent production observed between pigmented and white cultivars of Phlox stolonifera and Phlox bifida, but these differences were not in the same direction for both species. Moreover, other differences between cultivars for all examined species were attributable to differences in terpenoid abundance, against our predictions. Assessment of emission rates of individual compounds yields a similar pattern - most differences between cultivars showed increased release of some benzenoids or terpenoids with concurrent decreases in other compounds from the same biochemical category. These data suggest that patterns of scent emission in this genus are not primarily governed by tradeoffs with pigmentation; rather, species identity is more important for defining floral scent profiles.
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1 - Saint Mary's College, Department of Biology, State Route 933, Notre Dame, IN, 46556, USA
2 - Cornell University, Department of Neurobiology and Behavior, Room W355, Seeley G Mudd Hall, 215 Tower Road, Ithaca, NY, 14853, USA
3 - The University of Texas at Austin, Section of Integrative Biology, 1 University Station C0930, Austin, TX, 78712, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Lindell B/Chase Park Plaza
Date: Wednesday, July 13th, 2011
Time: 1:45 PM