Scent polymorphism & reproductive ecology in Oenothera caespitosa

Sources of Funding:

US National Science Foundation Grant DEB-0317217 "Patterns and Consequences of Fragrance Variation in Oenothera caespitosa".



  1. Natural populations of Oenothera caespitosa in Utah and Wyoming are polymorphic in floral scent chemistry, with up to 6 distinct chemical phenotypes or “chemotypes”.
  2. Other aspects of floral phenotype, including floral size, depth, anther-stigma distance also are variable in these populations.
  3. Flowers of O. caespitosa have several sub-optimal pollinators that visit for nectar or pollen as rewards. Hawkmoths are excellent pollinators but are either rare (Sphinx vashti [above; A]) or double as herbivores ( Hyles lineata [B]). Small crepuscular bees (Lasioglossum [C] and Andrena) are pollen thieves unless stigmas are nestled among anthers. Large crepuscular bees (Xylocopa) are nectar thieves.
  4. Plants of O. caespitosa are attacked by Puccinia rust fungi, the larvae of Altica beetles, Hyles and Mompha moths, and aphids (below, left to right).



  1. Do scent chemotypes co-vary with floral morphology?
  2. Do populations differ in the relative frequencies of different chemotypes?
  3. Are specific scent chemotypes significantly associated with different pollinators, herbivores or pathogens?
  4. Do plants under herbivore attack or rust infection show induced changes in their volatile chemical emissions?
  5. What are the fitness consequences (either direct or indirect) of variation in floral scent chemistry?