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".
- Natural populations of Oenothera caespitosa in Utah and Wyoming
are polymorphic in floral scent chemistry, with up to 6 distinct chemical
phenotypes or “chemotypes”.
- Other aspects of floral phenotype, including floral size, depth, anther-stigma
distance also are variable in these populations.
- 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.
- 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).
- Do scent chemotypes co-vary with floral morphology?
- Do populations differ in the relative frequencies of different chemotypes?
- Are specific scent chemotypes significantly associated with different
pollinators, herbivores or pathogens?
- Do plants under herbivore attack or rust infection show induced changes
in their volatile chemical emissions?
- What are the fitness consequences (either direct or indirect) of
variation in floral scent chemistry?