Dudley, Leah S. .
Sugar and spice and everything nice: similar phenolic chemistry may not mean similar defense in an alpine willow shrub, Salix glauca.
About 10% of plant species exhibit dioecy, the separation of male and female function into separate individuals. According to sex allocation theory, because females devote more resources to reproduction via fruits then males via flowers and pollen, tissue lost by females is relatively more expensive than tissue losses by males to antagonists. Consequently, selection from antagonists should drive females towards higher defense levels compared to males. This could ultimately result in males suffering higher levels of attack, and under extreme environmental conditions where time for growth and tissue replacement is limited, could lead to a female biased sex ratio. In this study, a dioecious willow Salix glauca displays highly female biased sex ratios in five populations in alpine habitats of the Colorado Rocky Mountains. However, I found little evidence for dimorphism in susceptibility to herbivores, inducibility of phenolic defenses or constitutive levels of phenolic concentration. Instead, preliminary evidence suggests that sexes may differ in tri-trophic interactions with female plants recruiting parasitoids in their defense. Selection appears to have selected for both male and female plants to have similar levels of phenolic defense, but multi-species interactions may reveal unique dimorphic strategies for countering herbivory.
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1 - University of Missouri-Columbia, Biological Sciences, 105 Tucker Hall, Columbia, Missouri, 65211, USA
Presentation Type: Oral Paper
Location: Salon A - Gov Ballroom/Hilton
Date: Tuesday, August 16th, 2005
Time: 4:30 PM