PARENT SESSION
Contributed Oral Session 36: Late Breaking and Newsworthy Research: Distribution; Disturbance
Monday, August 8, 1:30 PM - 5:00 PM, Meeting Room 524 C, Level 5, Palais des congrès de Montréal

Is there conflicting selection on floral traits by plant mutualists and antagonists?

Parachnowitsch, Amy^*,, Caruso, Christina,

ABSTRACT- Flowers can attract antagonists as well as mutualists. While attracting mutualistic pollinators increases plant fitness, attracting antagonistic herbivores reduces it, suggesting that antagonists and mutualists will exert conflicting selection on floral traits. We measured phenotypic selection on Lobelia siphilitica by a specialist pre-dispersal seed predator, Cleopmiarus hispidulus, and by generalist Bombus spp. pollinators. Preliminary data showed that attack is extensive and variable, and early season fruits experience greater predation. We experimentally manipulated both pollination and floral phenology within a L. siphilitica population to answer two questions: 1) Do pollinators and seed predators exert concordant or conflicting selection on floral traits? 2) Is phenology a direct target of phenotypic selection by pollinators and/or seed predators? We measured floral traits that were likely under selection by seed predators and pollinators including floral phenology, flower size, daily display size, and plant height. To differentiate selection by pollinators and seed predators, we hand-pollinated half the plants to eliminate selection by pollinators. Lobelia siphilitica fruit production was not pollen limited and phenotypic selection via relative fruit set did not differ between the open- and hand-pollinated treatments. Both suggest that selection by pollinators is not important for fruit production. However, L. siphilitica aborts few flowers and C. hispidulus limits seed, not fruit, production, therefore we expect that any conflicting selection will be evident through relative seed set. To manipulate phenology, two cohorts were planted in the greenhouse two weeks apart before transplanting to the field. The early cohort flowered significantly earlier when both pollinators and seed predators were more abundant suggesting phenology could be a target of selection by mutualists and antagonists in this system.

Key words: phenotypic selection, floral traits, pre-dispersal seed predator