Ancheta, Justin , Heard, Steve .
Herbivore damage and saline stress tolerance in the Gulf of St. Lawrence Aster.
The Gulf of St. Lawrence Aster, Symphotricum laurentianum (Fernald) Nesom (Asteraceae), is a rare annual halophyte restricted to dune slacks, salt marshes and similar habitats and endemic to the southern Gulf of St. Lawrence. In its native habitat, it grows in close proximity to related species that experience insect herbivore attack, making spill- over herbivory effects on this species likely. However, the impact of herbivore damage on plant fitness is unknown, as is the potential interaction of herbivore damage with costs of salinity tolerance. We used growth chamber experiments with simulated herbivory to examine interacting effects of salinity and leaf area removal on plant fitness. We subjected 300 individual plants to eight treatments, with two levels of leaf area removal (simulated herbivory) and four levels of salinity. We predicted that an interaction would be present, in that leaf area removal and salinity would have a synergistically negative effect on plant fitness. There was interaction effect of salinity and leaf area removal on both mean plant height and mean number of seedheads, but the plant may be able to tolerate moderate amounts of leaf damage even under saline conditions. Detectable but subtle differences in mean plant height were observed between undamaged and damaged plants at 5 g/L (13% increase) and 10 g/L (9% decrease) salinity. For damaged plants, there was an unexpected increase in mean seedhead count at 5 g/L (35%). Counts of filled and unfilled seeds (pending) will more accurately assess effects on plant fitness. These results may inform potential management strategies for this and other rare halophytic plants through the inclusion of the effects of insect herbivores, and will clarify the importance of considering insect herbivores in the conservation of this rare and endemic plant species.
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1 - University of New Brunswick, Department of Biology, #10 Bailey Drive, P.O. Box 4400, Fredericton, New Brunswick, E3B 5A3, Canada
Presentation Type: Poster:Posters for Topics
Location: Ball Room & Party Room/SUB
Date: Monday, July 28th, 2008
Time: 12:30 PM