PARENT SESSION
Poster Session 35: Evolutionary Ecology
Thursday, August 11, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Life history shifts and variation in resource availability and predation regimes.
Maurer, Eric*,1, O'Brien, W. John2, 1 University of Cincinnati, Cincinnati, OH, United States2 University of North Carolina, Greensboro, Greensboro, NC, United States
ABSTRACT- Life history theory predicts shifts both in traits and the trade-offs between different traits in response to changes in extrinsic mortality rates, and variation in resource availability can also result in changes in energy allocation patterns among different life history traits. We examined the patterns of variation in offspring number and the trade-off between offspring size and number in an arctic snail (Lymnaea elodes) from lakes of the North Slope of Alaska. Using a combination of field surveys and whole ecosystem manipulations conducted at the NSF Arctic Tundra LTER site at Toolik Lake, we examined the roles of resource availability and predation in determining these life history traits. Earlier studies had shown a marked difference in mean size of snails in lakes with and without the dominant predator in these systems, lake trout (Salvelinus namaycush), suggesting as one hypothesis that predator-induced life history shifts could be occurring in these arctic lakes. We took advantage of whole lake manipulations designed to examine the roles of nutrients and trophic interactions in determining arctic lake ecosystem structure and function. These manipulations included predator removal experiments (lake trout) and two different resource manipulations: i) nitrogen/phosphorus fertilization of a divided lake; and ii) whole lake fertilization in a pre-/post-design. The results indicate that resource manipulations did not significantly influence the number or size of Lymnaea offspring. Predator presence/absence did influence these traits, however, with snails having a larger number of smaller offspring in lakes with predators present. Further, offspring number from Lake I8, where lake trout have been removed for several years, was intermediate between lakes with and without predators, suggesting a graded response in life history to shifts in mortality rates.
Key words: life history, arctic lakes, trade-offs