PARENT SESSION
Oral Session # 51: Limnology II: Plankton; Carbon.
Presiding: K Forshay
Wednesday, August 6. 1:30 PM to 5:00 PM, SITCC Meeting Room 101.
Linking algal species' traits to environmental contexts: A test of the keystone predation hypothesis.
Darcy, Tara*,1, 1 W. K. Kellogg Biological Station, Hickory Corners, MI
ABSTRACT- Species face ecological and evolutionary tradeoffs that greatly impact their survival and abundance in different environments. For example, the "keystone predation hypothesis" posits that traits which confer greater competitive ability also may make species more vulnerable to predation. Thus, along gradients of increasing productivity and predators, the dominant species within communities shift from superior competitors to predator tolerant species. To determine whether such "keystone predator" tradeoffs operate within a system, one must investigate the correlations between species' traits and their predicted environmental associations. During 2002, I conducted a series of mesocosm and microcosm experiments to explore the traits of benthic algae that confer success in various environmental contexts. I used the fourth-corner matrix analysis, a recently-devised and powerful statistical approach, to study the correlation matrix of algal traits (superior competitive ability for limiting resources and predator tolerance) and environmental variables. Our results indicate that the tradeoffs assumed in the keystone predation hypothesis are valid for our system. For example, the ability of benthic algae to compete in a phosphorus limiting environment is significantly negatively correlated with environmental productivity, whereas the ability to resist predation by a grazing snail (Physa spp.) is significantly positively correlated with environmental productivity. These results demonstrate the usefulness of the fourth-corner analysis in studying species tradeoffs and they illustrate the value of a mechanistic approach to understanding the turnover of species across environmental gradients.
Key words: species turnover, benthic algae, fourth-corner analysis