Document: WIL-3-56-24

The influence of genetic diversity and temperature on the dynamics of freshwater predator-prey systems.

NELSON, W.A.* ¹, E.MCCAULEY ¹ and F.J.WRONA ²

University of Calgary, Calgary, Alberta, T2N 1N4 Canada ¹
National Water Research Centre, Saskatoon, Saskatchewan, S7N 3H5 Canada ²

Abstract:
The impact of temperature on the population dynamics of predator-prey systems is difficult to predict even when the response of the individuals is known. We tested both, the effect of temperature on the population dynamics of the zooplankton-phytoplankton predator-prey system, and the capacity of zooplankton genetic diversity to modify the systems response. Using Daphnia pulex and a mixture of edible green algae, we closely followed the population dynamics of sixty-six tanks for many generations. The treatments were either 15C or 25C with either single or multiple zooplankton clones. Theory predicts a wide range in population dynamics and equilibria for the zooplankton-phytoplankton system when non-linear predator and prey responses are used. This wide range of dynamics was observed in these tanks with the same general trend that is expected for temperature dependent vital rates. Specifically, low temperature tanks had more stable population dynamics, in terms of temporal variation in abundance, and some replicate tanks displayed very high prey equilibria with very low predator equilibria. High temperature tanks displayed greater instability in temporal dynamics, including evidence of limit cycles with high predator abundance and low prey abundance. Genetic diversity had a much larger effect at 15C where multiple clone tanks were frequently at an entirely different equilibrium than single clone tanks. Multiple clones at 25C did have a stabilizing effect on the equilibrium dynamics but not as large an effect as seen at 15C. The wide range of dynamics observed, and the agreement with theory, demonstrates that zooplankton and phytoplankton interact and respond to temperature in a complex and non-linear fashion. These results reveal that genetic diversity may influence the dynamical complexity observed in predator-prey systems.

Keywords: Predator-Prey, Population Dynamics, Genetic Diversity, Temperature

This abstract is being presented at: 2:45 PM in session:
Oral Session #47: Zooplankton Ecology.