PARENT SESSION
Oral Session #75: Evolutionary Ecology -- Life histories, interactions.
Presiding: S. Armbruster
Thursday, August 8. 9:00 AM to 11:30 AM. Graham Meeting Room, TCC.
Seasonal succession through phenotypically plastic life history trait shifts in Daphnia.
BERNOT, RANDALL*,1, DODDS, WALTER1, QUIST, MICHAEL1, GUY, CHRISTOPHER1, 1 Kansas State University, Manhattan, Kansas
ABSTRACT- The direct effects of changing temperatures, predation risks, and resources have been invoked as factors contributing to the annual succession of zooplankton in lakes. The role of evolved responses of key species to these selection pressures will theoretically contribute to community-level processes, but has not yet been studied in this light. We investigated how temperature and predation risk indirectly affected Daphnia populations in Glen Elder Reservoir through induced shifts in life history characteristics (phenotypic plasticity) and related these findings to seasonal succession events from 1999-2000. The zooplankton community in Glen Elder shifted from Daphnia pulicaria dominance to D. mendotae dominance as temperature and predation risk increased in each sampling year. In a laboratory experiment, we measured plastic life history characteristics of D. pulicaria and D. mendotae grown under different predation risk treatments at three temperatures to simulate changing environmental conditions. D. pulicaria abundance and size at first reproduction declined, while resting egg (ephippia) formation increased in the presence of predation risk at 20-25 °C , but not at 15 °C. In contrast, D. mendotae abundance and clutch size increased with predation risk at high temperatures, but produced few ephippia under all conditions. The results were in accordance with natural patterns of Daphnia life history and succession. This study elucidates the role of changing phenotypic traits in generating community patterns and provides a direct link between evolutionary ecology and broad ecological processes.
KEY WORDS: Daphnia, phenotypic plasticity, life history, ephippia