PARENT SESSION
Oral Session # 57: Evolutionary Ecology II: Animal.
Presiding: S Juliano
Wednesday, August 6. 1:30 PM to 5:00 PM, SITCC Meeting Room 201.
To be (dormant) or not to be (dormant): Life history tradeoffs in Daphnia pulicaria.
Caceres, Carla*,1, Tessier, Alan2, 1 Univerisity of Illinois at Urbana-Champaign, Urbana, IL2 Kellogg Biological Station, Hickory Corners, MI
ABSTRACT- It has been suggested that dormancy should be selected against in environments where a population can remain active in the water column year round. We tested this prediction with 12 populations of D. pulicaria. Differences among lakes in basin morphometry, predators and resources create a gradient of habitat suitability for the Daphnia. Some populations persist year-round while others are only found in spring. For three years of field sampling we found consistent differences among the lake populations in investment in diapause. In some populations, only a small fraction of females switched to producing diapausing eggs each year whereas in others the majority of the eggs produced in the late spring were dormant. In general, populations that were only seasonally abundant had a much higher investment in dormancy than populations that persisted in the water-column year round, but there were exceptions. We also investigated the annual hatching fraction of newly produced eggs in five of our 12 populations. After being incubated at the bottom of the lakes for one year, average hatching fraction ranged from 6% to 50% across the five populations. Our results suggest that investment in dormancy varies considerably among populations, but that seasonal phenology is not necessarily a good predictor of dormancy investment. Rather, the risks associated with both the active and dormant stage must be considered.
Key words: diapause, Daphnia pulicaria, life history