Dissertation Research: The Importance of the Egg Bank to the Genetics and Demography of a Resident Zooplankton Population

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An intriguing reproductive feature of Daphnia and other Cladocera in lake plankton is that they produce dormant eggs that can hatch after many years in lake sediments. Dormant Daphnia eggs in lake sediment are a zoological analog to the "seed banks" of terrestrial plants in soils. Dormant eggs in surface sediment are a reservoir of genetic diversity for active populations, and older eggs in deeper sediments are a record of genetic structure in past populations. This project will analyze the genetic composition of the Daphnia egg bank in sediments from a Minnesota lake to evaluate whether the population has evolved in response to natural selection imposed by predation by rainbow trout that have been stocked annually for the past 40 years. It will 1) compare the genetic composition of the egg bank at times in the past with that of the active resident population and 2) estimate the effects of hatching of dormant eggs in surface sediment on the demography of the active population. A novel feature is that for the past decade this lake has been monitored the genetics and demography of active zooplankton populations, permitting evaluation of the linkages between active populations and the pool of dormant eggs. The goal is to link short-term variations of genetic diversity to long-term evolutionary dynamics.