PARENT SESSION
Organized Oral Session 39: Consequences of dispersal and colonization: What happens when communities are opened?
Organizer(s): CG Guthrie and DA Yee
Wednesday, August 10, 1:30 PM - 5:00 PM, Meeting Room 516 C, Level 5, Palais des congrès de Montréal

Local population persistence in zooplankton assemblages: The role of history and interspecific interactions.

Caceres, Carla^*,1, Paczolt, Kimberly¹, Smith, Sigrid¹, Steiner, Christopher¹, ¹ University of Illinois at Urbana-Champaign, Urbana, IL, USA

ABSTRACT- Plankton ecologists have recently discovered a way to couple a description of past events with experimental tests of the mechanisms underlying the observed patterns. Diapausing eggs of zooplankton can accumulate in large numbers in lake sediments, where they remain viable for decades or centuries. When these eggs are removed from the lake and hatched in the laboratory, they provide a living link to past populations and communities. Dozens of lakes in east-central Illinois, USA, were formed within the past century when strip-mining created new basins. We are using the sediment record of these lakes to address questions regarding how genetic diversity, life-history variation and interspecific interactions influence the persistence ability of populations, and consequently, the development of planktonic communities. Sediment cores extending to the formation of each lake have been collected from 8 lakes, and often show clear patterns of species replacement in the cladoceran assemblage through time. In the majority of lakes, smaller species such as Daphnia ambigua and Ceriodaphnia quadrangula invaded early and were later replaced by larger-bodied species. A laboratory competition experiment from one of these lakes suggests that clones of D. ambigua from early in the colonization sequence cannot co-exist with the species that colonized later. We plan to combine the results of competition experiments with estimates of variation in life-history traits and clonal diversity to address the roles of colonization history and interspecific interactions in determining the current community composition in these 8 lakes.

Key words: competition, zooplankton, Daphnia