PARENT SESSION
Oral Session #39: Invasions: Effects of invaders -- Aquatic, marsh, riparian. Presiding: C. Kolar.
Wednesday, August 8, 2001. 8:00 AM to 11:45 AM. Madison Ballroom C.
Effects of exotic species invasion and species replacement on prey community structure.
Beisner, Beatrix1, Carpenter, Stephen1, Ives, Anthony1, 1
ABSTRACT- The introduction of exotic species and range expansions by native fish has become more common in recent decades. When these occur, native species can be replaced by new species with similar ecological roles. What effect does this change in species composition at one trophic level have on adjacent trophic levels? Does the co-evolutionary history of linked trophic levels matter? Two lakes that are part of the North Temperate Lakes LTER have been subject to a replacement of the native planktivore species (either Perca flavescens or Coregonus artedii) by the exotic rainbow smelt (Osmerus mordax). Long-term detailed data on the zooplankton communities has been collected prior, during and following the invasion periods. We use first order multivariate autoregressive models, a form of multivariate regression for time series, to look at the effects of the species replacement at the planktivore trophic level on zooplankton community structure. Potential drivers for change in the zooplankton communities included in the statistical model are primary production, seasonal components and the density and age-structure of planktivorous fish populations. Zooplankton communities shifted with planktivore species replacement to smaller body-size populations with less stable dynamics. It appears that the species composition of the fish community, not just the trophic status of a lake food web, can influence zooplankton communities.
KEY WORDS: invasive species, rainbow smelt, zooplankton community structure, planktivory