CS39A Zooplankton - Feeding, Reproduction, Growth and Molecular Diversity
Date: Tuesday, June 11, 2002
Time: 11:45:00 AM
Location: View Royal
 
YoungJD, SUNY College at Buffalo, Buffalo, USA, younjd92@mail.buffalostate.edu
Riessen, H, P, SUNY College at Buffalo, Buffalo, USA, riessehp@bscmail.buffalostate.edu
 
THE EFFECT OF DIFFERENT CHAOBORUS SPECIES AND INSTARS ON DAPHNIA POPULATION GROWTH RATES: A FIELD STUDY AND MODEL DEVELOPMENT
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The invertebrate predator Chaoborus is abundant and important in freshwater zooplankton communities. Its impact on Daphnia depends on its size, especially mouth gape diameter (which influences strike efficiency and the maximum prey size it can ingest) and migration pattern (which affects spatial overlap between predator and prey). These two features vary considerably in different Chaoborus species and instars. We analyzed the effect of predator size and behaviour on population growth of Daphnia through a field enclosure experiment and a matrix population model. The field experiment involved growth of a Daphnia population in four predator treatments (three replicates each) that included a control (no Chaoborus) and three combinations of instar III and IV Chaoborus of two species (C. trivittatus and C. americanus). The model was based on observed differences between Chaoborus species and instars in strike efficiency and overlap with Daphnia. The qualitative predictions of this model closely simulated the effects of each predator treatment on Daphnia population growth. We conclude that although interspecific morphological differences among the predators are important, predator-prey overlap is more so, and often underestimated in nature.