PARENT SESSION
Oral Session #55: Predator - Prey Interactions.
Presiding: R. Dueser
Wednesday, August 7. 8:00 AM to 11:30 AM. Cochise Meeting Room, TCC.
Evaluating the prevalence of non-additivity for multiple predator species in aquatic systems.
Vance, Heather*,1, Soluk, Daniel1,2, 1 University of Illinois, Urbana-Champaign, IL2 Illinois Natural History Survey, Champaign, IL
ABSTRACT- Understanding whether the consumption rates of two different predator species in isolation can be summed together to predict the consumption rate when those predator species are present simultaneously has widespread implications. Some studies have shown that the observed consumption rates match the predictions of a null model of additivity (an additive outcome) while other studies show that the observed and predicted values differ dramatically (a non-additive outcome). We address the question of how prevalent additive interactions are in comparison to non-additive interactions and discuss when additivity and non-additivity may occur. We measured the consumption of mayfly larvae (Isonychia sp.) under conditions of varying predator density and species composition in artificial stream tanks. Two predatory invertebrates, dragonfly larvae (Boyeria vinosa) and hellgrammites (Corydalus cornutus), and two fish, greenside darters (Etheostoma blennoides) and creek chubs (Semotilus atromaculatus) were used. The consumption of every two-predator species combination was monitored in the same controlled experimental conditions. Out of six interspecific combinations of two predator species, only one combination demonstrated even a trend toward non-additivity. The low occurrence of non-additivity observed in this study suggests the possibility that predicting the outcome of multiple predator species interactions may be easier than previously thought.
KEY WORDS: additive, non-additive, multiple predator species, predation