PARENT SESSION
Oral Session #19: Animal Community Ecology: Predation, community structure.
Presiding: G. Cumming
Monday, August 5. 1:00 PM to 3:45 PM. Cochise Meeting Room, TCC.
Combining predator effectiveness and abundance to evaluate the importance of predation on Hyla cinerea tadpoles.
Gunzburger, Margaret*,1, 1 Department of Biological Science, Tallahassee, FL
ABSTRACT- The effect of a predator species on prey is a function of the predator's abundance and its ability to capture that prey. For a prey species that occurs in a range of habitat types, the suite of most abundant predators is likely to vary across habitats. However, even if suites are different, the net predation pressure could be the same if individual predators in different habitats are ecological equivalents. The objectives of this project were to evaluate the community composition of predators of green treefrog (Hyla cinerea) tadpoles across habitat types and evaluate the individual effectiveness of predators on H. cinerea tadpoles. Eighteen aquatic habitats were sampled using a 0.5 m2 box sampler to quantify the frequency of eight predator species. Correspondence and cluster analysis of predator frequencies across habitats indicated that the majority of variance in community composition of predators was due to a division between permanent and temporary localities. A laboratory experiment evaluated the effect of each of nine predator species on survival of three sizes of H. cinerea tadpoles to determine which predators were most effective. The most effective predators over all size classes were aeshnid and libellulid odonate naiads, newts, and crayfish. With most predators the survival of the smallest size tadpoles was significantly lower than the survival of medium and large tadpoles, indicating that H. cinerea tadpoles probably reach a size refuge from predation. An index constructed by combining the effectiveness of predators in laboratory experiments with the abundance of each predator species from the habitat surveys suggested that the predation pressure on H. cinerea tadpoles varies across habitats due to variation in predator frequency across sites. The results of this research suggest that combining predator effectiveness with predator abundance presents a more accurate estimation of predator importance than either measure alone.
KEY WORDS: predator-prey, predation, Hyla cinerea, tadpole