PARENT SESSION
Poster Session #28: Animal Ecology.
Wednesday, August 8, 2001. Presentation from 3:30 PM to 5:00 PM. Exhibition Hall
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Abiotic and biotic factors affecting nonrandom distributions of four desert anurans.
Dayton, Gage1, Fitzgerald, Lee1, Jung, Robin2, Droege, Sam2, 1 2
ABSTRACT- Distributions of Texas toads (Bufo speciosus Couchs) spadefoot toad (Scaphiopus couchii), narrow mouthed toad (Gastrophryne olivacea, and red-spotted toad (Bufo punctatus) are non-randomly distributed across the Chihuahuan Desert landscape. In Big Bend National Park, pools containing tadpoles are clustered, and there is varying amounts of species overlap in individual pools. We found significant differences between observed and expected numbers of amphibian species associated with availability of soil and vegetation types. Patterns of species co-occurrence in pools was highly non-random. Competition and predation experiments showed tadpoles of S. couchii were significantly more active and more susceptible to predation than tadpoles of G. olivacea, B. speciosus, and B. punctatus. Mass of G. olivacea, B. speciosus, and B. punctatus was less when reared with S. couchii, demonstrating possible competitive dominance of S. couchii. These results suggest large-scale habitat associations may act as an initial filter for presence of all species, and a competition-predation tradeoff may determine species overlap in individual pools.
KEY WORDS: distribution, amphibians, predation, competition