This is kinda general, but it mentions bullfrogs and comes from a site
dedicated to the Sonoran desert:
http://www.desertmuseum.org/ISSDE/Aquatic/Aquatictext.html
Bullfrogs: Introduced Predators in Southwestern Wetlands at
http://biology.usgs.gov/s+t/noframe/x188.htm
http://ice.ucdavis.edu/Toads/aurora.html which is about the Red-legged Frog
and that refers to "...their exclusion from permanent aquatic habitats by
introduced predators (fish and bullfrogs Rana catesbeiana)".
http://biology.usgs.gov/s+t/SNT/noframe/pn171.htm, Spotted Frogs in the
Western Pacific Northwest, which states "Nonindigenous bullfrogs are
probably a primary cause of declining populations of spotted frogs".
This is one overview of the introduced species issue:
http://gcrio.gcrio.org/CONSEQUENCES/vol2no2/article2.html
And http://aquat1.ifas.ufl.edu/mccontnt.html is about introduced species in
Florida. The section on reptiles and amphibians has a few examples and the
literature cited list is pretty large.
I think that's a nice effort on your part, Rhonda.
-- Jay DeLong Olympia, WA
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