1. Department of Biological and Environmental Sciences, University of Houston Clear Lake, 2700 Bay Area Boulevard MC 39, Houston, Texas 77058, U.S.A.
2. Savannah River Ecology Laboratory, University of Georgia, Aiken, South Carolina 29802, U.S.A.
3. Department of Biology, University of Texas Rio Grande Valley, 1201 West University Drive, Edinburg, Texas 78539, U.S.A.