1. University of Wisconsin-Milwaukee; P.O Box 413 Milwaukee WI 53201 U.S.A
2. Smithsonian Tropical Research Institute; Apartado Postal 0843-03092 Panama
3. Departments of Ecology, Evolution & Behavior and Plant Biology; University of Minnesota; 1987 Upper Buford Circle St. Paul MN 55108 U.S.A
4. School of Geography; University of Leeds; LS2 9JT Leeds U.K