In addition, the scientists randomly selected points in native forests on Guam, Saipan and two other nearby islands, Tinian and Rota, searching for seedlings of a tree called Aglaia mariannensis and each seedling's most likely parent, the closest adult of that species. On Guam all seedlings were found within 16 feet of the nearest adult tree, most within 6 feet. On the other islands the nearest adult trees were found two to three times farther away from the seedlings.
"These findings could have global implications, since forests in areas that have had a decline in bird populations instead of outright extinction might show effects similar to those in the forests of Guam," Rogers said.
She notes that recent studies show bird populations are declining worldwide, and that as many as 25 percent of U.S. species face the threat of extinction.
Rogers presents her data Friday (Aug. 8) at the Ecological Society of America meeting in Milwaukee. Co-authors are Joshua Tewksbury and Janneke Hille Ris Lambers, both UW assistant professors of biology.
Further research, Rogers believes, could turn up other indirect impacts the brown tree snake has had on Guam. For example, she notes anecdotal evidence that there is a substantially higher spider population on Guam than on other nearby islands, and she speculates that could largely be because the native bird population has been decimated.
But the biggest indirect impact, she said, could be altered seed scattering that in turn might, in the near future, transform the remaining forest from a diverse mixture of tree species to clumps of trees of the same species, separated by open space. That could have serious consequences, including extinction, for plant and animal species that still live in the forests.
"It seems logical that if there are no birds then seeds are not able to get away from their parent trees, and that is exactly what
|Contact: Vince Stricherz|
University of Washington