The scientists have several theories why the pasture trees have such an overwhelming impact on gene flow. First, there is little competition for the pasture trees for sunlight and nutrients, giving them superior abilities to flower and fruit. Second, the abundance of flowers may attract more hummingbirds for pollination. Finally, bats have easy pickings of the fruit and take them from the pasture trees to the forest fragment, where they eat and then pass seeds back to soil in guano.
The study has important implications for conservation and forest restoration. And it shows that the impact of deforestation has been far more devastating that the simple removal of individual trees. At least in this species of tree, fragmentation has resulted in the possibility of a serious loss of genetic diversity in this test area.
Thus, areas that look healthy in terms of regrowth may not be healthy at all over the long term. They may be facing serious future problems due to problems with genetic drift and inbreeding. American farmers already know of the problems this can cause, since they barely avoided a near-disaster because of over-planting of corn with too little genetic diversity in the 1970s.
Still, scientists say it is beginning to become apparent that it will be difficult to make any kind of blanket statements about gene movement among populations of forest species. Indeed, botanists say we are now only beginning to understand what happens to genetic diversity in natural populations over time--and why.
"One of the important things this study has shown us is that the
superficial appearance of an area might not be telling you the whole story,"
said Hamrick. "Each situation has unique characteristics that make if very
difficult to say that tropical trees in a certain situation will behave
'"/>
Contact: Phil Williams
philwpio@arches.uga.edu
706/542-8501
University of Georgia
3-Jul-1998