DNA clears Ben Franklin of tallow-tree wrongdoing

Ben Franklin has long been credited -- and I use the term loosely -- with introducing tallow trees to the United States in the late 1700s. Like many species introduced from foreign places, they don't behave well in our climate. Franklin likely had no idea the trees would be overachievers on this side of the world and become an invasive species, just as kudzu vines are here on the East Coast, and like Asian carp is in the Great Lakes. Today, tallow trees are overrunning thousands of acres of coastal prairie from Florida to East Texas, and it's quite a mess. They're spreading so fast that they're destroying native habitats and causing economic damage in the south. As the story goes, "Franklin was living in London, and he had tallow seeds shipped to associates in Georgia," says Rice University biologist Evan Siemann, co-author a new study in this month's American Journal of Botany

That study was more than 10 years in the making. Siemann compiled evidence on the differences between U.S. and Chinese tallow trees, and found that the U.S. trees grow about 30 percent faster than their Chinese counterparts. And the insects that help keep the trees in check in Asia do not live in the United States. These are all things to consider when you travel overseas (or even to a different region of the U.S.) and feel you absolutely have to bring that beautiful plant home to your own garden. Don't do it.

Only wishing to study the tallow tree and compare it to tallows in Asia, Siemann and his colleagues obtained funding from the National Science Foundation and the Department of Agriculture in 2005 and got to work. But their genetic study comparing the trees'  DNA turned up some surprising evidence: Ben Franklin isn't responsible.

The tallow trees running amok in the U.S. aren't from the batch that Franklin imported. The descendants of  those trees are confined to a few thousand square miles of coastal plain in northern Georgia and southern South Carolina. All other U.S. tallows were found to have come from seeds brought to the U.S. by federal biologists around 1905.

"In some ways, this raises even more questions, but it clearly shows that if you are going to explore control methods for an invasive species, you to need to use appropriate genetic material to make certain your tests are valid," Siemann said, adding that with all the new species of plants and animals still being introduced from elsewhere each year, it's imperative that scientists understand the circumstances that cause them to become invasive.

Pennsylvania Academy of the Fine Arts photo of Benjamin Franklin