By Susan Milius
Despite the doubts of some botanists, plant species aren’t just some arbitrary human classification scheme, says a team of evolutionary biologists. What’s more, plants don’t deserve their reputation of being outrageously promiscuous, breeding across species boundaries, because some animals can do so even more freely.
Animal species can cross boundaries to mate more readily than plants do, says Loren H. Rieseberg of Indiana University in Bloomington. Among records of plant- and animal-hybridization tests, Rieseberg’s team found that 31 percent of attempted plant combinations readily yielded fertile offspring, whereas 61 percent of animal-species crosses did so. “That was a surprise to me,” says Rieseberg.