By Susan Milius
Two research teams have each used the biggest collection yet of flowering-plant genes to map out the floral family tree.
“We got the same answer,” says Michael J. Moore of Oberlin College in Ohio. Both family trees show the same basic arrangement of the eight lineages that still bloom today. Five of the eight appear as short branches at the top, a sign that the five more-recent lineages split from each other rapidly. The new analyses calculate that when these lineages split at least 125 million years ago, the divisions took place in less than 5 million years.
Fast divergences are hard to reconstruct, so botanists have struggled to sort out the relationships among the more-recent lineages. Both of the new trees show the same position for the eudicots, the biggest flowering lineage, which includes many common plants, from buttercups to mustards. It turns out to be the closest branch to the second-largest lineage, the monocots, which include grasses, lilies, and related plants with linear leaves.
To build the tree, Moore and his collaborators at the University of Florida in Gainesville used the 61 genes common to all chloroplasts. The other team, led by Robert K. Jansen at the University of Texas at Austin, used 81 chloroplast genes. Neither team’s tree structure is 100 percent certain, cautions Moore.
Both papers appear in the Dec. 4 Proceedings of the National Academy of Sciences.
