543: Jumping genes
From The Loom, Tangling the Tree:
Scientists at the European Bioinformatics Institute created [a phlyogeny of bacteria] by comparing 184 microbes. The scientists first identified genes that the microbes all inherited from a common ancestor that they then passed down in conventional parent-to-offspring fashion. By comparing their different sequences, the scientists were able to draw a conventional tree of the sort Darwin had in mind. Next, they scanned the genomes of these microbes for jumping genes. They drew the jumpers as vines from one branch to the next. They then produced this three-dimensional picture.Evolutionary hypotheses tested, and new information on the process of life's evolution.
As you can see, the branches rise from a common ancestor, but they are enmeshed in vines. What's particularly fascinating about it is the way in which the vines connect the branches. It is not a random mesh. Instead, a few species are like hubs, with spokes radiating out to the other species. This is the same pattern that turns up in many networks in life, from the genes that interact in a cell to the nodes of the Internet.