Figure 2.

The phylogeny of rats. This tree was built by using shared L1 oligonucleotide characters such as those numbered in Fig. 1. An open rectangle signifies that more than one oligonucleotide defines the branch, and an open square indicates that only one oligonucleotide character was used. The position of the oligonucleotide characters on a branch is arbitrary and not related to the “age” of the phylogenetic character. The length of the branches or positions of nodes in My was estimated, where possible, from the age of the indicated L1 subfamilies as described in the text. These subfamilies are a subset those in Fig. 1 and are positioned on the tree according to their age (solid circles). When no L1 subfamily was available to date a node or estimate a branch length they were drawn arbitrarily.