Figure 4. Phylogenetic tree of selected vertebrate type 2 cystatins. The alignment shown in Fig. 1 was used to generate a tree by neighbor-joining by means of the PAUP 4.0b8a software package (Swofford, 2000). The scale shows the genetic distance along branch lengths. Bootstrap values were obtained from 100 replicates and are shown as a percentage beside the branches. The large arrow indicates a possible position for the root of the tree, with proteins on the cystatin C branch of the tree to the top. Abbreviations used: hCys, human cystatin; rat S, rat salivary cystatin S; and adder, puff adder (Bitis arietans) venom cystatin.