EVOLUTION OF THE SMALL SUBUNIT RIBOSOMAL-RNA IN HIGHER VERTEBRATES

The potential value of rapid sequencing of the srRNA molecule for phylogenetic reconstruction of the higher vertebrates was investigated. The study involved partial sequencing of 19 taxa that, along with 6 sequences from the literature, covered all of the major groups of higher vertebrates. The results show that sequencing of the srRNA molecule is not suitable at this taxonomic level because: (i) there is insufficient nucleotide sequence variation; (ii) expansion segments, although common, have a high probability of convergence for both their position and their sequence; and (iii) the phylogenetic branching of the higher vertebrates has been mainly 'bush-like' rather than 'tree-like'.