Molecular Evolution of 18S rDNA in Angiosperms: Implications for Character Weighting in Phylogenetic Analysis

Abstract

Ribosomal DNAs (rDNAs) have inherent appeal for phylogeny estimation because they are present in all prokaryotic and eukaryotic organisms and thus have the potential to provide characters common to all of life. In fact, rDNA (or rRNA) sequences have been used to infer relationships in animals (e.g., Sogin et al., 1986; Field et al., 1988; Wainright et al., 1993; Wada and Satoh, 1994), protozoa (Schlegel et al., 1991; Van de Peer et al., 1996b), algae (e.g., Buchheim et al., 1990; Huss and Sogin, 1990; Kantz et al., 1990; Buchheim and Chapman, 1991; Chapman and Buchheim, 1991; Hendriks et al., 1991; Bakker et al., 1994; Ragan et al., 1994; Olsen et al., 1994; Medlin et al., 1996), fungi (e.g., Forster et al., 1990; Swann and Taylor, 1993; Hinkle et al., 1994; Berbee, 1996), lichens (e.g., Gargas et al., 1995), bryophytes (e.g., Waters et al., 1992; Mishler et al., 1994; Capesius, 1995; Kranz et al., 1995; Hedderson et al., 1996), pteridophytes (e.g., Kranz and Huss, 1996), gymnosperms (e.g., Chaw et al., 1993, 1995, 1997), and even among the deepest branches of life (e.g., Pace et al., 1986; Wolters and Erdmann, 1986; Olsen, 1987; Woese, 1987; Embley et al., 1994; Bhattacharya and Medlin, 1995). Despite this wide use, relatively few studies have focused on patterns of rDNA evolution, particularly in plants; most have concentrated instead on the phylogenetic patterns suggested by the rDNA sequences.