A Perspective on the Contribution of Plastid rbcL DNA Sequences to Angiosperm Phylogenetics

Abstract

The large rbcL analysis published in 1993 (Chase, Soltis, Olmstead et al., 1993) ranks as the largest phylogenetic analysis, molecular or otherwise, ever produced. These data represented over ten years of effort, but significantly the advent of the polymerase chain reaction, PCR, had greatly expanded the numbers of sequences available in the four years just prior to publication. Strategies for production of DNA sequences had become dramatically easier and faster. At the same time that sequencing was becoming more practical, the United States National Science Foundation was approving a large number of molecular systematics proposals, thus making substantial funding available (examine the number of NSF grant numbers listed in the footnotes of the 1993 paper), while Gerard Zurawski (DNAX Corporation) was making available without cost rbcL PCR and internal sequencing primers. Consequently, a large number of laboratories began working on this same plastid locus. To a very large extent and until just recently, protein-coding plastid DNA sequences have been the almost exclusive focus of vascular plant molecular systematists, whereas nearly all published work on other organisms has focused on ribosomal DNA (rDNA; see Chapter 1). By late 1991, the stage had been set for a dramatic increase in the amount of molecular data available on a wide range of seed plants, and this put workers focusing on rbcL in a position to discuss a large-scale analysis. Publication was not necessarily their goal; most simply felt that everyone would benefit from the interaction and that potentially we could use this sort of unpublished, but widely circulated, result as a way to focus better the many individual projects underway.