Familiar concepts and relationships in the conifers based on rbcL and matK sequence comparisons

Abstract

Analysis of sequence data for the chloroplast encoded genes rbcL and matK for 40 taxa representing all conifer families and subfamilies, rooted on Ginkgo biloba, provides robust support for the family concepts of Araucariaceae, Cupressaceae sensu lato, Pinaceae and Sciadopilyaceae. Whereas Phyllocladus and Cephalotaxus are robustly linked with, but separated from Podocarpaceae sensu stricto and Taxaceae, respectively, these distinctions decay at far fewer steps (+3.7 and +1.7 steps, respectively) than do any of the other families (>25 steps). It is argued that neither of these monogeneric families, Phyllocladaceae and Cephalotaxaceae, is warranted, and that recognition of a more broadly defined Podocarpaceae and Taxaceae is more informative of the relationships among conifers. The analysis provides strong support for Wollemia being sister to Agathis, rather than it being the first diverging lineage within the family. It also strongly supports sister relationships between Araucariaceae and Podocarpaceae, between Cupressaceae sensu lato and Taxaceae sensu lato, and between the latter clade and Sciadopityaceae. Pinaceae are strongly supported as the first lineage of extant conifers to diverge.