Phylogenetic position of hoop pine

Abstract

A variety of gymnosperms (13 species of conifer from 5 families and 2 species of non-conifer) were collected and the small ribosomal subunit (18S rRNA) was sequenced by direct sequencing. The 15 species examined included widely separated provenances of Araucaria cunninghamii, to determine its phylogenetic relationship to the other gymnosperms. Two of the 4 conifer families from Australia (Araucariaceae and Podocarpaceae) separated as expected, with further separation of genera and species within these families. Homology between the species varied from 89 to 98%. Four geographically distinct groups within A. cunninghamii were separated phylogenetically. It is suggested that A. cunninghamii was the most recent Araucaria species to evolve, with the Papua New Guinean provenances undergoing the fastest evolutionary changes. It is concluded that sequence information on the 18S rRNA genes provides a useful means of studying phylogeny in gymnosperms at the species and within-species levels