Nucleotide sequences of rbcL confirm the capparalean affinity of the Australian endemis Gyrostemonaceae

Abstract

Nucleotide sequences (1452 base pairs) from the chloroplast gene for the large subunit of ribulose-1, 5-bisphosphate carboxylase/oxygenase (rbcL) were obtained for three species of Gyrostemon and Tersonia of the Australian endemic family Gyrostemonaceae. Phylogenetic reconstruction based on parsimony robustly allies the family with other mustard oil-producing plants in Dahlgren's expanded order Capparales. Within this clade, Gyrostemonaceae are the sister group to Resedaceae, but the sequence data provide only weak support for this particular linkage. The new molecular data corroborate recent embryological and ultrastructural findings for Gyrosternonaceae and confirm results from Rodman's cladistic analysis of traditional morphological features of these plants. The rbcL sequences for the three species of Gyrostemonaceae were consistent in possessing a stop codon ending at position 1452, well beyond the usual 1428 site for many dicots. An extended terminus for the rbcL gene appears to be a marker within the expanded order Capparales for a derived clade that comprises the traditional core Capparales (Brassicaceae, Capparaceae, Resedaceae and Tovariaceae) plus Gyrostemonaceae, the sister taxa Batis + Koeberlinia, and Limnanthaceae.