Affinities of the Australian endemic akaniaceae: New evidence from rbcL sequences

Abstract

The affinities of the Australian monotypic endemic family Akaniaceae, traditionally assigned to the Sapindales, are reassessed on the basis of comparative sequence data for the chloroplast encoded gene, rbcL. Cladistic analyses show Akania to cluster robustly with Bretschneidera and then Tropaeolum, within the clade of glucosinolate Capparalean families. Eight species representing six other families assigned to the Sapindales, plus Leitneria, formed a monophyletic cluster in 100% of trees in a bootstrap analysis with 500 replicates. This Sapindalean clade is shown to be supported by 17 synapomorphs, only one of which occurs in Akania.

Relationships at the ordinal level, among the Sapindalean, Malvalean, Capparalean and Myrtalean clades, are, however, not well resolved. While the most parsimonious arrangement has the Malvales as sister-group to the Sapindales, with the Capparalean and Myrtalean clades joining in sequence, the occurrence of an apomorphic triplet of bases at positions 294–6 in all members of the Malvales, Myrtales and Sapindales so far examined is tentative evidence that these orders may constitute a monophyletic group.