Bipinnate acacias (Acacia subg. Phyllodineae sect. Botrycephalae) of eastern Australia are polyphyletic based on DNA sequence data

Abstract

A phylogenetic analysis of Acacia subg. Phyllodineae sect. Botrycephalae, endemic to eastern Australia, is presented based on a combined dataset of ITS and ETS sequences of nrDNA. A smaller set of species was sequenced also for the cpDNA trnK region. A limited number of morphological characters was also combined with the ITS+ETS dataset for most taxa. Thirty-eight of 41 Botrycephalae species were sequenced, together with a sample of ten uninerved phyllodinous species (sect. Phyllodineae). Although these DNA regions showed limited sequence divergence, bootstrap supported nodes of the consensus ITS+ETS tree indicate that Botrycephalae as currently defined is polyphyletic. Eight bipinnate species fell outside the main clade of Botrycephalae species while seven phyllodinous species were nested within it, near the base. The few derived but homoplasious morphological characters that were discovered included: presence of appressed unicellular hairs, presence of jugary and interjugary glands, number of pinnae > 7 and the funicle half–fully encircling the seed. Section Botrycephalae requires redefinition.