Phylogenetic analysis based on nuclear DNA and morphology defines a clade of eastern Australian species of Acacia s.s. (section Juliflorae): the 'Acacia longifolia group'

Abstract

Seventeen Australian, phyllodinous species of Acacia s.s. (from sections Juliflorae and Phyllodineae) were analysed to test the monophyly and relationships of ‘the Acacia longifolia group’, an informal group recognised in the Flora of Australia. Analyses were based on both morphological and molecular data, with A. triptera as an outgroup. A total of 92 herbarium specimens was investigated, with 15 phyllode, inflorescence, flower, pod and seed characters scored. The ITS and ETS regions of nuclear rDNA were sequenced and combined with a larger dataset sampled from species of all major clades of Acacia, totalling 65 accessions. Cladistic analyses provided evidence of a clade that defines the A. longifolia group as follows: A. alpina, A. axillaris, A. courtii, A. dallachiana, A. derwentiana, A. floribunda, A. longifolia subsp. longifolia and A. longifolia subsp. sophorae, A. longissima, A. maidenii, A. mucronata, A. obtusifolia, A. orites, A. oxycedrus, A. phlebophylla, A. rhigiophylla and A. riceana (all sect. Juliflorae), but excluding A. verticillata (section Juliflorae) and A. genistifolia (section Phyllodineae). The A. longifolia group is recognised as including south-eastern Australian species with cylindrically spiked inflorescences and phyllodes with prominent anastomosing venation.