Relationships of the Australo-Malesian genus Paraserianthes (Mimosoideae: Leguminosae) identifies the sister group of Acacia sensu stricto and two biogeographical tracks.

© The Willi Hennig Society 2011. ABSTRACT: Paraserianthes (tribe Ingeae) as circumscribed by Nielsen et al. includes four species and five subspecies in two sections endemic to Australia, Indonesia, New Guinea and the Solomon islands. An alternative classification, proposed by Barneby and Grimes, raised Nielsen's two sections to generic level, thereby reducing Paraserianthes to comprise just species, P. lophantha, and recognizing the genus Falcataria. Neither treatment has been adopted by all. Thus, a phylogenetic and systematic analysis of Paraserianthes is required to clarify the taxonomic circumscription of the genus and relationships among the species and subspecies. Furthermore, elucidation of the phylogenetic relationships of Paraserianthes is significant to an understanding of the evolutionary history and biogeography of Acacia sensu stricto (s.s.). The external transcribed spacer regions of nuclear ribosomal DNA and the rpl32-trnL intergenic spacer of chloroplast DNA were sequenced for all species of Paraserianthes, a representative sample of Acacia s.s. (phyllodinous group) and 18 other members of tribe Ingeae, including an outgroup Samanea tubulosa. These data were analysed with parsimony and Bayesian methods. The topologies of the resultant phylogenetic trees were congruent but with greater resolution in the Bayesian tree. The results show that Paraserianthes sensu Nielsen is paraphyletic and that P. lophantha is the sister group to Acacia, a finding supported by morphological characters. Paraserianthes shows a dual link between Australia and lands to the north. A western biogeographical track relates south-west Western Australia to Sumatra, Java, Bali and Flores (two subspecies of P. lophantha), and an eastern track relates north-east Queensland to the Moluccas, New Guinea, the Bismarck Archipelago and the Solomon Islands (P. toona and its relatives).