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Phylogenetic analysis of Zieria (Rutaceae) in Australia and New Caledonia based on nuclear ribosomal DNA reveals species polyphyly, divergent paralogues and incongruence with chloroplast DNA
This study presents a phylogeny of Zieria Sm. (Rutaceae) based on sequences of ITS and ETS regions of nrDNA and using Neobyrnesia suberosa as the outgroup. The phylogeny includes 109 samples, representing 58 of the 60 currently recognised species of Zieria, with multiple accessions of most. Ten species were resolved as monophyletic based on two, or in one case four, samples. Monophyly of four species was neither supported nor rejected, and all other species with more than one accession were resolved as polyphyletic or paraphyletic. Results showed that divergent paralogues of nrDNA are present in some individuals, although the underlying evolutionary process that gave rise to those paralogues is uncertain. Divergent paralogues within genomes could predate speciation and be variably retained or variably detected within the species sampled here; alternatively, they could represent novel nrDNA combinations formed through hybridisation after speciation. There was no strong evidence for recombination between paralogues or that paralogues represent pseudogenes. nrDNA variation was clearly incongruent with previously published cpDNA variation, with the nrDNA potentially providing a better indication of species relationships in Zieria. Evidence for this comes from the greater level of congruence, in some species at least, between nrDNA and existing species-level taxonomy than between cpDNA and taxonomy. Incomplete lineage sorting is proposed as a plausible cause for much of the conflict between nrDNA and cpDNA in Zieria, although in most cases there was insufficient information to identify the underlying causes with confidence. Implications for species-level taxonomy are also discussed.
SB16034 Accepted 17 November 2017
© CSIRO 2017