Molecular phylogenetic analysis of the Prostanthera phylicifolia (Lamiaceae) assemblage resolves relationships of the 'Critically Endangered' P. gilesii and other putative new species

Abstract

<p><i>Prostanthera gilesii</i> Althofer ex. B.J.Conn & T.C.Wilson is a critically endangered species from the Central Tablelands of New South Wales. A conservation management strategy is currently underway for this species, whose phylogenetic affinities are not known. Morphologically, <i>P. gilesii</i> resembles <i>P. phylicifolia</i> F.Muell. and a population of uncertain identity from Evans Crown Nature Reserve in the Central Tablelands of New South Wales known as <i>P.</i> sp. Evans Crown (G.M.Taseski NSW1055966). The taxonomy of <i>P. phylicifolia</i>, however, is unclear. <i>Prostanthera phylicifolia</i> was described from populations in the Victorian Alps and Monaro; however, populations spanning from Victoria to southern Queensland have been variously identified as either <i>P. phylicifolia</i> or <i>P. scutellarioides</i> (R.Br.) Briq. despite substantial geographic disjunctions and morphological dissimilarity. To examine the relationship between populations identified as <i>P. phylicifolia, P. gilesii</i> and <i>P.</i> sp. Evans Crown, nuclear (external transcribed spacer, ETS) and chloroplast (<i>trn</i>H-<i>psb</i>A intergenic spacer) regions were sequenced and combined with an existing <i>Prostanthera</i> dataset and analysed with maximum-likelihood and Bayesian-inference methods. <i>Prostanthera gilesii</i> and <i>P.</i> sp. Evans Crown were recovered as sister taxa within a clade consisting of populations morphologically similar to the type of <i>P. phylicifolia</i> from the Victorian Alps and Snowy Mountains, Monaro and Southern Tablelands of New South Wales. Populations from northern New South Wales and southern Queensland identified as <i>P. phylicifolia</i> or <i>P. scutellarioides</i> were recovered as an assemblage of unrelated clades. The molecular phylogeny supports <i>P. gilesii</i> and <i>P. phylicifolia</i> as closely related as hypothesised based on morphology and supports <i>P.</i> sp. Evans Crown as a population which requires additional study to assess its taxonomic status.</p>