Philotheca myoporoides

Batty, Erin L., Holmes, Gareth D., Murphy, Daniel J., Forster, Paul I., Neal, Will C. & Bayly, Michael J., 2022, Phylogeny, classification and biogeography of Philotheca sect. Erionema (Rutaceae) based on nrDNA sequences, Australian Systematic Botany 35 (4), pp. 326-338 : 334

Polyphyly of Philotheca myoporoides

A significant result from the phylogenetic study presented here is the strong evidence that Philotheca myoporoides is not monophyletic either in the current circumscription ( Forster 2005; Wilson 2013) or the previously broader circumscriptions of Wilson (1970), Bayly (1998) or Rozefelds (2001 b). The current circumscription of P. myoporoides should not be maintained and our results add weight to the argument for elevating the remaining subspecific taxa to the rank of species, as Forster (2005) did with the subspecies from south-eastern Qld. This would entail raising the segregate subspecies ( subsp. acuta , subsp. brevipedunculata , subsp. euroensis and subsp. petraea ) to species rank. Such an elevation in the rank of these taxa is supported by their generally allopatric distributions ( Fig. 1 ) and generally distinct morphology from each other (albeit largely in leaf shape and size; Bayly 1998; Rozefelds 2001 b), and from other species in the genus. Although the monophyly of each of these taxa was not explicitly tested in the current study, each being represented by a single accession, they are all resolved in distinct positions in the phylogeny. For subsp. acuta , an earlier name at species rank, Eriostemon affinis Sprague , is available ( Bayly 1998; Wilson 2013) but there are no existing names at species rank for the other segregate subspecies and therefore new combinations or new names are required.

An alternative response to the polyphyly of P. myoporoides would be to retain a broad circumscription of the species and to subsume into this, as synonyms or subspecies, all other members of the pedunculate clade (as identified on Fig. 2 ). That would require uniting 18 currently accepted taxa under one species, including long-accepted and morphologically distinct species such as P. verrucosa , P. hispidula , P. scabra and P. buxifolia . We consider this option as untenable, given the degree of morphological, ecological and genetic differentiation within the pedunculate clade, and such a broad species concept is inconsistent with other species in the family and would seem unparalleled in current classifications of any other group in the Australian vascular flora.

Figures

Fig. 1. Distributions of taxa of Philotheca sect. Erionema. Maps are based on those of Wilson (2013) and Rozefelds (2001a, 2001b) plus our examination of herbarium material. Note that infraspecific taxa for P. buxifolia, P. brucei and P. scabra are not mapped separately.

Fig. 2. Majority rule consensus tree based on BI analysis of combined ITS and ETS dataset, showing mean branch lengths. Bayesian posterior probabilities are shown (either first, or above branches) along with MP bootstrap values (either second or below branches; only shown where bootstrap support is>50%). Dashed branches were not present on the MP strict consensus tree.