Algidae

Duretto, Marco F., Heslewood, Margaret M. & Bayly, Michael J., 2023, A molecular phylogeny of Boronia (Rutaceae): placement of enigmatic taxa and a revised infrageneric classification, Australian Systematic Botany 36 (2), pp. 81-106 : 97-98

Sections Algidae and Alatae and the placement of Boronia corynophylla

Boronia section Algidae is polyphyletic with its three species never grouping together. The south-eastern Australian clade containing B. algida (NSW, ACT, Vic.) , the type species of the section, and B. edwardsii (SA) has strong support and is isolated with no clear affinity, with only the nuclear Bayesian analysis resolving it as sister to section Ovatae (0.99 PP, Supplementary Fig. S1 ). A narrower circumscription of the section, section Algidae sens. strict. ( Fig. 1, S1 , S2 ), is provided below in Taxonomy and the section can be defined by having imparipinnate leaves with flat leaflets, terminal inflorescences of 1(–3) flowers, imbricate sepals, valvate petals and globose stigmas that are much wider than the style .

Boronia corynophylla is restricted to a small area in inland south-western Australia and shows a strongly supported relationship with B. alata . Boronia alata is the sole member of section Alatae and is widespread in near coastal areas of south-western Australia. Branch lengths to both species are long, suggesting that they have had an extended period of isolation. This pairing is surprising, given the striking morphological differences between the two species, although they both have valvate petals. Boronia corynophylla has an exfoliating cuticle on its branches, which gives the branches a glaucous appearance and is unique in Boronia , in addition to simple, slender, terete leaves and an inflorescence of 1(–3) flowers and valvate petals. By contrast, B. alata has smooth branches, imparipinnate or bipinnate leaves with broad leaflets, inflorescences that are large, cymose panicles, and valvate and reduplicate petals. Seeds, which provide useful characters at the section and series level in Boronia ( Wilson 1998; Choi et al. 2012), have not been documented for B. corynophylla . With regard to a formal taxonomy, one alternative would be to expand section Alatae to accommodate B. corynophylla but this would create a heterogenous assemblage with no clear apomorphies. Therefore, as B. corynophylla is clearly isolated taxonomically, a new monotypic section, Corynophyllae Duretto & Heslewood , is formally described below to accommodate it. This will be the fourth section of Boronia , three of which are monotypic, that is endemic to south-western Australia.

Figures

Fig. 1. Bayesian 50% majority-rule consensus tree from the combined analysis of two nuclear (ITS, ETS) and three plastid markers (psbA–trnH, trnL–trnF and rbcL), with thick lines showing supported clades (≥0.95 PP). Jackknife percentages from MP analysis are indicated with symbols above branches: 100% JK (closed triangle); 90–99% JK (closed circle); 75–89% JK (open triangle); 50–74% JK (open circle). New or revised sectional assignments are indicated in bold. Section Boronia clade has been collapsed and is shown in detail in Fig. 2.