Prostanthera cineolifera

Status of Prostanthera cineolifera View in CoL

Previously, morphometric ( Palsson et al. 2024, fig. 2a), and molecular and phytochemical analyses ( Sadgrove et al. 2020, fig. 3; Palsson et al. 2024, fig. 2b, 3a, 4) supported the recognition of P. cineolifera . The monophyly, distinctive morphological and phytochemical characteristics reported here ( Table 1, Fig. 3–5 View Fig View Fig View Fig ) corroborate the status as a distinct species.

Putative new species

The three putative new species, P. sp. Hawkesbury, P. sp. Olney State Forest and P. sp. Oxley Wild Rivers National Park, that share relatively long, persistent hairy floral prophylls and recurved calyx lobes, clustered as three separate subgroups using morphometric data ( Palsson et al. 2024, fig. 2a). These three entities have sufficient morphological differences ( Table 1) to warrant recognition at the rank of species.

Recognition of the three entities is corroborated here by phylogenetic analysis ( Fig. 3 View Fig ), with the reciprocally monophyletic P. sp. Hawkesbury and P. sp. Olney State Forest form the strongly supported sister clade to the single sample of P. sp. Oxley Wild Rivers National Park. The last is represented in the phylogeny by one of two samples submitted for analysis because only one survived filtering of the DArT seq data. Clearly, further searching in the vicinity of the remote location for additional plants and populations is desirable. Although P. sp. Olney State Forest was represented by multiple samples, these were from the only known location for the species. Other populations in the vicinity and further afield in similar habitats were searched for without success. Narrowly endemic species known from only one population are known in Prostanthera , e.g. P. conniana T.C.Wilson ( Wilson et al. 2015) , P. gilesii Althofer ex B.J.Conn & T.C.Wilson ( Conn and Wilson 2015) , P. makinsonii B.J.Conn & T.C.Wilson ( Conn and Wilson 2015) and P. volucris R.P.O’Donnell ( O’Donnell et al. 2023) . We consider that further such species await circumscription, e.g. P. sp. Barren Mountain (L.M. Copeland 2256) NE Herbarium.

In Sadgrove et al. (2020, tables 2, 4) the specimen labelled OSF-3 was a mislabelling for a specimen here determined as P. sp. Hawkesbury. Given this amendment, the essential oil profiles of P. sp. Hawkesbury and P. sp. Olney State Forest differ and corroborate morphological ( Table 1) and molecular evidence ( Fig. 3 View Fig ) of two new species. In the field, P. sp. Olney State Forest can readily be distinguished from P. sp. Hawkesbury and other members of the study group by a strongly resinous smell on crushing the leaves and young stems. This resinous odour relates to the high levels of 1,8-cineole together with E -verbenol and menth-3- en-8-ol (Supplementary Table S4). There are examples of phytochemistry as a taxonomically informative source of data. In the Lamiaceae, Moshari-Nasirkandi et al. (2024) found that 20 Iranian Salvia L. species each contained a distinct phytochemical profile. Bruňáková et al. (2021) suggested that phytochemical profiling should be included in the integrated plant authentication system for Hypericum L. ( Hypericaceae ). Both Salvia and Hypericum contain pharmacologically important compounds. Phytochemical analysis is not always useful taxonomically (e.g. Yang et al. 2014; Jiawei et al. 2020) but in our study, despite the small sample sizes, phytochemistry appears to be taxonomically informative given that the results are corroborated by both morphological and DNA data.

Despite superficial similarity, P. sp. Oxley Wild Rivers National Park is morphologically and genetically distinct from P. sp. Hawkesbury and P. sp. Olney State Forest. The two known populations of P. sp. Oxley Wild Rivers in the Macleay Gorges subregion of the IBRA NSW North Coast bioregion (Department of Climate Change Energy the Environment and Water 2020) are ~ 12 km apart and separated geographically from both P. sp. Hawkesbury and P. sp. Olney State Forest by over 200 km. The flowering of P. sp. Oxley Wild Rivers National Park occurs later in the season (November) than that of P. sp. Hawkesbury and P. sp. Olney State Forest (September and October respectively).