The reinstatement of Plocamium robertiae (Rhodophyta, Plocamiales) and an updated species inventory of the genus in South Africa

ABSTRACT

The morphologically diverse and widespread red algal genus Plocamium has recently emerged as a source of bioactive compounds with potential application in the pharmaceutical industry. However, species identification and the taxonomy of the group remains problematic. An initial contribution to the taxonomy of Plocamium in South Africa was therefore carried out using combined morphological and molecular approaches and existing literature. Plocamium robertiae is reinstated as a distinct species based on molecular and morphological evidence, while Plocamium raphelisianum, a species from Spain, is placed in synonymy with P. suhrii. Along the South African coast, individuals of P. suhrii were genetically divergent in different bioregions and will require further investigation. Contrary to previous reports, we confirm the absence in South Africa of two Australasian species, P. microcladioides and P. mertensii, which were previosuly misidentified. The latter species likely represents a new, undescribed species in South Africa. Two additional species were also identified based on DNA but require further morphological assessment. We now recognize P. robertiae, along with eight other named species, plus five additional taxa, with varying levels of taxonomic confidence, and exclude P. microcladioides and P. mertensii from the South African flora. This study doubles the number of species recognized since the last biodiversity assessment of Plocamium and expands the distributional range of P. suhrii. Although our findings contribute an initial assessment assisted by DNA data, a full understanding of the taxonomy of Plocamium in South Africa is far from complete.

KEYWORDS:

• Biogeography
• Molecular systematics
• Phylogenetics
• Taxonomy

ACKNOWLEDGEMENTS

We are grateful to David Dyer and the Seaweed Unit for assisting with field collections and also thank the NRF, UCT and SU for funding and access to laboratory facilities. Lastly, we thank Dr. Han-Gu Choi and Professor Joe Zuccarello for their comments and suggestions that helped improve this manuscript.

Supplementary Information

Supplemental data for this article can be accessed online at https://doi.org/10.1080/00318884.2023.2174342

DISCLOSURE STATEMENT

No potential conflict of interest was reported by the authors.

Additional information

Funding

MMR received financial support from UCT and JCD from the NRF. This project was part of SeaKeys.