Rediscovery of Actinodontum lomaense: a range extension from Sierra Leone to southern Africa

Abstract

The history of Actinodontum lomaense has been marked by taxonomic revisions since its initial discovery in samples from Sierra Leone during 1984. The reassignment from the genus Docidium to the genus Actinodontum primarily resulted from pronounced morphological differences, including variations in cell size and shape, ornamentations on the cell wall, and the presence of conical teeth-like structures at the isthmus. This article reports on the discovery of A. lomaense in two locations in southern Africa, marking a significant expansion of the geographical distribution range of the genus, from the tropical regions of Sierra Leone to sub-tropical environments in South Africa and the Kingdom of Lesotho. Additionally, the preference of Actinodontum species for relatively high altitudes, observed in this study, confirms a biogeographical pattern characterising this genus. Cell dimensions recorded in the southern African samples slightly exceeded dimensions previously reported in the literature. As a result, an extention of the dimension ranges for this species is proposed. Findings presented in this article, along with physico-chemical variables measured in their habitat, contribute to our understanding of the ecological preferences and distribution patterns of A. lomaense. It also provides valuable insights into the biogeography of desmid species on the African continent.

Keywords:

• Biogeography
• desmid
• Docidium
• geographical distribution
• high altitude
• sub-tropical species
• taxonomy

Acknowledgements

Thank you to Prof. Jonathan Taylor (North-West University, South Africa) who assisted with sampling and diatom identification. We also acknowledge Willie Landman for his help with SEM preparation and investigations.

Disclosure statement

No potential conflict of interest was reported by the authors.