A taxonomic evaluation of the Thesium confine species complex (Santalaceae)

Abstract

Background: Thesium L. is the largest genus in the family Santalaceae (sandalwood family). The last taxonomic revision of the southern African species dates back to 1925. An urgent revision of the genus is required as indicated in a recent national biosystematics research strategy for South Africa.

Objectives: To revise the Thesium confine species complex (Thesium durum, T. confine and Thesium spartioides) and to update the typification, nomenclature, descriptions and distribution ranges.

Method: Morphological characters were studied using own field collections as well as herbarium specimens from K, NU, PRE and PRU and images on Global Plants (JSTOR). Distribution ranges of the studied species were updated.

Results: An examination of morphological characters revealed great similarity between T. spartioides and T. confine. Both species have an herbaceous habit, decumbent growth form, terminal (or less frequently axillary) inflorescences and a sympatric northern distribution in South Africa. Thesium durum differs from T. spartioides and T. confine in having a shrubby habit, erect growth form and axillary inflorescences and occurs in the southern part of South Africa.

Conclusion: Thesium spartioides is synonymised under T. confine, and T. durum is retained as a separate species.