Mzansi's mountain hemlocks: The identities of Hilliard and Burtt's Conium species 3 and 4 (Apiaceae) and a revised key for the genus in sub-Saharan Africa

Abstract

Southern Africa is the centre of diversity for the Apiaceae genus Conium L., notorious for the execution of Socrates. The recent expansion of Conium herbarium material from the southern Great Escarpment (Roggeveldberge to the Stormberg, South Africa) has allowed us to assess the taxonomic status of the two taxa (Conium species 3 and 4) for which, at the time of the last treatment of the genus in southern Africa by O.M. Hilliard and B.L. Burtt, there was insufficient material to formally recognise them. We consider only Conium sp. 4 to be sufficiently distinct to warrant formal recognition, and describe it here as the Cape Midlands Escarpment endemic C. hilliburttorum Magee and V.R. Clark. As a cliff-base specialist vulnerable to competition from several alien invasive species, and potentially climate change, we recommend a conservation status of Vulnerable. For the second taxon, Conium sp. 3, the shape and degree of fusion of the involucel bracts is more variable than originally thought. We therefore consider it to be conspecific with the eastern Great Escarpment species C. fontanum Hilliard and B.L. Burtt, expanding the range westwards onto the Sneeuberg. We also present collections of C. sphaerocarpum from the Nuweveldberge, effectively also expanding the known distribution of this winter-rainfall species slightly eastwards. A revised key to the now five species of Conium recognised in sub-Saharan Africa (including the introduced C. maculatum) is provided.