Lithops gracilidelineata subsp. mopane (Aizoaceae): a new subspecies from Mopane-Pachypodium shrubland in northwestern Namibia

Summary During a comprehensive survey and conservation assessment of populations of Lithops gracilidelineata (Aizoaceae), a population at the northern limit of its distribution was identified as profoundly morphologically and ecologically distinct. Following a taxonomic revision of the infraspecific limits of Lithops gracilidelineata , a new subspecies is described from Mopane- Pachypodium shrubland in northwestern Namibia. Lithops gracilidelineata subsp. mopane S.Hatt can be distinguished by its completely smooth leaf surface relief (vs distinctly rugose), that is very pale, whitish-grey, occasionally with a very pale. pinkish-yellowish tint (vs pale pinkish-beige to very pale, greyish-beige in subsp. gracilidelineata ; or pinkish or reddish-brown, rarely more beige or yellowish in subsp. brandbergensis ) and being almost exclusively 1-headed (vs often 2 – 3 headed). It differs from all other Lithops species by growing in Mopane shrubland of Colophospermum mopane , with interspersed Pachypodium lealii , amongst quartz pebbles and gravel. Descriptions, photographic illustrations and preliminary conservation assessments are provided for all accepted subspecies of Lithops gracilidelineata . An infraspecific key is also given, completing a revised classification of this threatened and horticulturally important succulent species.