Solanum burchellii
Not known.
South Africa and Namibia; growing on red sand, rocky outcrops and dry stream beds; 500-1300 m elevation.
Solanum burchellii is a member of the Old World Clade within subgenus Leptostemonum, and is probably most closely related to the South African species S. tomentosum (Vorontsova et al. 2013).
Wright, C.H. 1904. Solanaceae. In: W. T. Thiselton-Dyer, Flora Capensis, volume 4(2), pp. 87-121.
Bitter, G. 1923. Solana Africana. IV. Spec. Nov. Regni Veg. Beihefte 16: 1-320.
Jaeger, P.-M.L. 1985. Systematic studies in the genus Solanum in Africa. PhD thesis, University of Birmingham, United Kingdom.
Vorontsova, M. S., S. Stern, L. Bohs, and S. Knapp. 2013. African spiny Solanum (subgenus Leptostemonum, Solanaceae): a thorny phylogenetic tangle. Bot. J. Linn. Soc. 173: 176-193. doi:10.1111/boj.12053
Solanum burchellii is easy to recognize by its uniform, pale yellow, and almost entire leaves. It is morphologically largely uniform across the northern Cape and Namibia.
The closest relative of S. burchellii is almost certainly the more southern but allopatric S. tomentosum; the two species are members of a weakly supported polytomy in the Anguivi grade (Vorontsova et al. 2013), along with other South Africa taxa and the Macaronesian endemics S. vespertilio and S. lidii. Solanum burchellii can be distinguished by its uniform yellow-green leaf drying color (versus red-green, pale gray-green or pale yellow-green leaf drying color in S. tomentosum), elliptic (-ovate) almost entire leaves (versus ovate and usually lobed leaves in S. tomentosum), cuneate or sometimes rounded leaf bases (versus basally rounded to cordate leaf bases in S. tomentosum), and leaf and stem trichomes with stalks up to 0.1 mm (versus up to 0.3 mm in S. tomentosum). Solanum burchellii was considered to be a part of S. tomentosum by Wright (1906) but it is a geographically and morphologically coherent entity, an opinion shared with Bitter (1923), Jaeger (1985), and Kolberg (1992). The distributions of the two species do not seem to overlap and no intermediate specimens have been seen.
The northern populations of S. burchellii are sympatric with the widespread and variable S. catombelense; the two species can appear similar with the same yellowish drying color, almost entire leaves and lack of prickles. Solanum burchellii differs from S. catombelense by its elliptic leaves 1.7-4(5) cm long (versus ovate to oblong leaves 3-8 cm long in S. catombelense), corolla 1.5-2.2 cm in diameter (versus 0.9-1.3 cm in diameter in S. catombelense), and anthers 3.5-5.2 mm long (versus 2.5-3.5 mm long in S. catombelense). Solanum burchellii is also sympatric with the following more easily distinguishable species: S. capense with curved prickles, S. humile with more deeply dissected leaves, and S. supinum with single flowers, calyx lobes that elongate in fruit, and yellow berries. The filiform prickles and prominent leaf venation of some young S. burchellii plants can be reminiscent of the invasive S. elaeagnifolium from North America but the resemblance is superficial; the prickles of S. elaeagnifolium are red, the leaves are narrower and the flowers are larger.
The lectotypes chosen for S. rangei and S. burchellii var. parcearmatum are the only known duplicates of the type collections which were cited as being held in Berlin by Bitter in the protologues.