Solanum wittei
Not known
Democratic Republic of the Congo, Rwanda, Uganda, and Tanzania, in the area surrounding Lake Victoria, Lake Albert, Lake Edward, Lake Kivu, and the northern part of Lake Tanganyika; growing in grassland, savanna, and dry forests, especially on ant hills and termite mounds; 1200 – 1900 m elevation.
Solanum wittei has not yet been included in phylogenetic analyses; it is probably related to Solanum tettense (see commentary) in the Giganteum Clade (Vorontsova et al. 2013) of the Old World spiny solanums (Leptostemonum sensu Levin et al. 2006).
Bitter, G. 1921. Solana Africana III. Bot. Jahrb. Syst. 57: 248-286.
Edmonds, J. M. 2012. Solanum spp. 1-25, 46-51, 63-64, 67-72. In: J.M. Edmonds, Solanaceae, Flora of Tropical East Africa. Kew: Royal Botanic Gardens, Kew.
Jaeger, P.-M. L. 1985. Systematic studies in the genus Solanum in Africa. PhD thesis. United Kingdom: University of Birmingham.
Levin, R. A., N. R. Myers, and L. Bohs. 2006. Phylogenetic relationships among the “spiny solanums” (Solanum subgenus Leptostemonum, Solanaceae). Amer. J. Bot. 93: 157-169.
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
Local Names. Rwanda (all Kinyaruanda language): Igitarasoyo (Troupin 6604), Umukarihya (Troupin 8355), Umukarishya (Troupin 8632), Umukarisha (Troupin 4143). Uganda: Munubwa Nymyi (Luganda language, Purseglove 1834), Omulyanyonyi (Thomas 3988).
Solanum wittei is a rare shrub with entire acuminate leaves, erect inflorescences, and deltate prickles usually visible on young stems. Its stellate trichomes have fewer longer rays than many members of the Giganteum clade and many trichomes are often reduced to a midpoint. Solanum wittei is included within S. tettense by Edmonds (2012). We have chosen to recognize this species as distinct from the undoubtedly closely related S. tettense; it differs from the latter in its concolorous to weakly discolorous leaves (versus strongly discolorous leaves in S. tettense), acuminate leaf apices (versus leaf apices usually acute and finely rounded at the tip in S. tettense), anthers 3.5-4 mm long (versus 4-6 mm long in S. tettense), stem and leaf stellate trichome midpoints elongated to 0.4-1(2) mm (versus midpoints the same length as the rays in S. tettense), and stellate trichomes on the leaves with only 0-12 rays (versus 4-20 rays in S. tettense). The inflorescences of S. wittei are usually longer and bear fewer flowers than those of S. tettense, although due the variability encompassed in S. tettense the inflorescence differences are not clear when measurement ranges for the two species are compared. The boundary between S. wittei and S. tettense in somewhat unclear where the two species may be sympatric. Tanner 1061, Tanner 4928, and Procter 847 have a combination of discolorous leaves, dense inflorescences, and elongated midpoints and have been provisionally placed in S. wittei. We recognize collections from western Uganda as S. tettense with the exception of Thomas 3988 with long midpoints and short anthers which has been placed in S. wittei.
The acuminate glabrescent leaves and medium-sized erect inflorescences of S. wittei resemble the bristle-free types of the high montane S. schumannianum. Solanum wittei can be distinguished from S. schumannianum by its deltate stem prickles 2.5-6 mm wide at base (versus no deltate prickles, only thin bristles on S. schumannianum), seeds 2.7-3 × 2-2.4 mm (versus seeds 3.5-4.5 × 3-4 mm in S. schumannianum), and occurrence at 1200 – 1900 m elevation (versus 1800-2600 m elevation for S. schumannianum). Solanum wittei and S. schumannianum are not sympatric as S. schumannianum is restricted to the eastern African Arc Mountains in Tanzania and Kenya, outside the distribution range of S. wittei. Solanum wittei is fully sympatric with the widespread S. giganteum ; S. wittei can be distinguished by its leaves 6-10 cm long (versus 12-40 cm long in S. giganteum), 15-30 flowers per inflorescence (versus 30-150 flowers per inflorescence in S. giganteum), and anthers 3.5-4 mm long (versus anthers 2.5-3 mm long in S. giganteum). The smaller individuals of S. wittei somewhat resemble the largely sympatric inland S. cyaneopurpureum, but S. cyaneopurpureum is a smaller plant with yellow leaves on herbarium specimens (versus leaves drying green-brown in S. wittei), smaller unbranched inflorescences with 3-10 flowers (versus inflorescences with primary and secondary branching and 15-30 flowers in S. wittei), and exclusively stellate trichomes with 8 rays or less (versus trichomes with 0-20 rays in S. wittei).
Jaeger (1985) provisionally placed S. wittei in his tentative “Solanum kagehense group” with S. kagehense, S. muansense, and S. sordidescens, all names for which he could not locate type material. Solanum kagehense has been placed in synonymy under S. schumannianum in spite of its lack of type specimens as Lynes s. n. (Tanzania) a specimen cited by Bitter (1921), who had seen Dammer’s type specimens, as belonging S. kagehense belongs to our concept of S. schumannianum. Solanum sordidescens is a synonym of S. giganteum. The identity of S. muansense cannot be confirmed as no extant type material has been found, but the description suggests it is also a synonym of S. tettense (see above).