Solanum zanzibarense
Not known.
Coastal areas of southern Kenya, Tanzania, and Mozambique; wet or dry forest undergrowth, forest edges, and rocky outcrops on sand or sandy loam; 0-700 m elevation.
Solanum zanzibarense is a member of hte Old World clade of the spiny solanums (Leptostemonum, Levin et al. 2006); within that group it belongs to the strongly supported Climbing Clade (Vorontsova et al. 2013) with Solanum richardii and Solanum stipitatostellatum.
Jaeger, P.-M.L. 1985. Systematic studies in the genus Solanum in Africa. PhD thesis, University of Birmingham, United Kingdom.
Jaeger, P.-M.L. & F.N. Hepper 1986. A review of the genus Solanum in Africa. In: W.G. D’Arcy (ed.), Solanaceae. Biology and Systematics. Proceedings of the Second International Symposium on the Biology and Systematics of the Solanaceae, pp. 41-55. Columbia University Press, New York, USA.
Levin, R.A., N.R. Myers, & L. Bohs 2006. Phylogenetic relationships among the "spiny" solanums (Solanum subgenus Leptostemonum). 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
White, F. 1983. The vegetation of Africa: a descriptive memoir to accompany the UNESCO/AETFAT/UNSO vegetation map of Africa. UNESCO, Paris, France.
Local Names. Tanzania: Mlura (Musk 115); Kitulam Vago (Kizigua language, Frontier-Tanzania Coastal Forest Research Programme 558).
Solanum zanzibarense can be recognized by its small white flowers with long narrow corolla lobes, scrambling or climbing habit, slightly recurved or sometimes straight prickles over 2 mm long, and trichomes with stalks under 0.1 mm long and short midpoints. This species includes a wide range of populations across the Zanzibar-Inhambane regional mosaic (White 1983, Jaeger & Hepper 1986) in coastal eastern Africa from Kenya to Mozambique, encompassing a variety of leaf shapes and prickle morphologies. Jaeger (1985) separated S. vagans and S. zanzibarense citing differences in indumentum, leaf shape, inflorescence size, and altitude. Specimens with entire leaves and more sessile trichomes do seem more likely to occur further south into Mozambique, but this is not consistent enough to warrant their distinctness at the specific level.
Solanum zanzibarense can be confused with the inland S. cyaneopurpureum and several more local species within its distribution range ( S. inaequiradians, S. lamprocarpum, S. stipitatostellatum, and S. usaramense) as well as the ubiquitous S. anguivi. Solanum zanzibarense can be distinguished from S. cyaneopurpureum by the following combination of characters; lobed leaves usually > 5 cm long (versus usually entire leaves < 5 cm long in S. cyaneopurpureum), prickles usually present and over 2 mm long (versus prickles usually absent or under 2 mm long in S. cyaneopurpureum), branches long, slender, and prostrate (versus branches shorter and erect in S. cyaneopurpureum), and trichomes on the leaves and stems sessile or with stalks under 0.1 mm long (versus trichomes with stalks ca. 0.1 mm long in S. cyaneopurpureum). None of the distinguishing characters are applicable to all specimens, but the combination of leaf size and shape, number of prickles, habit, and trichome stalk length correlate with geographical distribution.
Solanum zanzibarense differs from S. stipitatostellatum by its smaller flowers with corollas 1.5-2 cm in diameter (versus corolla diameter 1.8-3 cm in S. stipitatostellatum), anthers 4-6.5 mm long (versus anthers 6-8 mm long in S. stipitatostellatum), prickles over 2 mm long (versus prickles inconspicuous if present and less than 2 mm long in S. stipitatostellatum), and trichomes sessile or with stalks up to 0.1 mm long (versus trichomes with stalks 0.1-0.4 mm long in S. stipitatostellatum). Solanum inaequiradians differs from S. zanzibarense by its calyx lobes 7-9 mm long at anthesis and elongating to 10-12 mm (versus fruiting calyx lobes only up to 4 mm long in S. zanzibarense) and trichomes with midpoints 1-2.5 mm long (versus less than 0.2 mm long or reduced to glands in S. zanzibarense). The leaves of S. lamprocarpum can be reminiscent of S. zanzibarense, but S. zanzibarense can be distinguished by its recurved stem prickles (versus straight prickles in S. lamprocarpum), calyx 2.5-4 mm long in fruit (versus calyx lobes elongating to 8-10 mm long in S. lamprocarpum), and trichomes with reduced midpoints (versus trichomes with midpoints 0.7-1 mm long in S. lamprocarpum). Solanum zanzibarense is easy to distinguish from S. usaramense by its corolla 1.5-2 cm in diameter that is pale yellow in herbarium specimens (versus corolla 2.5-3 cm in diameter drying dull yellow to red-brown in S. usaramense), and corolla lobes 1.5-2 mm wide (versus corolla lobes 3.5-5 mm wide in S. usaramense).