Solanum schliebenii
Not known
Endemic to the Uluguru Mountains in Tanzania; growing in closed forest understory; 1500-1800 m elevation.
Solanum schliebenii is a member of the Old World clade of the spiny solanums (Leptostemonum; Levin et al. 2006); within that group is belongs to the Giganteum Clade and is sister to Solanum schumannianum (Vorontsova et al. 2013).
Carvalho, L. d’A., and R. D. Machado. 1991. Morphology of indumentum and trichomes in species of Solanum sections Cernuum and Lepidotum (Solanaceae). In Solanaceae III: taxonomy, chemistry, evolution, ed. J.G. Hawkes, R.N. Lester, M Nee and N. Estrada, 271-281. Kew: Royal Botanic Gardens, Kew.
Knapp, S. 2002c. Solanum section Geminata (G. Don) Walpers (Solanaceae). Fl. Neotrop. 84: 1-405.
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.
Roe, K. E. 1971. Terminology of hairs in the genus Solanum. Taxon 20: 501-508.
Seithe, A. 1962. Die Haararten der Gattung Solanum L. und ihre taxonomische Verwertung. Bot. Jahrb. Syst. 81: 261-336.
Seithe, A. 1979. Hair types as taxonomic characters in Solanum. In: The biology and taxonomy of the Solanaceae, ed. J. G. Hawkes, R. N. Lester and A. D. Skelding, 307-319. London: Academic Press.
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. Tanzania: Ndugut (Kiluguru language, Werdermann 1934).
Solanum schliebenii is a rare and odd species with multiple branched inflorescences, long soft bristles, and a peculiar indumentum. It has two unique characters not found in any other African Solanum species; soft bristles and collapsed multangulate trichomes. The bristles are long floppy epidermal outgrowths almost certainly homologous to the prickles of many other species and to the erect bristles in S. schumannianum. These bristles consist of the stalk of a stellate trichome that elongates until it develops into a soft white structure 4-7 mm long and 0.4-0.7 mm wide at base, itself densely covered in stellate trichomes. These bristles form a dense covering on most young stems.
The stellate trichomes of S. schliebenii are similar to those in other spiny species of Solanum but are structurally weak and flexible. Solanum trichome classification systems (Seithe 1962, 1979; Roe 1971) are based on overall structure and do not account for different levels of structural strength, although trichomes with weak and collapsing walls somewhat similar to those of S. schliebenii are also found in the New World Solanum section Geminata (G. Don) Walp. (e.g., the arachnoid dendritic trichomes of S. maturecalvans Bitter; Knapp 2002c) and New World Solanum section Cernuum Carv. & Sheph. (e.g. the chaffy dendritic trichomes of S. pachimatium Dunal; Carvalho & Machado 1991). Details of the stellae are almost impossible to distinguish because the trichomes are collapsed flat against the epidermis and partly transparent, appearing as a mealy white coating that is soft to the touch on the stems and leaf undersides. On Paulo 39 (K000441558) and Bruce 618 (K000441559, K000441562) the trichomes are so collapsed that identifying their structure is almost impossible; on Harris et al. 5135 (K000441561) and Jannerup & Mhoro 201 (K000441560) the structural integrity of the trichome cells is more clear such that the individual rays protrude from the surface and it is often possible to count them.
Solanum schliebenii is most similar to the more widespread S. schumannianum. The two species share large entire leaves clustered towards the tips of younger branches and multiply branched inflorescences. Solanum schliebenii occurs between 1500 and1800 m while S. schumannianum has only been recorded above 1800 m, and it is not clear how close together in space the two species occur. Solanum schliebenii can be easily distinguished from S. schumannianum by its soft white stem bristles 0.4-0.7 mm at base (versus erect rigid purple-black or brown bristles 0.2-0.4 mm wide at base in S. schumannianum), soft collapsed stellate trichomes (versus erect rigid stellate trichomes in S. schumannianum), leaves ca. 2 times longer than wide (versus leaves 2.5-2.3 times longer than wide in S. schumannianum), pedicels 0.3-0.5 mm long in flower and 0.7-0.9 mm long in fruit (versus pedicels 0.6-1 mm long in flower and 1-1.6 mm long in fruit in S. schumannianum), and seeds 2.7-3.2 × ca. 2.5 mm (versus seeds 3.5-4.5 × 3-4 mm in S. schumannianum).
The protologue of S. schliebenii cites “Schlieben 3415” but all specimens we have found appear with the number “3415a”. The choice of lectotype follows Richard Lester’s unpublished choice of the duplicate in BR.