Solanum pauperum
Not known
Endemic to Angola; growing in secondary vegetation and abandoned cultivation; elevation not known.
Solanum pauperum is a member of the Old World clade of the spiny solanums (Leptostemonum; Levin et al. 2006); within that group it probably belongs to the Giganteum Clade, along with Solanum anomalum and Solanum goetzei (Vorontsova et al. 2013).
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
Solanum pauperum is a modest slender shrub with small leaves on long petioles and comparatively large flowers in few-flowered inflorescences. Mature leaves are almost glabrous and are dark brown on herbarium specimens; indumentum density on the stem is variable but the stem appears lighter colored than the leaves.
Solanum pauperum is partly sympatric with the only other member of Giganteum clade in Angola, the widespread West African S. anomalum. Solanum pauperum seems to occupy drier places but the relationship between the two species is unclear due to the paucity of Angolan collections. It differs from S. anomalum by its lack of prickles (versus deltate prickles on flowering branches of S. anomalum), entire leaves with long-attenuate leaf bases (versus leaves usually lobed, with cuneate bases in Angolan populations of S. anomalum), petiole 1/3-2/3 of the leaf blade length (versus petiole 1/6-1/4 of the leaf blade length in S. anomalum), 4-8 flowers per inflorescence (versus 10-20 flowers per inflorescence in S. anomalum), pedicels 0.8-1.5 cm long (versus 0.4-0.5 cm long in S. anomalum), and mauve corolla (versus white corolla in S. anomalum). Monteiro s. n. (Angola, comm. to Kew Jan. 1873) appears to display characters intermediate between S. pauperum and S. anomalum.
Solanum pauperum also resembles the eastern African species S. goetzei. The two species share lack of prickles, entire leaves with attenuate bases, and similar trichome morphology. Solanum pauperum can be separated by its peduncle less than 1 mm long (versus peduncle 3-17 mm long in S. goetzei), 4-8 flowers per inflorescence (versus 8-15 flowers per inflorescence in S. goetzei), acute calyx lobes (versus long-acuminate calyx lobes in S. goetzei), petioles 1/3-2/3 as long as the adult leaves (versus petioles 1/6-1/4 as long as the adult leaves in S. goetzei), and seeds 2.8-3.5 mm (versus seeds 3.6-4.8 × 2.8-4 × 2.5-3.5 mm in S. goetzei). Jaeger (1985) suggests that S. pauperum may be synonymous with S. goetzei but in our opinion the allopatric occurrence and morphological differences between these species provide sufficient evidence for recognising them as separate taxonomic entities.
We have chosen the Kew sheet of Welwitsch 6054 (K000414105) as the lectotype of Solanum pauperum as it has been annotated by the species author and the collection has a wider global distribution of duplicates than the other syntype (Luanda, Welwitsch 6075 [BM000778203, K000414106]). The duplicate of Welwitsch 6054 at BM (BM000778200) has different collection details and is probably not a true duplicate of the lectotype at Kew. Welwitsch often numbered multiple collections with the same number, even though they had been collected at different times and sometimes in different localities.