Solanum trichopetiolatum
Not known.
Solanum trichopetiolatum is narrowly endemic to northeastern Madagascar in the area around the mountain of Marojejy, Antsiranana province. To grows in wet montane forests, often growing as a epiphyte in cloud forests; 500 to 1500 m elevation.
Madagascar. Antsiranana: liaña vato (Miller & Lowry 4072).
Preliminary conservation status (IUCN 2014). Vulnerable (VU B1a, biii). EOO 12,121 km2 (VU), AOO 28 km2 (EN). Solanum trichopetiolatum is a species of wet forests, and these are shrinking in extent due to habitat alteration. It does, however, occur in protected areas (e.g., the Marojejy Reserve). In common with other members of the ANS clade in Madagascar, the paucity of collections, indicative of local rarity, coupled with the ongoing habitat threats in Madagascar, indicate monitoring and further collection to assess local rarity are priorities.
Solanum trichopetiolatum is a slender liana endemic to the Marojejy area of Antsiranana, with obovate leaves and pale violet flowers. The species is characterised primarily by its unusual pubescence of straight or curved simple 4-8-celled appressed or spreading trichomes 0.5-1.5 mm long on the petioles and sometimes on the young stems. Solanum trichopetiolatum is the only one of the several species morphologically similar to S. madagascariense described by D’Arcy and Rakotozafy (1994) that we consider distinct enough to merit species status. In addition to the indumentum described above, Solanum trichopetiolatum can be distinguished from the widespread S. madagascariense by its slender, loose inflorescences (Fig. 28 in Knapp and Vorontsova 2016) with usually fewer than 10 flowers (versus denser more robust inflorescences with more than 10 flowers), glabrous (versus glabrous to densely pubescent) corolla, and leaves that are more obovate and discolorous on herbarium specimens than is typical of S. madagascariense. Solanum trichopetiolatum differs from S. humblotii in its possession of a branched inflorescence with usually more than 10 flowers, rather than a few-flowered, unbranched inflorescence. It can also usually be distinguished by its calyx that is not lobed or has minute lobes to only 1 mm long (versus calyx lobes 3-4.5 mm long), but Birkinshaw 1281 from 2500 m elevation in Mahajanga has the distinctive trichomes of S. trichopetiolatum but has unusual filiform calyx lobes ca. 2 mm long. Although the plate of S. trichopetiolatum in D’Arcy and Rakotozafy (1994) illustrates what appears to be a papillate anther, the protologue describes the anthers as smooth; all specimens we have seen have smooth, rather than papillate anthers. We have removed this part of the original illustration of D’Arcy and Rakotozafy (1994) in our Fig. 28.
The part of Antsiranana surrounding mountain Marojejy has been identified by D’Arcy (1992) as an area of high diversity for wet forest Solanum. The overall aspect of Solanum trichopetiolatum on herbarium sheets is highly reminiscent of those specimens considered by D’Arcy and Rakotozafy (1994) to belong to S. marojejy (here recognised as belonging to S. madagascariense), and leaves of the two species dry a similar dark golden-brown colour on herbarium sheets; the long trichomes and slender inflorescences of S. trichopetiolatum allow easy identification. Field and population studies are necessary to further understand the relationship between S. trichopetiolatum and S. madagascariense.