Solanum betroka
Not known.
Solanum betroka is endemic to Toliara province in southern Madagascar. It occurs in open dry forest and scrub on limestone or sand; 600-1100 m elevation.
None recorded.
Preliminary conservation status (IUCN 2014). Least Concern (LC). EOO 62,716 km2 (LC), AOO 36 km2 (EN). Solanum betroka is confined to the arid southern part of Madagascar, with some disjunct populations to the north, giving the EOO indicating least concern. Given the paucity of collections of all of the Malagasy members of the ANS clade, and the widespread and continuing habitat alteration in Madagascar, we feel this species would merit conservation concern, but the AOO may also be indicative of collection deficit or bias.
Solanum betroka is a spindly shrub or liana endemic to southern Madagascar. It has small membranous lobed leaves with prominent finer venation clustered on the tips of branches, no more than 3 flowers per inflorescence, and no tufts of trichomes in the axils of the major leaf veins on leaf undersides (domatia). It is the only species of Solanum endemic to Madagascar not a member of the Leptostemonum clade to commonly exhibit lobed leaves (Fig. 5) on reproductive stems; lobed leaves in S. madagascariense occasionally occur but are rare.
Solanum betroka can be difficult to distinguish from the very similar and possibly closely related S. sambiranense and S. imamense. It differs from S. sambiranense by its ovate to elliptic (versus elliptic to obovate) leaves under 5 cm (versus over 5 cm) long, with cuneate to truncate (versus attenuate) bases, inflorescences with 1-3 (versus 3-10) flowers, and calyx lobes 2-3 mm (versus 4-6 mm) long. Solanum betroka bears a strong resemblance to S. sambiranense: both have a clearly visible brown fine venation network, membranous glabrescent leaves that dry greenish brown, and a similar habit. Typical representatives of the southern S. betroka and northern S. sambiranense are clearly distinct but specimens from the centre of Madagascar are more difficult to determine. Further sampling may prove that these two taxa are in fact conspecific. Solanum betroka can be distinguished from S. imamense by its inflorescences with 1-3 (versus 7-13) flowers, flowers under 2 cm (versus over 2 cm) in diameter, and anthers 3.5-5 mm (versus 4-5 mm) long.
Solanum betroka has also been confused with unarmed specimens of the spiny solanums S. batoides D’Arcy & Rakot. and S. erythracanthum Dunal; these can be distinguished easily based on pubescence and anther morphology. Solanum betroka has dendritic trichomes and ellipsoid anthers while S. batoides and S. erythracanthum have the stellate trichomes and long-tapered anthers typical of members of the Leptostemonum clade (Vorontsova et al. 2013; Vorontsova and Knapp 2016).
Solanum betroka occurs primarily in the unique arid southern ecoregion of Madagascar, with a few records further north in the somewhat wetter western ecoregion (Humbert 1955; Faramalala 1988, 1995). It is the only member of the African non-spiny clade restricted to such severely dry climate, although a few spiny Solanum species also occur in the area: Solanum batoides, S. bumeliifolium Dunal, S. croatii D'Arcy & R.C.Keating, and S. heinianum D'Arcy & R.C.Keating; the related S, imamense is partly sympatric with S. betroka in the wetter more northern parts of its distribution range. The habitat niche of S. betroka is significantly different from that of S. imamense and S. sambiranenese both of which occur in wetter habitats further north.
The type collection has smaller leaves with more lobes and denser indumentum than the majority of specimens, and does not exhibit the characteristic pronounced brown venation on dry leaves.