Streptocarpus betsiliensis Humbert, 1967

Möller, Michael, Nishii, Kanae, Callmander, Martin W., Phillipson, Peter B. & Poncy, Odile, 2015, Rearranging specimens on herbarium type sheets of Streptocarpus betsiliensis Humbert (Gesneriaceae), Candollea 70 (1), pp. 145-150 : 149

Streptocarpus betsiliensis Humbert in Adansonia ser. 2, 7: 289. 1967.

≡ Colpogyne betsiliensis (Humbert) B. L. Burtt in Humbert, Fl. Madagascar Comores 180: 148. 1971.

Typus: MADAGASCAR. Prov. Fianarantsoa: Mt Analamamy , Perrier de la Bâthie 12482A (holo-: P [ P00088746 ]!; iso-: P [P00088748]!) .

Distribution and ecology. – Streptocarpus betsiliensis , S. ibityensis and S. lanatus form an intriguing triplet, not only because of their taxonomic history, but of their morphology, and distribution. Geographically S. lanatus occurs in very close sympatry with S. betsiliensis on Mt. Itremo, and both are absent from Mt. Ibity, where S. ibityensis occurs. This is very interesting to note, because S. itremensis B. L. Burtt , a close relative of the three species mentioned above, occurs in both places. Whether S. betsiliensis is absent on Mt. Ibity, or overlooked, would be interesting to study further, as the area between the two mountains ranges has not been explored extensively so far.

In their natural environments plants of the triplet often occupy spaces under rocks or in deep crevices in very dark environments. Occupying these marginal ecological niches may have been enabled by the ability to enlarge one of their cotyledons from a basal meristem (a characteristic which is recorded for other species of Streptocarpus: BURTT, 1970 ; JONG & BURTT, 1975), which are raised into the path of better light, probably to maximize light capture in these marginal habitats.

Conservation Status. – Streptocarpus betsiliensis occurs on the Itremo massif with countless individuals present under many rocks and in crevices (MM, pers. obs.). The species is restricted to the Itremo massif and has an “Extent of Occurrence” (EOO) of 1,150 km 2, an “Area of Occupancy” (AOO) of 63 km 2 and with seven known sub-populations (four occurring in the proposed Protected Area of Itremo) (calculated following CALLMANDER et al., 2007), S. betsiliensis is provisionally assessed as “Vulnerable” [VU B1ab(i, iii)+ B2ab(i, iii)] following IUCN Red List Categories and Criteria ( IUCN, 2012) given the restricted range of the species and the current temporary protection of the Itremo massif, but the threat to the species will certainly increase if the temporary protection is removed.