Hibiscus involucratus (Hochr.) M. Hanes, G.E. Schatz & Callm., comb. nov.

 Macrostelia involucrata Hochr. in Notul. Syst. (Paris) 14: 230. 1952.

Holotypus: MADAGASCAR. Reg. Atsimo-Atsinanana [Prov. Fianarantsoa]: Vondrozo, [22°49'S 47 °19'E], 11.IX.1926, fl., Decary 5257 (P [P00037126]!; iso-: G [G00014442]!, P [P00365083, P00037127]!, TEF) .

Distribution and ecology. – Hibiscus involucratus is known from the low elevation tropical evergreen forests around Vondrozo at c. 450 m elevation (Fig. 2).

Conservation status. – Hibiscus involucratus is known only from a single location near Vondrozo, collected in 1926. It is possible that the collection has been made in what is now known as the Ambositra-Vondrozo protected area. With a single collection in the low elevation moist evergreen forests, which are highly threatened in Madagascar, this species is assigned a conservation status of “Critically Endangered” [CR B2ab(iii)] using the IUCN Red List Categories and Criteria (IUCN, 2012).

Notes. – Hibiscus involucratus can be distinguished from all other pendent Hibiscus in Madagascar by its tubular epicalyx with 6 irregular teeth that completely hides the calyx.

We consider the sheet [P00037126] as the holotype, as it is the only specimen with Hochreutiner’s handwriting in P.