Two new species of Rhipidoglossum (Orchidaceae, Angraecinae) from Central Africa, probably pollinated by settling moths

A revision of Central African specimens of Rhipidoglossum has revealed two new species from the Cameroon Volcanic Line (CVL) and the lowland and peripheric forests of the Guineo-Congolian rainforest block. Rhipidoglossum acuminifolium sp. nov. is endemic to the CVL and is morphologically related to R. delepierreanum from the Western Rift Mountains. This disjunction may suggest historical connectivity or long-distance dispersal between these montane systems.

Footage from Mount Cameroon recorded the settling moth Afroracotis cf. squalida (Lepidoptera, Erebidae) as a potential pollinator of R. acuminifolium, as well as numerous other plant – animal interactions, including only the second documented orchid – orthopteran interaction, involving nectaring by raspy crickets (Orthoptera, Gryllacrididae). Rhipidoglossum acuminifolium is preliminarily assessed here as Endangered (EN) under the IUCN Red List criteria.

The morphologically allied R. delepierreanum is here newly recorded for Burundi, the Democratic Republic of the Congo (DRC), and Uganda. In turn, Rhipidoglossum falcatulum sp. nov. is described from the Central African Republic and the DRC, where it occurs in the Congolian and Central Zambezian regions, in Guineo-Congolian lowland forests and muhulu vegetation. It is preliminarily assessed as Endangered (EN), and it is also hypothesised to be phalaenophilous.

These two novelties increase the species diversity of Rhipidoglossum up to 56 species in Tropical Africa and the Gulf of Guinea Islands.