A new species and hybrid in the St Helena endemic genus Trochetiopsis

Abstract

The discovery in historic herbaria of an overlooked extinct endemic from the island of St Helena is reported. The first descriptions of St Helena Ebony, Trochetiopsis melanoxylon (Sterculiaceae), and the specimens associated with them in the herbaria of Oxford University (OXF) and the Natural History Museum, London (BM), do not match living and later-collected material, and instead represent an extinct plant. A new name is therefore needed for living St Helena Ebony: Trochetiopsis ebenus Cronk sp. nov. The hybrid between this species and the related T. erythroxylon is also described here: Trochetiopsis × benjamini Cronk hybr. nov. (Sterculiaceae), and chromosome counts of 2n = 40 are reported for the hybrid and both parents for the first time. The re-assessment of the extinct ebony emphasizes the importance of historic herbarium collections for the study of species extinction.