Epitypification and ecological notes for the Malagasy holoparasite Hydnora esculenta (Hydnoraceae)

The root holoparasite, Hydnora esculenta is a poorly known perennial herb described from southwestern Madagascar. The key character in the original diagnosis was floral dimorphism, a hermaphroditic form and an apparently thinner and longer sterile form. Other useful diagnostic characters are lacking. The type specimens consist only of slices of fruit, and lack important diagnostic characters, thus, an epitype is designated here. The original description is amplified based on field collections and examination of available herbarium material. Flowers of H. esculenta are variable in size (11.6–26.9 cm long) and merosity (3–6), but are uniformly hermaphroditic like all other Hydnoraceae. Osmophores situated on tepal apices combined with angular rhizomes separate H. esculenta from other known Hydnora spp. Additionally, ribbed tepal margins for H. esculenta are diagnostic and are preserved on herbarium specimens. Pollination biology follows the general pattern for the genus, brood‐site mimicry with insect imprisonment and release. Floral mobbing events by the putative pollinator, a scavenger scarab beetle (Kuijtenous laviceps) are reported. The most common observed host of H. esculenta was the invasive tree Pithocellobium dulce. The range of H. esculenta maybe increasing due to the spread of P. dulce in riparian areas and disturbed habitats in southern Madagascar.