A Taxonomic Revision of the Endemic New Caledonian Genus Storthocalyx (Sapindaceae)

The endemic New Caledonian genus Storthocalyx is only known from two of this South West Pacific archipelago's main vegetation types, maquis and humid evergreen forest, and within the latter it occurs on both ultramafic and volcano-sedimentary substrates. Recent phylogenetic studies confirm its monophyly and indicate that it forms a clade with two other endemic genera, Gongrodiscus and Podonephelium. Storthocalyx is characterized by leaflets with a glaucous lower surface (due to the presence of papillae) and a lack of domatia, actinomorphic flowers, distinct sepals, petals with many long trichomes and lacking appendages, and a three-locular capsule whose inner surface is covered with a dense indument. As part of a collaborative effort to clarify the taxonomy of New Caledonian Sapindaceae, a revision of Storthocalyx is presented. Species delimitation is based on results from a recently published multivariate morphometric analysis, and descriptions were prepared using the resulting data matrix coupled with examination of all available herbarium collections and extensive field observations. Five species are recognized, including one that is newly described (Storthocalyx corymbosus). A key to species is provided, along with descriptions, distribution maps, color photos, a line drawing (for the new species), and risk of extinction assessments following IUCN red list categories and criteria.