Revision of Strychnos sect. Breviflorae subsect. Eriospermae (Loganiaceae): a fibrous testa seeded group

Strychnos (Loganiaceae: Strychneae) is a monophyletic genus of woody plants with c. 200 pantropical species (c. 80 spp. in the Neotropical region). Except for African S. sect. Spinosae and American S. sect. Breviflorae subsect. Eriospermae, most of the sections of Strychnos have been recovered as non-monophyletic in recent molecular studies. The latter group is distributed from central Mexico to southern Brazil, in moist to dry forests, savannas, or grasslands, inhabiting coastal to mountainous regions (sea level to 1,500 m) with tropical or subtropical climate, rarely temperate or semi-arid. The morphological, potentially synapomorphous character that defines this subsection is a fibrous testa enveloping the seeds like a bag; other remarkable features that are sometimes present are tendrils in 1–2 pairs, quadrangular (sometimes winged) branches, conspicuous lenticels, leaf blades usually darkened when dry, secondary and tertiary leaf veins generally inconspicuous (not strongly reticulated), and the underside of leaves with domatia. We present a taxonomic treatment of S. sect. Breviflorae subsect. Eriospermae, resolve nomenclatural issues, and discuss important and novel morphological traits. In total, we examined 511 collections from 42 herbaria. We recognize 12 species: Strychnos alvimiana, S. brachistantha, S. cerradoensis, S. malacosperma, S. mattogrossensis, S. neglecta, S. nicaraguensis, S. nigricans, S. pachycarpa, S. poeppigii, S. schunkei, and S. tarapotensis, a new synonymization (S. schultesiana under S. malacosperma), and provide descriptions, illustrations, maps, and identification keys. We designated four lectotypifications (S. alvimiana, S. malacosperma, S. mattogrossensis, and S. poeppigii) and two epitypifications (S. alvimiana, S. pachycarpa).