Two new species of Psychotria L. (Psychotrieae-Rubiaceae) from Dinagat Island, Philippines

Psychotria alejandroi and P. nitidifolia, two new species from Dinagat Island, Philippines, are described and illustrated. Both species belong to the Pilosella species group sensu Sohmer and Davis (2007), characterized by inflorescences with defined axes bearing sessile flowers and fruits. Psychotria alejandroi is similar to P. pilosella but can be distinguished by having truncate, lobed stipules with its inner lobes extending into long aristae, lanceolate to narrowly ovate leaves that are coriaceous and scabrous, longer inflorescences (2–4 cm long), bracts with entire margins, 5- to 6-merous flowers, and weakly ribbed pyrenes with weakly ruminate endosperms. Psychotria nitidifolia resembles P. castroi but differs by its smaller habits (0.6–1.5 m), shorter petioles ((0.8)1.3–1.7 cm), smaller leaves ((4.0)9.2–11.2 cm × (1.5)3.2–3.9 cm), blades drying dark khaki brown, monochotomous to trichotomous inflorescences, prolate fruits with smaller, obscure calyx lobes (0.2–0.3 mm), and strongly ridged pyrenes with weakly ruminate endosperms. Field images, a distribution map, and an identification key to the Psychotria species (Pilosella group) occurring on Dinagat Island are also provided. Based on the IUCN categories, the two new species are evaluated as critically endangered (CR). The discovery of these species highlights the urgency for further biological explorations and to conserve the remaining forested habitats of Dinagat Island, as this area serves as the only sanctuary for a multitude of narrowly endemic species.