A Taxonomic Revision of Philippine Mussaenda (Rubiaceae, Mussaendeae)
The Philippine taxa of Mussaenda Burm. ex L. (Rubiaceae, Ixoroideae, Mussaendeae) are revised here, based on field observations and study of herbarium specimens. Twenty-four species and four varieties are recognized, with three new species and one new variety. In the Philippines, M. grandibracteata Alejandro is described from the province of Occidental Mindoro, M. liedeae Alejandro from Palawan, and M. milleri Elmer ex Alejandro from Nueva Ecija; M. philippica A. Rich var. pubescens Alejandro is described from Davao Oriental. A lectotype is newly designated for M. benguetensis Elmer, and the invalid name M. milleri is validated herein. Mussaenda macrophylla Wall. var. grandisepala (Jayaw.) Alejandro has new status for its rank as variety rather than form, and the epithet grandisepala is lectotypified. Subsequent lectotypifications are designated for M. scandens Elmer and M. vidalii Elmer. The morphology of Philippine Mussaenda is compared with Asian and African Mussaenda and is distinguished from other genera of Mussaendeae by its reduplicate-valvate corolla aestivation. The forms of trichomes and morphology of the calyx and corolla are valuable characters for species recognition. Variation of trichomes inside the corolla exists between the short- and long-styled flower morphs and is an important character in recognizing some Philippine Mussaenda.