Revision of Gasteranthus (Gesneriaceae)

Gasteranthus (Gesneriaceae-Beslerieae) comprises 35 species, including three subspecies. Its range extends from Guatemala and nearby Mexico, Costa Rica, and Panama through western South America south to Bolivia. The center of diversity is in western Ecuador where 25 species occur. Species of Gasteranthus are terrestrial herbs or short subshrubs, and display a diverse array of corolla variation. Corollas may be pale, whitish and funnelform with a large limb and patterns of darker dots and lines inside the throat, or may be relatively uniformly bright yellow, orange, or red, and urceolate with an often strongly inflated ventral pouch and a small throat and limb; intermediate corolla shapes have a ventricose, subventricose, or funnelform tube with a small limb. Species of Gasteranthus grow in forests throughout the range, mainly in shady and permanently humid places, usually in ravines with streams or near waterfalls, but particularly in cloud forests in the permanently wet understory vegetation. The high diversity of Gasteranthus in western Ecuador apparently reflects the speciation of the genus in separate low- and high-elevation cloud forests. Ten species of Gasteranthus are found predominantly in the low-elevation forests between 500 and 800 m elevation, and another 10 species are restricted to the higher forests above 1,800 m elevation. The remaining species appear to be less habitat-specific and consequently more widespread. Because of their limited distribution in cloud forests, the species of Gasteranthus are vulnerable to extinction. Particularly, the low-elevation cloud forests have been nearly completely destroyed; at least 5 endemic species already may be extinct in western Ecuador and an additional 7 throughout the entire range of Gasteranthus. Due to loss of habitat, the survival of more than 10 other species of Gasteranthus may be questionable. Eleven species are here newly described: G. adenocalyx, G. bilsaensis, G. epedunculatus, G. extinctus, G. glaber, G. mutabilis, G. orientandinus, G. osaensis, G. tenellus, G. ternatus, and G. villosus. Two new combinations are proposed: G. calcaratus subsp. calceolus and G. calcaratus subsp. oncogastrus.