A New Species of Rustia (Rubiaceae, Rondeletieae) from Bilsa Biological Station, Esmeralda Province, Ecuador

Abstract

A new species of Rustia from Ecuador (Esmeraldas Province), R. bilsana, is described and illustrated. The new species is represented by trees endemic to the cloud forests of northwestern Ecuador, and is easily recognizable by having floral buds pointed at the apex, capsules widely obovoid, inflorescences 16-26 cm long, and purple corollas. RESUMEN. Se describe e ilustra una nueva especie de Rustia del Ecuador (Provincia de Esmeraldas), R. bilsana. La nueva especie esti representada por grboles endamicos de los bosques nublados del Noroeste del Ecuador, y es fcilmente distinguible por sus botones florales agudos, cipsulas anchamente obovoides, inflorescencias 16-26 cm de largo y corolas color pdirpura. Rustia is a genus of approximately 14 species of shrubs and trees, ranging from Costa Rica to southern Brazil. This genus is unique in having terminally poricidal anthers and pellucid-punctate leaves. Its sister genus, Tresanthera, is represented by trees endemic to the coastal forests of Venezuela and Trinidad and Tobago; it also has pellucid-punctate leaves but has laterally poricidal anthers. A full monographic treatment of Rustia is given by Delprete (in press-1999), and an account of the species present in Ecuador has been prepared by Delprete (1998). Rustia and Tresanthera have traditionally been placed in the tribe Condamineeae, but this tribe has been shown to be paraphyletic (Delprete, 1996b), and both genera are included in the tentatively delimited tribe Rondeletieae (Delprete, 1996b). Ecuador has the highest number of species of Rustia (6 out of a total of 14), representing the center of diversity for this genus. The high degree of biodiversity in Ecuador is correlated with the varied vegetational zones present in the country, the adaptation of the species to certain ecological niches, and the latitude being near the equator. In the case of Rustia, one species (R. occidentalis (Bentham) Hemsley) is a shrub endemic to coastal swamps, two are trees found in the wet forests of the western slopes of the Andes (R. alba Delprete from Carci Province and R. bilsana Delprete described below, from Esmeralda Province) and the remaining three (R. schunkeana Delprete, R. viridflora Delprete, and R. rubra Standley ex D. Simpson) are trees occurring on the forested slopes of the Amazonian region. During routine identification of Rubiaceae from Ecuador, while I was still a doctoral student at the University of Texas at Austin in fall 1995, a specimen (Clark, Bass & Pitman 139) of Rustia caught my attention. It was collected at the Bilsa Biological Station, and it was clearly an undescribed species of this genus. Several other species of Rustia occurring in Ecuador have recently been described (Delprete, 1995, 1996a), and the taxonomic position of the genus has been analyzed (Delprete, 1996b). The only specimen (Clark et al. 139) known to me in fall 1995 had inflorescences with only a few old flowers and immature fruits. One year later, John Clark returned to the original site in order to provide complete herbarium specimens (Clark 2979), pickled flowers for morphological studies, and photographs (see Fig. 2). The new species is still known only from the Bilsa Biological Station. The Bilsa Biological Station is a nature preserve of approximately 2500 ha, with an altitudinal range from 300 to 800 m and is located in the Mache Mountains portion of the northwestern province of Esmeraldas. Bilsa was founded in 1994 by the Jatun Sacha Foundation in memory of the late biologists Al Gentry (botanist) and Ted Parker (ornithologist), who died in an airplane crash in the Ecuadorian mountains. This reserve represents one of the few remnant patches of premontane wet forest in northwestern South America, of which less than 1% remains. This premontane forest ecosystem is extremely endangered and quickly disappearing due to farming practices and indiscriminate logging. The Bilsa reserve houses a unique composition of flora and fauna, with elements related to both the coastal rainforest of Colombian Choc6 Province and Andean cloud forests, and many of i s species are rare or still unknown to science. The NovoN 8: 231-234. 1998. This content downloaded from 207.46.13.99 on Sun, 04 Jun 2017 17:46:04 UTC All use subject to http://about.jstor.org/terms