Notes on Neotropical litter-gathering Rubiaceae, and distinction between Faramea tinguana from southern Brazil, and F. humicapiens sp. nov. from French Guiana

Background and aims – Single-stemmed plants 20–100 cm tall, with sessile or subsessile leaves in terminal rosettes gathering leaf litter, and axillary, 1–3 - flowered inflorescence, from the state of Rio de Janeiro, southern Brazil, and from French Guiana, have traditionally been identified as Faramea tinguana. The disjunction of more than 3,200 km air distance between French Guiana and Rio de Janeiro stimulated an in-depth analysis of the specimens from those regions to evaluate if any morphological character might distinguish them.

Material and methods – This study is based on examinations of herbarium specimens, material preserved in 60 % ethanol, and field observations. Herbarium specimens were studied either on site or through loans from the CAY, CEPEC, G, G-DC, K, L, MO, NY, P, RB, U herbaria. Digital images of herbarium specimens were analysed through virtual herbaria.

Traditional practices of herbarium taxonomy have been applied. A preliminary conservation status assessment of each species studied was made using the IUCN Red List Categories and Criteria. Results – The names F. tinguana and F. megalophylla are here lectotypified, and are treated as synonymous.

Numerous reproductive characters support a clear distinction between the specimens from Rio de Janeiro and those from French Guiana traditionally identified as F. tinguana. Hence, the two distant populations are here treated as two distinct species. Faramea humicapiens, endemic to French Guiana, is newly described, and F. tinguana is restricted to the state of Rio de Janeiro.

Faramea humicapiens is evaluated as Vulnerable and F. tinguana as Critically Endangered. A discussion on Neotropical litter-gathering Rubiaceae is also presented.