A new species of Pentagonia (Rubiaceae, Dialypetalantheae) from Santander, Colombia, with an identification key to the Colombian species
Pentagonia santanderensis (Rubiaceae, Dialypetalantheae) is described and illustrated from the department of Santander, occurring in the municipalities of Cimitarra, La Belleza, and Landázuri in fragmented forests and primary forest edges associated with water sources. We compare this new taxon with morphologically similar species; the size of its leaves, the magenta coloration of the strongly pleated leaf bases, and the color, indumentum, and size of the corolla, as well as the fruits, are diagnostic characters. This new species increases the number of Pentagonia species recorded in Colombia to 23. Based on the IUCN criteria, P. santanderensis is assessed as Endangered (EN B2a(ii)b(iii)) due to its restricted distribution and continuing decline in habitat quality.