An assessment of Coutaportla (Chiococceae, Rubiaceae) with the description of a new species from Mexico

Background and aims – Ongoing studies on Mexican Rubiaceae revealed an undescribed species of Coutaportla endemic to the Sierra Madre Occidental pine-oak forests in the state of Sinaloa, near the border with Durango, Mexico. The species is here described and illustrated, and its morphological characters are compared with those of the other species in the genus. Material and methods – This study is based on field observations, examination of herbarium specimens including digital images, and morphological studies based on samples from dried and spirit specimens. Key results – The morphological comparison of taxonomically important characters among the species of Coutaportla reveals conditions that were previously not reported for the genus. The placentation and ovule number of C. lorenceana, which belongs in the Portlandia complex, is comparable to that in the Chiococceae tribe. This tribe was proposed to include the latter complex based on molecular data, but the classification was controversial according to the morphology. Coutaportla lorenceana hence provides a morphological link between the Portlandia complex and the taxa traditionally placed in Chiococceae. The new species is assessed as Critically Endangered following the IUCN Red List criteria.