Borreria (Rubiaceae) from Paraguay: occurrences, richness, geographical distribution, and nomenclatural novelties

Abstract

Borreria is a genus into the Spermacoce clade with ca 80 native species in the Americas, from southem EE.UU. to center of Argentina. In South America, taxonomic and floristic contributions were performed in the genus to Bolivian, Brazilian, and Argentinian floras. In this context, nomenclatural changes, new records, and new species have been published in the last decades for Paraguay, but until now there is no comprehensive taxonomic treatment. In addition, this country has a great diversity of ecoregions as the Atlantic Forest, Cerrado, “Cordillera de los Altos”, Dry and Humid Chaco, Pantanal, and “Sabanas Mesopotámicas”. Our goal is to present an overview of Borreria in Paraguay, its geographical distribution, and the association of its occurrences in diíferent ecoregions. We studied collections deposited in BM, CTES, F, FACEN, FCQ, G, HUEFS, MO, P, SI, and SP. Coordinates were taken from the labels on each specimen, and when these were absent, the point was georeferenced using Google Earth according the locality ñames. A total of 503 datapoints were obtained corresponding to 21 species of Borreria. Each occurrence and ecoregions were mapped using QGIS. A map o f known richness was generated with this information and was quantified with 5 x 5 km cells using the Biodiverse software. As result, B. verticillata is the widest distribution species, whereas B. viridiflora is the only endemic species for Paraguay. Besides that, the ecoregion with the higher richness is the Atlantic Forest since it has 20 species, with B. diacrodonta, B. remota, and/i. runkii exclusive for it. In contrast, Pantanal and Dry Chaco have only one species each, B. cupularis and B. spinosa, respectively. Borreria alata is registered as a new record for the country, lectotypes for three varietal ñames are chosen, and five new synonyms for B. argéntea, B. orinocensis, and B. verticillata are proposed.