Randia brevituba (Rubiaceae), a new species from the Southern Cone of America and comments on Randia armata

Abstract

Randia brevituba is a new species of the Paranean region of Argentina and Paraguay. It differs from the closest species, R. ferox, which is sympatric, in having short corolla tubes of 4.7‐5.4 mm in the pistillate flowers and 2.8‐7.9 mm in the staminate flowers, calyx lobes varying in shape and size in the same pistillate flower, and globose fruits 14‐17 mm long (versus corolla tubes of 25.0‐27.0 and 22.6‐34.0 mm long, respectively, calyx lobes equal in shape and size, and fruit 3‐5 cm and ovoid, ellipsoid or subglobose in R. ferox). We also discuss the taxonomic concept and geographic distribution of Randia armata, and conclude that it is markedly different from R. brevituba and the other species in the Southern Cone studied here, and moreover, that it does not occur in the Southern Cone. We provide a taxonomic key to distinguish the new species from other species of Randia in the Southern Cone of America.