Disentangling the Simaba ferruginea Species Complex (Simaroubaceae), With a New Species from Northern South America

Abstract

As recognized traditionally and until recently, Simaba ferruginea A.St.-Hil. sensu Engler was a polymorphic taxon with a disjunct distribution on dry formations of central and northeastern Brazil, and the northernmost region of Colombia and adjacent Venezuela. A detailed morphological survey of this complex based on fieldwork and herbarium specimens recovered three closely related but clearly distinct groups of plants, including a new species endemic to La Guajira, Colombia. A recentmolecular phylogenetic study strongly corroborates the relatedness of the three groups and places them in the genus Homalolepis. Each group, herein treated as a distinct species, has distinctive morphological features, specific habitat preferences, and is allopatric from the other groups. Homalolepis ferruginea sensu strictu is endemic to the cerrado formation on the Brazilian Central Plateau. Homalolepis bahiensis, reinstated here as a distinct species, occurs along the sandy coastal plains in northeastern Brazil. Homalolepis guajirensis is described as a new species, and it is endemic to La Guajira peninsula in Colombia. We present a table and a key to distinguish the three species, full descriptions, geographical and ecological data, and assess the conservation status for each, following IUCN criteria.