Posición filogenética del género Araracuara Fern. Alonso

Abstract

The Rhamnaceae family includes a total of 54 genera and more than 1,000 species distributed in diverse ecosystems throughout the world, although it is better represented in the xerophytic zones of the tropical regions. The Araracuara genus includes only the Araracuara vetusta species, endemic to rock outcrops in the Araracuara and Chiribiquete regions of Colombian Guiana. The genus is considered primitive within the family because it has unique characters in the Rhamnaceae as for example the habit, since it is small, spindly trees, and also because the leaves are perennial and are grouped in terminal fascicles. According to Fernández-Alonso & Arbeláez (2008), Araracuara presents morphological affinities with different genera of the Rhamnaceae: the inflorescences are similar to those of Ampelozizyphus, Emmenosperma, Gouania and Pomaderris; the flowers with a nectariferous disc attached to the ovary and the hypanthium, as well as the semi-insular ovary, are similar to those of Colubrina, Lasiodiscus, Paliurus, Pomaderris, Ventilago and Ampelozizyphus; the trilocular capsular fruits with explosive dehiscence are similar to those of the genera Ampelozizyphus, Colubrina and Noltea. As a result, Araracuara has not been included in any of the recognized tribes, and it is classified within the group "incertae sedis" (Richardson et al., 2010b). It has been suggested that Araracuara is closely related to Colubrina, a genus of pantropical distribution, and to a lesser extent to Ampelozizyphus, a genus of Amazonian distribution (Fernández-Alonso & Arbeláez, 2008). Considering the phylogenetic relationships of the genus within the family are unknown, our goal is to evaluate the systematic position of Araracuara within the Rhamnaceae using chloroplast (rbcL, trnL-F) and nucleus (ITS2) DNA sequences, as well as morphological characters. The phylogenetic analysis of the combination of molecular and morphological data confirms the affinity between Araracuara with Colubrina, a genus of pantropical distribution.