XVI International Botanical Congess

The Oxalis tuberosa alliance was originally described by cytologists as sharing a base chromosome number rare in Oxalis (x = 8). Molecular data of the internal transcribed spacer of nuclear ribosomal DNA (ITS) and chloroplast-expressed glutamine synthetase (ncpGS) support the group as monophyletic, with the inclusion of additional species of unknown chromosome number. The members of the alliance are found from the high Andean steppes to the cloud forests of middle elevations, and include both restricted endemics and variable widespread species complexes. Geographic and altitudinal distributions of members of the alliance and some other Oxalis species are compared with results of phylogenetic analysis of combined data of ITS and ncpGS. Groups within the alliance (i.e., clades on the molecular trees) occur across widespread regions in the Andes, yet some are restricted to certain altitudinal/ecological zones.