XVI International Botanical Congess

The extensive morphological variability in habit and form shown by members of the Cactaceae, coupled with a wide range of floral syndromes, phenotypic plasticity, and evolutionary parallelisms have significantly influenced previous attempts to provide a comprehensive classification for the family. Throughout the history of classificatory systems, a shift in the philosophy of generic and species concepts was evidenced. The earliest systems of classification were largely artificial, as best exemplified by the monograph of Linneus and deCandolle. The first attempt at a natural classification was proposed by Schumann, particularly with respect to subfamilial division. This philosophy was continued by Britton and Rose in their well known monograph. Extreme viewpoints of generic circumscription were also evidenced ranging from very broadly defined genera (Schumann and Benson) to recognition of a large number of narrowly defined groups (Britton and Rose and Backeberg). With the development of a phylogenetically based taxonomic philosophy, a major change in cactus classification was evidenced following the work of Buxbaum. Previous classification systems and their influence on modern systems are reviewed.