Evolutionary Trends in Orchidaceae

Dressler and Dodson (1960) have pointed out that as a family undergoing rapid evolution, Orchidaceae provides excellent material for the study of evolution. It is true that fossil wealth, which would have helped considerably in piecing together the past history of the orchids, is singularly lacking in this group of plants.But evidences of the various channels though which evolution has progressed in the family, are well documented in the living species themselves. Gradation forms which interconnect the primitive with the advanced with unsual clarity, exist in almost all lines of evolution in orchids. Ames (as quoted by Schweinfurth, 1959) is of opinion that there has been large scale extinction in the family. Dressler and Dodson, on the other hand, believe that the family is characterised by the lack of extinct forms and because of this very fact, the process of evolution is much less complicated than in other plant families and comparatively easy to trace.