Plant Molecular Phylogenetics – Where We Are Now?

Dr. H. S. Kathriarachchi
Department of Plant Sciences, University of Colombo

Phylogenetics – the study of the evolutionary history and relationships of biological taxa has been revolutionized by the molecular data. Last half of the twentieth century has been a time of rapid development of applying macromolecular data to plant systematics. During the last 2–3 decades especially DNA sequence data have successfully contributed to the tremendous progress in clarifying the phylogenetic relationships and many other evolutionary aspects of higher plants.

Understanding of phylogenetics of large angiosperm families has dramatically increased, particularly with the analysis of DNA sequences from multiple genes of plastid, mitochondrial and nuclear genomes. Large, combine DNA sequence data sets were produced across angiosperms. Rigorous analytical tools were developed and the cladistic approach on these extensive data was employed. Based on the molecular phylogenies classifications those reflect the evolutionary relationships were synthesized. A revised and updated classification (APG=Angiosperm Phylogeny Group Classification) for the families and orders of the flowering plants was produced mainly based on DNA sequence data. These phylogenetic analyses do not support the traditional binary division of angiosperms as dicots and monocots.

Well developed strong phylogentic hypotheses can now be used as a frame work for many significance questions on the biology, ecology and evolutionary aspects of flowering plants. These studies further explore our understanding on the origin and diversification of angiosperms and many other flowering plant groups. Divergence time of flowering plant taxa were estimated using “molecular clock” approach, however fossil-based time estimations disagree with this method.

Controversies are there, however, molecular phylogenetics has contributed positively and enormously to the field of plant systmeatics. It is not all about relationships among fascinating diversity of plants now exist but also about how the diversity was created indeed continues to be formed.