Plant Systematics

Systematics deals with the identification and ranking of all plants. It includes classification and nomenclature (naming) and enables the botanist to comprehend the broad range of plant diversity and evolution.

Plant systematics is a science that includes and encompasses traditional taxonomy; however, its primary goal is to reconstruct the evolutionary history of plant life. It divides plants into taxonomic groups, using morphological, anatomical, embryological, chromosomal and chemical data. However, the science differs from straight taxonomy in that it expects the plants to evolve, and documents that evolution. Determining phylogeny – the evolutionary history of a particular group – is the primary goal of systematics.

Classification Systems For Plant Systematics

Approaches to classifying plants include cladistics, phenetics, and phyletics.

• Cladistics: Cladistics relies on the evolutionary history behind a plant to classify it into a taxonomic group. Cladograms, or “family trees”, are used to represent the evolutionary pattern of descent. The map will note a common ancestor in the past, and outline which species have developed from the common one over time. A synapomorphy is a trait that is shared by two or more taxa and was present in their most recent common ancestor but not in earlier generations. If a cladogram uses an absolute time scale, it is called a phylogram.
• Phenetics: Phenetics does not use evolutionary data but rather an overall similarity to characterize plants. Physical characteristics or traits are relied upon, although the similar physicality can reflect evolutionary background as well. Taxonomy, as brought forth by Linnaeus, is an example of phenetics.
• Phyletics: Phyletics is difficult to compare directly with the other two approaches, but it may be considered as the most natural approach, as it assumes new species arise gradually. Phyletics is closely linked to cladistics, though, as it does clarify ancestors and descendants.