Taxonomy_of_the_coffee_plant

Several traits can be exploited to classify plants, and traditional ones are based on plant morphology, which
studies the plant form and their specific structural features. Here, botanists distinguish vegetative traits like the
appearance of the leaves (Coffea: leaves with smooth margins and the shape is elliptic-ovate to oblong), plant
growth = habitus (Coffea: shrub or a small tree), phyllotaxy (Coffea: opposite growth, where two leaves attach at
each point (node) on the branch), branching pattern of a tree (Coffea: opposite again) or specific structures of the
stem (no specific trait for Coffea). Next, an important source of information lies in the morphology of the flowers.
As those traits are of reproductive importance, already small deviations from the mean could have an immediate
effect on forming new species. Here, structure (Coffea: white flowers, radial symmetry (identical parts are
arranged in a circular fashion around a central axis), 5 petals (modified leaves that surround the reproductive
parts, often coloured to attract pollination) that form a tube (the base of the petals are fused) and the actual
appearance as inflorescence (Coffea : flowers grow in clusters (= inflorescence) in the axils of the leaves) as well
as the resulting fruits (Coffea: red drupe in the size of a cherry that contains usually two seeds) are important.
Next to morphology also ecology can give hints on the relationship of a species. Or that closely related species
share certain secondary plant metabolites, which serve a certain purpose in the plant, e.g. nicotine was invented
for defense purposes. The resulting taxonomy is therefore also called chemotaxonomy, which is in turn closely
related to biochemical analyses of the metabolism of the plant that is also similar among closely related species.
Embryology could be used, where the development of the embryo is used to study its origin. Fossil botany in turn
is used to judge the age of a trait. If a certain trait was already present in fossils this trait (symplesiomorph) has
been developed a long time ago and is likely shared by many species, compared to a rather new trait (apomorph)
that has originated only recently based on an “invention”.
More recently, genetic analyses or molecular methods in general are becoming more and more relevant in
determining the classification of life on earth, e.g. the already mentioned new classification of angiosperms by the
APG was based of DNA sequencing.
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