History of plant systematics
The
history of plant systematics—the
biological classification of
plants—stretches from the work of ancient Greek to modern
evolutionary biologists. As a field of science, plant systematics came into being only slowly, early plant lore usually being treated as part of the study of medicine. Later, classification and description was driven by
natural history and
natural theology. Until the advent of
evolution, nearly all classification was based on the
scala naturae. The professionalization of botany in the 18th and 19th century marked a shift toward more holistic classification methods, eventually based on evolutionary relationships.
Historians of botany generally begin the history of botanical classification with
folk taxonomy or with
Theophrastus's
Historia Plantarum, the earliest surviving treatise on plants. Theophrastus, a student of
Aristotle, did not articulate a formal classification scheme; instead he relied on the common groupings of folklore combined with growth form: tree shrub; undershrub; or herb. The
Materia medica of
Dioscorides was also an important early compendium of plant descriptions (over five hundred); it was in use from its publication in the 1st century until the 16th century.
[Mayr, Ernst. The Growth of Biological Thought: Diversity, Evolution, and Inheritance. The Belknap Press of Harvard University Press: Cambridge, Massachusetts, 1982. pp. 154-155.]In the 16th century, works by
Otto Brunfels,
Hieronymus Bock, and
Leonhart Fuchs helped to revive interest in natural history based on first-hand observation; Bock in particular included environmental and life cycle information in his descriptions. With the influx of exotic species in the
Age of Exploration, the number of known species expanded rapidly, but most authors were far more interested in the medinical properties of individual plants than an overarching classification system. Later influential Renaissance books include those of
Caspar Bauhin and
Andrea Cesalpino. Bauhin described over 6000 plants, which he arranged into 12 books and 72 sections based on a wide range of common characteristics. Cesalpino based his system on the structure of the organs of fructification, using the Aristotelian technique of
logical division.
[Mayr, The Growth of Biological Thought, pp. 155-161] In the late 17th century, the most influential classification schemes were those of English botanist and natural theologian
John Ray and French botanist
Joseph Pitton de Tournefort. Ray, who listed over 18,000 plant species in his works, is credited with establishing the
monocot/
dicot division and some of his groups â€"
mustards,
mints,
legumes and
grasses â€" stand today (though under modern family names). Tournefort used an artificial system based on logical division which was widely adopted in France and elsewhere in Europe up until Linnaeus.
[Mayr, The Growth of Biological Thought, pp 162-165.]The book that had an enormous accelerating effect on the science of plant systematics was the
Species Plantarum by
Linnaeus, although this work does not deal with the relationships of plants, as such. It assumed that plant species were given by God and that what remained for humans was to recognise them and use them (a Christian reformulation of the
scala naturae or
Great Chain of Being). The
Species Plantarum presented a complete list of the plant species then known, ordered for the purpose of easy identification, by the number and arrangement of the male and female sexual organs of the plants. Of the groups in this book, the highest rank that continues to be used today is the
genus. However, the consistent use of
binomial nomenclature and the fact of having a complete listing of all plants provided a huge stimulus for the field.
Linnaeus was quite aware that the arrangement of species in the
Species Plantarum was not a ‘natural system', i.e. did not express relationships. Elsewhere Linnaeus did present some ideas of plant relationships. The earliest
system of plant classification probably was that by
de Jussieu (inspired on the work of Adanson) and the early nineteenth century saw the start of the work by the de Candolle's, culminating in the
Prodromus.
A major influence on plant systematics was the theory of
evolution (
Charles Darwin published
Origin of Species in 1859), resulting in the aim to group plants by their
phylogenetic relationships. To this was added the interest in plant anatomy, aided by the use of the
light microscope and the rise of chemistry, allowing the analysis of
secondary metabolites. A fairly late development was the advent of
cladistics, which only came into its own with the availabity of the computer and the enormous flood of
molecular data: the
APG II system is only the latest in a long line of systems (see the
list of systems of plant taxonomy).
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*: [In English, with list of systems since 1703 (John Ray) until 1845; available online at
Gallica]
