Order from Chaos • Life can only be understood backwards; but it must be lived forwards. • Soren Aabye Kierkegaard
Classification Historical Review The Relationships of Plants
Plants • Organisms supplied with chlorophyll, capable of trapping the radiant energy of sunlight, transforming it into stored potential energy while at the same time releasing oxygen to the atmosphere. • An assemblage of organisms lacking chlorophyll but morphologically very similar to certain groups of the lower plants supplied with chlorophyll.
So Many, Many Plants • We know that there are hundreds of thousands of different plants inhabiting this world. • We know that there is a structured order to how these plants are grouped together. • How did this happen?
Classification • Any classification is the placing of similar things together. • The problem in biological classification is the meaning of the word SIMILAR.
Classification Expectations • Easy to use • Stable • An aid to memory • Predictive • Concise
Throughout history, • Scientists have tried to determine the best way to classify plants. • Ideas on how to do this have changed considerably over time. • Understanding plant classification means that we have to understand its history.
When did it start? • We can only speculate when humanity first started to classify plants. • Historians of botany generally begin the history of botanical classification with folk taxonomy.
Folk Taxonomy • Folk biological classification is the way rural or indigenous peoples make sense of and organize their natural surroundings (the world around them,) typically making generous use of descriptors like bushes, bugs, ducks, and the likes. • Folk taxonomies are generated from social knowledge and are used in everyday speech. They are distinguished from scientific taxonomies that claim to be disembodied from social relations and thus objective and universal.
Disembodied from social relations???Maybe…maybe not! • Ambrosia trifida L. (aka Ragweed) • Ragweeds are rank-smelling (to some) plants that uglify (beautify?) waste places in late summer. Linnaeus invented the genus Ambrosia which means ‘food of the gods’ to describe them. Did he picture generations of botanists and gardeners smiling at his joke?
History of Plant Systematics • The history of plant systematics as a science (organized biological classification of plants) stretches from the work of ancient Greek to modern evolutionary biologists. One of you in the future? Aristotle and pal Theo?
Historia Plantarum • Historia Plantarum, by Theophrastus, is the earliest surviving treatise on plants. The work served as a reference point in botany for many centuries. • Historia Plantarum was organized in ten books, and is an encyclopedia of the plant kingdom, in which a draft taxonomy is sketched with a basic classification of plant "elements". • Theophrastus did not articulate a formal classification scheme; instead he relied on the common groupings of folklore combined with growth form: tree, shrub, sub-shrub, herb.
Theophrastus Who???(could he really have lived for 116 years?) • Theophrastus (371 – c. 287 BC), was a student and eventually the successor of Aristotle in the Peripatetic school, a school of philosophy in ancient Greece founded by Aristotle. • His two surviving botanical works, Enquiry into Plants and On the Causes of Plants, were an important influence on medieval science. • On the strength of these works, some call him the "father of taxonomy".
The Science of Plant Systematics • 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 how scientists of the time understood nature. Until the advent of Darwin’s theory of evolution, nearly all classification was based on the scala naturae. • Botany’s elevation to a professional science in the 18th and 19th century marked a shift toward more holistic classification methods, eventually based on evolutionary relationships.
Scala Naturae What??? • The great chain of being or scala naturae is a classical and western medieval conception of the order of the universe, whose chief characteristic is a strict hierarchical system. • The chain of being is composed of a great number of hierarchical links, from the most basic and foundational elements up through the very highest perfection, in other words, God.
Rudbeckia hirtaBlack-eyed Susan • Kingdom Plantae – Plants • Subkingdom Tracheobionta – Vascular plants • Superdivision Spermatophyta – Seed plants • Division Magnoliophyta – Flowering plants • Class Magnoliopsida – Dicotyledons (Eudicots now) • Subclass Asteridae • Order Asterales • Family Asteraceae – Aster family • Genus Rudbeckia – coneflower • Species Rudbeckia hirta – black-eyed Susan • Source: USDA and the Great Chain of Being…
Carolus Linnaeus syn Karl Linnsyn Carl von Linne • Classification was a complex and strange thing before Linnaeus developed his system, and became even stranger and more complex after. Linnaeus
Linnaeus Methodology • By combining the binomial method with his (originally) simple method of counting stamens, Linnaeus created a working system of classification that became widely embraced, as it proved on the whole, to be much more practical and flexible than any previous method devised.
Genus and species • The genus name indicates a group of similar plants and renders unnecessary a great deal of description because all members of a genus share certain details of structure. • The species name specifies one kind of plant within that genus, and often adds unique identifying information such as leaf shape, flower color, or how the plant is used.
The future is not what it used to be (aka when Linneaus worked out his classification scheme. ) • Darwin’s publication of On the Origin of Species was more than a hundred years in the future. • Geologists were not yet appreciating the antiquity of Earth. • Paleontology had yet to be born. • Extinction was unknown. No dinosaur bone had yet been recognized.
Question • How do you think Linneaus would have replied to the notion that extant species have evolved from previous, now extinct, species? • 1) Ya sure ya betcha • 2) “There are now as many species as the infinite being created diverse forms in the beginning.”
Who was the zillion-times great-grandma (pa) of all living things? • Linnaeus didn’t have to trouble himself about that question. In his day, the division between the plant and animal kingdoms was to him and his contemporaries manifest from the instant of Creation, when every species had been given life simultaneously, and since when all had remained unchanged.
Taxonomy Today • Attempts to encode each organism’s place within evolutionary history. • As more of that history becomes known, and as sophisticated technology allows a more penetrating study of both living and fossil plants, quite a few plants once named on gratuitous resemblances have been renamed to reflect their genealogy.
Evolution Solution? • The complete classification of an organism is its evolutionary address. • Each step up the hierarchy is a step back in time.
Evolutionary TheoryMonerans to Protistans Perhaps? • Those most primitive organisms, the ones whose kind appear to have arisen earliest in the course of evolution are unicellular Monerans, the prokaryotes, bacteria, and cyanobacteria • The Protistans, a noncommittal name for unicellular or communal eukaryotes that means ‘the first’ without specifying animal, vegetable, or fungal.
Onward Protistans SoldiersYou Are How You Eat • Those that tend to feed their needs like PLANTS by photosynthesis. • Those that tend to digest like FUNGI outside their bodies. • Those that tend to ingest food like ANIMALS.
Notables to Remember • Cesalpino, Andrea (1519-1603) • (aka Andreas Caesalpinus) • Italian botanist who showed that plants could be and should be classified by their anatomy and structure. In De plantis(1583) Cesalpino offered the first remotely modern classification of plants. Before this plants were classed by their location - for example marsh plants, moorland plants, and even foreign plants.
Notables to Remember • Joseph Pitton De Tournefort (1656-1708) • A French botanist, notable as the first to make a clear definition of the concept of genus for plants. • His principal work was the 1694 Eléments de botanique, ou Méthode pour reconnaître les Plantes • The work's most important contribution was a clear distinction between genus and species. With the concept of the genus, Tournefort was able to cluster the 7,000 plant species he described into 700-plus genera, making classification easier, and preparing the way for Linnaeus. Linnaeus used many of the genus names and descriptions as defined by Tournefort. • The word “herbarium" also seems to have been an invention of Tournefort; previously herbaria had been called by a variety of names.
Notables to Remember • Carolus Linnaeus (1707-1778) • A Swedish botanist, physician and zoologist, who is known as the father of modern taxonomy. • His father adopted the Latin-form name Linnaeus after a giant linden tree on the family homestead. • Linnaeus's main contribution to taxonomy was to establish conventions for the naming of living organisms that became universally accepted in the scientific world, the starting point of binomial nomenclature. • In addition Linnaeus developed what became known as the Linnaean taxonomy; the system of scientific classification now widely used in the biological sciences.
Notables to Remember • Antoine-Laurent De Jussieu (1748-1836) • A French botanist, notable as the first to propose a natural classification of flowering plants; much of his system remains in use today. • In his study of flowering plants, Genera plantarum (1789), Jussieu adopted a methodology based on the use of multiple characters to define groups. • This was a significant improvement over the original system of Linnaeus, who classified plants into classes and orders based on the number of stamens and pistils. Jussieu did keep Linnaeus' binomial nomenclature, resulting in a work that was far-reaching in its impact; many of the present-day plant families are still attributed to Jussieu.
Notables to Remember • Michel Adanson (1727 - 1806) • A French naturalist of Scottish descent. • In 1763 he published his Familles naturelles des plantesin which he developed the principle of a system of classification distinct from that of Linnaeus. • Those beings possessing the greatest number of similar organs were referred to one great division, and the relationship was considered more remote in proportion to the dissimilarity of organs.
Notables to Remember • Jean-Baptiste Pierre Antoine de Monet Chevalier de Lamarck (1744 –1829) • A French soldier, naturalist, academic and an early proponent of the idea that evolution occurred and proceeded in accordance with natural laws (nature is all there is and all basic truths are truths of nature.) • Lamarck's contribution to evolutionary theory consisted of the first truly cohesive theory of evolution, in which an alchemical complexifying force drove organisms up a ladder of complexity, and a second environmental force adapted them to local environments through "use and disuse" of characteristics, differentiating them from other organisms.
Notables to Remember • Augustin Pyramus de Candolle (1778 - 1841) was a Swiss botanist. The authority abbreviation used in citing plant names he published is "DC.". • He originated the idea of "Nature's war", writing of plants being "at war one with another" with the meaning of different species fighting each other for space which influenced Charles Darwin. • His Principes élémentaires de botanique, contained the first exposition of his principles of classification, following a natural method as opposed to the artificial Linnaen method.
Artificial versus natural classification • An artificial classification is an arrangement that is based on superficial or arbitrary attributions. It is constructed rather than based on discoveries. A natural classification, on the other hand, is a classification that reflects a natural order supposed to exist and be discovered by science.
Notables to Remember • George Bentham 1800–1884) • An English botanist considered by some to be the premier systematic botanist of the nineteenth century. • The author abbreviation Benth. is used to indicate this individual when citing a botanical name. • George Bentham had neither a formal school nor a college education, but at an early age acquired the power of giving sustained and concentrated attention to any subject that occupied him. • His greatest work was the Genera Plantarum, begun in 1862, and concluded in 1883 in collaboration with Sir Joseph Dalton Hooker.
Notables to Remember • Asa Gray (1810 - 1888) • Asa Gray is considered the most important American botanist of the 19th century. • He was instrumental in unifying the taxonomic knowledge of the plants of North America. Of Gray's many works on botany, the most popular was his Manual of the Botany of the Northern United States, from New England to Wisconsin and South to Ohio and Pennsylvania Inclusive. This book, known simply as Gray's Manual, has gone through a number of editions and remains a standard in the field.
Notables to Remember • Heinrich Gustav Adolf Engler (1844 – 1930) • A German botanist, Engler is notable for his work on plant taxonomy and phytogeography, like Die Natürlichen Pflanzenfamilien (The natural plant families). • He was one of the pioneers in phytogeography, highlighting the importance of factors like geology on biodiversity, and defined biogeographical regions in 1879.
Notables to Remember • Emil Hans Willi Hennig (1913-1976) • A German biologist who is considered the founder of phylogenetic systematics, also known as cladistics. With his works on evolution and systematics he revolutionized the view of the natural order of beings.
Some Say Phylogenetics,Some Say Cladistics • Cladistics (syn phylogenetics) is the hierarchical classification of species based on evolutionary ancestry. Cladistics is distinguished from other taxonomic systems because it focuses on evolution rather than similarities between species, and because it places heavy emphasis on objective, quantitative analysis. • Cladistics generates diagrams called cladograms that represent the evolutionary tree of life. DNA and RNA sequencing data are used in many important cladistic efforts.
Now What? • There have been a few other methods of classification since the days of Linnaeus, but it would seem that all will soon fall by the wayside, as DNA classification is likely to replace all previous methods. However, the binomial system of applying names will nonetheless remain (probably?)