What is Plant Systematics?

It is the study of the kinds of plants, living and extinct, and 

the relationships among these plants


I.  Goals of Plant Systematics

1.  Inventory the world's flora
2.  Provide names and descriptions of the plants
3.  Provide a system of classification
4.  Link the classification system to the evolutionary process

II.  Definitions

Taxonomy: (A. P. de Candolle, 1813).  The study of classification, including its rules, theories, principles and procedures (= “alpha taxonomy”)

Systematics: the discovery, description and interpretation of biological diversity as well as the synthesis of information on diversity in the form of predictive classification systems.

Biosystematics: (Camp and Gilly 1943 “biosystematy”).  “To delimit the natural biotic units and to apply to these units a system of nomenclature adequate to the task of conveying precise information regarding defined limits, relationships, variability, and dynamic structure.”  This definition focused mainly on species relationships.  More recently, biosystematics has come to mean “experimental systematics”.

Identification: Assigning an existing name or taxonomic group to an unknown organism.

Keying: The process that is used to identify (determine the name of) an unknown organism.

Nomenclature: The application of a set of agreed upon rules in determining the correct scientific name of an organism.  For plants, the rules are outlined in the International Code of Botanical Nomenclature. Why are names so important?  A plant's name is your key to information about it.  Scientific names are part of a hierarchy which serves the needs of other biological sciences and provides an organizational framework. 

Classification: The orderly arrangement of organisms into a hierarchical system.  Classifications come in three basic types: artificial, natural, phylogenetic.

III.  Why is Taxonomy Valuable to You?

A.  How much have you traveled?

• only in Illinois (may not want to raise your hand!)
• only to the states bordering Illinois
• only to the East coast
• only to the West coast
• Mexico
• Central/South America
• Europe and/or Asia
• Africa
• Australia
• Others (Antarctica, Malaysia, Madagascar, etc.)
"A traveller should be a botanist, for in all views plants form the chief embellishment. Group masses of naked rock, even in the wildest forms, may for a while afford a sublime spectacle, but they will soon grow monotonous. Paint them with bright and varied colors and they become fantastic, clothe them with vegetation and they must form a decent, if not beautiful, picture." Charles Darwin

B.  General edification.  Example: Australian pine (Casuarina in the family Casuarinaceae) and real pines (Pinus family Pinaceae).  With some botanical education, you will become more aware of the differences in the world around you.  Plants will become more than just the green background for landscapes or food items for your favorite furry creature.  Knowledge of plants is in many ways comforting and reassuring.  When some people walk through the woods, they are afraid because they don't know the plants and would be reluctant to touch or eat them for fear of them being poisonous.

C. Skills you gain in this course you can use the rest of your life.  For example, to identify a plant that you do not know, you use a key (a series of choices that eventually sends you to a name).  With some knowledge of the morphological structures of plants, you will be able to more effectively use a key - and, in some cases, identify a plant (at least to family) going on your background knowledge.

D.  People with botanical training are employed in many different fields.  Most systematists find jobs at universities, museums, federal and state agencies, arboreta and botanical gardens.  Federal and state agencies need systematists in the areas of public health, agriculture, wildlife management and forestry. They also help prepare environmental impact statements and work in natural heritage and endangered species programs.  In industry, agricultural processors, pharmaceutical firms, and horticultural companies employ systematists.  And those systematists that learn molecular techniques can be employed in any laboratory that uses these methods.  See booklet "Careers in Biological Systematics" (1986, Amer. Soc. Plant Taxonomists).

E.  A major role of systematists today is conservation.  Relationship to taxonomy?  You can’t know what you’ve lost if you don’t know what you have!  All of you know via a barage of information from the media that the world is loosing much of its biological diversity -  mainly in the tropics. 

IV. Why is Phylogeny Important?

Phylogeny = Evolution

Your book has arranged the organisms in a phylogenenetic sequence.  Why is phylogeny so imporant?  If a classification system is arranged according to evolutionary relationships, the system has greater predictive value.  For example, Catharanthus roseus (Madagascar periwinkle) contains compounds known to cure childhood leukemia.  What if we wanted to know about other plants with such compounds?  Where among the several hundred thousand species should one begin?  You might logically say "look at relatives of this plant", but what if the "traditional" classification system does not reflect natural relationships?  Having a classification system based on robust phylogeny that reflects geneological (descent) relationships provides the best guide to finding the closest relatives of Catharanthus (or any other plant).

V. How to Succeed in this Course

• This class is similar to learning a foreign language.  There are lots of terms that you must know and be able to apply to plants and their morphological parts. 
• It is critical that you keep up, especially by reading the material in the text and lab manual before coming to class. 
• Many of the images shown in class are on the CD that accompanies the text or on various web pages (esp. PhytoImages and PlantSystematics.org).  Please get into the habit of using that these resources from the very start.
•  The laboratory experience is crucial to understanding plant systematics.  Taking the drawings seriously will pay off!
SIUC / College of Science / Elements of Plant Systematics
URL: http://www.science.siu.edu/nickrent/PLB304/IntroLecture.html
Last updated: 21-Jan-08 / dln