1. Plant Taxonomy

2. Taxonomic Systems Predicitivity - Ideally our systems of classification should allow us to place similar species of plants together in the same category

4. Two Types of Classification Schemes Artificial classification schemes - these systems allow one to quickly categorize a particular organism, usually so that it can be quickly found in a book, a garden or an herbarium Natural classification scheme - organize together related groups of plants and have a high degree of predictive power

5. Artificial Classification Scheme Red Trillium

6. Natural Classification Scheme – For Seed Plants

7. Ancient Classifications

8. Pennisetum – a grass - Poaceae

9. Carex – sedge meadow - Cyperaceae

10. Carex Flowers Cyperaceae

11. Juncus – rushes - Juncacaea

12. Vegetables from Brassica oleracea Brassicaceae

13. Theophrastus 370-285 BCE

14. Dioscorides – 1st Century AD

15. Page from 15th century Arabic edition of Dioscorides herbal

16. Leonhart Fuchs - 1542

17. Fuchs’s History of Plants - 1542

18. Gerard’s Herbal 1597

19. Cesalpino - De Plantis 1583

20. Gaspar Bauhin - 1623

21. 1623 – first use of binomial names

22. John Ray – Catalog 1688

23. John Ray’s Catalog of English Plants

24. Carolus Linneaus

25. Systema Naturae – first published 1735

26. Genera Plantarum – 1737 – Linneaus’s copy with notes

27. Species Plantarum - 1753

28. Linneaus - Artificial Classification Scheme

29. A. P. de Candolle - 1813

30. De Candolle – Flore Francaise

31. Classification After Darwin

32. Ideal Classification Scheme Ideally we would construct a classification scheme which progresses from primitive or ancestral traits to advanced or derived traits Ideally each taxon would be monophyletic - arisen by diversification from a single ancestor – the Plant Kingdom – whether the Embrophytes (land plants) or Viridiplantae (green algae plus land plants) In contrast polyphyletic groups have arisen from more than one ancestor - the Protista A paraphyletic group is one in which all members possess a single ancestor in common, but which does not constitute all descendents of that ancestor - the Dicots

33. Developing Classification Systems In developing classification systems, we attempt to group plants which share derived characteristics - presumably these characters have only arisen once or at most a few times - it is not always easy to tell what is a derived character though Derived characters may arise independently in different groups of plants through convergent evolution or parallel evolution convergent - unrelated plants develop similar characteristics due to common environment parallel - plants with common ancestor develop similar characteristics even though the ancestor did not have that characteristic

34. Adolf Engler - 1887

35. Elymus (rye) flowers - Poaceae

36. Charles Bessey - 1911

37. Magnolia grandifolia - Magnoliaceae

38. Arthur J. Cronquist - 1981

39. The figure above (redrawn from Cronquist, 1988, fig. 6.1) depicts phyletic relationships among subclasses of the Class Magnoliopsida, as envisioned by Cronquist. This alignment features the Magnoliidae as including extant dicot elements that carry the greatest number of archaic features (similar to the 'original' flowering plant) and the Asteridae (Sunflowers and relatives) as the most 'derived' or specialized element of the Class. The size of the 'balloons' is roughly proportional to the number of species per subclass.

40. Basics of Characters A taxonomic character is any expressed attribute of an organism that can be evaluated and that has two or more discontinuous states or conditions - for example the number of petals on a flower - can be in 3's, 4's or 5's - thus distinct states and they are discontinuous The taxonomic value of a characteristic is increased if the biological significance of the characteristic has been determined

41. Usefulness of Characters Different characteristics have differing degrees of utility in terms of classification - a uniform characteristic may be very good at demonstrating cohesion or relatedness at a higher level of classification such as the family Conversely, some characters which have a great deal of variability may be of little value in differentiating higher orders of classification, such as family, but may be very valuable in differentiating lower taxonomic groups such as the genus or species

42. Goat Dandelion - Asteraceae

43. Buttercup - Ranunculaceae

44. Morphology Plants are highly plastic in their growth forms - how tall they grow, their shape will vary depending upon environment and growing conditions However reproductive structures tend not to differ in form from plant to plant of the same species - they may differ in number, but form is conservative - flowers, cones tend to be similar within all members of a species - thus much plant classification and identification is based upon reproductive structures

45. Umbel – flower head in Apiaceae

46. White Pasque Flower - Ranunculaceae

47. American Licorice

48. Mint

51. Chickweed - Caryophyllaceae

52. Oak acorns - Fagaceae

53. Birch catkin Betulaceae