1. Herbivory
Monarch caterpillar and Milkweed leaf

2. Plant Resource Defense
Qualitative defense - highly toxic substances, small doses of which can kill predators
high nutrient environment/fast growth (high turnover in plants) - use toxins (plant secondary compounds) that often require N, expensive to make (must be replaced often), but can be made rapidly - cyanide compounds, cardiac glycosides, alkaloids - small molecules

3. Plant Resource Defense
Quantitative defense - substances that gradually build up inside an herbivore as it eats and prevent digestion of food
low nutrient environment/slow growth (low turnover in plants) - primarily use carbon structures - wood, cellulose, lignin, tannins - large molecules - makes plant hard or unpleasant to eat (woodiness, silica), but plants are slow to make these defenses

4. Evolutionary “Arms” Races
Monarch and milkweed

5. Evolutionary “Arms” Races

6. Evolutionary “Arms” Races
California garter snake
Pacific newt

7. Other Plant Defenses Include:
mechanical defenses - plant thorns and spines deter many vertebrate herbivores, but may not help much against invertebrate herbivores
failure to attract predators - plants somehow avoid making chemicals which attract predators
reproductive inhibition - some plants such as firs (Abies) have insect hormone derivatives which if digested, prevent successful metamorphosis of insect juveniles
masting - the synchronous production of very large numbers of progeny (seeds) by trees of one species in certain years

8. Traumatic Resin Ducts – Norway Spruce
Produces terpene containing resins to inhibit feeding

9. Eurasian Jay with Acorn

10. Masting

11. Masting

12. Fagus sylvaticus – European Beech

13. Dipterocarp distribution

14. Dipterocarp trees

15. Dipterocarp seeds

16. Beech seeds and boring moth

17. Lyme’s disease life cycle

18. Masting and Human Health - Lyme’s Disease

19. Induced Defenses
Another aspect of plant defenses is that plants do not always have tissues loaded with defensive chemicals - in many plants, defensive chemicals are only produced when they are needed, usually after the plant has experienced some herbivory - this is an induced defense

20. Impact of Herbivores Is Not Uniformly Experienced

21. Aphids attacking Alfalfa
Spotted Alfalfa Aphid

22. Induced defenses in Birch Trees

23. Induced defenses in Birch Trees

24. Induced defenses in Birch Trees

25. Rubus prickles

26. Acacia depanolobium

27. Giraffe and Acacia

28. Plant defenses are developed at a cost to fitness when:
1. Organisms evolve more defenses if they are exposed to much damage and fewer defenses if cost of defense is high
2. More defenses are allocated within an organism to valuable tissues that are at risk
3. Defense mechanisms are reduced when enemies are absent and increased when plants are attacked - mostly true for chemicals not structures
4. Defense mechanisms are costly and cannot be maintained if plants are severely stressed by environmental factors

29. Plant defenses are developed at a cost to fitness when:
1. Organisms evolve more defenses if they are exposed to much damage and fewer defenses if cost of defense is high
2. More defenses are allocated within an organism to valuable tissues that are at risk
3. Defense mechanisms are reduced when enemies are absent and increased when plants are attacked - mostly true for chemicals not structures
4. Defense mechanisms are costly and cannot be maintained if plants are severely stressed by environmental factors

30. Pine beetle infestation – British Columbia

31. Pine Beetle and Pitch Tube

32. Serengeti Grazing System

33. Serengeti Grazing System

34. Serengeti Grazing System
1 million wildebeest
600,000 Thompson’s gazelles
200,000 zebra
65,000 Cape buffalo
Unknown numbers of 20 other species of large grazing mammals
36 species of rodents
38 species of grasshoppers
Area of about 23,000 square kilometers

35. Serengeti Grazing System

36. Grazing facilitation
Grazing facilitation occurs when the feeding activity of one herbivore species improves the food supply for a second species

37. Opuntia stricta – prickly pear

38. Prickly pear infestation in Australia

39. Area infested with prickly pear before biocontrol

40. Same area after biocontrol

41. Biocontrol Agent – Cactoblastis cactorum

42. Symbiosis

43. Symbiosis Symbioses - species living in close association
Parasitism +,- parasite benefits, host harmed
Commensalism +,0 or 0,0 can have positive effect for one species or for neither
Mutualism +,+ both species benefit

44. Gopher Tortoise – Commensal Host

45. Gopher Tortoise Distribution

47. Epiphytes
Bird’s Nest
Fern

48. Nalini Nadkarni
studying
epiphytes

49. Epiphytes
Figure 1: Hypothetical tree illustrating how vascular epiphytes in humid forests tend to partition substrates illustrating sensitivity to micro climate, particularly humidity, and associated development of the organic rooting media required by some populations.

50. Parasitism and Disease
Lyme Disease Cycle in the UK

51. Parasitism
Parasitism - intimate association between two species in which the parasite obtains its nutrients from a host - parasite usually causes some degree of harm to its host - either reduced growth or reproduction
Pathogen – disease causing agent
Disease – abnormal condition of host due to infection by a pathogen that impairs physiological functioning