2. Biodiversity, Species Interactions, and Population Control Chapter 5

3. Key Concepts Species interactions Responses to changes in environmental conditions Factors determining number of species in a community

4. Species Diversity and Ecological Stability  Many different species provide ecological stability  Some exceptions  Minimum threshold of species diversity (10 - 40 producer species?)  Many unknowns  Net primary productivity (NPP)  Essential and nonessential species

5. Species diversity by latitude Animation

6. Types of Species  Native  Nonnative (invasive or alien)  Indicator-  Keystone -  Foundation

7. Indicator Species  Provide early warnings of ecosystem damage  Indicator of water quality (trout)  Birds as environmental indicators (affected by habitat loss, chemicals)  Butterflies  Amphibians

8. Keystone Species  What is a keystone?  Keystone species play critical ecological roles a. Pollination b. Top predators c. decomposition  EXAMPLES: Dung beetles, Sharks, bees, bats, wolves, alligators,

9. Foundation Species  Relationship to keystones species  Play important roles in shaping communities  Elephants  Contributions of bats and birds

10. Species Interactions  Interspecific competition  Predation  Symbiosis = close long term association 2 or more species A. Parasitism + - B. Mutualism + + C.Commensalism + 0

11. Types of two species interactions animation. Animation

12. Species Interactions: Competition  Interspecific Competition  Fundamental niches  Fighting for limited resources  Competition from humans

13. Reducing or Avoiding Competition  Resource partitioning  Role of natural selection  Specialization and sharing of resources  Resource partitioning of warblers

14. Number of individuals Resource use Species 1Species 2 Region of niche overlap Species 1Species 2 Resource Partitioning and Niche Specialization

15. Resource Partitioning of Warbler Species

16. How Do Predators Increase Their Chances of Getting a Meal?  Speed  Senses  Camouflage and ambush  Chemical warfare (venom)

17. Avoiding and Defending Against Predators  Escape  Senses  Armor  Camouflage  Chemical warfare  Warning coloration  Mimicry  Behavior strategies  Safety in numbers

18. Span worm Bombardier beetle Viceroy butterfly mimics monarch butterfly Foul-tasting monarch butterfly Poison dart frog When touched, the snake caterpillar changes shape to look like the head of a snake Wandering leaf insect Hind wings of io moth resemble eyes of a much larger animal How Species Avoid Predators “If it is small and strikingly beautiful, it is probably poisonous. If it is strikingly beautiful and easy to catch, it is probably deadly.” - E.O Wilson camouflage Chemical warfare / Warning mimicry Deceptive behavior

19. Parasites  Parasitism + -  Hosts  Inside or outside of hosts  Harmful effects on hosts  Important ecological roles of parasites

20. Mutualism + +  Both species benefit  Pollination  Benefits include nutrition and protection  Mycorrhizae - fungi that helps plants extract nutrients and water from soil  Gut inhabitant mutualism

21. Oxpeckers and black rhinocerosClown fish and sea anemone Lack of mycorrhizae fungi on juniper seedlings in sterilized soil Fig. 6-7, p. 117 Examples of Mutualism © 2006 Brooks/Cole - Thomson Mycorrhizae fungi on juniper seedlings in normal soil

22. Commensalism + 0  Species interaction that benefits one and has little or no effect on the other  Example: Small plants growing in shade of larger plants  Epiphytes  Forehead mites

23. Bromeliad Commensalism

24. Ecological Succession: Communities in Transition  What is ecological succession? (Gradual change in species composition)  Primary succession = establishment of communities on nearly lifeless ground (no soil) ex. glacier retreat, landslide, lava, abandoned parking lot  Secondary succession - community disturbed, soil remains. Burned / cut forests, polluted stream, flood

25. Two types of ecological succession animation. Animation

26. Limits on Population Growth  Biotic potential (capacity for growth)  Intrinsic rate of increase (r) (assumes unlimited resources)  No indefinite population growth  Environmental resistance = all the factors that limit population growth  Carrying capacity (K) - determined by biotic potential & enviro resistance

27. Carrying capacity (K) Environmental resistance Biotic potential Exponential growth Population Growth Curves Time (t) Population size (N)

28. Exponential and Logistic Population Growth  Resources control population growth  Exponential growth - J-shaped curve  Logistic growth - S-shaped curve

29. Logistic Growth of Sheep Population Overshoot Carrying Capacity Year Number of sheep (millions) 2.0 1.5 1.0.5 180018251850187519001925

30. When Population Size Exceeds Carrying Capacity  Switch to new resources, move or die  Overshoots  Reproductive time lag  Population dieback or crash  Human Famines - Irish potato famine 1845 - 1 million dead  Factors controlling human carrying capacity- technology has increased carrying capacity for humans

31. Exponential Growth, Overshoot and Population Crash of Reindeer Population Overshoots Carrying Capacity Population crashes Carrying capacity Year Number of sheep (millions) 2,000 1,500 1,000 500 0 19101920193019401950