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

2. How Do Species Interact? Five types of interactions between species that share limited resources –Interspecific Competition –Predation –Parasitism –Mutualism –Commensalism They have an impact on resources use and population size of species in an ecosystem. (sustainability!!)

3. Most Species Compete with One Another for Certain Resources Competition-for limited resources Most competition involves one species becoming more efficient at obtaining resources than another species.

4. Greater the overlap =more competition

5. Competitive Exclusion Principle Gause’s Law (Gause’s Principle) Some species share their niche, but no two species can occupy exactly the same niche for very long.Some species share their niche, but no two species can occupy exactly the same niche for very long. This causes both species to have limited resources.This causes both species to have limited resources. One (or both) species must change their niche (if possible)One (or both) species must change their niche (if possible)

6. P. Caudatum are outcompeted, they die.

7. Most Consumer Species Feed on Live Organisms of Other Species Predators may capture prey by –Walking –Swimming –Flying –Pursuit and ambush –Camouflage –Chemical warfare Prey may avoid capture by –Camouflage –Chemical warfare –Warning coloration –Mimicry –Deceptive looks –Deceptive behavior

8. Some Ways Prey Species Avoid Their Predators

9. Predator and Prey Species Can Drive Each Other’s Evolution Predator and prey populations exert intense natural selection pressures on one another Prey develop traits that make them harder to catch...predators face selection pressures that favor traits to catch prey Coevolution: Populations of two species interact and exert selective pressure forcing species to adapt. EX: Caribbean crab/snail and bats/moths

10. Remember, coevolution is an example of populations responding to changes in environmental conditions. Species cannot design strategies to increase their chances of survival. »

11. Some Species Feed off Other Species by Living on or in Them PARASITISM EX: tapeworms, mosquitoes, mistletoe plants, sea lampreys, ticks, and cowbirds Parasite-host interaction may lead to coevolution- nature’s way of controlling populations and biodiversity

12. Parasitism Tree with Parasitic Mistletoe Trout with Blood-Sucking Sea Lampreys

13. In Some Interactions, Both Species Benefit Mutualism Nutrition and protection relationship Gut inhabitant mutualism

14. In Some Interactions, One Species Benefits and the Other Is Not Harmed Commensalism Epiphytes (take no nutrients from the tree EX: mosses, ferns, orchids) Birds nesting in trees Bromeliad on Tree

15. How Can Natural Selection Reduce Competition between Species? Resource partitioning Reduce niche overlap Use shared resources at different –Times –Places –Ways

16. Sharing the Wealth: Resource Partitioning

17. Specialist Species of Honeycreepers

18. What Limits the Growth of Populations? Populations differ in –Distribution –Numbers –Age structure –Density Population dynamics: how populations change in response to changes in environmental conditions. Changes in population characteristics due to: –Temperature –Presence of disease organisms or harmful chemicals –Resource availability –Arrival or disappearance of competing species

19. Most Populations Live Together in Clumps or Patches Look at how populations are distributed or dispersed –Clumping –Uniform dispersion –Random dispersion-pretty rare

20. Dispersion Patterns Random (smaller plants) Clumping (flocks) Uniform (trees)

21. Why clumping? –Species tend to cluster where resources are available –Groups have a better chance of finding clumped resources –Protects some animals from predators –Packs allow some to get prey –Temporary groups for mating and caring for young

22. Populations Can Grow, Shrink, or Remain Stable –Births –Deaths –Immigration –emigration Age structure: proportion of individuals at various ages –Pre-reproductive age –Reproductive age –Post-reproductive age

23. No Population Can Grow Indefinitely Biotic potential -capacity for population growth under ideal conditions –Low…Large animals like elephants –High… Small organisms like insects Intrinsic rate of increase (r)- population growth with unlimited resources Individuals in populations with high r –Reproduce early in life –Have short generation times –Can reproduce many times –Have many offspring each time they reproduce

24. Size of populations limited by –Light –Water –Space –Nutrients –Exposure to too many competitors, predators or infectious diseases There are always limits to population growth in nature….Sustainability!!! Limiting Factors

25. Environmental resistance: combination of all factors that limit the growth of a population Carrying capacity (K)= Biotic Potential + Environmental resistance Exponential growth-J Curve Logistic growth-S Curve

26. Limiting factors!!

27. When a Population Exceeds Its Habitat’s Carrying Capacity, Its Population Can Crash Carrying capacity: not fixed…can change during seasons or years Reproductive time lag may lead to overshoot –Dieback (crash)- time needed for birth rate to fall and death rate to rise in response to resource overconsumption Damage may reduce area’s carrying capacity. Ex overgrazing

28. Exponential Growth, Overshoot, and Population Crash of a Reindeer

29. Moose and Wolf Population http://vicksta.com/wolf%20and%20moose %20graph7.htmlhttp://vicksta.com/wolf%20and%20moose %20graph7.html

30. Different Reproductive Patterns r-Selected species, opportunists –Capacity for high rate of population increase –ex. Small, lots of offspring, no parental care K-selected species, competitors –Reproduce later in life, small # of offspring, long life span –Large mammals, birds of prey

31. Positions of r- and K-Selected Species on the S-Shaped Population Growth Curve GROSS!!!!

32. Genetic Diversity Can Affect the Size of Small Isolated Populations Founder effect -colonize new habitat, limits genetic diversity Demographic bottleneck- only a few survive a catastrophe ex. fire Genetic drift- certain individual breeding more than others and genes dominate gene pool Inbreeding- increases frequency of defective gens Minimum viable population size- # of individuals needed for long term survival of the population

33. Population Density Can Affect Population Size Density-dependent population controls –Predation –Parasitism –Infectious disease –Competition for resources Density-Independent

34. Patterns of Variation in Population Size Stable- slight fluctuations in carrying capacity Irruptive- High peak then crash to stable lower level (ex: seasonal changes-die in winter) Cyclic fluctuations (boom-and-bust cycles) regular cycles of population –Top-down population regulation –Bottom-up population regulation Irregular – severe weather?

35. Cyclic fluctuations for the Snowshoe Hare and Canada Lynx

36. Humans Are Not Exempt from Nature’s Population Controls Ireland –Potato crop in 1845, 1 million people died, 3 million migrated Bubonic plague (Cats of Borneo!!) –Fourteenth century, 25 million killed AIDS –Global epidemic, 25 million killed between 1981 and 2007

37. Counting Populations See interactive of mark and recapture of butterflies (Miller ppt) Random sampling

38. Communities and Ecosystems Change over Time: Ecological Succession Natural ecological restoration –Primary succession –Secondary succession

39. Some Ecosystems Start from Scratch: Primary Succession No soil in a terrestrial system No bottom sediment in an aquatic system Early successional plant species, pioneer Midsuccessional plant species Late successional plant species

40. Primary Ecological Succession

41. Secondary Succession Some soil remains in a terrestrial system Some bottom sediment remains in an aquatic system Ecosystem has been –Disturbed –Removed –Destroyed

42. Some Ecosystems Do Not Have to Start from Scratch: Secondary Succession Primary and secondary succession –Tend to increase biodiversity –Increase species richness and interactions among species Primary and secondary succession can be interrupted by –Fires –Hurricanes –Clear-cutting of forests –Plowing of grasslands –Invasion by nonnative species

43. Natural Ecological Restoration of Disturbed Land Secondary Succession

44. Succession Doesn’t Follow a Predictable Path Traditional view – Balance of nature and a climax community Current view –Ever-changing mosaic of patches of vegetation –Mature late-successional ecosystems State of continual disturbance and change

45. Living Systems Are Sustained through Constant Change Inertia, persistence –Ability of a living system to survive moderate disturbances Resilience –Ability of a living system to be restored through secondary succession after a moderate disturbance Tipping point

46. Core Case Study: Southern Sea Otters: Are They Back from the Brink of Extinction? Habitat Hunted: early 1900s Partial recovery Why care about sea otters? –Ethics –Keystone species –Tourism dollars

47. Southern Sea Otter

48. Why Are Protected Sea Otters Making a Slow Comeback? Low biotic potential Prey for orcas Cat parasites Thorny-headed worms Toxic algae blooms PCBs and other toxins Oil spills

49. Population Size of Southern Sea Otters Off the Coast of So. California (U.S.)

50. Video: Kelp forest (Channel Islands)

51. Video: Otter feeding