1. Chapter 53 Community Ecology

2. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings What Is a Biological Community? a grouping of populations of various species living close enough for potential interaction How big is a community? – As big as you define it

3. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 25000 species of plants 1600 birds 369 mammals 350 reptiles 400 amphibians 800 fish in Amazon 450 in Pacific 100,000s of inverts 413 birds 17 reptiles 12 amphibians 56 fish What’s in a Community? 2,301,000 km 2 256,370 km 2

4. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings How do communities interact? Who eats who? interactions include – competition – predation – herbivory – symbiosis – disease

5. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Inter-species interactions Table 53.1

6. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Competition Species compete for resource in short supply Competitive exclusion principle – Competing species cannot coexist in the same niche

7. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ecological Niches The ecological niche – Use of abiotic and biotic resources – Competitors cannot coexist unless niches change When Connell removed Balanus from the lower strata, the Chthamalus population spread into that area. The spread of Chthamalus when Balanus was removed indicates that competitive exclusion makes the realized niche of Chthamalus much smaller than its fundamental niche. RESULTS CONCLUSION Ocean Ecologist Joseph Connell studied two barnacle species  Balanus balanoides and Chthamalus stellatus  that have a stratified distribution on rocks along the coast of Scotland. EXPERIMENT In nature, Balanus fails to survive high on the rocks because it is unable to resist desiccation (drying out) during low tides. Its realized niche is therefore similar to its fundamental niche. In contrast, Chthamalus is usually concentrated on the upper strata of rocks. To determine the fundamental of niche of Chthamalus, Connell removed Balanus from the lower strata. Low tide High tide Chthamalus fundamental niche Chthamalus realized niche Low tide High tide Chthamalus Balanus realized niche Balanus Ocean Figure 53.2

8. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Competition Fundamental niche (what you want) Realized niche (what you can get)

9. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A. insolitus usually perches on shady branches. A. distichus perches on fence posts and other sunny surfaces. A. distichus A. ricordii A. insolitus A. christophei A. cybotes A. etheridgei A. alinigar Figure 53.3 Resource Partitioning Resource partitioning allows similar species to coexist in a community

10. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Predation Predator kills and eats prey (+/-) Includes herbivory and parasitism

11. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Predation Feeding adaptations – Claws, teeth, fangs, stingers, poison Defensive adaptations – Camouflage, mimicking

12. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Plant defenses Tobacco plant - nicotine Cinnamon plant Thorns

13. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Animal Defenses Cryptic coloration Chemical defenses Fleeing

14. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Aposematic coloration Warns predators - stay away! Figure 53.6

15. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Batesian mimicry palatable or harmless species mimics an unpalatable or harmful model (a) Hawkmoth larva (b) Green parrot snake Figure 53.7a, b

16. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Parasitism (+/-) Ectoparasite: a parasite that feeds on the external surface of a host Endoparasite: a parasite that lives within the host

17. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Parasitism Derive nourishment from another organism, – Host is harmed in the process – Complex life cycle – May effect predation

18. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Behavior changes

19. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Symbiosis Mutualism: interspecific interaction benefits BOTH species Commensalism: interspecific interaction benefits ONE species, neutral to the other Symbiosis can include parasitism, mutualism, and commensalism

20. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 25000 species of plants 1600 birds 369 mammals 350 reptiles 400 amphibians 800 fish in Amazon 450 in Pacific 100,000s of inverts 413 birds 17 reptiles 12 amphibians 56 fish 2,301,000 km 2 256,370 km 2 SPECIES DIVERSITY

21. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Diversity has 2 components: Species richness – Is the total number of different species in the community Relative abundance – Is the proportion each species represents of the total individuals in the community

22. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 2 communities Same richness – different abundance – More diversity where abundance is similar Community 1 A: 25%B: 25%C: 25%D: 25% Community 2 A: 80%B: 5%C: 5%D: 10% D C B A Figure 53.11

23. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Trophic Structure Feeding relationships between organisms in a community

24. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Food chains Link the trophic levels from producers to top carnivores Quaternary consumers Tertiary consumers Secondary consumers Primary consumers Primary producers Carnivore Herbivore Plant Carnivore Zooplankton Phytoplankton A terrestrial food chainA marine food chain Figure 53.12

25. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Food Webs Branching food chain, complex trophic interactions Humans Baleen whales Crab-eater seals Birds Fishes Squids Leopard seals Elephant seals Smaller toothed whales Sperm whales Carnivorous plankton Euphausids (krill) Copepods Phyto- plankton Figure 53.13

26. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Limits on Food Chain Length Each usually only a few links long Energetic hypothesis suggests length limited by inefficiency of energy transfer – 100kg – 10 kg – 1 kg Dynamic stability hypothesis - long food chains less stable than short ones – Shocks travel up the food chain

27. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Dominant and keystone species In general, a small number of species in a community exert strong control on community’s structure

28. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Dominant Species Most abundant or have the highest biomass – Exert control over occurrence and distribution of other species – Exploit limited resources better or.. – Successfully avoid predators

29. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Keystone species Not necessarily abundant Control by niche or role Figure 53.16a,b (a) The sea star Pisaster ochraceous feeds preferentially on mussels but will consume other invertebrates. With Pisaster (control) Without Pisaster (experimental) Number of species present 0 5 10 15 20 1963 ´64´65 ´66 ´67 ´68 ´69 ´70´71 ´72 ´73 (b) When Pisaster was removed from an intertidal zone, mussels eventually took over the rock face and eliminated most other invertebrates and algae. In a control area from which Pisaster was not removed, there was little change in species diversity.

30. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Brazil nut tree

31. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

33. No longer a keystone

34. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Community organization The bottom-up model – influence from lower to higher trophic levels – presence or absence of abiotic nutrients – think “primary producers”

35. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Community organization Top-down model: – Control comes from the trophic level above – Predators control herbivores – Herbivores control primary producers

36. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Disturbance Influences species diversity and composition Equilibrium model – stable unless disturbed by humans Non-equilibrium model – constant change due to disturbances

37. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings What Is Disturbance? A disturbance – Is an event that changes a community – Removes organisms from a community – Alters resource availability

38. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Community Stability Communities are constantly changing, they are in nonequilibrium – many are in some state of recovery from disturbance Drought Fire Clearcut Flood

39. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fire Is a significant disturbance in most terrestrial ecosystems – Is often a necessity in some communities (a) Before a controlled burn. A prairie that has not burned for several years has a high propor- tion of detritus (dead grass). (b) During the burn. The detritus serves as fuel for fires. (c) After the burn. Approximately one month after the controlled burn, virtually all of the biomass in this prairie is living. Figure 53.21a–c

40. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Yellowstone fires, 1988 Communities can often respond very rapidly to a massive disturbance Figure 53.22a, b (a) Soon after fire. As this photo taken soon after the fire shows, the burn left a patchy landscape. Note the unburned trees in the distance. (b) One year after fire. This photo of the same general area taken the following year indicates how rapidly the community began to recover. A variety of herbaceous plants, different from those in the former forest, cover the ground.

41. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Yellowstone wolves

42. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Dying aspen grove

43. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Streamside elk grazing

44. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Hey, what’s that noise?

45. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

46. Yellowstone Ecosystem

47. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Lunch grew back! Beaver dams – Can transform landscapes on a very large scale Figure 53.18

48. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Succession Moraines in Glacier Bay, Alaska – Follows a predictable pattern of change in vegetation and soil characteristics (b) Dryas stage (c) Spruce stage (d) Nitrogen fixation by Dryas and alder increases the soil nitrogen content. Soil nitrogen (g/m 2 ) Successional stage Pioneer Dryas Alder Spruce 0 10 20 30 40 50 60 (a) Pioneer stage, with fireweed dominant - Some species improve environment for followers

49. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Eastern US Ecological Succession