1. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chapter 53 Community Ecology

2. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings What Is a Community? Assemblage of populations of various species living close enough for potential interaction

3. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Savanna community in southern Africa Figure 53.1

4. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Community’s interactions include competition, predation, herbivory, symbiosis, and disease Populations are linked by interspecific interactions

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

6. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Competition Species compete for a particular resource that is in short supply

7. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Competitive Exclusion Principle Two species competing for the same limiting resources cannot coexist in the same place

8. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ecological Niches The total of an organism’s use of the biotic and abiotic resources in its environment

9. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ecologically similar species can coexist in a community if there are one or more significant difference in their niches 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

10. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings As a result of competition – A species’ fundamental niche may be different from its realized niche

11. 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 Differentiation of niches that enables similar species to coexist in a community

12. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings G. fortis Beak depth (mm) G. fuliginosa Beak depth Los Hermanos Daphne Santa María, San Cristóbal Sympatric populations G. fuliginosa, allopatric G. fortis, allopatric Percentages of individuals in each size class 40 20 0 40 20 0 40 20 0 810121416 Figure 53.4 Character Displacement There is a tendency for characteristics to be more divergent in sympatric populations of two species than in allopatric populations of the same two species

13. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Predation One species, the predator, kills and eats the other, the prey

14. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Feeding adaptations of predators include – Claws, teeth, fangs, stingers, and poison Animals also display – A great variety of defensive adaptations

15. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cryptic coloration, or camouflage – Makes prey difficult to spot Figure 53.5

16. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Aposematic coloration – Warns predators to stay away from prey Figure 53.6

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

18. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Müllerian mimicry – Two or more unpalatable species resemble each other (a) Cuckoo bee (b) Yellow jacket Figure 53.8a, b

19. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Herbivory Herbivore eats parts of a plant –  evolution of plant mechanical and chemical defenses and consequent adaptations by herbivores

20. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Parasitism One organism, the parasite, derives its nourishment from another organism, its host, which is harmed in the process

21. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Disease Pathogens, disease-causing agents – Are typically bacteria, viruses, or protists

22. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mutualism (mutualistic symbiosis) Interspecific interaction that benefits both species Figure 53.9

23. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Commensalism One species benefits and the other is not affected Figure 53.10

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

25. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Species Diversity Variety of different kinds of organisms that make up the community – 2 components 

26. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Species richness – total number of different species in the community Relative abundance – proportion each species represents of the total individuals in the community

27. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 2 different communities  same species richness, but a different relative abundance 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

28. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A community with an even species abundance – Is more diverse than one in which one or two species are abundant and the remainder rare

29. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Trophic Structure Feeding relationships between organisms in a community – key factor in community dynamics

30. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Food chains 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 – Link the trophic levels from producers to top carnivores

31. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Food Webs branching food chain, more complex 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

32. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Food webs can be simplified – By isolating a portion of a community that interacts very little with the rest of the community Sea nettle Fish larvae Zooplankton Fish eggs Juvenile striped bass Figure 53.14

33. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Dominant Species Species in a community that are most abundant or have the highest biomass Exert powerful control over the occurrence and distribution of other species

34. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings One hypothesis suggests that dominant species – Are most competitive in exploiting limited resources Another hypothesis for dominant species success – Is that they are most successful at avoiding predators

35. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Keystone Species Are not necessarily abundant in a community Exert strong control on a community by their ecological roles, or niches

36. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sea stars, keystone species in intertidal communities 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.

37. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Observation of sea otter populations and their predation Figure 53.17 Food chain before killer whale involve- ment in chain (a) Sea otter abundance (b) Sea urchin biomass (c) Total kelp density Number per 0.25 m 2 19721985198919931997 0 2 4 6 8 10 0 100 200 300 400 Grams per 0.25 m 2 Otter number (% max. count) 0 40 20 60 80 100 Year Food chain after killer whales started preying on otters – Shows the effect the otters have on ocean communities

38. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ecosystem “Engineers” (Foundation Species) Beaver dams – Can transform landscapes on a very large scale Figure 53.18

39. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Some foundation species act as facilitators – That have positive effects on the survival and reproduction of some of the other species in the community Figure 53.19 Salt marsh with Juncus (foreground) With Juncus Without Juncus Number of plant species 0 2 4 6 8 Conditions

40. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Pollution – Can affect community dynamics But through biomanipulation – Polluted communities can be restored Fish Zooplankton Algae Abundant Rare Abundant Rare Polluted State Restored State

41. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings What Is Disturbance? Changes a community Removes organisms from community Alters resource availability

42. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fire – significant disturbance in most terrestrial ecosystems – 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

43. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The large-scale fire in Yellowstone National Park in 1988 – Demonstrated that 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.

44. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Human Disturbance most widespread agents of disturbance

45. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ecological Succession Sequence of community and ecosystem changes after a disturbance

46. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Primary succession – no soil exists when succession begins Secondary succession – where soil remains after a disturbance

47. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Early-arriving species 1.May facilitate the appearance of later species by making the environment more favorable 2.May inhibit establishment of later species 3.May tolerate later species but have no impact on their establishment

48. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings McBride glacier retreating 0510 Miles Glacier Bay Pleasant Is. Johns Hopkins Gl. Reid Gl. Grand Pacific Gl. Canada Alaska 1940 1912 1899 1879 1949 1879 1935 1760 1780 1830 1860 1913 1911 1892 1900 1879 1907 1948 1931 1941 1948 Casement Gl. McBride Gl. Plateau Gl. Muir Gl. Riggs Gl. Retreating glaciers  field-research opportunity on succession Figure 53.23

49. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Succession on the moraines in Glacier Bay, Alaska – Follows a predictable pattern of change in vegetation and soil characteristics Figure 53.24a–d (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

50. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Biogeographic factors affect community diversity 2 key factors correlated with a community’s species diversity – Are its geographic location and its size

51. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Species richness generally declines along an equatorial-polar gradient The greater age of tropical environments  greater species richness

52. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Climate – Is likely the primary cause of the latitudinal gradient in biodiversity

53. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 2 main climatic factors correlated with biodiversity – solar energy input and water availability (b) Vertebrates 500 1,000 1,500 2,000 Potential evapotranspiration (mm/yr) 10 50 100 200 Vertebrate species richness (log scale) 1 100 300 500700 900 1,100 180 160 140 120 100 80 60 40 20 0 Tree species richness (a) Trees Actual evapotranspiration (mm/yr) Figure 53.25a, b

54. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Area Effects All other factors being equal, the larger the geographic area of a community, the greater the number of species

55. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A species-area curve of North American breeding birds Area (acres) 11010010 3 10 4 10 5 10 6 10 7 10 8 10 910 Number of species (log scale) 1 10 100 1,000 Figure 53.26

56. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Island Equilibrium Model Species richness on islands – Depends on island size, distance from the mainland, immigration, and extinction

57. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Studies of species richness on the Galápagos Islands – Support the prediction that species richness increases with island size The results of the study showed that plant species richness increased with island size, supporting the species-area theory. FIELD STUDY RESULTS Ecologists Robert MacArthur and E. O. Wilson studied the number of plant species on the Galápagos Islands, which vary greatly in size, in relation to the area of each island. CONCLUSION 200 100 50 25 10 0 Area of island (mi 2 ) (log scale) Number of plant species (log scale) 0.1 1 10100 1,000 5 400 Figure 53.28