Community Interactions. Community An assemblage of all the populations interacting in an area

Transcription

1 Community Interactions Community An assemblage of all the populations interacting in an area

2 Populations are affected by: Available living space habitat Resource Availability niche Species interactions Symbiosis living together commensalism mutualism parasitism Competition Predation Coevolution

3 Available Living Space Habitat an organism s mailing address the type of place where the individuals normally live

4 Resource Availability Niche an organism s profession (role) in the community

5 Species Interactions Symbiosis Living together for at least some part of the life cycle Most interactions are neutral; they have no effect on either species Commensalism Mutualism Parasitism

6 Commensalism One species benefits and has no effect on the other

7 Mutualism Both species benefit Some are obligatory; partners depend upon each other (coevolution) Yucca plants and yucca moth Mycorrhizal fungi and plants Anemone fish and anemone

8 Mutualism Protection

9 photograph Alex Wild 2004

10 Mutualism Birds get food, help plant disperse seeds

11 Mutualism Pollination

12 Yucca and Yucca Moth Example of an obligatory mutualism Each species of yucca is pollinated only by one species of moth Moth larvae can grow only in that one species of yucca

13 Yucca Moth Yucca Plant Obligate Mutualism

14 Mycorrhizae Obligatory mutualism between fungus and plant root Fungus supplies mineral ions to root Root supplies sugars to fungus

15 Parasitism Parasites draw nutrients from hosts live on or in host body Vectors Convey a parasite from host to host Parasitoids Develop inside another species Consume and kill host

16 Protozoan - flagellate Micro Parasites bacteria fungus

17 Macro parasites tick flea

18 Macro parasite lamprey

19 Parasites

20 Parasites as biological controls Some parasites and parasitoids are used as biological controls Adapted to specific host and habitat Good at locating host High population growth rate Offspring disperse

21 Biological Controls Wasp and aphid

22 Social Parasite Brown-headed cowbird

23 Competition Interspecific: among different species Exploitative competition Interference competition Intraspecific: between members of the same species Intraspecific competition is most intense Territoriality Allelopathy Some species have eliminated ways of avoiding competition: Resource partitioning

24 Interspecific Competition

25 Intraspecific Competition

26 Intraspecific Competition Territoriality

27 Intraspecific Competition Allelopathy (sibling harming) Eucalyptus oils harm young saplings of same species. Can also affect other species

28 Forms of Competition Exploitative competition Species have equal access to resource; compete to exploit resource Interference competition One species prevents another from using resource usually through aggressive behavior

29 Interference Competition

30 Competitive Exclusion Principle When two species compete for identical resources, one will be more successful and will eventually eliminate the other

31 Gause s Experiment Species grown together Paramecium caudatum Paramecium aurelia

32 Resource Partitioning Apparent competitors may have slightly different niches May use resources in a different way or time Minimizes competition and allows coexistence

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35 Predation Predators animals that feed on other living organisms free-living do not reside on their prey Carnivores and omnivores

36 Predator Prey Relationships: Canada Lynx and the Showshoe Hare Species are limited by the number of available prey In some cases predators limit a prey species

37 Coevolution Two or more species exert selection pressure on each other Prey defenses evolve Predator responses to prey evolve

38 Prey Defenses Camouflage Warning coloration Mimicry

39 Camouflage

40 Warning Coloration & Mimicry

41 Predator Responses Predators counter prey defenses with new adaptations stealth camouflage avoidance of chemical repellents

42 Predator Responses

43 Community Dynamics Factors affecting changes in community structure Intermediate Disturbance Hypothesis Community Instability (Alternate stable states) Keystone Species Exotic (introduced species) Ecological Succession Primary Secondary

44 Species Diversity Species diversity Variety, Abundance of Species in a Particular Place Species richness: The number of different species in a given area Species evenness: Comparative number of individuals

45 Variations in Species Richness and Species Evenness Higher richness and evenness lower richness and evenness Fig. 4-12, p. 93

46 Species Diversity: Diversity varies with geographical location The most species-rich communities Tropical rain forests Coral reefs Ocean bottom zone Large tropical lakes

47 # seaweed species log # seaweed species Species are not assembled randomly in nature. Physical stress Species richness Nov-75 May-76 Oct-76 May-77 Low Mid High Disturbance level (Sousa 1979 Ecology) Herbivory Herbivore Density (snails/m 2 ) (Lubchenco 1978 Am Nat) Nitrogen availability log ammonium loading (micromol/l/h) (Bracken & Nielsen 2004 Ecology)

48 Intermediate Disturbance Hypothesis Ecological Community stability is an uneasy balance Areas with moderate levels of disturbance have greater species diversity

49 Community Instability Disturbances can cause a community to change in ways that persist even if the change is reversed. In some cases these are considered alternate stable states

50 Keystone Species A species that has a disproportionately large effect on community structure Removal of a keystone species can cause drastic changes in a community can increase or decrease diversity

51 sea star community 15 species coexist - 1 sea star is removed 8 remain in community

52 Keystone species exert an important regulating effect on other species in a community. Populations are limited by competition for resources Fig Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings

53 If Keystone Species are removed, community structure is greatly affected.

54 Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings

55 Over time, one array of species is replaced by another Ecological Succession

56 Types of Succession Primary succession: new environments Begins with foundation species Ends with climax community Secondary succession: communities destroyed or displaced May not have foundation species Also ends with climax community

57 Climax Community Stable array of species that does not change over time In a particular habitat, succession produces the same climax community

58 Most communities are disturbed by events like fire, weather, or human activities

59 Marine communities are subject to disturbance by tropical storms. Fig

60 Volcanic Island Succession Foundation Species Climax Community

61 Glacial Succession

62 Primary succession begins in a new or lifeless area where soil has not yet formed. Lake Succession

63 Sand Dune Succession

64 Secondary succession occurs where an existing community has been cleared, but the soil is left intact. Relatively rapid succession Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings

65 Secondary Succession: Disturbed Habitats Along Roadsides Abandoned Fields

66 Cyclic Replacement Fire Damage Disease Damage Sudden Oak Death Storm Damage

67 Cyclic Replacement: Fire Climax Chaparral fire adapted plant community

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70 Giant Sequoia High intensity crown fire destroys forest No fire no seedlings, growth of white fir Low intensity allows Giant Sequoia to re-seed Medium intensity kills competing fir trees

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