2. COMMUNITY ECOLOGY

3. Community Structure Depends on 4 factors : –Physical appearance –Species diversity –Species abundance –Niche structure

4. Factor 1: Physical Appearance A) biomes –Aquatic ecosystems B) Differences within communities ex. (edge effect)

5. Edge Effects Transitions between ecosystems (ecotones) such as forest and field: differences in sunlight, temp., wind, etc. Some animals like “edges” (deer, quail)

6. Edge Effects Due to habitat fragmentation, “edges” are on the rise Negative impacts: –Increasing predation, fires, disease, parasitism, road mortality –Creates barriers preventing species from finding food, mates

7. Edge Effects – Habitat Fragmentation Fragmentation

8. Edge Effects Nest parasitism

9. Edge Effects Road Mortality

10. Edge Effects Preventing mortality by creating “habitat corridors”habitat corridors”

11. Factor 2: Species Diversity Number of different species 3 factors determine diversity: –Latitude: diversity decreases as you increase latitude (move away from the equator) –Depth: increasing diversity as increasing depth to approx. 2,000 meters, then decreases with depth, until you get to the bottom

12. Factor 2: Species Diversity (con.) 3 factors affecting diversity (con.): pollution: increasing pollution causes a decrease in diversity

13. Factor 2: Species Diversity Other factors: (in general these cause an increase in species diversity) –Increased sunlight –Increased precipitation –Pronounced seasons

14. Factor 2: Species Diversity Theory of Island Biogeography (MacArthur & Wilson) Species number on an island is determined by a balance between 2 factors: –Rate of immigration (new species arriving) –Rate of extinction

15. Island Biogeography

16. Factor 2: Species Diversity (island) Rate of immigration and extinction depends on 2 factors: –Size of the island –Proximity to the mainland

17. Factor 2: Species Diversity (island) The bigger the island, the more diversity –Small islands are a smaller target for immigrators & fewer resources The closer it is to the mainland, the more diversity –Close island has a higher immigration rate

18. Factor 3: Species Abundance The number of individuals in each species: although tropical rainforests and coral reefs have high diversity, these areas tend to have low species abundance

19. Factor 4: Niche Structure Number of niches (roles) in ecosystem, similarities and differences between these niches, and species interaction determines niche structure

20. Factor 4: Niche Structure Different niches in an ecosystem (a niche is defined as the role and organism plays in the ecosystem): –Native –Nonnative (exotic, alien, invasive)Nonnative –Indicator –keystone

21. Niches Native: species that normally live and thrive in a particular ecosystem

22. Niches Nonnative: species that migrate or are accidentally or deliberately introduced into an ecosystem by humans Can out-compete native species and crowd them out (invasive species) –Exs.: zebra mussels, kudzu

23. Niches -- Invasives Zebra mussel

24. Niches -- Invasives kudzu

25. Niches – Indicator Species Indicators: species that serve as early warnings to damage to an ecosystem Exs. Migratory songbirds, frogs

26. Niches – Indicator Species Migratory songbirds respond quickly to environmental change –Habitat fragmentation in both winter and summer habitat (can’t find suitable nesting sites, increased predation) –Forest interior loving species

27. Niches – Indicator Species Frogs (25% of all known amphibian sp. are extinct, endangered, or vulnerable) Eggs have no protective shells to block out UV rays Adults take in water and air through skin, also absorbing pollutants

28. Niches – Indicator Species frogs

29. Niches: Keystone Species Role in ecosystem is more important than abundance or biomass would suggest Strong interactions with other species Loss could lead to population crashes or extinctions of other sp.

30. Niches: Keystone Species Critical Roles: –Pollination –Seed dispersal –Habitat modification –Predation by top predators –Improve ability for nutrient uptake by plants –Efficiently recycle animal wastes

31. Niches: Keystone Species Pollination and seed dispersalPollination

32. Niches: Keystone Species Habitat modification

33. Niches: Keystone Species Predation by top predators

34. Niches: Keystone Species Recycling of animal wastes

35. Niche Structure: Species Interactions Species Interactions: –Intraspecific competition –Interspecific competition –Predation –Symbiotic relationships Parasitism Mutualism commensalism

36. Niche Structure: Species Interactions INTRAspecific competition: competition for resources between members of the same species

37. Niche Structure: Species Interactions (intraspecific) Allelopathy: one species releases a chemical substance to inhibit growth near it. Ex. Black walnut

38. Niche Structure: Species Interactions (intraspecific) Black walnut

39. Niche Structure: Species Interactions (intraspecific) Territoriality:organisms mark and defend an area around home, nest site

40. Niche Structure: Species Interactions (intraspecific) territoriality

41. Niche Structure: Interspecific INTERspecific competition: competition between two or more different species for food, space, or any other limited resource –Fundamental niche: the niche a species would occupy if there was no competition

42. Niche Structure: Species Interactions (interspecific) The more two species’ niches overlap, the more competition –Competitive exclusion principle: one species eliminates another in a particular area because they out- compete for limited resources

43. Niche Structure: Species Interactions (interspecific) Competitive exclusion principle:

44. Niche Structure: Species Interactions (interspecific) How do species reduce competition? –Over time, species that compete for the same resources evolve adaptations that reduce competition or overlaps of their fundamental niches –Resource partitioning

45. Niche Structure: Species Interactions (interspecific) Resource partitioning: dividing up of scarce resources so that species can use them at different times, different ways, or different places –Exs. Hawks hunt by day, owls by nightlions take larger prey, while cheetah take smaller

46. Niche Structure: Species Interactions (interspecific) Resource partitioning and niche specialization

47. Interference Competition A species may limit another’s access to some resource Ex. Hummingbird’s defending patches of wildflowers by chasing away other humming bird species

48. Exploitation Competition Competing species have equal access to a specific resource, but differ in how fast or efficiently they exploit it Ex. humans

49. Niche Structure: Species Interactions (Predator-Prey) Predator-Prey Relationship: as prey pops. Increase, after an initial delay, the predator pops. Increase, eventually causing a decrease in prey, thereby after an initial delay, causing a decrease in predator pops… and so on (cycle)

50. Niche Structure: Species Interactions (Predator-Prey) Predator-prey relationship

51. Niche Structure: Species Interactions (Predator-Prey) Predator-prey – didinium & paramecia

52. Niche Structure: Species Interactions (Predator-Prey) Seems to harm prey population, but in reality it often reduce sick, aged, weak members Increase food supply for prey and genetic stock (increasing reproductive success and long- term survival

53. Niche Structure: Species Interactions (Predator-Prey) How do predators increase their chance for success of prey acquisition? –Speed, stealth, keen senses, cooperation, camouflage

54. Niche Structure: Species Interactions (Predator-Prey) Camouflage – preying mantis (in memory of Darwin)Camouflage

55. Niche Structure: Species Interactions (Predator-Prey) How do prey protect themselves? Prey Avoidance Protective shell

56. Niche Structure: Species Interactions (Prey Adaptations) Spines or thorns

57. Niche Structure: Species Interactions (Prey Adaptations) mimicry

58. Niche Structure: Species Interactions (Prey Adaptations) mimicry mimicry

59. Niche Structure: Species Interactions (Prey Adaptations) Poison and warning colors

60. Niche Structure: Species Interactions (Prey Adaptations) camouflage

61. Niche Structure: Species Interactions (Prey Adaptations) Changing color camouflagecamouflage

62. Niche Structure: Species Interactions (Prey Adaptations) Behavioral strategies

63. Niche Structure: Species Interactions (Prey Adaptations) Schooling, flocking (safety in numbers)

64. Niche Structure: Species Interactions (parasitism) Parasitism: one species feeds on part of another; parasite benefits, host is harmed (rarely killed)

65. Niche Structure: Species Interactions (ectoparasite)

66. Niche Structure: Species Interactions (endoparasite)

67. Niche Structure: Species Interactions (mutualism) Mutualism: the two species involved benefit from the relationship (nutritional, protection, reproductive) –Ex. Lichen:fungi collect and hold moisture, photosynthetic algae provide food –Birds remove parasites from rhinos –Clownfish gain protection from anemones and vice versa

68. Niche Structure: Species Interactions (mutualism)

70. Niche Structure: Species Interactions (commensalism) Commensalism: one species benefits and the other one is neither harmed nor benefited

71. Niche Structure: Species Interactions (commensalism) Epiphytes: use other plants for support, to reach elevations for increased sunlight

72. Ecosystems Respond to Change Ecological succession: gradual change in species composition of a given area –Primary succession –Secondary successionSecondary succession

73. Primary Succession

74. Ecological succession Primary succession –Soil formation begins when pioneer species attach themselves to bare rock, over time adding organic material and breaking the rock down further

75. Ecological succession Pioneer species example:

76. Ecological succession After patches of soil are built up, small grasses and herbs can grow Characteristics: –Large pops. Under harsh conditions –Short lives

77. Ecological succession Next, more grasses, herbs and shrubs, and small trees begin to grow Characteristics –Need lots of sunlight (shade intolerant)

78. Ecological succession Finally a mature forest is in place (oak, hickory) – climax community Characteristics –Shade tolerant

79. Ecological succession

80. Fig. 8.17, p. 190 Early Successional Species Rabbit Quail Ringneck pheasant Dove Bobolink Pocket gopher Midsuccessional Species Elk Moose Deer Ruffled grouse Snowshoe hare Bluebird Late Successional Species Turkey Martin Hammond’s Flycatcher Gray squirrel Wilderness Species Grizzly bear Wolf Caribou Bighorn sheep California condor Great horned owl Ecological succession

81. Secondary succession: begins when a natural area has been disturbed or removed Examples: abandoned farmland, burned or cut forests, land that has been dammed or flooded, heavily polluted streams

82. Ecological succession 3 factors that affect rate of succession –Facilitation –Inhibition –tolerance

83. Ecological succession Facilitation: one set of species makes an area suitable for species with different niche requirements Ex. Legumes add nitrogen to soil

84. Ecological succession Inhibition: early species prevent the growth of other species (allelopathy)

85. Ecological succession Tolerance: late successional species are unaffected by earlier species

86. Ecological Stability Stability is maintained only by constant dynamic change in response to changing environmental conditions 3 factors affect stability: inertia, constancy, resilience

87. Ecological Stability Inertia or persistence: the ability of a living system to resist disturbance

88. Ecological Stability Constancy: ability of a living system to keep its numbers within limits imposed by available resources

89. Ecological Stability Resilience: ability of a living system to bounce back after an external disturbance

90. Ecological Stability Intermediate Disturbance Hypothesis: moderate disturbance in communities promote greatest species diversity

91. Ecological Stability Intermediate Disturbance Hypothesis

92. Precautionary Principle When evidence indicates that an activity can harm human health, we should take measures to prevent harm even if cause- and-effect relationships have not been fully established scientifically