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  • Figure 54.1 Which species benefits from this interaction?
  • Figure 54.UN03 Summary figure, Concept 54.1
  • Figure 54.2 Resource partitioning among Dominican Republic lizards.
  • Figure 54.3 Inquiry: Can a species ’ niche be influenced by interspecific competition?
  • Figure 54.4 Character displacement: indirect evidence of past competition.
  • Figure 54.5 Examples of defensive coloration in animals.
  • Figure 54.5 Examples of defensive coloration in animals.
  • Figure 54.5 Examples of defensive coloration in animals.
  • Figure 54.7 Mutualism between acacia trees and ants.
  • Figure 54.8 A possible example of commensalism between cattle egrets and water buffalo.
  • Figure 54.10 Which forest is more diverse?
  • Figure 54.13 Examples of terrestrial and marine food chains.
  • Figure 54.14 An Antarctic marine food web.
  • Figure 54.17 Inquiry: Is Pisaster ochraceus a keystone predator?
  • Figure 54.19 Beavers as ecosystem engineers.
  • Figure 54.22 Glacial retreat and primary succession at Glacier Bay, Alaska.
  • Figure 54.22 Glacial retreat and primary succession at Glacier Bay, Alaska.
  • Figure 54.22 Glacial retreat and primary succession at Glacier Bay, Alaska.
  • Figure 54.22 Glacial retreat and primary succession at Glacier Bay, Alaska.
  • Figure 54.23 Changes in soil nitrogen content during succession at Glacier Bay.
  • Figure 54.26 Species-area curve for North American breeding birds.

Transcript

  • 1. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsPowerPoint Lectures forBiology, Seventh EditionNeil Campbell and Jane ReeceLectures by Chris RomeroChapter 53Community Ecology
  • 2. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsOverview: Communities in Motion• A biological community is an assemblage ofpopulations of various species living close enoughfor potential interaction− For example, the “carrier crab” carries a seaurchin on its back for protection against predators© 2011 Pearson Education, Inc.
  • 3. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 54.1
  • 4. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsCommunity interactions are classified by whetherthey help, harm, or have no effect on the speciesinvolved• Ecologists call relationships between species in acommunity interspecific interactions• Examples are competition, predation, herbivory,symbiosis (parasitism, mutualism, andcommensalism), and facilitation• Interspecific interactions can affect the survivaland reproduction of each species, and the effectscan be summarized as positive (+), negative (–),or no effect (0)© 2011 Pearson Education, Inc.
  • 5. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 54.UN03
  • 6. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsCompetition• Interspecific competition (–/– interaction) occurswhen species compete for a resource in shortsupply© 2011 Pearson Education, Inc.
  • 7. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsCompetitive Exclusion• Strong competition can lead to competitiveexclusion, local elimination of a competingspecies• The competitive exclusion principle states that twospecies competing for the same limiting resourcescannot coexist in the same place© 2011 Pearson Education, Inc.
  • 8. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsEcological Niches and Natural Selection• The total of a species’ use of biotic and abioticresources is called the species’ ecological niche• An ecological niche can also be thought of as anorganism’s ecological role• Ecologically similar species can coexist in acommunity if there are one or more significantdifferences in their niches© 2011 Pearson Education, Inc.
  • 9. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Resource partitioning is differentiation ofecological niches, enabling similar species tocoexist in a community© 2011 Pearson Education, Inc.
  • 10. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 54.2A. distichus perches onfence posts and othersunny surfaces.A. insolitus usuallyperches on shadybranches.A. ricordiiA. alinigerA. insolitusA. distichusA. christopheiA. cybotesA. etheridgei
  • 11. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• A species’ fundamental niche is the nichepotentially occupied by that species• A species’ realized niche is the niche actuallyoccupied by that species• As a result of competition, a species’ fundamentalniche may differ from its realized niche– For example, the presence of one barnaclespecies limits the realized niche of anotherspecies© 2011 Pearson Education, Inc.
  • 12. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 54.3ChthamalusBalanusEXPERIMENTBalanusrealized nicheChthamalusrealized nicheHigh tideLow tideHigh tideChthamalusfundamental nicheLow tideOceanRESULTSOcean
  • 13. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsCharacter Displacement• Character displacement is a tendency forcharacteristics to be more divergent in sympatricpopulations of two species than in allopatricpopulations of the same two species• An example is variation in beak size betweenpopulations of two species of Galápagos finches© 2011 Pearson Education, Inc.
  • 14. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 54.4G. fuliginosa G. fortisLos HermanosG. fuliginosa,allopatricG. fortis,allopatricSympatricpopulationsSanta María, San CristóbalBeakdepthBeak depth (mm)161412108020406002040600204060DaphnePercentagesofindividualsineachsizeclass
  • 15. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsPredation• Predation (+/– interaction) refers to interactionwhere one species, the predator, kills and eats theother, the prey• Some feeding adaptations of predators are claws,teeth, fangs, stingers, and poison© 2011 Pearson Education, Inc.
  • 16. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Prey display various defensive adaptations• Behavioral defenses include hiding, fleeing,forming herds or schools, self-defense, and alarmcalls• Animals also have morphological andphysiological defense adaptations• Cryptic coloration, or camouflage, makes preydifficult to spot© 2011 Pearson Education, Inc.
  • 17. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsCryptic coloration, or camouflage, makes preydifficult to spot
  • 18. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Animals with effective chemical defense oftenexhibit bright warning coloration, calledaposematic coloration• Predators are particularly cautious in dealing withprey that display such coloration© 2011 Pearson Education, Inc.
  • 19. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 54.5b(b) AposematiccolorationPoison dart frog
  • 20. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• In some cases, a prey species may gainsignificant protection by mimicking the appearanceof another species• In Batesian mimicry, a palatable or harmlessspecies mimics an unpalatable or harmful model© 2011 Pearson Education, Inc.
  • 21. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 54.5c(c) Batesian mimicry: A harmless species mimics a harmful one.HawkmothlarvaGreen parrot snake
  • 22. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• In Müllerian mimicry, two or more unpalatablespecies resemble each other© 2011 Pearson Education, Inc.
  • 23. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 54.5d(d) Müllerian mimicry: Two unpalatable speciesmimic each other.Cuckoo beeYellow jacket
  • 24. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsHerbivory• Herbivory (+/– interaction) refers to an interactionin which an herbivore eats parts of a plant or alga• It has led to evolution of plant mechanical andchemical defenses and adaptations by herbivores© 2011 Pearson Education, Inc.
  • 25. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsSymbiosis• Symbiosis is a relationship where two or morespecies live in direct and intimate contact with oneanother© 2011 Pearson Education, Inc.
  • 26. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsParasitism• In parasitism (+/– interaction), one organism, theparasite, derives nourishment from anotherorganism, its host, which is harmed in the process• Parasites that live within the body of their host arecalled endoparasites• Parasites that live on the external surface of a hostare ectoparasites© 2011 Pearson Education, Inc.
  • 27. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsMutualism• Mutualistic symbiosis, or mutualism (+/+interaction), is an interspecific interaction thatbenefits both species• A mutualism can be– Obligate, where one species cannot survivewithout the other– Facultative, where both species can survivealone© 2011 Pearson Education, Inc.
  • 28. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 54.7(a) Acacia tree and ants (genus Pseudomyrmex)(b) Area cleared by ants at the base of an acacia tree
  • 29. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsCommensalism• In commensalism (+/0 interaction), one speciesbenefits and the other is neither harmed norhelped• Commensal interactions are hard to document innature because any close association likely affectsboth species© 2011 Pearson Education, Inc.
  • 30. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 54.8A possible example of commensalism between cattle egrets and water buffalo
  • 31. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsDiversity and trophic structure characterizebiological communities• In general, a few species in a community exertstrong control on that community’s structure• Two fundamental features of community structureare species diversity and feeding relationships© 2011 Pearson Education, Inc.
  • 32. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsSpecies Diversity• Species diversity of a community is the variety oforganisms that make up the community• It has two components: species richness andrelative abundance– Species richness is the total number of differentspecies in the community– Relative abundance is the proportion eachspecies represents of the total individuals in thecommunity© 2011 Pearson Education, Inc.
  • 33. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 54.10Community 1A: 25% B: 25% C: 25% D: 25%Community 2A: 80% B: 5% C: 5% D: 10%A B C DTwo communities can have the same speciesrichness but a different relative abundance
  • 34. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Communities with higher diversity are– More productive and more stable in theirproductivity– Better able to withstand and recover fromenvironmental stresses– More resistant to invasive species, organismsthat become established outside their nativerange© 2011 Pearson Education, Inc.
  • 35. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsTrophic Structure• Trophic structure is the feeding relationshipsbetween organisms in a community• It is a key factor in community dynamics• Food chains link trophic levels from producers totop carnivores© 2011 Pearson Education, Inc.
  • 36. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsCarnivoreCarnivoreHerbivoreCarnivorePlantA terrestrial food chainCarnivoreCarnivoreCarnivoreZooplanktonPhytoplanktonA marine food chainQuaternaryconsumersTertiaryconsumersSecondaryconsumersPrimaryconsumersPrimaryproducersFigure 54.13
  • 37. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFood Webs• A food web is a branching food chain withcomplex trophic interactions© 2011 Pearson Education, Inc.
  • 38. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 54.14HumansSpermwhalesSmallertoothedwhalesBaleenwhalesCrab-eatersealsLeopardsealsElephantsealsSquidsFishesBirdsCarniv-orousplanktonCope-podsEuphau-sids(krill)Phyto-plankton
  • 39. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsLimits on Food Chain Length• Each food chain in a food web is usually only afew links long• Two hypotheses attempt to explain food chainlength: the energetic hypothesis and the dynamicstability hypothesis© 2011 Pearson Education, Inc.
  • 40. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• The energetic hypothesis suggests that length islimited by inefficient energy transfer– For example, a producer level consisting of 100kg of plant material can support about 10 kg ofherbivore biomass (the total mass of allindividuals in a population)• The dynamic stability hypothesis proposes thatlong food chains are less stable than short ones• Most data support the energetic hypothesis© 2011 Pearson Education, Inc.
  • 41. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsSpecies with a Large Impact• Certain species have a very large impact oncommunity structure• Such species are highly abundant or play a pivotalrole in community dynamics© 2011 Pearson Education, Inc.
  • 42. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsDominant Species• Dominant species are those that are mostabundant or have the highest biomass• Dominant species exert powerful control over theoccurrence and distribution of other species– For example, sugar maples have a major impacton shading and soil nutrient availability in easternNorth America; this affects the distribution of otherplant species© 2011 Pearson Education, Inc.
  • 43. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsKeystone Species• Keystone species exert strong control on acommunity by their ecological roles, or niches• In contrast to dominant species, they are notnecessarily abundant in a community• Field studies of sea stars illustrate their role as akeystone species in intertidal communities© 2011 Pearson Education, Inc.
  • 44. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 54.17EXPERIMENTRESULTSWith Pisaster (control)Without Pisaster(experimental)Year’73’72’71’70’69’68’67’66’65’64196305101520Numberofspeciespresent
  • 45. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Observation of sea otter populations and theirpredation shows how otters affect oceancommunities© 2011 Pearson Education, Inc.
  • 46. LE 53-17100806040020Sea otter abundanceOtternumber(%max.count)4003002000100Sea urchin biomassGramsper0.25m21086402Total kelp densityNumberper0.25m219971993198919851972YearFood chain beforekiller whaleinvolvement inchainFood chain afterkiller whales startedpreying on otters
  • 47. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Ecosystem engineers (or “foundation species”)cause physical changes in the environment thataffect community structure– For example, beaver dams can transformlandscapes on a very large scale© 2011 Pearson Education, Inc.
  • 48. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 54.19
  • 49. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFacilitation• Facilitation (+/+ or 0/+) describes an interactionwhere one species can have positive effects onanother species without direct and intimatecontact– For example, the black rush makes the soil morehospitable for other plant species© 2011 Pearson Education, Inc.
  • 50. LE 53-19Numberofplantspecies86402ConditionsWithJuncusWithoutJuncusSalt marsh with Juncus(foreground)
  • 51. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsDisturbance influences species diversity andcomposition• Decades ago, most ecologists favored the viewthat communities are in a state of equilibrium• Recent evidence of change has led to anonequilibrium model, which describescommunities as constantly changing after beingbuffeted by disturbances• A disturbance is an event that changes acommunity, removes organisms from it, and altersresource availability© 2011 Pearson Education, Inc.
  • 52. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsCharacterizing Disturbance• Fire is a significant disturbance in most terrestrialecosystems• A high level of disturbance is the result of a highintensity and high frequency of disturbance© 2011 Pearson Education, Inc.
  • 53. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• The intermediate disturbance hypothesissuggests that moderate levels of disturbance canfoster greater diversity than either high or lowlevels of disturbance• High levels of disturbance exclude many slow-growing species• Low levels of disturbance allow dominant speciesto exclude less competitive species© 2011 Pearson Education, Inc.
  • 54. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• The large-scale fire in Yellowstone National Parkin 1988 demonstrated that communities can oftenrespond very rapidly to a massive disturbance• The Yellowstone forest is an example of anonequilibrium community© 2011 Pearson Education, Inc.
  • 55. LE 53-22Soon after fire. As this photo taken soon after the fireshows, the burn left a patchy landscape. Note theunburned trees in the distance.One year after fire. This photo of the same general areataken the following year indicates how rapidly the com-munity began to recover. A variety of herbaceous plants,different from those in the former forest, cover the ground.
  • 56. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsEcological Succession• Ecological succession is the sequence ofcommunity and ecosystem changes after adisturbance• Primary succession occurs where no soil existswhen succession begins• Secondary succession begins in an area wheresoil remains after a disturbance© 2011 Pearson Education, Inc.
  • 57. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Early-arriving species and later-arriving speciesmay be linked in one of three processes– Early arrivals may facilitate appearance of laterspecies by making the environment favorable– They may inhibit establishment of later species– They may tolerate later species but have noimpact on their establishment© 2011 Pearson Education, Inc.
  • 58. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Retreating glaciers provide a valuable field-research opportunity for observing succession• Succession on the moraines in Glacier Bay,Alaska, follows a predictable pattern of change invegetation and soil characteristics1. The exposed moraine is colonized by pioneeringplants including liverworts, mosses, fireweed,Dryas, willows, and cottonwood© 2011 Pearson Education, Inc.
  • 59. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 54.22-1Pioneer stage, withfireweed dominantAlaska1760GlacierBay1860190719411 0 5 10 15Kilometers
  • 60. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings2. Dryas dominates the plant community© 2011 Pearson Education, Inc.
  • 61. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 54.22-2Pioneer stage, withfireweed dominantAlaska1760GlacierBay186019071941Dryas stage120 5 10 15Kilometers
  • 62. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings3. Alder invades and forms dense thickets© 2011 Pearson Education, Inc.
  • 63. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 54.22-3Pioneer stage, withfireweed dominantAlaska1760GlacierBay186019071941Dryas stageAlder stage1230 5 10 15Kilometers
  • 64. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings4. Alder are overgrown by Sitka spruce, westernhemlock, and mountain hemlock© 2011 Pearson Education, Inc.
  • 65. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 54.22-4Pioneer stage, withfireweed dominantSpruce stageAlaska1760GlacierBay186019071941Dryas stageAlder stage14230 5 10 15Kilometers
  • 66. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Succession is the result of changes induced bythe vegetation itself• On the glacial moraines, vegetation lowers the soilpH and increases soil nitrogen content© 2011 Pearson Education, Inc.
  • 67. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsSuccessional stagePioneer Dryas Alder Spruce01020304050Soilnitrogen(g/m2) 60Figure 54.23
  • 68. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsBiogeographic factors affect communitybiodiversity• Latitude and area are two key factors that affect acommunity’s species diversity© 2011 Pearson Education, Inc.
  • 69. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsLatitudinal Gradients• Species richness is especially great in the tropicsand generally declines along an equatorial-polargradient• Two key factors in equatorial-polar gradients ofspecies richness are probably evolutionary historyand climate© 2011 Pearson Education, Inc.
  • 70. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Temperate and polar communities have startedover repeatedly following glaciations• The greater age of tropical environments mayaccount for the greater species richness• In the tropics, the growing season is longer suchthat biological time is faster© 2011 Pearson Education, Inc.
  • 71. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Climate is likely the primary cause of the latitudinalgradient in biodiversity• Two main climatic factors correlated withbiodiversity are solar energy and water availability• They can be considered together by measuring acommunity’s rate of evapotranspiration• Evapotranspiration is evaporation of water fromsoil plus transpiration of water from plants© 2011 Pearson Education, Inc.
  • 72. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsArea Effects• The species-area curve quantifies the idea that,all other factors being equal, a larger geographicarea has more species• A species-area curve of North American breedingbirds supports this idea© 2011 Pearson Education, Inc.
  • 73. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsArea (hectares; log scale)Numberofspecies(logscale)0.1 1 10 100 10310410510610710810910101101001,000Figure 54.26