Outline

Community Ecology

Chapter 47

Community Community EcologyEcology 2

OutlineOutline

The Concept of the CommunityThe Concept of the CommunityDiversity and Composition ModelsDiversity and Composition Models

The Structure of CommunitiesThe Structure of Communities Island BiogeographyIsland BiogeographyHabitat and Ecological NicheHabitat and Ecological NicheCompetition Between PopulationsCompetition Between PopulationsPredator-Prey InteractionsPredator-Prey InteractionsSymbiotic RelationshipsSymbiotic Relationships

Community DevelopmentCommunity DevelopmentCommunity BiodiversityCommunity Biodiversity


Community ConceptCommunity Concept

An assemblage of populations An assemblage of populations interacting with one another within interacting with one another within the same environmentthe same environment

Composition is a listing of various Composition is a listing of various species in the communityspecies in the community

Diversity includes both species Diversity includes both species richness and species diversityrichness and species diversity

4Community Structure


Diversity and Composition ModelsDiversity and Composition Models

Gleason - Individualistic ModelGleason - Individualistic Model

Each population is there because its Each population is there because its abiotic requirements are metabiotic requirements are met

Clements - Interactive ModelClements - Interactive Model

Community is the highest level of Community is the highest level of organizationorganization

Dependent on biotic interactionsDependent on biotic interactions

6Species Richness of Communities


Island BiogeographyIsland Biogeography

MacArthur and WilsonMacArthur and Wilson

Developed a general model of island Developed a general model of island biogeographybiogeography

Explains and predicts how the Explains and predicts how the community diversity of an island is community diversity of an island is affected byaffected by

Distance from the mainland, andDistance from the mainland, and

Size of the islandSize of the island

8Model of Island Biogeography


Community StructureCommunity Structure

CompetitionCompetition

When two species compete, the When two species compete, the abundance of both species is abundance of both species is negatively impactednegatively impacted

Predation (or parasitism)Predation (or parasitism)

Expected to increase the abundance of Expected to increase the abundance of the predator (or parasite)the predator (or parasite)

And reduce the abundance of the prey And reduce the abundance of the prey (or host)(or host)


Habitat and Ecological NicheHabitat and Ecological Niche

HabitatHabitatThe area an organism lives and The area an organism lives and reproduces inreproduces in

Ecological nicheEcological nicheThe role a species plays in its communityThe role a species plays in its community Includes its habitat, andIncludes its habitat, and

Its interactions with other organismsIts interactions with other organisms

Fundamental niche - All conditions under Fundamental niche - All conditions under which the organism can survivewhich the organism can survive

Realized niche - Set of conditions under Realized niche - Set of conditions under which it exists in naturewhich it exists in nature

11Feeding niches for Wading Birds


Competition Between PopulationsCompetition Between PopulationsInterspecific competitionInterspecific competition

Members of different species require Members of different species require the same resourcethe same resource

The supply of the resource is limitedThe supply of the resource is limited

Competitive Exclusion PrincipleCompetitive Exclusion Principle

No two species can occupy the same No two species can occupy the same niche at the same timeniche at the same time

Resource Partitioning decreases Resource Partitioning decreases competitioncompetition

Can lead to character displacementCan lead to character displacement

13Competition BetweenTwo Laboratory Populations of

Paramecium

14Character Displacement in Finches

on the Galápagos Islands

15 Niche Specialization AmongFive Species of Coexisting

Warblers

16 Competition Between

Two Species of Barnacles


Predator-Prey InteractionsPredator-Prey Interactions

PredationPredation

One living organism, the predator, One living organism, the predator, feeds on another, the preyfeeds on another, the prey

Predator is largerPredator is larger

Predator has lower reproductive ratePredator has lower reproductive rate

Prey usually entirely consumedPrey usually entirely consumed

Presence of predators can decrease Presence of predators can decrease prey densities, and vice-versaprey densities, and vice-versa

18 Predator-prey Interaction BetweenParamecium caudatum and

Didinium nasutum

19 Predator-prey InteractionBetween a Lynx and a

Snowshoe Hare


Prey DefensesPrey Defenses

Prey defensesPrey defenses

Mechanisms that thwart the possibility Mechanisms that thwart the possibility of being eaten by a predatorof being eaten by a predator

SpinesSpines

Tough EpidermisTough Epidermis

Poisonous ChemicalsPoisonous Chemicals

CamouflageCamouflage

Bright ColorationBright Coloration

Flocking BehaviorFlocking Behavior

21 Camouflage in the Anglerfish

22 Anti-predator Defenses


MimicryMimicry

MimicryMimicry

One species resembles another One species resembles another speciesspecies

Mimicked species possesses an overt Mimicked species possesses an overt antipredator defenseantipredator defense

Batesian Mimicry - Mimic lacks Batesian Mimicry - Mimic lacks defense of the organism it resemblesdefense of the organism it resembles

MMüüllerian Mimicry - Mimic shares same llerian Mimicry - Mimic shares same protective defenseprotective defense

24Mimicry Among Insects with

Yellow and Black Stripes


Symbiotic RelationshipsSymbiotic Relationships

SymbiosisSymbiosis

Interactions in which there is a close Interactions in which there is a close relationship between members of two relationship between members of two speciesspecies

ParasitismParasitism

Parasite derives nourishment from a Parasite derives nourishment from a host, and may use host as habitat and host, and may use host as habitat and mode of transmissionmode of transmission

EndoparasitesEndoparasites

EctoparasitesEctoparasites

26The Life Cycle of a Deer Tick


CommensalismCommensalismSymbiosis, cont.Symbiosis, cont.

CommensalismCommensalism

A symbiotic relationship in which one A symbiotic relationship in which one species benefits and the other is species benefits and the other is indifferentindifferent

Remoras and SharksRemoras and Sharks

Many supposed examples may turn out Many supposed examples may turn out to be mutualism or parasitismto be mutualism or parasitism

Inferred amount of harm or benefit two Inferred amount of harm or benefit two species do to one another is subject to species do to one another is subject to investigator biasinvestigator bias

28Clownfish AmongSea Anemone’s

Tentacles


MutualismMutualismSymbiosis, cont.Symbiosis, cont.

MutualismMutualism

A symbiotic relationship in which both A symbiotic relationship in which both members of the association benefitmembers of the association benefit

Need not be equally beneficial to both Need not be equally beneficial to both speciesspecies

Cleaning SymbiosisCleaning Symbiosis

Often help each other obtain food or Often help each other obtain food or avoid predationavoid predation

Bacteria in human intestinal tractBacteria in human intestinal tract

30Mutualism Betweenthe Bullhorn Acacia Tree

and Ants

31Cleaning Symbiosis


Community DevelopmentCommunity Development

Ecological SuccessionEcological Succession

A predictable pattern of change in A predictable pattern of change in species replacements following a species replacements following a disturbancedisturbance

Primary Succession occurs in areas Primary Succession occurs in areas where there is no soil formationwhere there is no soil formation

Secondary Succession begins in areas Secondary Succession begins in areas where soil is presentwhere soil is present

Pioneer SpeciesPioneer Species

33Secondary Succession

34Secondary Successionin a Forest


Succession ModelsSuccession Models

Facilitation ModelFacilitation Model

Each stage facilitates invasion and Each stage facilitates invasion and replacement by organisms of the next replacement by organisms of the next stagestage

Succession in a particular area will Succession in a particular area will always lead to the same type of always lead to the same type of communitycommunity

Climax CommunityClimax Community


Succession ModelsSuccession Models

Inhibition ModelInhibition Model

Colonists remain and inhibit growth of Colonists remain and inhibit growth of other plants until the colonists are other plants until the colonists are damaged or diedamaged or die

Tolerance ModelTolerance Model

Different types of plants can colonize Different types of plants can colonize an area at the same timean area at the same time

Chance determine which seeds arrive Chance determine which seeds arrive firstfirst


Community DiversityCommunity Diversity

Community stability can be recognized Community stability can be recognized in three waysin three ways

Persistence through timePersistence through time

Resistance to changeResistance to change

Recovery once a disturbance has Recovery once a disturbance has occurredoccurred

Community Community EcologyEcology 38Intermediate Disturbance Intermediate Disturbance

HypothesisHypothesis

If widespread disturbances occur If widespread disturbances occur frequently, diversity will be limitedfrequently, diversity will be limited

If diversity is high, only moderate If diversity is high, only moderate disturbances have been occurring disturbances have been occurring with moderate frequencywith moderate frequency

39The Intermediate Disturbance Hypothesis

Community Community EcologyEcology 40Predation, Competition, and Predation, Competition, and

BiodiversityBiodiversity

Predation by a particular species may Predation by a particular species may reduce competition and increases reduce competition and increases diversitydiversity

Such predators are referred to as Such predators are referred to as keystone predatorskeystone predators

Exotic speciesExotic species

May lead to unbridled competitionMay lead to unbridled competition

Resultant reduction in biodiversityResultant reduction in biodiversity

41Effect of a Keystone Species


ReviewReview

The Concept of the CommunityThe Concept of the CommunityDiversity and Composition ModelsDiversity and Composition Models

The Structure of CommunitiesThe Structure of Communities Island BiogeographyIsland BiogeographyHabitat and Ecological NicheHabitat and Ecological NicheCompetition Between PopulationsCompetition Between PopulationsPredator-Prey InteractionsPredator-Prey InteractionsSymbiotic RelationshipsSymbiotic Relationships

Community DevelopmentCommunity DevelopmentCommunity BiodiversityCommunity Biodiversity

Community Ecology

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