Community EcologyCommunity Ecology

Chapter 47Chapter 47

OutlineOutline Diversity and Composition ModelsDiversity and Composition Models Island BiogeographyIsland Biogeography Habitat and Ecological NicheHabitat and Ecological Niche Competition Between PopulationsCompetition Between Populations Predator-Prey InteractionsPredator-Prey Interactions Symbiotic RelationshipsSymbiotic Relationships Community DevelopmentCommunity Development Community DiversityCommunity Diversity

Community ConceptCommunity Concept

What is a community?What is a community? Factors to considerFactors to consider

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

DiversityDiversity includes both species richness includes both species richness and species diversity.and species diversity.

Diversity and Composition Diversity and Composition ModelsModels

GleasonGleason - - Individualistic ModelIndividualistic Model Each population in community is there Each population in community is there

because its own particular abiotic because its own particular abiotic requirements are met by a particular requirements are met by a particular habitat.habitat.

ClementsClements - - Interactive ModelInteractive Model Community is the highest level of Community is the highest level of

organization.organization. Dependent on biotic interactions.Dependent on biotic interactions.

Island BiogeographyIsland Biogeography

MacArthur and WilsonMacArthur and Wilson--effects of --effects of distance from the mainland and size distance from the mainland and size of an island on community diversity.of an island on community diversity.

Conclusions?Conclusions?

Model of Island Model of Island BiogeographyBiogeography

Habitat and Ecological NicheHabitat and Ecological Niche HabitatHabitat -- Home. -- Home. Ecological nicheEcological niche ---occupation in ---occupation in

the communitythe community Fundamental nicheFundamental niche - potential - potential Realized nicheRealized niche - actual - actual

Feeding Niches for Wading Feeding Niches for Wading BirdsBirds

Species interactionsSpecies interactions Community interactions can be potent Community interactions can be potent

selective pressures selective pressures CompetitionCompetition

IntraspecificIntraspecific InterspecificInterspecific

Predator/PreyPredator/Prey SymbiosisSymbiosis

RESULTS OF INTERACTIONRESULTS OF INTERACTION

(+) organism benefits (how?)(+) organism benefits (how?) (-) organism suffers (how?)(-) organism suffers (how?) (0) neutral, no benefit or loss (0) neutral, no benefit or loss

(RU sure?)(RU sure?)

Competition Between Competition Between PopulationsPopulations

Intraspecific competition (?)Intraspecific competition (?) Interspecific competition (?)Interspecific competition (?)

Competitive Exclusion PrincipleCompetitive Exclusion Principle Resource PartitioningResource Partitioning decreases decreases

competition.competition.Can lead to Can lead to character character displacementdisplacement..

Resource Partitioning –more specialized niches

Competition Between Barnacle Competition Between Barnacle SpeciesSpecies

Character Displacement in Character Displacement in GalGaláápagos Finchespagos Finches

Predator-Prey InteractionsPredator-Prey Interactions

PredationPredation Selective pressure?Selective pressure? Interaction = +, -Interaction = +, - Population effectsPopulation effects

Lynx-Snowshoe Hare Lynx-Snowshoe Hare InteractionsInteractions

Prey DefensesPrey Defenses

Prey defenses -adaptations that thwart Prey defenses -adaptations that thwart the possibility of being eaten by a the possibility of being eaten by a predator.predator. Concealment/cryptic coloration/other Concealment/cryptic coloration/other

colorationcoloration Warning colorationWarning coloration Armor/weaponryArmor/weaponry ChemicalsChemicals BehaviorBehavior

GeckoGecko

Gecko?Gecko?

Gecko?Gecko?

StoneplantStoneplant

WalkinWalking stickg stick

Camouflage in the Camouflage in the AnglerfishAnglerfish

MimicryMimicry

MimicryMimicry occurs when one species occurs when one species resembles another that possesses resembles another that possesses an overt antipredator defense.an overt antipredator defense. BatesianBatesian – Harmless mimics – Harmless mimics

harmfulharmful MMüüllerianllerian – Harmful mimics – Harmful mimics

harmfulharmful

Batesian Batesian I: Coral I: Coral

snake or snake or Milk Milk

Snake? Snake? Would Would

you bet you bet your life your life

on it?on it?

Batesian or Mullerian?Batesian or Mullerian?

Vertebrate Eye Vertebrate Eye MimicryMimicry

Similar to BatesianSimilar to Batesian Can startle or confuse Can startle or confuse

predator predator

Eye Mimicry 2Eye Mimicry 2

Aposematic (Warning) Aposematic (Warning) ColorationColoration

Chemical DefensesChemical Defenses

Chemical Defenses 2Chemical Defenses 2

Deceptive Coloration Deceptive Coloration Example Example

Sea HareSea Hare

PHAGOMIMICRYPHAGOMIMICRY

Symbiotic RelationshipsSymbiotic Relationships

Symbiosis Symbiosis close relationship close relationship between members of two between members of two populations. We’ll be interested populations. We’ll be interested in 3:in 3: Parasitism (+, -)Parasitism (+, -) Commensalism (+, 0)Commensalism (+, 0) Mutualism (+,+)Mutualism (+,+)

Parasitism (+, -)Parasitism (+, -)

Endoparasites Ex?Endoparasites Ex? Ectoparasites EX? Ectoparasites EX? Social ParasitesSocial Parasites

Brood parasitesBrood parasites KleptoparasitesKleptoparasites

Endoparasite Life cyclesEndoparasite Life cycles

Complex, spend different stages in Complex, spend different stages in different hostsdifferent hosts Definitive host (primary host)Definitive host (primary host) Intermediate hostIntermediate host

Tapeworm Life CycleTapeworm Life Cycle

SchistosomiasisSchistosomiasis

ElephantiasiElephantiasiss

The behavior of The behavior of the cuckoo the cuckoo hatchling hatchling ejecting the ejecting the host eggs from host eggs from the nestthe nest

The feeding The feeding behavior of a behavior of a foster mother to foster mother to the cuckoo the cuckoo chickchick Figure 37.3B

Brood Parasitism--European Cuckoo

Kleptoparasite—Red Billed GullKleptoparasite—Red Billed Gull

Commensalism --+, Commensalism --+, 00 Shark Shark

(0)(0) RemorRemor

a (+)a (+)

PseudocopulationPseudocopulationSome orchids offer no nectar at all, but they resemble the female of various insect species. Or at least, resemble closely enough to fool a desperate male of the species – the mimicry is chemical as well as visual. The unfortunate male has to be deceived twice and engage in two acts of pseudocopulation before pollination takes place. Common european species doing this are the bee orchids in the genus Ophrys. In fact some populations of bee orchid seem to be self-fertile in the absence of pollination.

Bee orchid Ophrys apifera

MutualismMutualism MutualismMutualism (+,+) both members (+,+) both members

of the association benefit.of the association benefit. ADVANTAGES?ADVANTAGES? EX?EX?

Mutualism Between Bullhorn Mutualism Between Bullhorn Acacia and AntsAcacia and Ants

Cleaning SymbiosisCleaning Symbiosis

Community DevelopmentCommunity Development

Ecological SuccessionEcological Succession A change involving a series of species A change involving a series of species

replacements in a community following replacements in a community following a disturbance.a disturbance. Primary Succession Primary Succession Secondary Succession Secondary Succession

Pioneer SpeciesPioneer Species Climax SpeciesClimax Species

Secondary Succession in a Secondary Succession in a ForestForest

Succession ModelsSuccession Models

Facilitation ModelFacilitation Model 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 Community—Endpoint of Climax Community—Endpoint of successionsuccession

Oldest, most supportedOldest, most supported

Changes in soil structure over Changes in soil structure over timetime

Soil changes over time.Soil changes over time.Nitrogen levels start out low and Nitrogen levels start out low and increase because of symbiotic increase because of symbiotic nitrogen-fixing bacteria in alder.nitrogen-fixing bacteria in alder.Then other trees can survive.Then other trees can survive.

Succession ModelsSuccession Models

Inhibition ModelInhibition Model Colonists hold onto their space and Colonists hold onto their space and

inhibit growth of other plants until the inhibit growth of other plants until the colonists are damaged or die.colonists are damaged or die.

Tolerance ModelTolerance Model Different types of plants can colonize an Different types of plants can colonize an

area at the same time.area at the same time. Chance determine which seeds arrive first.Chance determine which seeds arrive first.

Ecological succession: Ecological succession: Primary successionPrimary succession

retreating glaciers leave retreating glaciers leave moraines. autotrophic moraines. autotrophic bacteria are first bacteria are first colonizers.colonizers.

mosses and lichens are mosses and lichens are first macroscopic first macroscopic autotrophs. soil forms autotrophs. soil forms graduallygradually

pioneering plant pioneering plant species are nextspecies are next

Succession continues until a Succession continues until a climax community is formed.climax community is formed.

spruce replace alder and spruce replace alder and cottonwoodcottonwood

final stage is a spruce and hemlock final stage is a spruce and hemlock forestforest

Secondary succession occurs after Secondary succession occurs after disturbance that leaves the soil intact. disturbance that leaves the soil intact. Other examples?Other examples?

Fig. 53.18 – 1988 fires in Yellowstone

Community DiversityCommunity Diversity

Community stability can be Community stability can be recognized in three ways.recognized in three ways. Persistence through time.Persistence through time. Resistance to change.Resistance to change. Recovery once a disturbance has Recovery once a disturbance has

occurred.occurred.

Intermediate Disturbance Intermediate Disturbance HypothesisHypothesis

Moderate amounts of disturbances at Moderate amounts of disturbances at moderate frequency are required for moderate frequency are required for a high degree of community a high degree of community diversity.diversity. If widespread disturbances occur If widespread disturbances occur

frequently, diversity will be limited.frequently, diversity will be limited.

Intermediate Disturbance Intermediate Disturbance HypothesisHypothesis

Predation, Competition, and Predation, Competition, and BiodiversityBiodiversity

In certain communities, predation by a In certain communities, predation by a particular species reduces competition particular species reduces competition and increases diversity.and increases diversity. Predators that regulate competition and Predators that regulate competition and

maintain community diversity are referred to maintain community diversity are referred to as keystone predators.as keystone predators.

Introduction of exotic species into a new Introduction of exotic species into a new area may lead to unbridled competition area may lead to unbridled competition and resultant reduction in biodiversity.and resultant reduction in biodiversity.

Predation, Competition, and Predation, Competition, and BiodiversityBiodiversity

In certain communities, predation by a In certain communities, predation by a particular species reduces competition particular species reduces competition and increases diversity.and increases diversity. Predators that regulate competition and Predators that regulate competition and

maintain community diversity are referred to maintain community diversity are referred to as keystone predators.as keystone predators.

Introduction of exotic species into a new Introduction of exotic species into a new area may lead to unbridled competition area may lead to unbridled competition and resultant reduction in biodiversity.and resultant reduction in biodiversity.

ReviewReview

Diversity and Composition ModelsDiversity and Composition Models Island BiogeographyIsland Biogeography Habitat and Ecological NicheHabitat and Ecological Niche Competition Between PopulationsCompetition Between Populations Predator-Prey InteractionsPredator-Prey Interactions Symbiotic RelationshipsSymbiotic Relationships Community DevelopmentCommunity Development Community DiversityCommunity Diversity