AgriculturalAgricultural EcologyEcology ByBy Dr.Dr. RensenRensen ZengZeng DepartmentDepartment ofof EcologyEcology CollegeCollege ofof AgricultureAgriculture Email: [email protected] Phone: 38604978 ChapterChapter 1010

Habitats,, NichesNiches andand populationpopulation interactionsinteractions QuestionsQuestions

What are population and ? Why

do we study them in ? TheThe NatureNature ofof EcologyEcology BiosphereBiosphere ¾¾EcosystemEcosystem organizationorganization ¾¾OrganismsOrganisms ¾¾PopulationsPopulations Communities ¾¾CommunitiesCommunities Populations ¾¾EcosystemsEcosystems

¾¾BiosphereBiosphere Fig. 4.2, p. 72 1.1. HabitatsHabitats ((生境）生境） • Definition: The natural place of growth or occurrence of a species is called .

• A place where an lives or could be found. Crane in swamp 仙鹤 Penguin in polar region 企鹅 OceanOcean habitatshabitats HabitatHabitat isis thethe HomeHome ofof anan organismorganism

However, due to human activity and , Habitats of many organisms are losing. These organisms are becoming Homeless and extinct HabitatHabitat lossloss duedue toto humanhuman activitiesactivities HabitatHabitat LossLoss

• Single greatest threat to

– Approx. 50+% of all species extinctions have been

involved habitat loss

– Island theory predicts that around 50%

of species are lost with 90% habitat loss ImpactsImpacts ofof HabitatHabitat ModificationModification

• Loss of Habitat

• Habitat Alteration

• Fragmentation

• Increased Human Presence

• ImpactsImpacts ofof HabitatHabitat ModificationModification • Increased Human Presence – Alteration leads to more alteration – People arrive, then their influence expands and intensifies ImpactsImpacts ofof HabitatHabitat ModificationModification

• Introduced Species – Other species come with us as we fragment – Intentionally – Unintentionally 2.2. NicheNiche 生态位生态位 • In ecology it came to stand for the precise way in which a species fits into its environment. • Total role of an organism in the environment •Multiple factors Æ

•Factors interact •additive •multiplicative •A single factor may limit success -(Leibig’s law of the minimum) •Genetic variation •Dynamic environments •Lags in response Leibig’s law of the minimum Tradeoffs between A single factor may limit success interacting factors * niche

(1)the limits, for all important environmental variables, within which individuals of a species can survive, grow, and reproduce.

(2) The specific set of environmental/habitat conditions that permit the full development and completion of the life cycle of an organism (K) EcologicalEcological NicheNiche

• Total role of an organism in the environment. • Fundamental Niche: Maximum niche a species can occupy, absent. • Realized Niche: Portion of the fundamental niche occupied by the species, competition present. RealizedRealized NicheNiche (schematic(schematic representation)representation) High Light e w r o tu L Low is o M h Nutrients ig Low High H n-dimensional hyper-volume (n = number of parameters used to characterize the niche) fundamental TheThe realizedrealized nicheniche ofof anan organismorganism niche isis smallersmaller thanthan thethe fundamentalfundamental nicheniche duedue toto competition,competition, realized ,predation, ,parasitism, andand niche recruitmentrecruitment limitationslimitations fundamental TheThe realizedrealized nicheniche ofof anan organismorganism niche isis largerlarger thanthan thethe fundamentalfundamental nicheniche duedue toto resourceresource realized enhancement,enhancement, habitathabitat amelioration,amelioration, niche predationpredation refuge,refuge, andand recruitmentrecruitment enhancementenhancement 生态位的重叠生态位的重叠 NicheNiche overlapoverlap

• Niche of an individual or species is critical in determining the degree of competition with other species or individuals. • Large niche overlap generally results in intense competition WhatWhat happenshappens whenwhen thethe twotwo speciesspecies havehave thethe samesame niche?niche? CompetitiveCompetitive ExclusionExclusion PrinciplePrinciple

TwoTwo speciesspecies competingcompeting forfor thethe samesame resourceresource cannotcannot existexist indefinitely.indefinitely. CompetitionCompetition exclusionexclusion principleprinciple

竞争排斥原理（也称高斯原理）指出：具有相同生态位 的不同物种，在同一生境中不能长期共存。 Gause’s competitive exclusion principle • states that two species with identical niche cannot coexist indefinitely.

If two species compete in a stable environment, there are two possible outcomes: • (1)One species is excluded, or • (2)Both species coexist if the species niches are differentiated. FailureFailure ofof speciesspecies toto coexistcoexist inin lablab culturescultures ledled toto thethe CompetitiveCompetitive ExclusionExclusion HypothesisHypothesis:: TwoTwo speciesspecies cancan’’tt coexistcoexist onon thethe samesame limitinglimiting .resource. OutcomeOutcome ofof interspecificinterspecific competitioncompetition isis sometimessometimes dependentdependent onon abioticabiotic conditions.conditions.

29.1 °C

32.3 °C NicheNiche breadthbreadth decreasesdecreases withwith competitors.competitors. IntraspecificIntraspecific competition:competition: createscreates selectiveselective pressurepressure forfor broaderbroader resourceresource use.use. Frequency w/o of pop. with Food size utilized • Interspecific competition: may select for narrower resource use. with Frequency w/o of pop.

Food size utilized InvasionInvasion byby newnew speciesspecies bringsbrings nicheniche overlapoverlap maymay ---->> reducedreduced nicheniche breadthbreadth maymay---->> moremore speciesspecies packedpacked intointo communitycommunity.. NicheNiche separationseparation viavia resourceresource partitioningpartitioning 3)3) CharacterCharacter displacement:displacement: MorphologicalMorphological traitstraits andand foodfood selectionselection ofof speciesspecies shiftshift dependingdepending onon presencepresence oror absenceabsence ofof closelyclosely relatedrelated species.species. NicheNiche separationseparation 生态生态 位分离位分离 viavia resourceresource partitioningpartitioning amongamong relatedrelated species.species. ReducedReduced nicheniche overlapoverlap:: closelyclosely relatedrelated speciesspecies useuse differentdifferent partsparts ofof resourceresource gradientsgradients whenwhen sympatric.sympatric. HabitatHabitat shift:shift: UseUse ofof habitathabitat oftenoften changeschanges dependingdepending onon presencepresence oror absenceabsence ofof closelyclosely relatedrelated species.species. Habitat – actual location or place where an organism lives

vs.

Niche – “the physical and biological variables that affect an organisms well-being” aka “n-dimensional hypervolume” 3.3. PopulationPopulation interactionsinteractions 生物种间的相互关系生物种间的相互关系 无相互作用 No interactions 偏利 正相互作用 原始合作 protocooperation Positive interaction 互利共生 直接干涉 竞争 competition 间接抑制 负相互作用 捕食 predation Negative 偏害 amensalism interaction 寄生 parasitism

3.13.1 CompetitionCompetition

• Use the same resource

(1) Exploitation

(2) Interference 3.23.2 PredationPredation ++ HerbivoryHerbivory

InIn foodfood chains,chains, allall lifelife formsforms areare bothboth consumersconsumers andand victimsvictims ofof consumers.consumers. • Predators • Parasitoids • Parasites • • •

• 螳螂捕蝉，黄雀在后 HerbivoryHerbivory:: EffectsEffects onon plantsplants OutbreaksOutbreaks ofof insectsinsects cancan defoliatedefoliate forests.forests.

Spruce budworm HerbivoryHerbivory hashas greatgreat effectseffects onon plantplant ,productivity, populationpopulation size,size, andand speciesspecies composition.composition.

• If prefer dominant species---> increase species #. • If prefer subdominant species---> decrease species #. NaturalNatural enemiesenemies hypothesishypothesis::

• Introduced species escape from their natural enemies.

• Biological control: • Introduce natural enemy to control introduced species. InIn spitespite ofof plantplant defenses,defenses, herbivoresherbivores cancan controlcontrol plantplant populationpopulation size.size.

Klamath weed + beetle (biological control agent) TheThe jawsjaws ofof snakessnakes areare adaptedadapted forfor graspinggrasping andand swallowingswallowing largelarge prey.prey.

PredatorsPredators varyvary inin sizesize relativerelative toto theirtheir prey.prey. 3.3 Parasitism寄生

www.defra.gov.uk/planth/ pestnote/sudden.htm www.nps.gov/plants/alien/ fact/hehe1.htm 3.43.4 AntagonisticAntagonistic (Exploitation)(Exploitation)

• At least one partner is adversely (negatively) affected

– Exploitation (Non C. or Consumptive) • Physical (NC) – physically hindering host – climbing and extensive bird nesting • Parasitism (C) – consuming part of tissues or blood/ weakening and sometimes killing, smaller than host – Dutch Elm’s Disease, Sudden Oak Death • Predation (C) – consuming all or part / killing or weakening, larger than prey – Herbivores eating plants, Wolves eating chickens ExploitationExploitation (Physical(Physical oror Consumptive?)Consumptive?) mistletoe Phoradendron macrophyllum

www.montereylawngarden.com/ info/florel.html AntagonisticAntagonistic (Antibiosis)(Antibiosis)

• At least one partner is adversely (negatively) affected

– Antibiosis: Chemical Interactions between organisms • with chemicals unpalatable to prey (Monarch) • Plants with chemicals unpalatable to prey (Chemicals in heartwood, Rot resistant) – Allelopathy: Antibiosis between plants • Root exudates which adversely affect growth and survival of surrounding plants (Walnut Trees)

Salvia leucophylla and bare zones Eucalyptus spp. 1、植物和微生物的化感作用

荔枝霜疫霉病 SymbioticSymbiotic Interactions:Interactions: 4.54.5 CommensalismCommensalism 偏利偏利

¾¾ OneOne speciesspecies benefits,benefits, butbut dodo notnot harmharm oror helphelp thethe otherother speciespecie

¾¾ IndirectIndirect:: smallsmall plantsplants growinggrowing inin shadeshade ofof largerlarger plantsplants

¾¾ DirectDirect:: epiphytesepiphytes ((兰花兰花)) rootsroots onon treetree forksforks (not(not soil)soil) CommensalismCommensalism ((共栖、偏利）共栖、偏利）:: EpiphytesEpiphytes（附生植物）（附生植物） 4.6 原始合作 protocooperation PlantPlant--seedseed disperserdisperser mutualismmutualism AntAnt--plantplant defensedefense mutualism:mutualism: AcaciaAcacia andand PseudomyrmexPseudomyrmex antsants 3.73.7 MutualismMutualism （互利共生）（互利共生）

Intimate living together of members of two or more species. • Commensalism - One member benefits while other is neither benefited nor harmed. – Cattle and Cattle Egrets • - Both members benefit. – Lichens (Fungus and cyanobacterium) • Parasitism - One member benefits at the expense of other. – Humans and Tapeworms SymbiosisSymbiosis -- LichensLichens LichensLichens CoveringCovering aa RockRock 专性互利共生：地衣 （藻类和真菌的共生体） MycorrhizaeMycorrhizae EnhanceEnhance PlantPlant GrowthGrowth

MycorrhizaeMycorrhizae LegumesLegumes andand RhizobiumRhizobium

PollinationPollination syndromessyndromes provideprovide circumstantialcircumstantial evidenceevidence ofof atat leastleast diffusediffuse coevolutioncoevolution.. SummarySummary

• （ 1 ） A habitat is the place where an organism is found in nature. • （2）Any one environment contains many microhabitats. • （3）The niche of an organism is a complete description of how the organism fits into its physical and biological environment. （4）Hutchinson proposed that the niche of an organism could be defined as an n-dimensional hypervolume with separate environmental variables plotted on the axes. （5）Gause's competitive exclusion principle states that no two species can coexist if they occupy the same niche. HomeworkHomework

1. What are effects of population interactions

on community structure and function?

2. How can we use niche theory in Agriculture?