BIO20C | Week 9 - Community Ecology
BIO20C | Week 9 - Community Ecology BIOE 20C - 01
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This 6 page Class Notes was uploaded by echen30 on Saturday December 5, 2015. The Class Notes belongs to BIOE 20C - 01 at University of California - Santa Cruz taught by Marinovic,B.B. in Fall 2015. Since its upload, it has received 40 views.
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Date Created: 12/05/15
Week 9 Community Ecology BIO 20C Baldo Marinovic Community Ecology 0 Community interacting species within a given area 0 Population lt community lt biomes Species Interactions 0 Interaction between two species 0 Affect tness of both species 0 Fitness effects or 0 0 Five basic types of interactions Competition 0 0 Both species experience fitness decrease o Niche I Sum total resources used by a species I Range of conditions it can tolerate 0 Species with overlapping niches compete with each other Competition Exclusion 0 GE Gause I Hypothesized that 2 species with same niche cannot coexist 0 Competitive exclusion principle g TVpe of Competition 0 Symmetric I Each species experiences the same decrease in tness 0 Asymmetric I One species has greater f1tness decrease than other 0 Asymmetric is more common than symmetric Mseauence of Asvmmetric Competition 0 Why aren t there just a few superior competitors 0 A most niches don t completely overlap Fundamental vs Realized Niche o Fundamental niche total possible use of the environment by a species 0 Realized niche actual observed used of the environment by a species Two Categories for Competitive Interactions o Interference competition I One species interferes with another s use of a resource 0 Exploitation competition I Species both utilize a resource I Most ef cient consumer wins Consum tion Anta onistic Interactions 0 One species consume all or part of another 0 3 types I Herbivory I Parasitism I Predation Herbivory o Grazing organisms herbivores consume plant tissue 0 e g oxens zebras etc Week 9 Community Ecology BIO 20C Baldo Marinovic Parasitism o Parasite consumes relatively small amount of tissue from a plant or animal host 0 e g leeches mosquitos Predation o Predator kills and consumes all or most of another organism species 0 e g lions sharks etc Defense From Consumption o Prey evolve defenses to counter predators 0 Two basic types of defenses I Constitutive always presented I Inducible produced in response to predators o e g camou age constitutive schooling safety in numbers weaponry quills Certain Defenses are Advertised o Aposematism warning coloration that advertise defense 0 e g bright color stripe patterns Mimich o Constitutive defenses have led to 2 types of mimicry o Mullerian mimicry I Species with similar defense resemble each other 0 Batesian mimicry I Species without defense resemble those with defense Inducible Defense 0 Variable responses 0 Triggered by presence of predator 0 Defense represents a fitness cost 0 Inducible defense minimize tness cost Top Down vs Bottom Up Control of Consumption o Predatorprey populations undergo cycles 0 What controls these cycles 0 Bottom up amount of prey regulates predator abundance 0 Top down predator control prey abundance o e g hare vs lynx population Mutualistic Interaction 0 Both organisms bene t 0 Not cooperative or altruistic I Rare case where 0 Both organism attempt to profit 0 Both are successful I May change to consumptivecompetition relationship AntTree Interaction o Acacia tree provide home to ants sometime food 0 Ant defend tree from grazers 0 Plant with ant have better survival rate Commensalism o 0 0 One species gains in tness Week 9 Community Ecology BIO 20C Baldo Marinovic o Other species unaffected o e g remoras and large f1shwhale remora get protection food scraps free ride 0 e g fat innkeeper worm and guest I worm create safe well ventilated burrow to feed Indirect Interactions 0 Two species that do not interact exert in uence on each other 0 In uence is indirect o Consequence of interaction with another species I Trophic cascade o eg Lamar Valley in Yellowstone Park tree elk wolves Trophic Cascade in Yellowstone Pzik o Wolves remove in 1925 restore in 1995 0 Elk culled until 1968 afterward population grows rapidly o Aspens grazed by elk increase in absence of wolves no new recruits until wolves return 0 Effected habitats and other species population Another Example 0 Fish dragon ies and insect pollinators in and around ponds ecosystems 0 Absence of fish result in lower pollination rate for plants around ponds Kevstone Species 0 Species with effects on communities that are disproportionate to their biomass o ie small part of ecosystem but play a major role in structuring the community 0 tend to be top level predators Species Diversitv 0 Key feature of community 0 Can be measured in two ways I Species richness total of species I Species diversity weighted measure that include both species and abundance QuseRole of Species Diversity 0 Why are some community more diverse than other 0 What effect does species diversity have a community structurefunction Global Pattern of Species Diversity 0 Many terrestrial ecosystems show pattern of decreasing diversity with latitude o No such distinct global patterns in marine ecosystems Factors that In uence Community Diversity 0 Productivity 0 Disturbance 0 Habitat size Productivity Hypothesis 0 High productivity supports more species 0 Supported by natural patterns 0 Contradicted by experimental studies Intermediate Disturbance vaothesig o Frequent disturbance few species I r selected species dominate 0 Rare disturbance few species I K selected species dominate Week 9 Community Ecology BIO 20C Baldo Marinovic 0 Intermediate disturbance highest species I Mix of K and r selected species Area Hypothesis 0 Large areas support more species 0 Tropic only area with adjacent NS hemisphere regions 0 More area more species 0 Supported by experimentalobservational studies Role of Ecological Diversitv o How does diversity affect I Productivity I Stability Community Productivity 0 Net primary productivity NPP o amount of plant material available to herbivores amp decomposers 0 Q how does species diversity affect NPP Community Stability 0 Two measures 0 Resistance measure of how much disturbance affects a community 0 Resilience measure of how quickly a community recovers from disturbance o A diverse community able to use more of the resource base resulting in higher productivity 0 Diverse communities more likely to have redundant species 0 These can fill the role of species with similar function if they are reducedlost Island Biography 0 Study of spatially isolated communities 0 True island I Chunk of terrestrial habitat surrounded by water 0 Have distinct speciesarea relationships with sleeper slopes than comparable mainland Eguilibrium Theory 0 MacArthur and Wilson 1967 0 Dynamic equilibrium between I Rate of colonization I Rate of extinction o S species number as S increase I Rate of new species colonization decrease I Rate of extinction increase Experimental Test of Equilibrium Theory 0 Simberloff and Wilson 1969 Arthropod species diversity on mangrove islands in Florida Did species removal with insecticide Documented return of species Result I Similar number of species recolonized island I Overall species composition was very different 0 O O O Week 9 Community Ecology BIO 20C Baldo Marinovic Kicking It Up a Notch o Simberloff 1976 0 Reduce island habitat size I Remove portion of mangrove trees 0 Compared species number change to unaltered island 0 Result smaller islands had few species Community Dmamics 0 Two views 0 Frederick Clements I Saw communities as superorganisms I Species worked cooperatively 0 Henry Gleason I Community collection of individual species with unique physiological tolerance I Individualistic view of community dynamics m 0 Recovery of a community after disturbance 0 Primary succession I All species soilpropagulas removed I eg glacier lava ow 0 Secondary succession I Some or all species removed but soilpropagulas left intact I eg re strong storms Sequence of Succession 0 Early succession community I Pioneer species high dispersal fast growing short lived 0 Late successional community I Long lived slow growing superior competitors 0 Climax community stable persistent community Two views of Succession o Clements I Primary succession like embryology I Secondary succession like wound healing I Succession follows order sequence of distinct communities seres o Gleason I Succession result of individual species response I Community sequence can vary following disturbance Species Interaction During Succession o Facilitation I One species make conditions more tolerable for another 0 Inhabitation I One species prevent the establishment of another 0 Tolerance I Existing species do not in uence the arrival of a new species Who Was Right 0 Initially Clement view widely accepted Week 9 Community Ecology BIO 20C Baldo Marinovic 0 Data increasingly support Gleason s view I Keystone species Modern View of Succession 0 Outcome of succession depends on 3 components I Trait of species involved 0 Who can live there I Species interaction 0 Who does What to Whom I Environment circumstances 0 What happened before or next door Qse In Point Glacier Bay 0 Natural experiment 0 Glacier retreating for 200 years 0 Provide opportunity to compare different successional communities Mt Accounts For the Different Pattern of Succession 0 Species trait 0 Species interaction 0 Historicalenvironment context Species Trait o Hemlock seedlings I Need organic material I Can tolerate shade but bright sunlight I Hemlock has limited dispersal capability Species Interaction o Alder I Facilitate grth of Sitka spruce via symbiotic bacteria in root nodule I Spruce grow faster in presence of alder o Shading of alder I Reduces grth of spruce I Eventually spruce outshades alder mstoricgl Context 0 Ice levels higher than tree line in upper glacier o No source of tree recruits in upper valley
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