biol 4120: principles of ecology lecture 12: interspecfic competition dafeng hui room: harned hall...
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BIOL 4120: Principles of EcologyBIOL 4120: Principles of Ecology
Lecture 12: Interspecfic Lecture 12: Interspecfic competitioncompetition
Dafeng HuiDafeng Hui
Room: Harned Hall 320Room: Harned Hall 320
Phone: 963-5777Phone: 963-5777
Email: [email protected]: [email protected]
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OutlineOutline (chapter 13)(chapter 13)13.1 Interspcific competition13.1 Interspcific competition13.2 Lotka-Volterra model13.2 Lotka-Volterra model13.3 Laboratory experiments support L-V model13.3 Laboratory experiments support L-V model13.4 Competitive exclusion principle13.4 Competitive exclusion principle13.5 Competition is influenced by nonresource factos13.5 Competition is influenced by nonresource factos13.6 Temporal variation in environmental factors13.6 Temporal variation in environmental factors13.7 Multiple resources13.7 Multiple resources13.8 Competition change along environmental 13.8 Competition change along environmental
gradientsgradients13.9 Niches of species13.9 Niches of species13.10 Resource partitioning13.10 Resource partitioning13.11 Competition influence national selection13.11 Competition influence national selection13.12 Competition involves biotic and abiotic factors13.12 Competition involves biotic and abiotic factors
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13.1 Interspecific competition A relationship in which the populations of
two or more species are affected adversely (--)
Seek a common resource in short supply Food; Living space; etc An example: squirrels, mice, deer, various birds
competing for acorns Model One. Two forms
• Exploitation• Interference
Model Two. Six forms• Consumption• preemption• Overgrowth• Chemical interaction• Territorial• encounter
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Consumption• Utilization of a shared resource by 2 species
Preemption• Occupation of a site by 1st organism stops occupation by 2nd
organism Usually sessile organisms
Overgrowth• Where organism covers another preventing access to a
resource. Trees shade other plants Chemical interaction
• Release of toxin to inhibit or kill competing organisms Allelopathy in plants
Territorial• Behavioral exclusion of 1st organism by 2nd organism defending
territory Encounter
• Non-territorial encounters cause a negative effect on one or both species
Lion and wild dogs over a antelope kill
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12.2 Possible outcomes of 12.2 Possible outcomes of Interspecific competitionInterspecific competition
When two species compete, how many outcomes?When two species compete, how many outcomes?1.1. Species 1 wins, species 2 losesSpecies 1 wins, species 2 loses2.2. Species 1 loses, species 2 winsSpecies 1 loses, species 2 wins3.3. Coexistence (stable equilibrium)Coexistence (stable equilibrium)4.4. Competition can go wither way (unstable Competition can go wither way (unstable
equilibrium) equilibrium)
These competition results can be described by Lotka-These competition results can be described by Lotka-Volterra model.Volterra model.
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Lokta-Volterra ModelLokta-Volterra Model
Derived from logistic equationDerived from logistic equation
Add influence of another species (a competition Add influence of another species (a competition component)component)
alpha(2,1)=alpha
Alpha(1,2)=beta
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Lokta-Volterra ModelLokta-Volterra Model
αN2 and βN1: effect of interspecific competition, namely, where α and β per capita effects of competition
In term of resource use, an individual of species 2 is equal to α individuals of species 1
No interspecific competition, then α and β are 0 and normal growth to carrying capacity
Interspecific competition is density dependent
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(a) Species 1 alone or no competition
Diagonal line is zero growth isocline
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(b) Species 2 alone or no competition
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(c) Species 1 inhibits growth of species 2 and latter goes extinct
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(d) Species 2 inhibits growth of species 1 and latter goes extinct
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(e) Unstable situation, both inhibit in a density dependent manner. Depending on initial density,
either can make other extinct
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(f) Each species inhibits its own population growth more than competitor. Neither can
eliminate competitor
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13.3 Laboratory experiments support the Lotka-Volterra Equations
Russian biologist G.F. Gause
Competition between two species
P. aurelia has a high growth rate and can tolerate a higher population density
Two Paramecium (unicellular ciliated protozoan)One with higher rate of growth: Extinction of slower growerWith different food supplies:
Coexistence
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Diatom experiment
David Tilman, University of Minnesota
Asterinella formosa (Af) and Synedra ulna(Su) compete for silica for the formation of cell walls.
Adequate silica, coexist
Insufficient silica, Su drove Af to extinction
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13. 4 Competitive exclusion principle
Complete competitors can not coexist. One species must go extinct
Complete competitions: two species that live in the same place and possess exactly the same ecological requirements.
Assumptions:• Exactly the same resource requirement
(no more, no less)• Environmental conditions remain
constant Most of the time species can coexist
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13.5 Competition is influenced by non-resource factors
Many non-resource factors would influence the outcomes of the competition. For example, space, light.
Favor species with high photosynthetic rate, allocate C to height growth and leaves production (fast-grow species)
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Patterns of seed germination along T gradient
Fakhri Bazzaz, Harvard University (Retired)
Five annual species
T influences the germination, thus seedling establishment, resource competition and structure of community.
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13.6 Temporal variation in environment influences competition
interactions As environmental
conditions vary, the competition advantages change
No one species can reach sufficient density to displace its competitors;
Thus lead to co-exist.
Shift in dominant grass species caused by moisture
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13.7 Competition occurs for multiple resources
Systems are not simple one resource situations• Usually competition for more than one resource
Territorial defense against wide range of other species Plants
• Monoculture• Root competition
Skeleton weed reduce by 35%• Shoot competition
Skeleton weed reduced by 53%• Root and shoot competition
Skeleton weed reduced by 69%• Thus clover superior to skeleton weed for all resources
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Effect of interspecific competition across an environmental gradient
Note changes in response when in mixture
13.8 Relative competition abilities change along environmental gradients
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Similar effect for summer annuals and moisture gradient
Also happens in nature with water, anoxia and salt stress in a salt marsh
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ChipmunksAlpine
Cold tolerantLodgepole
Most aggressiveNeeds shade
Yellow Pineaggressive
LeastHeat tolerant
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13.9 Niche of a species Concepts of niche
• describes how an organism or population responds to the distribution of resources and competitors (e. g., by growing when resources are abundant, and predators, parasites and pathogens are scarce) and how it in turn alters those same factors.
• dimensions of a niche: represent different biotic and abiotic variables.
• These factors may include descriptions of the organism's life history, habitat, trophic position (place in the food chain), and geographic range.
• According to the competitive exclusion principle, no two species can occupy the same niche in the same environment for a long time.
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Concepts of niche• Fundamental niche: range of conditions
and resources a species can use to survive and reproduce under no interference by other species
• Realized niche: portion of fundamental niches that a species actually exploits as a result of interactions with other species (e.g., competition).
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ExamplesDistribution of twp species of cattail (Typha latifolia and T. angustifolia)
Fundamental Niche:
Tl: water depth: -20~ 70 cm
Ta: -20~110 cm
Realized Niche:
Tl: -20 ~ 70 cm
Ta: 20 ~ 110 cm (Changes)
Niche overlap: 20-70 cm
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Fundamental and realized niches
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Competition release
A species expands its niche in response to the removal of a competitor
Two examplesResponse of Stipa neomexicana plantsCommercial whaling in Antarctic Ocean
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Response of Stipa neomexicana plants
Jessica Gurevitch
University of New York at Stony Brook
Stipa: C3 perennial grass
Semi-arid grassland in Arizona
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Commercial whaling in Antarctic Ocean
Baleen whales: 1 million a century ago
eat Antarctic krill (4% of body weight)
Now, less than 200,000
Other krill-dependent predators such as seals and penguins have been found greatly increased in abundance Competition release due to the
dramatic decrease in baleen whale population
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13.10 Resource partitioning “Complete competitors can not co-exist” Why did not the best competitor force
others out? Co-existing species must be different in
the use of resources Niche differentiation: differences in the
range of resources used or environmental tolerance
Examples:• Plants grow together• Animals share the same habitat
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Resource partitioning
Use water and nutrients at different depths
Spatial differentiation.
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Resource partitioning
Size (diameter) of canine teeth for small cat that co-occur in Israel. Size is correlated with size of prey selected by different species.
Morphological differentiation.
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Another example Seven Anolis lizards in tropical rainforest Share common food needs — mainly insects. They avoid competition by occupying different
sections of the rainforest• the leaf litter floor• shady branches
All resources are subject to partitioning, such as space, food, nesting sites.
This minimizes competition between similar species.
(Temporal differentiation.)
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Niche dimensions
Rarely do two or more species possess exactly the same combination of requirement. Species may overlap on one D of the niche, but not on another.
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13.11 Competition can influence natural selection
Competition is at the heart of Darwin’s theory of natural selection. Characteristics that enable an organisms to reduce competition will function to increase fitness.
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Character displacement
The outcome of the competition was a shift in feeding niches. When the shift involves features of the species’ morphology, behavior, or physiology
The process of evolution toward niche divergence in the face of competition
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13.12 Competition involves both biotic and abiotic factors
Removal experiment is an effective method to study competition
Hidden treatment effects: removal changes space, light, soil temperature, and moisture, evaporation.
Competition is a complex interaction involving a variety of environmental factors that directly influence survival, growth, and reproduction.
Outcome of competition may differ markedly under different set of environmental conditions.
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EndEnd
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FACILITIES MANAGEMENT FACILITIES MANAGEMENT DEPARTMENTDEPARTMENT
DEPARTMENTAL NOTIFICATIONDEPARTMENTAL NOTIFICATION
LOCATION LOCATION CAMPUS-WIDECAMPUS-WIDE PROJECTPROJECT IN RESPONSE TO THE DROUGHT AND HEAT THIS SUMMER, IN RESPONSE TO THE DROUGHT AND HEAT THIS SUMMER,
ALL TREES THAT ALL TREES THAT HAVE EXCEEDED THEIR PERMANENT HAVE EXCEEDED THEIR PERMANENT WILTING POINTS WILL WILTING POINTS WILL BE REMOVEDBE REMOVED
DURATION DURATION TWO DAYS, OCTOBER 15-16, 2007 (FALL BREAK)TWO DAYS, OCTOBER 15-16, 2007 (FALL BREAK)
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ScienceScience 12 October 2007:12 October 2007:Vol. 318. no. 5848, pp. 268 – 271Vol. 318. no. 5848, pp. 268 – 271
ReportsReports
Functional Divergence of Former Alleles in Functional Divergence of Former Alleles in an Ancient Asexual Invertebratean Ancient Asexual Invertebrate
Natalia N. Pouchkina-Stantcheva, et al. Natalia N. Pouchkina-Stantcheva, et al. Theory suggests it should be difficult for asexual Theory suggests it should be difficult for asexual
organismsorganisms to adapt to a changing environment to adapt to a changing environment because genetic diversitybecause genetic diversity can only arise from can only arise from mutations accumulating within direct mutations accumulating within direct antecedentsantecedents and not through sexual exchange.and not through sexual exchange.
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ScienceScience Reports (cont.)Reports (cont.) Functional Divergence of Former Alleles in Functional Divergence of Former Alleles in
an Ancient Asexual Invertebratean Ancient Asexual Invertebrate Natalia N. Pouchkina-Stantcheva, et al. Natalia N. Pouchkina-Stantcheva, et al. In an asexual microinvertebrate,In an asexual microinvertebrate, the bdelloid the bdelloid
rotifer, we have observed a mechanism by whichrotifer, we have observed a mechanism by which
such organisms could acquire the diversity such organisms could acquire the diversity needed for adaptation.needed for adaptation. Gene copies most likely Gene copies most likely representing former alleles have divergedrepresenting former alleles have diverged in in function so that the proteins they encode play function so that the proteins they encode play complementarycomplementary roles in survival of dry conditions. roles in survival of dry conditions.
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ScienceScience Reports (cont.)Reports (cont.) Functional Divergence of Former Alleles in Functional Divergence of Former Alleles in
an Ancient Asexual Invertebratean Ancient Asexual Invertebrate Natalia N. Pouchkina-Stantcheva, et al. Natalia N. Pouchkina-Stantcheva, et al. One protein prevents desiccation-sensitiveOne protein prevents desiccation-sensitive
enzymes from aggregating during drying, enzymes from aggregating during drying, whereas its counterpartwhereas its counterpart does not have this does not have this activity, but is able to associate with activity, but is able to associate with phospholipidphospholipid bilayers and is potentially involved bilayers and is potentially involved in maintenance of membranein maintenance of membrane integrity. The integrity. The functional divergence of former alleles observedfunctional divergence of former alleles observed
here suggests that adoption of asexual here suggests that adoption of asexual reproduction could itselfreproduction could itself be an evolutionary be an evolutionary mechanism for the generation of diversity.mechanism for the generation of diversity.
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Al Gore, UN panel share Al Gore, UN panel share Nobel for Peace Nobel for Peace
Al Gore &Al Gore &
U.N.'s IPCC (Intergovernmental Panel U.N.'s IPCC (Intergovernmental Panel on Climate Change)on Climate Change)
For Global warmingFor Global warming