Competition

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Competitive Interactions

Back 1

- Interactions in which two species negatively influence each other's population growth rates and depress each other's population sizes through their acquisition for resources
- Exploitive, interference, and prermptive

Front 2

Exploitive Competition

Back 2

- One pop depressed another through use of shared resources

Front 3

Interference Competition

Back 3

- When an individual or population behaves in a way that reduces the exploitation efficiency of another individual or pop
- through direct behavior

Front 4

Pre-emptive competition

Back 4

- Organism competes for space as a limited resources
- Elements of EC and IC
- space is a renewable resource

Front 5

Intra-specific competition

Back 5

-Competition that occurs among members of the same species
- Ex: LGM, growth rate diminishes as pop becomes more crowded

Front 6

Inter specific competition

Back 6

- Occurs between individuals or 2 or more different species

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Self-thinning

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- More and more biomass is composed of fewer and fewer individuals
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Front 8

Niche

Back 8

- Summary of the environmental factors that influence the growth, survival, and reproduction of a species

Front 9

Competitive Exclusion Principle

Back 9

- States that 2 species with identical niches cannot coexist indefinitely due to inter-specific competition

Front 10

Ghost of competition past

Back 10

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Competition coefficients

Back 11

- Measure the effect of species 2 on growth of species 1.
- relative importance, per individual of inter-specific and intra-specific competition.

Front 12

Equilibrium solutions

Back 12

- Finds equilibrium pop density of one species in the prescience of another

Front 13

State Space

Back 13

- Graph that compares the abundance of. 2 species in relation to each other

Front 14

Character Displacement

Back 14

- The process of evolution toward niche divergence in the face of competition

Front 15

Niche Concept

Back 15

- Fundamental niche: hyper volume and physical conditions that a species may live
- Realized Niche: the actual niche of a species whose distribution is limited by biotic interactions like competition, predation, disease, and parasitism

Front 16

The Lotka-Volterra (L-V) competition model

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Front 17

Intra-specific competition among plants and plant hoppers

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- Plant hoppers: enclosed in different densities. At high densities- reduced survivorship, decreased body length and increased development time. Attributed to reduced food quality.

Front 18

Evidence of self-thinning in plants

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- Biomass plotted against density, plant pop declines more rapidly as biomass increases
- average weight against density, slope of line averages -3/2 called the -3/2 self thinning rule

Front 19

Interference competition among terrestrial isopods

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-2 densities studied
- given unlimited food
- higher density had lower survival which is attributed to cannalbalism
- IC even in the absence of obvious resource limitation

Front 20

Niche Concept; feeding niches of Galapagos finches

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- Drought caused all soft seeds to be depleted so only finches with bigger beaks survived

Front 21

Empirical examples of competition: Paramecia

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- 2 species in prescience of 2 diff concentrations of food
- observed sigmoid all curve
- K was lower with half concentration of food
- with a species in isolation, K depends on intra specific competition
- when grown together, the species with a higher carrying capacity survived and the other died

Front 22

Empirical examples of competition: Flour beetles

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- Tested inter- specific competition in varying environmental conditions
- in hot/wet cond., T. castaneum excludes T. confusum
- in cool/dry, confusum excludes castaneum
- in intermediate cond., competition is not predictable

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Empirical examples of competition: Plants

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- Competition resulting in desperation of 2 plant species on different soils
- sylvestre found in basic soils, saxatile found in acidic soils
- sylvestre overgrew and eliminated saxatile in basic soil
- on acidic soils growth for both species was low. Saxatile was competitively dominant but did not exclude sylvestre

Front 24

Empirical examples of competition: Barnacles

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- Niche overlap and competition
- 2 species, balanus and chthamalus
- balanus in middle and lower intertidal zones
- chthamalus. Upper zones but larvae settle in zones below adults
- Results middle intertidal: CS survived at higher rates in absence of Bb
- Results upper intertidal: removal of BP had no effect on C survival since BP concentrations were too low to compete
- C is excluded from middle zone by inter specific competition with Bb
- C can live in broader zone without Bb ( fundamental niche), but is restricted by Bb (realized niche)

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4 cases of state space graphs

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- Case 1: species 1 wins . Species 1 isocline is above and parallel to species 2. K1 is on X axis
- Case 2: species 2 wins, S2 isocline above and parallel to S1. K2 is on Y axis
- Case 3: coexistence in stable equilibrium, isoclines are crossed and position vectors point to equilibrium
- Case 4: competitive exclusion in an unstable equilibrium, isoclines crossed, lower right and upper left move away from equilibrium