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COMPETITION

COMPETITION. Krebs cpt. 12; pages 179-205. 1. DEFINITIONS 2. INTRASPECIFIC COMPETITION i. Effects of density on individuals a. growth  Linum usitatissimum  Limpets b. form and reproduction  Corn cockle  Lolium perenne genets and ramets (pages 117-119)

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COMPETITION

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  1. COMPETITION Krebs cpt. 12; pages 179-205

  2. 1. DEFINITIONS 2. INTRASPECIFIC COMPETITION i. Effects of density on individuals a. growth Linum usitatissimum  Limpets b. form and reproduction Corn cockle Lolium perenne genets and ramets (pages 117-119) ii. Effects of density on populations a. growth (rate)  Law of constant final yield  Growth rate of Rana tigrina b. mortality  3/2 power law of self thinning

  3. 3. INTERSPECIFIC COMPETITION i. Theory  Lotka-Volterra (pages 180-182)  Tilman (pages 182-185) ii. Examples (pages 185-199)  salamanders (pages 80-81)  bedstraws  barnacles(Fig 7.9; pages 94-95)  Yeast (pages 187-189); Paramecium (page 190)  diatoms (Fig. 12.6; page 186)

  4. 4. CONSEQUENCES OF COMPETITION i. Ecological a. distribution barnacles (Fig 7.9; pages 94-95) Typha ii. Evolutionary a. niche differentiation (pages 190-192; Fig 12.20) b. competitive ability (pages 199-201) c. character displacement (page 201-202) d. competitive release

  5. COMPETITIONoccurs when an organism uses more energy to obtain, or maintain, a unit of resource due to the presence of other individuals than it would otherwise do.

  6. COMPETITION • ESSENTIAL COMPONENTS: • Two or more organisms that require a single resource that is in short supply. • The supply of that resource must be affected by its use by the consumer: • Food supply • Pollinators • Nest space etc.

  7. COMPETITION • ESSENTIAL COMPONENTS: • Two or more organisms that require a single resource that is in short supply. • The supply of that resource must be affected by its use by the consumer: • Food supply • Pollinators • Nest space etc.

  8. COMPETITION • The contest for that resource reduces the fitness of one or both competitors. • Competing organisms may be the: • Same INTRASPECIFIC • Different INTERSPECIFIC • Organisms may compete by: • EXPLOITATION • INTERFERENCE

  9. 1. DEFINITIONS etc. 2. INTRASPECIFIC COMPETITION i. Effects of density on individuals a. growth Linum usitatissimum  Limpets b. form and reproduction Corn cockle Lolium perenne genets and ramets (pages 117-119) ii. Effects of density on populations a. growth (rate)  Law of constant final yield  Growth rate of Rana tigrina b. mortality  3/2 power law of self thinning

  10. Flax

  11. Balsam Fir

  12. Keyhole limpet

  13. 1. DEFINITIONS etc. 2. INTRASPECIFIC COMPETITION i. Effects of density on individuals a. growth Linum usitatissimum  Limpets b. form and reproduction Corn cockle Lolium perenne genets and ramets (pages 117-119) ii. Effects of density on populations a. growth (rate)  Law of constant final yield  Growth rate of Rana tigrina b. mortality  3/2 power law of self thinning

  14. Corn cockle

  15. Ryegrass

  16. Ryegrass

  17. 1. DEFINITIONS etc. 2. INTRASPECIFIC COMPETITION i. Effects of density on individuals a. growth Linum usitatissimum  Limpets b. form and reproduction Corn cockle Lolium perenne genets and ramets (pages 117-119) ii. Effects of density on populations a. growth (rate)  Law of constant final yield  Growth rate of Rana tigrina b. mortality  3/2 power law of self thinning

  18. Bromus (rescue grass)

  19. Rana tigrina

  20. Buck wheat

  21. 1. DEFINITIONS etc. 2. INTRASPECIFIC COMPETITION i. Effects of density on individuals a. growth Linum usitatissimum  Limpets b. form and reproduction Corn cockle Lolium perenne genets and ramets (pages 117-119) ii. Effects of density on populations a. growth (rate)  Law of constant final yield  Growth rate of Rana tigrina b. mortality  3/2 power law of self thinning

  22. 3. INTERSPECIFIC COMPETITION i. Theory Lotka-Volterra (pages 180-182)  Tilman (pages 182-185) ii. Examples(pages 185-199)  salamanders (pages 80-81)  bedstraws  barnacles(Fig 7.9; pages 94-95)  Yeast (pages 187-189); Paramecium (page 190)  diatoms (Fig. 12.6; page 186)

  23. LOTKA - VOLTERRA COMPETITION MODELS

  24. READING FOR THESE LECTURES: Krebs: Scan cpt.11, especially pp. 160-162 Krebs: Cpt. 12, especially 180-184

  25. Start with the logistic equation. In populations that have overlapping generations, the logistic curve is described by the logistic equation (Krebs 161):

  26. The Lotka-Volterra equations, which describe competition between organisms, are based on the logistic curve. Each of these two equations shows the effect of intra-specific (within a species) competition only. (Krebs 180)

  27. Suppose 10 individuals of species 2 have the same inhibitory effect on an individual of species 1 as does a single individual of species 1. Then the TOTAL competitive effects ON species 1 (intra and inter-specific) will be equivalent to: (N1 + (N2/10)) species 1 individuals 1/10 (in the case of this example) is the COMPETITION COEFFICIENT and is called .

  28. The COMPETITION COEFFICIENT …. , is the per capita competitive effect ON species 1 OF species 2. ,is the per capita competitive effect ON species 2 OF species 1 is. (see footnote in Krebs p182)

  29. So the total inhibitory effect of individuals of species 1 (intra-specific force) and species 2 (inter-specific force) on the growth of population 1 will be: in which N2 converts N2 to a number of “N1 equivalents” (Krebs p181, eq. 12.3)

  30. Removing the inner brackets: Krebs p181 Thus there are two “sources of slowing” for the growth of species 1: 1. its own density, and 2. the density of the second species weighted by the second species’ relative impact.

  31. For species 2, we have the equivalent formulation: Krebs p181 These two constitute the Lotka-Volterra model - a logistic model for two species.

  32. Now we wish to determine the conditions under which each population would be at equilibrium, that is the conditions under which dN/dt would be zero. In some cases only one population will be able to achieve an equilibrium stable density, and in other cases both can. (Krebs p182-183)

  33. For Species 1 • All the space for species 1 is used up when there are: • K1 ind. of sp.1 • K1/ind. of sp. 2 • i.e. dN1/dt = 0 Along the isocline dN1/dt = 0 Krebs: Fig 12.1 p182

  34. All the space for species 2 is used up when there are: • K2 ind. of sp.2 • K2/ind. of sp. 1 • i.e. dN2/dt = 0 For Species 2 Along the isocline dN2/dt = 0 Krebs: Fig 12.2 p182

  35. Krebs: Fig 12.3 p183

  36. 3. INTERSPECIFIC COMPETITION i. Theory Lotka-Volterra (pages 180-182) Tilman (pages 182-185) ii. Examples(pages 185-199)  salamanders (pages 80-81)  bedstraws  barnacles(Fig 7.9; pages 94-95)  Yeast (pages 187-189); Paramecium (page 190)  diatoms (Fig. 12.6; page 186)

  37. THE RESOURCE RATIO HYPOTHESIS (OF PLANT SUCCESSION) David TILMAN

  38. TILMAN, D. 1985. The resource-ratio hypothesis of plant succession.American Naturalist 125:827-852 READING FOR THESE LECTURES: Krebs: selections from pp. 182-186

  39. Evelyn G. HUTCHINSON: • Why are there so many kinds of animals? • Because there are so many different kinds of food to eat. • Why are there so many kinds of plants? • Water, CO2, light, nutrients • Ratios of resources (light and nitrogen)

  40. Evelyn G. HUTCHINSON: • Why are there so many kinds of animals? • Because there are so many different kinds of food to eat. • Why are there so many kinds of plants? • Water, CO2, light, nutrients • Ratios of resources (light and nitrogen)

  41. Evelyn G. HUTCHINSON: • Why are there so many kinds of animals? • Because there are so many different kinds of food to eat. • Why are there so many kinds of plants? • Water, CO2, light, nutrients • Ratios of resources (light and nitrogen)

  42. Evelyn G. HUTCHINSON: • Why are there so many kinds of animals? • Because there are so many different kinds of food to eat. • Why are there so many kinds of plants? • Water, CO2, light, nutrients • Ratios of resources (light and nitrogen)

  43. Evelyn G. HUTCHINSON: • Why are there so many kinds of animals? • Because there are so many different kinds of food to eat. • Why are there so many kinds of plants? • Water, CO2, light, nutrients • Ratios of resources (light and nitrogen)

  44. Resource Ratio Hypothesis • One species and one resource • One species and two resource • Two species and two resources • Multiple species and two resources

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