COMPETITION Krebs cpt 12 pages 179 205 Biol
COMPETITION Krebs cpt. 12; pages 179 -205 Biol 303 Competition 1
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 Biol 303 Competition 2 3/2 power law of self thinning
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) Biol 303 Competition 3
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 Biol 303 Competition 4
COMPETITION occurs 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. Biol 303 Competition 5
COMPETITION ESSENTIAL COMPONENTS: 1. Two or more organisms that require a single resource that is in short supply. 2. The supply of that resource must be affected by its use by the consumer: • Food supply • Pollinators • Nest space etc. Biol 303 Competition 6
COMPETITION ESSENTIAL COMPONENTS: 1. Two or more organisms that require a single resource that is in short supply. 2. The supply of that resource must be affected by its use by the consumer: • Food supply • Pollinators • Nest space etc. Biol 303 Competition 7
COMPETITION 3. The contest for that resource reduces the fitness of one or both competitors. 4. Competing organisms may be the: • Same INTRASPECIFIC • Different INTERSPECIFIC 5. Organisms may compete by: • EXPLOITATION • INTERFERENCE Biol 303 Competition 8
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 Biol 303 Competition 9 3/2 power law of self thinning
Flax Biol 303 Competition 10
Balsam Fir Biol 303 Competition 11
Biol 303 Competition 12
Keyhole limpet Biol 303 Competition 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 Biol 303 Competition 14 3/2 power law of self thinning
Corn cockle Biol 303 Competition 15
Ryegrass Biol 303 Competition 16
Ryegrass Biol 303 Competition 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 Biol 303 Competition 18 3/2 power law of self thinning
Bromus (rescue grass) Biol 303 Competition 19
Rana tigrina Biol 303 Competition 20
Buck wheat Biol 303 Competition 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 Biol 303 Competition 22 3/2 power law of self thinning
Biol 303 Competition 23
Biol 303 Competition 24
Biol 303 Competition 25
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) Biol 303 Competition 26
LOTKA - VOLTERRA COMPETITION MODELS Biol 303 Competition 27
READING FOR THESE LECTURES: Krebs: Scan cpt. 11, especially pp. 160 -162 Krebs: Cpt. 12, especially 180 -184 Biol 303 Competition 28
Start with the logistic equation. In populations that have overlapping generations, the logistic curve is described by the logistic equation (Krebs 161): Biol 303 Competition 29
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) Biol 303 Competition 30
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: (N 1 + (N 2/10)) species 1 individuals 1/10 (in the case of this example) is the COMPETITION COEFFICIENT and is called . Biol 303 Competition 31
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 p 182) Biol 303 Competition 32
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 N 2 converts N 2 to a number of “N 1 equivalents” (Krebs p 181, eq. 12. 3) Biol 303 Competition 33
Removing the inner brackets: Krebs p 181 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. Biol 303 Competition 34
For species 2, we have the equivalent formulation: Krebs p 181 These two constitute the Lotka-Volterra model - a logistic model for two species. Biol 303 Competition 35
Now we wish to determine the conditions under which each population would be at equilibrium, that is the conditions under which d. N/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 p 182 -183) Biol 303 Competition 36
For Species 1 Along the isocline d. N 1/dt = 0 All the space for species 1 is used up when there are: - K 1 ind. of sp. 1 - K 1/ ind. of sp. 2 i. e. d. N 1/dt = 0 Krebs: Fig 12. 1 Biol 303 Competition p 182 37
For Species 2 Along the isocline d. N 2/dt = 0 All the space for species 2 is used up when there are: - K 2 ind. of sp. 2 - K 2/ ind. of sp. 1 i. e. d. N 2/dt = 0 Biol 303 Competition Krebs: Fig 12. 2 38
Krebs: Fig 12. 3 p 183 Biol 303 Competition 39
TROUT 2 nd species K 1 = 400 K 2 = 300 =4 = 0. 5 K 1 / = 100 K 2 / = 600 Biol 303 Competition 40
TROUT 2 nd species K 1 = 400 K 2 = 300 =4 = 0. 5 K 1 / = 100 K 2 / = 600 Biol 303 Competition 41
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) Biol 303 Competition 42
THE RESOURCE RATIO HYPOTHESIS (OF PLANT SUCCESSION) David TILMAN Biol 303 Competition 43
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 Biol 303 Competition 44
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, CO 2, light, nutrients • Ratios of resources (light and nitrogen) Biol 303 Competition 45
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, CO 2, light, nutrients • Ratios of resources (light and nitrogen) Biol 303 Competition 46
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, CO 2, light, nutrients • Ratios of resources (light and nitrogen) Biol 303 Competition 47
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, CO 2, light, nutrients • Ratios of resources (light and nitrogen) Biol 303 Competition 48
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, CO 2, light, nutrients • Ratios of resources (light and nitrogen) Biol 303 Competition 49
Resource Ratio Hypothesis • • One species and one resource One species and two resource Two species and two resources Multiple species and two resources Biol 303 Competition 50
Resource Ratio Hypothesis • • One species and one resource One species and two resource Two species and two resources Multiple species and two resources Biol 303 Competition 51
Resource Ratio Hypothesis • • One species and one resource One species and two resource Two species and two resources Multiple species and two resources Biol 303 Competition 52
Resource Ratio Hypothesis • • One species and one resource One species and two resource Two species and two resources Multiple species and two resources Biol 303 Competition 53
Resource Ratio Hypothesis • • One species and one resource One species and two resource Two species and two resources Multiple species and two resources Biol 303 Competition 54
Population growth [death] rate Species A birt h mortalit y 0 1 2 3 4 5 6 7 8 9 10 R* Resource level Biol 303 Competition [1] 55
OPTIMAL FORAGING Any (plant) species will absorb resources in the proportion by which it is equally limited by them. This proportion is the ratio of the two values of R* R* = the Requirement Value i. e. the level of resource required to hold a population (of a species) at equilibrium: i. e. where birth rate = death rate Biol 303 Competition 56
OPTIMAL FORAGING Any (plant) species will absorb resources in the proportion by which it is equally limited by them. This proportion is the ratio of the two values of R* R* = the Requirement Value i. e. the level of resource required to hold a population (of a species) at equilibrium: i. e. where birth rate = death rate Biol 303 Competition 57
OPTIMAL FORAGING Any (plant) species will absorb resources in the proportion by which it is equally limited by them. This proportion is the ratio of the two values of R* R* = the Requirement Value i. e. the level of resource required to hold a population (of a species) at equilibrium: i. e. where birth rate = death rate Biol 303 Competition 58
Population growth [death] rate Species A birt h mortalit y 0 1 2 3 4 5 6 7 8 9 10 R* Resource level Biol 303 Competition [2] 59
Population growth [death] rate Species B birt h mortalit y 0 1 2 3 4 5 6 7 8 R* 9 10 Biol 303 Competition Resource level 60
SPECIES A 3 0 1 2 3 4 5 6 7 8 9 10 SPECIES B Population growth [death] rate 1 4 0 1 2 3 4 5 6 7 8 9 10 Resource 1 Biol 303 Competition 0 1 2 3 4 5 6 7 8 9 10 2 0 1 2 3 4 5 6 7 8 9 10 Resource 2 61
Resource Ratio Hypothesis • • One species and one resource One species and two resource Two species and two resources Multiple species and two resources Biol 303 Competition 62
Species A 8 7 Births [A] > Deaths [A] Population increases Resource [2] 6 5 4 Zero Net Growth Isocline [ZNGI]: Births = Deaths 3 2 Births [A] < Deaths [A] Population declines 1 0 1 2 3 4 5 6 7 8 9 10 Resource [1] Biol 303 Competition 63
Species B 8 7 Resource [2] 6 Births [B] > Deaths [B] Population increases 5 4 3 2 Zero Net Growth Isocline [ZNGI]: Births = Deaths Births [B] < Deaths 1 [B] Population declines 0 1 2 3 4 5 6 7 8 9 10 Resource [1] Biol 303 Competition 64
Resource Ratio Hypothesis • • One species and one resource One species and two resource Two species and two resources Multiple species and two resources Biol 303 Competition 65
Species A and B 8 7 Resource [2] 6 5 4 ZNGI [A] ZNGI [B] 3 2 1 0 1 2 3 4 5 6 7 8 9 10 Resource [1] Biol 303 Competition 66
8 A B 7 A wins Resource [2] 6 5 Both species can grow 4 3 2 1 Neither species can survive B wins ZNGI [A] ZNGI [B] 0 1 2 3 4 5 6 7 8 9 10 Resource [1] Biol 303 Competition 67
8 A B 7 Resource [2] 6 5 4 ZNGI [A] 3 2 ZNGI [B] 1 0 1 2 3 4 5 6 7 8 9 10 Resource [1] Biol 303 Competition 68
8 A B 7 A wins Resource [2] 6 5 A & B coexist 4 3 2 1 Neither species can survive B wins ZNGI [A] ZNGI [B] 0 1 2 3 4 5 6 7 8 9 10 Resource [1] Biol 303 Competition 69
8 A B 7 A wins Resource [2] 6 5 A & B coexist ? 4 3 2 1 Neither species can survive B wins ZNGI [A] ZNGI [B] 0 1 2 3 4 5 6 7 8 9 10 Resource [1] Biol 303 Competition 70
8 A B 7 Resource [2] 6 5 4 ZNGI [A] 3 2 ZNGI [B] 1 0 1 2 3 4 5 6 7 8 9 10 Resource [1] Biol 303 Competition 71
8 A B 7 Resource [2] 6 5 4 ZNGI [A] 3 2 ZNGI [B] 1 0 1 2 3 4 5 6 7 8 9 10 Resource [1] Biol 303 Competition 72
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) Biol 303 Competition 73
Salamanders in Appalachian Mts. (S. Carolina) p 80 -81 Plethodon glutinosus Plethodon jordani Biol 303 Competition 74
Bedstraws in Europe Galium sylvestre (calcareous) Galium saxatile (acidic) Biol 303 Competition 75
Krebs Fig. 7. 9; p 95 Chthamalus Balanus Biol 303 Competition 76
Paramecium Biol 303 Competition 77
GENERAL FEATURES • • Species do compete in nature Competition may cause exclusion Competition may lead to coexistence Is frequently asymmetric Biol 303 Competition 78
4. CONSEQUENCES OF COMPETITION i. Ecological a. distribution a. barnacles (Fig 7. 9; pages 94 -95) b. Typha c. competitive release ii. Evolutionary a. niche differentiation (pages 190 -192; Fig 12. 20) b. competitive ability (pages 199 -201) c. character displacement (page 201 -202; Fig. 79 Biol 303 Competition 12. 23)
Krebs Fig. 7. 9; p 95 Chthamalus Balanus Biol 303 Competition 80
Bullrush Cattail Biol 303 Competition 81
Biol 303 Competition 82
4. CONSEQUENCES OF COMPETITION i. Ecological a. distribution barnacles (Fig 7. 9; pages 94 -95) Typha competitive release ii. Evolutionary a. niche differentiation (pages 190 -192; Fig 12. 20) b. competitive ability (pages 199 -201) c. character displacement (page 201 -202; Fig. 83 12. 23) Biol 303 Competition
Krebs Fig. 12. 20, p 198 Biol 303 Competition 84
15 White clover Biol 303 Competition 85
Krebs Fig. 12. 22, p 202 Biol 303 Competition 86
Biol 303 Competition 87
Krebs Fig. 12. 23, p 202 Darwin’s finches, Geospiza Biol 303 Competition 88
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