Chap. 9 Competition

Chap. 9 Competition

鄭先祐生態主張者 Ayo 工作室

Ecology 2001 Chap. 9 2

Part III Community EcologyChap. 9 CompetitionChap.10 PredationChap.11 Community structureChap.12 Species diversityChap.13 Succession


Chap. 9 CompetitionThe concept of the nicheTypes of competition definedMethods for obtaining evidence of

competitionThe relationship between intra-specific

and inter-specific competitionThe Effects of competition


資源 ( 食物 )隨時間會增長，但族群成長更加快速。



The concept of the niche( 職位 )Habitat ( 棲息地 )Niche (ecological niche, functional nich

e)The first to use the term niche was Char

les Elton(1927).The concept of Hutchinsonian niche


Three dimensions of the niche



Types of competition definedResource competitionpreemptive competition (for space)Exploitation competition ( 使用權 ) Interference competition ( 干擾權 )Diffuse competition ( 多種影響 ) Interspecific and intraspecific competitio

n


Methods for obtaining evidence of competition

Experimentation A classic example was performed by J. H. Co

nnell (1961) in his study of two species of barnacles that inhabit the rocky intertidal zone off Scotland.(Fig. 9-5, 9-6, 9-7)

Observation and inference Diamond (1975) noted that some closely relat

ed species of birds have a “checkerboard” distribution pattern. (Fig. 9-8)







Observation and inference


現象與推論 The mainland has snowshoe hares in taiga h

abitats and arctic hares in the tundra (Fig. 9.9).

Both habitats in Newfoundland island were occupied by arctic hares, the only species on the island.

When the snowshoe hare was introduced to the island, arctic hares were soon found only in tundra habitats.

推論：因為競爭，迫使 arctic hares 讓出 taiga habitats 給 snowshoe hare 。


結果發現這是錯誤的推論！ A predator, the lynx, plays a critical role. When the snowshoe hare was introduced to

Newfoundland, lynx numbers increased because of the greater abundance of prey.

The arctic hare is far more vulnerable to predation in taiga than is the snowshoe hare.

結果：這是因為掠食者的壓力，而不是因為來自種間的競爭。


Intra-specific and inter-specific competition In plants, a phenomenon known as self-thinni

ng attests to the importance of intra-specific competition.

The rye grass Lolium perenne, exemplifies this phenomenon.(Fig. 9.10)

The straight line associated with the decline in density over time has a slope of –3/2.

This slope is found in many plant self-thinning lines (Fig. 9.11)


Fig. 9.10 Self-thinning in the rye grass.


Fig. 9.11 Regression lines from self-thinning curves for 31 stands of different species of plants.


Replacement series 實驗 128 seeds of the two species were planted in

each pot. But the relative numbers of seeds of the two s

pecies varied in the series of pots. At one extreme, all 128 seeds were A. fatua;

at the other extreme, all 128 seeds were A. barbata.

Other pots were shown with 16 fatua and 112 barbata, 32 fatua and 96 barbata, and so forth.


Intra- vs. inter-specific Approximately 75% of all seedlings

survive under pure stands of each species. (pure intra-specific competition)

If intra- and inter-specific competition were equivalent, we would expect 75% of the seedlings to survive.

What they found? (Fig. 9.12)


Fig. 9.12 Results of replacement series competition experiments in Avena barbata and A. fatua (a) survival of seedlings.

The dotted lines represent the expected result based on pure intra-specific competition.The solid lines and data points represent the actual performance in competition.


Fig. 9.12 Results of replacement series competition experiments in Avena barbata and A. fatua (b) seed production.The dotted lines represent the expected result based on pure intra-specific competition.The solid lines and data points represent the actual performance in competition.


The effects of competitionThe long-term effect, known as

character displacement, operates on an evolutionary time scale – that is, over many generations.

The short-term effect, called competitive exclusion, occurs in ecological time – that is, within a single or a few generations.


Character Displacement

相近的物種，於重疊分布的區域，其間的差異會因為競爭而擴大。

這是否普遍存在？


Fig. 22-25 The phenomenon of character displacement.


Fig. 9.13 The process of character displacement(a) individuals of one species that use resources in regions that do not overlap with the other species have a selective advantage.


Fig. 9.13 The process of character displacement(b) over time, selection will separate the niches of the two species.


Fig. 9.14 Head-body lengths of male weasels as a function of latitude.


Fig. 9.15 The coefficient of variation (CV) in mandible length in Veromessor pergandei as a function of the number of granivorous ants in the community.


Fig. 9.16a Frequency distributions of mandible sizes at different sites. The mean mandible lengths of the most similar competitors of Veromessor pergandei are indicated by the arrows.


Fig. 9.16b Frequency distributions of mandible sizes at different sites. The mean mandible lengths of the most similar competitors of Veromessor pergandei are indicated by the arrows.


Fig. 9.16d Frequency distributions of mandible sizes at different sites. The mean mandible lengths of the most similar competitors of Veromessor pergandei are indicated by the arrows.


Fig. 9.16e Frequency distributions of mandible sizes at different sites. The mean mandible lengths of the most similar competitors of Veromessor pergandei are indicated by the arrows.


Fig. 9.16f Frequency distributions of mandible sizes at different sites. The mean mandible lengths of the most similar competitors of Veromessor pergandei are indicated by the arrows.


Fig. 22-26 Proportions of individuals with breaks of different sizes in populations of ground finches on several of the Galapagos islands.


Fig. 1 The considerable difference in beak morphology between these three species of Darwin's finches, Geospiza, which coexist on many Galapagos islands, has been the subject of much debate concerning its cause.


Fig. 2 The beak morphology of Geospiza conirostris shows significant variation on different species on different islands.


Fig. 3. The average beak depths of four species of Darwin's finches on three islands where they coexist show considerable variation from island to islands, even though the same set of possible competition occurs on each island.


範例： filareeTwo species of annual plantsErodium cicutarium 和 E. obtusiplicatu

m運用 replacement series 方法。分成三類：1. Sympatric populations.2. Allopatric populations.3. Transposed populations.


Fig. 9.17 The experimental design to examine the evolution of competitive interactions.


Fig. 9.18 Total seed production at different levels of intra- and interspecific competition for populations of two species of Erodium.


Competitive exclusionGause’s law ： the competitive exclusio

n principle

Fig. 9.19 Growth curves for Paramecium aurelia and P. caudatum in separate and mixed cultures.


Fig. 9.20 The skulls of the saber-toothed cat Smilodon californicus, a placental mammal, and the marsupial cat Thylacosmilus.


Introduced species: Potentially devastating competitors

Environmental application

Zebra mussels were released into North America from the ballast of ships from Asia and Europe.


Major invasions to Australia

The European rabbit was imported from Great Britain and soon reached such numbers that it destroyed immense tracts of rangeland.

Estimates made in the 1950s put the population at over 1 billion rabbits.


Why do these introduced species cause such problem?Two factors probably account for the

more intractable exotics: (1) the species’s ability to colonize new

habitats (2) its ability to out-compete native

biota.


範例： freshwater fishes in California 48 of 137 species of freshwater fish are

nonnative. Of these 48 introduced species, only 6 are

found in undisturbed or pristine waters, and 4 of those are species of trout or salmon introduced into fishless lakes in the high Sierra.

Of the 26 species of exotics for which data exist, 24 are known to have a negative impact on native fish.


Fugitive speciesSpecies that inhabit transient

environments are often very susceptible to competitive exclusion.

Fugitive species typically colonize habitats immediately after a disturbance.

They are called fugitives because they or their offspring must always be in search of the next disturbance site for colonization.


Fig. 9.21 Blossoms of fireweed, a fugitive species that depends on fire disturbance.


The prairie forb colonizes small disturbed area caused by badger excavations of ground squirrel burrows.


The Lotka-Volterra Models


The logistic equation dN/dt = rN (K-N)/KdNi/dt = riNi (1-Ni/Ki - aijNj/Ki) dNj/dt = rjNj (1-Nj/Kj - ajiNi/Kj) at equilibrium (Ki - Ni - aijNj) / Ki = 0 (Kj - Nj - ajiNi) / Kj = 0


Fig. 9.22 (b) Ki - Ni - aijNj = 0

(c) Kj - Nj - ajiNi = 0

二元一次方程式 Ni 和 Nj .


Fig. 9.23 Graphic representation f the equilibrium conditions for two species of which species i is the better competitor.


Fig. A-1. The course of competition between two populations.


Fig. 9.24-25 (a) conditions for the stable coexistence of two competing species. (b) outcome of competition between two species that are both more strongly limited by interspecific competition than by intraspecific competition. The populations tend to diverge from the equilibrium point.


請應用 Lotka-Volterra model 預測兩種相互競爭的族群 , 其間競爭的最後結果。假設甲族群對乙族群的競爭系數是 β; 乙族群對甲族群的競爭系數是 α; 甲族群的族群數量是Ｎ 1; 而其承載量是Ｋ 1; 乙族群的族群數量是Ｎ 2; 而其承載量是Ｋ 2。起初時 , 甲族群數量是50, 乙族群有 90 。請按下列 (4與 5題 )的數值 , 寫出甲乙族群最後的數量 ( Ｎ 1, Ｎ 2) 。

※同時必要寫出其相關的計算過程，才可得分。公式如下 ( 參考用 ) ：※ dN1/dt = r1N1 (k1 - N1 - αN2)/K1 ，※ dN2/dt = r2N2 (k2 - N2 - βN1)/K2 。


計算出其結果

(1) 若 α=1.2 β=0.8 Ｋ 1 =200 Ｋ 2 =200,

(2) 若 α=0.8 β=1.2 Ｋ 1 =160 Ｋ 2 =250,

(3) 若 α=1.4 β=1.4 Ｋ 1 =260 Ｋ 2 =260,

期末考題範例


Empirical examples of the Models’ predictions

In the laboratory one can determine the critical light intensity for a species, the minimum amount of light required to sustain population growth.

The predicted competitive abilities of the four species were as follows:

Chlorella > Aphanizomenon > Microcystis > Scenedesmus


Fig. 9.26a Results of competition between pairs of Phytoplankton species.


Fig. 9.26b Results of competition between pairs of Phytoplankton species.


Fig. 9.26c Results of competition between pairs of Phytoplankton species.

Aphanizomenon


Fig. 9.26d Results of competition between pairs of Phytoplankton species.


Fig. 9.26e Results of competition between pairs of Phytoplankton species.

Chlorella


Fig. 9.26f Results of competition between pairs of Phytoplankton species.


Empirical examples of the Models’ predictionsK1 = K2 =1.0 a12 = a21 Populations of Drosophila melanogaster

and D. simulans in the laboratory.These populations do not exhibit compe

titive exclusion, as the Lotka-Volterra models predict for these values.


Fig. 9.27 Lotka-Volterra competition graphs for Drosophila serrata and D. pseudoobscura. The solid lines are observed isoclines; the dashed lines are isoclines predicted by the model.


•於不同的環境狀態，競爭的能力與結果就可能會有所不同。


兩種蚊子的競爭Native North American treehole mosquit

o, Aedes triseriatus Introduced Asian species, A. albopictus. In Figure 9.28 we see that stable coexis

tence is expected in tree holes, whereas extinction of A. triseriatus is predicted in abandoned tires containing small pools of water.



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Chap. 9 Competition