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Chap. 21 Competition theory Chap.22 Competition in nature

Chap. 21 Competition theory Chap.22 Competition in nature. Ecology 2000. Competition. Intraspecific or interspecific competition Interference competition occurs when one individual actively interferes with another individual's access to a resource.

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Chap. 21 Competition theory Chap.22 Competition in nature

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  1. Chap. 21 Competition theoryChap.22 Competition in nature Ecology 2000

  2. Competition • Intraspecific or interspecific competition • Interference competition occurs when one individual actively interferes with another individual's access to a resource. • Exploitative competition is usually an interspecific interaction. While the use of the resource by the individuals of one species reduces the availability of the resource to the other. Ecology 2000

  3. Competition • 21.1 The emergence of competition as a central theory in ecology was slow and tentative. • 21.2 The experiments of Tansley, Gause, and Park provided early experimental demonstrations of competition. • 21.3 The competitive exclusion principles states that two species cannot coexist on a single limiting resource. Ecology 2000

  4. Fig. 21-1 (a) Increase in population of two species of Paramecium when grown in separate cultures. • (b) when grown together. • (Gause 1934) Ecology 2000

  5. 21.4 Populations may be regulated by intraspecific and interspecific competition. • 21.5 The logistic equation can be modified to incorporate interspecific competition. • 21.6 Equilibrium competition models reveal conditions for coexistence of tw competing populations. • 21.7 A graphic representation illustrates the basic features of logistic cometition. Ecology 2000

  6. The logistic equation • dNi/dt = riNi (1-Ni/Ki) • dNi/dt = riNi (1-Ni/Ki - aijNj/Ki) (21-3) • dNj/dt = rjNj (1-Nj/Kj - ajiNi/Kj) (21-4) at equilibrium • (Ki - Ni - aijNj) / Ki = 0 • (Kj - Nj - ajiNi) / Kj = 0 Ecology 2000

  7. Fig. 21-4(b) Ki - Ni - aijNj = 0(c) Kj - Nj - ajiNi = 0二元一次方程式Ni 和 Nj . Ecology 2000

  8. Fig. 21-5 Graphic representation f the equilibrium conditions for two species of which species i is the better competitor. Ecology 2000

  9. Fig. 21-6 The course of competition between two populations. Ecology 2000

  10. Fig. 21-7 (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. Ecology 2000

  11. 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Ｎ1; 而其承載量是Ｋ1; 乙族群的族群數量是Ｎ2; 而其承載量是Ｋ2。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(Ｎ1, Ｎ2)。 • 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 。 Ecology 2000

  12. 計算出其結果 • (1) 若α=1.2 β=0.8 Ｋ1 =200 Ｋ2 =200, • (2) 若α=0.8 β=1.2 Ｋ1 =160 Ｋ2 =250, • (3) 若α=1.4 β=1.4 Ｋ1 =260 Ｋ2 =260, 期末考題範例 Ecology 2000

  13. Chap.22 competition in nature • How does competition occur? • 1. Consumptive competition (可再生資源) • 2. Preemptive competition (open space的佔有) • 3. Overgrowth competition (個體成長) • 4. Chemical competition (產出 toxin) • allelopathy • 5. Territorial competition (defense of space) • 6. Encounter competition Ecology 2000

  14. Ecology 2000

  15. Chemical competition • Several species of sage of the genus Salvia apparently use chemicals to inhibit the growth of other vegetation. • Clumps of Salvia usually are surrounded by a halo of bare soil separating the sage from neighboring grassy areas (Fig. 22-1). • Bartholomew (1970) suggested that the halo zone around Salvia could be caused by grazing or by seed eating birds and mammals. Ecology 2000

  16. Fig. 22-1 (a) bare patch at edge of a clump of sage includes a 2-meter-wide with no plants (A-B) and a wider area of inhibited grassland (B-C).(b) aerial view shows sage and California sagebrush invading annual grassland in the Santa Inez Valley of California. Ecology 2000

  17. Chemical competition • In order to test his hypothesis, he placed cages in the halo zone to keep out small birds and mammals. • After 1 year, the exclosure cages contained about 20 times as much plant biomass as the controls, and about the same amount as found in the grassy area beyond the halo. • Harper interpreted these results as suggesting that "the toxin hypothesis is unnecessary to account for the observed pattern of vegetation. Ecology 2000

  18. Fig. 22-25 The phenomenon of character displacement. Ecology 2000

  19. Fig. 22-26 Proportions of individuals with breaks of different sizes in populations of ground finches on several of the Galapagos islands. Ecology 2000

  20. 問題與討論 • 請提出問題！ Ecology 2000

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