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Chap.16 Population Regulation

Chap.16 Population Regulation. Ecology 2000. 目錄. 16.1 The logistic equation describes the growth of a regulated population. 16.2 A qualitative model of continuous population growth reveals the relationship between population density and growth rate.

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Chap.16 Population Regulation

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  1. Chap.16 Population Regulation Ecology 2000

  2. 目錄 • 16.1 The logistic equation describes the growth of a regulated population. • 16.2 A qualitative model of continuous population growth reveals the relationship between population density and growth rate. • 16.3 Populations may be regulated by the effects of density-dependent factors. chap.16 population regulation

  3. 目錄 • 16.4 Andrewartha and Birch Challenged density-dependent regulation of population size. • 16.5 The theory of density independence created a major controversy among ecologists. chap.16 population regulation

  4. 16.1 The logistic equation describes the growth of a regulated population. • dN / dt = rN • dN / dt = r0 N( 1- N/K) • K is the carrying capacity chap.16 population regulation

  5. Fig. 16-1 美國於1790-1910年間的族群成長情況。垂直線代表每10年的exponential rate。 chap.16 population regulation

  6. Fig. 16-2 美國人口的成長之exponential rate。 chap.16 population regulation

  7. Fig. 16-3 族群size於K/2時，增加速率最快。於K時，增加率等於0。 chap.16 population regulation

  8. dN / dt = r0 N( 1- N/K) Fig. 16-4 a S-shaped curve chap.16 population regulation

  9. Fig. 16-5 A logistic curve fitted to the population of the United States between 1790-1910. chap.16 population regulation

  10. 16.2 A qualitative model of continuous population growth reveals the relationship between population density and growth rate. • dN / dt = rN = f (N) = b(N) - d(N) • 當 b(N) = d(N) ，達到平衡。 • 當 dN / dt > 0，族群增加。 • 當 dN / dt < 0，族群減少。 chap.16 population regulation

  11. Break point Fig. 16-6 (a) per capita growth rate (b) dN/dt chap.16 population regulation

  12. 16.3 Populations may be regulated by the effects of density-dependent factors. • Density-dependent factors effects increase with crowding can bring a population under control. • Density-independent factors may influence the exponential growth rate , but they do not regulate the size that the population will attain in the environment. chap.16 population regulation

  13. 壽命 生育力 密度 Fig. 16-7 density-dependent population regulation in laboratory populations of the fruit fly Drosophila melanogaster. chap.16 population regulation

  14. Larvae的密度愈高，遷移開的，或是死亡的數量愈高。Larvae的密度愈高，遷移開的，或是死亡的數量愈高。 Fig. 16-8 effects of density (number of larvae per grain) on migration and mortality in the grain beetle. 穀物虫 chap.16 population regulation

  15. 高密度 Fig. 16-9 Fecundity in laboratory populations of Daphnia pulex as a function of age at different densities. chap.16 population regulation

  16. 8 ind. Per cm3 16 ind. 32 ind. 4 ind. 1 ind. 2 ind. Fig. 16-9 survival probality in laboratory populations of Daphnia pulex as a function of age at different densities. chap.16 population regulation

  17. A stable population size 跳蚤密度 Fig. 16-10 Values of , calculated from the life table of Daphnia pulex. The population growth rate decreases as a function of density. chap.16 population regulation

  18. Floaters增加。Floaters指的是沒有能建地盤的雄性。Floaters增加。Floaters指的是沒有能建地盤的雄性。 平均每個雌鳥的young fledged Fig. 16-11 Density dependence in the Mandarte Island song sparrow population. Proportion of juveniles surviving chap.16 population regulation

  19. 白尾鹿 五個不同地區 最好 最差的環境 環境的好壞，決定生育力。 chap.16 population regulation

  20. 獵捕之前 獵捕之後 獵捕減少族群數量，刺激族群生長。 chap.16 population regulation

  21. Density dependence in plants • Like animals, plants experience increased mortality and reduced fecundity at high densities. • Fig.16-12：密度愈高，個體的平均體重愈輕。 • Fig. 16-13：幼苗成長，許多死亡，密度持續下降。 • Fig. 16-14：self-thinning curve (自我疏伐曲線)，通常關係是- 3/2 power law. chap.16 population regulation

  22. 平均個體可以有近1.0g 乾重 絕大部份的個體都很小 Fig. 16-12 distribution of dry weights of individuals in populations of flax plants in a low density (a) and at two high densities ( b 和 c ). chap.16 population regulation

  23. Fig. 16-13 horseweed (a) 存活數量持續下降，植物體重量持續上升。(b) 平均植物體乾重持續上升，存活數量的密度持續下降。 chap.16 population regulation

  24. Fig. 16-14 兩種不同的植栽。密度與平均體重的關係。斜率都是 - 3/2 。 chap.16 population regulation

  25. 16.4 Andrewartha and Birch Challenged density-dependent regulation of population size. • 1954 Lack的看法：the regulation of population size by density-dependent factors, principally food, predators, and disease. • Andrewartha 和 Birch (昆虫學者)：族群成長受到三項因素限制：(a) 資源有限、(b) 獲取資源的困難 、 (c) 時間有限 • 其中以最後一個最為重要；第一個卻是最不重要。 chap.16 population regulation

  26. Fig. 16-15 Thrips 小虫，寄生於花朵。澳洲(1933)。 點點是每天的數量，曲線是每15天的平均。 chap.16 population regulation

  27. Thrips 數量與食物量無關 • 甚至在thrips量最大的時候，整體的密度並未呈現過度的現像( 除了一些局部地點和暫時的時段)。 • Thrips快速繁殖，但花朵的增加更加快速。 • 當Thrips數量開始下降，密度下降，花朵的量仍很多。 • Thrips populations 和 氣候的關係。 chap.16 population regulation

  28. Thrips數量與氣候的關係 • Dependent variable ，Y：平均每朵花上的 thrips 數量。 • Independent variables ， • X1：the effective degree-days from the first rains of the winter season to August 31. • X2：the rainfall during Sept. and Oct. • X3：the effective degree-days during Sept. and Oct. • X4：the same as X1, but for the previous year. chap.16 population regulation

  29. Fig. 16-16 Observed peak numbers of thrips per rose between 1932 and 1945(green vertical lines) compared with the predictions of a regression equation based upon four climate variables (black line). chap.16 population regulation

  30. 16.5 The theory of density independence created a major controversy among ecologists. • Smith (1961) argued that Davidson and Andrewartha(1948) had analyzed their data in such a way that they could not have detected density dependence. • Smith 運用同樣的data，作不同的分析處理。(Fig. 16-17) • dN 與 log N ，呈現負相關。 chap.16 population regulation

  31. Fig. 16-17 Increase in the size of the thrips population between October and November as a function of the size of the population in October. chap.16 population regulation

  32. Fig. 16-18 (a) monthly mean numbers of thrips per rose recorded over nearly 7 years (b) The mean and variance for each month of the year. 若是d N 與 N 間無關，variance 應該會隨著 log(N)升降。但結果於October 和 November間，variance有明顯的下降，但log(N)仍是在上升。 chap.16 population regulation

  33. The contemporary view of density dependence • demographic stochasticity • variation in the birth and death rates • environmental stochasticity • variation in the environment • density vagueness • random fluctuations or noise, compared with density-dependent responses chap.16 population regulation

  34. 鳥類族群的regulation • 雖然鳥類一般被認為是主要受到density-dependent的影響，但是資料顯示並不是如此。 • Greenwood and Baillie (1991) analyzed population trends for 39 species of British passerine birds, or • Murdoch (1994) looked at time series density data for 59 species of birds • 這兩份報告顯示只有少部份呈現出是受density-dependent 的影響。 chap.16 population regulation

  35. Density-dependence 的證據 • Woiwod 和 Haski (1992) looked for evidence of density dependence in 5,715 time series of 447 species of moths and aphids and found strong evidence of its presence. chap.16 population regulation

  36. Equilibrium vs. non-equilibrium • Equilibrium dynamics vs. non-equilibrium dynamics • The notion of equilibrium is central to regulation. • Non-equilibrium dynamics, in which metapopulations are key • metapopulation theory (Chap.17) chap.16 population regulation

  37. Fig. 16-19 Possible interactions between density-dependent and density-independent mortality factors. (a) A population with a constant rate of reproduction, R, and a density-dependent mortality rate, dm, showing an equilibrium point at K1 (b) A population having both a density-dependent mortality rate and a density-independent mortality factor, m. The presence of the density-independent factor lowers the population equilibrium density to K2 (c) A population in which the density-independent mortality factor fluctuates (within the green shaded area) in response to environmental stochasticity, creating a situation in which the equilibrium density fluctuates between K2 and K3. chap.16 population regulation

  38. Suggested readings • Clutton-Brock, T. H., M. Major, and F. E. Guinness (1985) Population regulation in male and female red deer. Journal of Animal Ecology 54:831-846. • Murdoch, W. W. (1994) Population regulation in theory and practice. Ecology 75:271-287. • Myers, R. A., N. J. Barrowman, J. A. Hutchings, and A. A. Rosenberg (1995) Population dynamics of exploited fish stocks at low populations levels. Science 269:1106-1108. • Weller, D. E. (1987) A reevaluation of the -3/2 power rule of plant self-thinning. Ecological Monographs 57:23-43. chap.16 population regulation

  39. 問題與討論 • 請提出問題！ chap.16 population regulation

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