Chap.11 Community Structure

1. Chap.11 Community Structure 鄭先祐 生態主張者 Ayo工作室

2. Community Structure • Equilibrium views • Predation as a structuring force • Non-equilibrium views • Tallgrass prairie, Bison, and Fire – A synthesis • Environmental Application (niche specialization and extinction) 生態學 2001 chap.11 Community structure

3. Introduction • Community • Guild, a group of coexisting, ecologically similar organisms. • Adaptive radiation of Cichlid fish in Lake Malawi, East Africa (Fig 11.1) • Size relationships among granivorous rodents in three desert communities in the American Southwest (Fig. 11.2) 生態學 2001 chap.11 Community structure

4. Fig. 11.1 Adaptive radiation of Cichlid fish in Lake Malawi, East Africa 生態學 2001 chap.11 Community structure

5. Fig. 11.2Size relationships among granivorous rodents in three desert communities in the American Southwestniche 不重疊。 生態學 2001 chap.11 Community structure

6. Equilibrium views • Inter-specific competition as a structuring • Changes in niche dimensions • Fundamental niche and realized niche. • Five similar species of warblers foraging in the same tree (Fig. 11.3 and 11.4) 生態學 2001 chap.11 Community structure

7. Fig. 11.3 The five species of warblers. Note the similarity in size and bill shape. 生態學 2001 chap.11 Community structure

8. Fig. 11.4 Feeding positions of five sympatric warblers. 生態學 2001 chap.11 Community structure

9. Fig. 11.4 Feeding positions of five sympatric warblers. 生態學 2001 chap.11 Community structure

10. 提高diversity的可能途徑 • Increased niche overlap • Decreased niche breadth • Increased range of resources utilized. 生態學 2001 chap.11 Community structure

11. 生態學 2001 chap.11 Community structure

12. Niche specialization and extinction • A highly specialized niche makes a species vulnerable to competitive effects, particularly from exotic species introduced into the habitat. • The bird faunas of island systems like the Hawaiian island exemplify this problem. • Originally, the Hawaiian islands supported 84 species of endemic birds.其中以honeycreeper species 演化最為radiation，有47種。其中有18種已經在古老時代滅絕，另外8種於西方勢力進入後就滅絕。剩下來的有20種是頻危的。 生態學 2001 chap.11 Community structure

13. 圖11B-1. The diversity of honeycreeper species found on the Hawaiian islands. 生態學 2001 chap.11 Community structure

14. Predation as a structuring force • R. T. Paine (1966) studied the communities of invertebrates and algae in the rocky intertidal zone at Neah Bay, Washington (Fig. 11.7). • This system is composed of a large group of invertebrates and algae, with a single top carnivore, the starfish, Pisaster ochraceous. • 移走starfish 之後，種類從原本的15種，下降到只有8 種。 • Keystone predator hypothesis. 範例 生態學 2001 chap.11 Community structure

15. Fig. 11.17 The rocky inter-tidal community. 生態學 2001 chap.11 Community structure

16. 範例：Kangaroo rats in a desert • 移走kangaroo rats ，經過12年。 • 植被有顯著的改變(圖11.18)。 • Annual and perennial grasses colonized and increased three fold in the removal plots (Fig. 11.9). 生態學 2001 chap.11 Community structure

17. 圖11.18 圍牆的左邊是將kangaroo rats移走的地區。其植被明顯的較多。 生態學 2001 chap.11 Community structure

18. 圖11.19 Effects of kangaroo rat (Dipodomys) removal from enclosures. 生態學 2001 chap.11 Community structure

19. Non-equilibrium views • In the past 20-years, ecologists have come to suspect that most of the time, most populations and communities are not at equilibrium. • If change in the community is frequent and devastating, process such as competition and predation will be less important as determinants of community structure. • Disturbance and Patch dynamics models 生態學 2001 chap.11 Community structure

20. The Role of disturbance • Abiotic factors such as fire, volcanic eruptions, floods, and storms have different impacts on the various species in a community and thus affect community organization. 生態學 2001 chap.11 Community structure

21. 範例：bird community • Wiens and Rotemberry (1980) study the bird community structures in the Great Basin. 結果發現於大區域是有consistent community composition，但是於小區域，so much variation among sites and among years within a site 因此無法有固定的community composition。 • The severe and unpredictable climate characteristic of the Great Basin prevents the local species assemblages from achieving full ecological saturation and resource limitation. 生態學 2001 chap.11 Community structure

22. Intermediate disturbance • J. H. Connell (1979) introduced the intermediate disturbance hypothesis to explain the number of species coexisting in a community. (Fig. 11.23) • At low levels of disturbance, competition or predation– processes Connell termed “compensatory mechanisms” – reduces species diversity. 生態學 2001 chap.11 Community structure

23. Fig. 11.23 Connell’s intermediate disturbance hypothesis. The number of species in a community is maximal at intermediate levels of disturbance. 生態學 2001 chap.11 Community structure

24. Patch dynamics models The models emphasis the following properties of communities: • 1. Spatial variation in the nature of the community. • 2. Movement between patches via dispersal of individuals. • 3. Disturbance as an important feature of communities. 生態學 2001 chap.11 Community structure

25. Three mechanisms • 1. Functional relationships between species counteract biologically induced instability. • 2. Environmental disturbance decreases the effect of biotic instability. • 3. Species have compensatory mechanisms that operate at low population densities to prevent extinction. 生態學 2001 chap.11 Community structure

26. DeAgelis and Waterhouse (1987) • 4. The isolation of subpopulations determines the degree to which dispersal can lead to repopulation of extinct patches. • 5. Spatial hetrogeneity in physical and biological factors leads to movement of individuals to obtain important resources. • (Fig. 11.24) 生態學 2001 chap.11 Community structure

27. 生態學 2001 chap.11 Community structure

28. 範例：mussel community • The structure os the community over time is determined by the combined forces of competitive interactions and physical disturbance. (Fig. 11.25) • Disturbance is sufficiently frequent that the community is a mosaic of local sites, each with a slightly different disturbance and competitive history. 生態學 2001 chap.11 Community structure

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30. 範例：fossil mammal faunas • Graham and colleagues (1996) analyzed fossil mammal faunas from 2945 sites in the US. • The fossil record shows that most modern communities emerged very recently. • These data support the Gleasonian view of communities as random, nonequilibrium assemblages of species. 生態學 2001 chap.11 Community structure

31. Tall grass Prairie, Bison, and Fire – A synthesis • Deterministic biotic factors such as competition and predation • Stochastic influences such as disturbance • The tall grass prairie of North American occupied some 68 million hectares before Europeans arrived. • C4 grasses, and C3 forbs, and with fire • Bison numbering between 30 and 60 million. • Fig.11.26, 11.27 生態學 2001 chap.11 Community structure

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33. 生態學 2001 chap.11 Community structure

34. 沒有食草地區，fire frequency 增加，導致C4 grasses 增加覆蓋度。C3植物則減少。(Fig. 11.28) • 火燒使得植被物種減少(Fig. 11.29) • The mechanism for this effect is shown in Figure 11.30. • Bison preferentially select burned areas because of their preference for C4 grasses. • Grazing reduces the dominance of these species and allows the C3 forbs to increase in numbers. • The largest numbers of species were found in plots that were grazed or grazed and burned (Fig. 11.29). • Bison are considered to be keystone species in this system. 生態學 2001 chap.11 Community structure

35. 生態學 2001 chap.11 Community structure

36. 生態學 2001 chap.11 Community structure

37. 生態學 2001 chap.11 Community structure

38. 問題與討論！ ayo@faculty.pccu.edu.tw Ayo 文化站http://faculty.pccu.edu.tw/~ayo 生態學 2001 chap.11 Community structure