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Community structure

Community structure. Physical structure Dispersal-driven structure Predation-driven structure Competition-driven structure. Physical structure. Physical template Biological template Paradox of the plankton Dominant species Trees Corals Surfaces Ecological engineers impoundments

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Community structure

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  1. Community structure Physical structure Dispersal-driven structure Predation-driven structure Competition-driven structure

  2. Physical structure • Physical template • Biological template • Paradox of the plankton • Dominant species • Trees • Corals • Surfaces • Ecological engineers • impoundments • cavities • mounds

  3. Habitat template

  4. Whittaker’s analysis of the Smoky Mountains

  5. Dominant species provide structure

  6. Ecological engineers • Dams • Holes • Mounds

  7. Dispersal-based structure • Supply-side ecology • Propagule pressure • Predictability • Carousel mode • Temporal mass effects

  8. Scoured Island River Bedrock Scour Bar River Floodplain

  9. Carousel model

  10. Temporal mass effect The tingle tree in SW Australia has not reproduced in over 1000 years.

  11. Seed banks as a form of temporal mass effect

  12. Dispersal-based structure • Supply-side ecology • Propagule pressure • Predictability • Carousel model • Temporal mass effects

  13. Competition-based structure • Niche differentiation • In space • In time • Assembly rules • Diamond’s birds • Brown’s mice • Lawlor’s and Wilson’s null models • Ghost of competition past

  14. Niche theory • Grinnell 1917. The ultimate distributional unit. Physical and climatic limits • Elton 1927. Fundamental role of a species. It’s occupation, or how it makes its living. • Hutchinson 1958. N-dimensional hypervolume. • Hutchinson. Fundamental & Realized Niche • Whittaker, Levin & Root. 1973. Niche, habitat & ecotope

  15. Consider the concept of niche, if I knew what it meant I'd be rich Its dimensions are n, and a knowledge of Zen is essential to fathom the bitch Cottam and Parkhurst

  16. And NUH is the letter I use to spell Nutches Who live in small caves, known as Nitches, for hutches. These Nutches have troubles, the biggest of which is The fact that there are many more nutches than niches. Each nutch in a Nitch knows that some other Nutch Would like to move into his nitch very much. So each Nutch in a nitch has to watch that small Nitch Or Nutches who haven't got nitches will snitch. Dr. Zuess On beyond zebra

  17. Niche structure as a consequence of competitive displacement Brown 1975

  18. Diamond 1975

  19. Null models – Reorganization algorithms RA1: species number and resource categories retained. Randomly assign values for proportion of diet (between 0 & 1 such that for a species values sum to 1). Since 0 is rare, niche breadth was too high RA2: Retained 0s, and randomly assigned other values (perhaps should have randomly assigned 0s?).

  20. RA3: Retained not only the original degree of specialization, but also the original consumer nichne breadths – randomly reassigned all values including 0s. • RA4: Reassigned only the non-0 values

  21. Competition-based structure • Niche differentiation • In space • In time • Assembly rules • Diamond’s birds • Brown’s mice • Lawlor’s and Wilson’s null models • Ghost of competition past

  22. Predation-based structure • Food web structure • Complexity and stability • Representation • Keystone species • Factors influencing food web stability • Top-down/bottom up control • Fertilizations and cages • Are food webs all wet?

  23. Multiple steady states

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