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Competition

Competition. Georgii F. Gause. Paramecium. Competitive Exclusion Principle. "Two competing species cannot coexist in a stable environment if both require the same limiting resource."

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Competition

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  1. Competition

  2. Georgii F. Gause

  3. Paramecium

  4. Competitive Exclusion Principle • "Two competing species cannot coexist in a stable environment if both require the same limiting resource." • if two competing species do coexist in a stable environment, they do so because of niche differentiation - their realized niches are slightly different and thus competition between them is lessened

  5. Robert MacArthur, 1930-1972

  6. MacArthur’s Warblers

  7. MacArthur’s Warblers

  8. Limiting Similarity • The competitive exclusion principle led to a whole suite of questions which basically asked: Is there a minimum amount of niche differentiation that has to be exceeded for stable coexistence? • or put another way: Is there a limit to the similarity of coexisting competitors?

  9. Caveats to Resource Utilization Curves 1) Are we examining right resource? Is something else really limiting? 2) Is there variation in when the resource is limiting? If it is only limiting occasionally, then it may not matter much. 3) How do we quantify resource use by species in nature? Do resource utilization curves have to be normal? Does competition change during life history changes in the species? 4) How does overlap really affect the species? Is overlap really only on 1 dimension?

  10. Resource Utilization in Cattails Typha latifolia – shallow 0-60 cm water depth Typha angustifolia – deeper 60-90 cm water depth

  11. Resource Utilization in Cattails

  12. Resource Utilization – Spiny Mice Aconomys russatus dirunal but may become nocturnal Aconomys cahirinus nocturnal

  13. Resource Utilization and Competition

  14. Cyclotella Asterionella Two species of competing Diatoms

  15. Species can compete for two resources and can coexist when 2 conditions are met: 1) The habitat must be such that one species is more limited by one resource and the other species is more limited by the other resource. 2) Each species must consume more of the resource that more limits its own growth.

  16. RUE can be expanded to many species

  17. Another look at plant strategies – from Peter Grime

  18. Grime’s C-S-R strategies • Competitive - plants such as perennial herbs, shrubs and trees typically have dense leaf canopies, high growth rates, low seed production and relatively long life spans • Stressful -stress-tolerant plants that often have small evergreen leaves, low growth rates, low seed production and long life spans • Disturbed environments - the plants are primarily Ruderals – plants which are usually small, grow rapidly, short life spans and produce many seeds

  19. Grime’s C-S-R strategies

  20. Fynbos – South African Mediterranean shrubland

  21. Fynbos burning

  22. Fynbos recovery

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