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How many species?<br />Perhaps 50 million species <br />287,655 plants<br />74,000–120,000 fungi<br />1,250,000 animals:<b...
Why bother?<br />Moral/ethical reasons<br />Medicine: Antibiotics<br />Tropical frogs<br />Silk moths, salamanders, snakes...
Speciation & coexistence<br />Allopatric speciation<br />Sympatric speciation<br />Requires coexistence<br />
Coexistence in Animals<br />Main niche: prey (resource)<br />
Gause’s Exclusion principle<br />“The struggle for existence” 1934<br />Discovered antibiotic used in WWII<br />1910-1986<...
Plants<br />Limited range of resources<br />Light, water, nutrients<br />Rain forest<br />Panama 320spp 50ha<br />Grasslan...
Interactions<br />Mutualism		+	+<br />Competition		-	-<br />Predation/parasitism	-	+<br />Amensalism		0	-<br />Commensalis...
Arbuscular<br />Crop plants<br />Herbs, trees<br />Roots appear normal<br />Staining shows fungi inside the roots structur...
Ectomycorrhizas<br />Broad leaved trees and conifers<br />Pine; spruce; fir; beech; birch<br />Most trees in London<br />C...
Root (darker)<br />Fungus (white) on root hairs<br />
Nitrogen cycle<br />
Legumes<br />N essential for life<br />DNA; RNA; amino acids<br />Fixed by many plants<br />Symbiosis<br />Rhizobia (nodul...
Nitrogen fixing bacteria<br />
Nitrogen fixing bacteria<br />
Benefits<br />Plant<br />Improved uptake of soil nutrients<br />Ecto: N<br />Arb: P<br />Immunity to pathogens<br />Drough...
Possible consequences<br />Positive feedback<br />Seedlings perform well near to parent<br />Nurse plants<br />Monodominan...
Ectomycorrhizal networks<br />Larch seedling<br />Low nutrient<br />(tropics nutrient cycles are faster)<br />Soils can be...
Early advantage<br />
Negative feedbacks<br />Build up of soil pathogens<br />Seed predators<br />Crop rotation<br />Janzen-Connell hypothesis<b...
Grassland experiment<br />Petermann et al. (2008) Ecology, 89(9): 2399–2406<br />
Summary<br />Microbes important<br />Poor soils<br />Early establishment<br />Modulate competition?<br />Negative feedback...
Competition<br />Lotka-Volterra theory 1920’s<br />Tested by Gause in 1930’s<br />Coexistence most likely when: <br />Intr...
New theory<br />
References<br />David Read in Nature (November 1998) 396, 22-23; and the full paper on pp. 69-72 in the same issue<br />Be...
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Complex cp2011

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Complex cp2011

  1. 1.
  2. 2. How many species?<br />Perhaps 50 million species <br />287,655 plants<br />74,000–120,000 fungi<br />1,250,000 animals:<br />1,190,200 invertebrates:<br />950,000 insects,<br />molluscs, crustaceans, etc.<br />58,808 vertebrates:<br /> 29,300 fish,<br /> 5,743 amphibians,<br /> 8,240 reptiles,<br /> 10,234 birds,<br /> 5,146 mammals<br />
  3. 3. Why bother?<br />Moral/ethical reasons<br />Medicine: Antibiotics<br />Tropical frogs<br />Silk moths, salamanders, snakes, sharks, honeybees<br />Ecosystem function<br />Higher diversity = higher productivity<br />
  4. 4. Speciation & coexistence<br />Allopatric speciation<br />Sympatric speciation<br />Requires coexistence<br />
  5. 5. Coexistence in Animals<br />Main niche: prey (resource)<br />
  6. 6. Gause’s Exclusion principle<br />“The struggle for existence” 1934<br />Discovered antibiotic used in WWII<br />1910-1986<br />Two (or more) similar species cannot coexist on a single resource<br />
  7. 7. Plants<br />Limited range of resources<br />Light, water, nutrients<br />Rain forest<br />Panama 320spp 50ha<br />Grassland<br />UK, 35spp 1m2<br />WHAT PROCESSES MAINTAIN THE DIVERSITY?<br />
  8. 8. Interactions<br />Mutualism + +<br />Competition - -<br />Predation/parasitism - +<br />Amensalism 0 -<br />Commensalism 0 +<br />8<br />
  9. 9.
  10. 10. Arbuscular<br />Crop plants<br />Herbs, trees<br />Roots appear normal<br />Staining shows fungi inside the roots structure<br />Endo-symbiont<br />Clover<br />1. Vesicles (storage)<br />2. Hyphae<br />3. Arbuscules (exchange)<br />
  11. 11. Ectomycorrhizas<br />Broad leaved trees and conifers<br />Pine; spruce; fir; beech; birch<br />Most trees in London<br />Common mushrooms and toadstools in woodland –fruiting bodies<br />No penetration of plant cell<br />Form sheath on the root<br />Hyphae extend into the soil<br />
  12. 12. Root (darker)<br />Fungus (white) on root hairs<br />
  13. 13. Nitrogen cycle<br />
  14. 14. Legumes<br />N essential for life<br />DNA; RNA; amino acids<br />Fixed by many plants<br />Symbiosis<br />Rhizobia (nodules)<br />Legumes release N into soil on death. <br />Farmers crop rotation<br />
  15. 15. Nitrogen fixing bacteria<br />
  16. 16. Nitrogen fixing bacteria<br />
  17. 17. Benefits<br />Plant<br />Improved uptake of soil nutrients<br />Ecto: N<br />Arb: P<br />Immunity to pathogens<br />Drought tolerance<br />Microbe<br />Carbon<br />
  18. 18. Possible consequences<br />Positive feedback<br />Seedlings perform well near to parent<br />Nurse plants<br />Monodominance?<br />Depends on early conditions/densities<br />Rain forests<br />Species rich<br />Large patches >50% of trees of one species<br />
  19. 19. Ectomycorrhizal networks<br />Larch seedling<br />Low nutrient<br />(tropics nutrient cycles are faster)<br />Soils can be nutrient poor<br />Seedlings with access to an ECM network had greater growth<br />(73% greater),<br />leaf number (55% more), and survivorship (47% greater) than seedlings without such access<br />
  20. 20. Early advantage<br />
  21. 21. Negative feedbacks<br />Build up of soil pathogens<br />Seed predators<br />Crop rotation<br />Janzen-Connell hypothesis<br />Negative frequency dependence<br />Advantage of rarity<br />Coexistence<br />Seedling establishment<br />Better further away from parent<br />
  22. 22. Grassland experiment<br />Petermann et al. (2008) Ecology, 89(9): 2399–2406<br />
  23. 23. Summary<br />Microbes important<br />Poor soils<br />Early establishment<br />Modulate competition?<br />Negative feedback<br />Temporal variation?<br />Stochastic model required<br />
  24. 24. Competition<br />Lotka-Volterra theory 1920’s<br />Tested by Gause in 1930’s<br />Coexistence most likely when: <br />Intraspecific > interspecific competition<br />Niche differentiation<br />Coexistence when species most limited by themselves<br />
  25. 25. New theory<br />
  26. 26. References<br />David Read in Nature (November 1998) 396, 22-23; and the full paper on pp. 69-72 in the same issue<br />Bever (2003) New Phytologist, 157: 465-473.<br />Bever et al. (2010) Trends in Ecology and Evolution, 25: 468-478.<br />

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