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Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level

Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level III. Multispecies Interactions across Trophic Levels IV. Succession V. Biodiversity: Patterns and Processes The Species-Area Relationship The Latitudinal Trend in Diversity 1. The patterns. Amphibians.

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Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level

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  1. Community Ecology • I. Introduction • II. Multispecies Interactions with a Trophic Level • III. Multispecies Interactions across Trophic Levels • IV. Succession • V. Biodiversity: Patterns and Processes • The Species-Area Relationship • The Latitudinal Trend in Diversity • 1. The patterns

  2. Amphibians Lizards Snakes

  3. Moss

  4. Bivalves Ants

  5. Lizards Birds

  6. Community Ecology • I. Introduction • II. Multispecies Interactions with a Trophic Level • III. Multispecies Interactions across Trophic Levels • IV. Succession • V. Biodiversity: Patterns and Processes • The Species-Area Relationship • The Latitudinal Trend in Diversity • The patterns • Potential Causes • a. energy-diversity hypothesis

  7. "Bottom-Up" - more Energy, more sp. - quantitative effects

  8. "Bottom-Up" - more Energy, more sp. - quantitative effects

  9. a. ENERGY – DIVERSITY HYPOTHESIS

  10. PET = amount of water that a plant would lose to the environment; increases with radiation and decreases with increasing humidity.

  11. "Bottom-Up" - more Energy, more sp. - qualitative effects: energy increasing types of diversity The tropics not only have MORE productivity, they have more KINDS of productivity – more types of plants, allowing greater specialization by more types of animals. We tend to see this diversity evolving by sister species using slightly different resources. This should make sense; sister species are probably very similar, and so they would have to partition some important resources in order to coexist without competitive exclusion.

  12. This diversity evolves by sister species using slightly different resources. This should make sense; sister species are probably very similar, and so they would have to partition some important resources in order to coexist without competitive exclusion.

  13. "Bottom-Up" - more Energy, more sp. "Top-Down" – more energy, more predators, less, competitive exclusion at each trophic level.

  14. "Bottom-Up" - more Energy, more sp. "Top-Down" - more predators, less competitive exclusion. "Faster Evolution" and speciation

  15. "Faster Evolution" and speciation Rohde, K. 1992. Latitudinal Gradients in Species Diversity: The Search for the Primary Cause. Oikos 65: 514-527. Mutation rates are increased by radiation and heat - so mutation rates should be higher in the tropics...Confirmed developmental rate is faster at higher temps, so generation time should be shorter.... Confirmed So, with greater variation and more rapid generational turnover, responses to selection (and other evolutionary agents) should be more rapid in the tropics... divergence and speciation should be more rapid in the tropics.

  16. "Faster Evolution" and speciation Weir, JT, and D Schluter. 2007.The Latitudinal Gradient in Recent Speciation and Extinction Rates of Birds and Mammals.Science 315: 1574 - 1576. Compared pairs of sister bird and mammal taxa in the tropics and temperate zone. Compared DNA, and estimated time since divergence for these pairs. IF species diversify more rapidly in the tropics, THEN tropical species pairs should have a more recent common ancestor. RESULTS: Temperate pairs of birds and mammals had MORE RECENT divergence times than pairs of tropical species.

  17. BIRDS MAMMALS Time since divergence of species pairs. Age of intraspecific haplotype variation. Age of deepest phylogroup splits all relationships are strongly significant (p < 0.001)....

  18. Community Ecology • I. Introduction • II. Multispecies Interactions with a Trophic Level • III. Multispecies Interactions across Trophic Levels • IV. Succession • V. Biodiversity: Patterns and Processes • The Species-Area Relationship • The Latitudinal Trend in Diversity • The patterns • Potential Causes • a. energy-diversity hypothesis • b. habitat heterogeneity – diversity hypothesis

  19. Andes, Equator Rockies, 60 N

  20. V. Biodiversity: Patterns and Processes • The Species-Area Relationship • The Latitudinal Trend in Diversity • The patterns • Potential Causes • a. energy-diversity hypothesis • b. habitat heterogeneity – diversity hypothesis • c. Species – Area effects

  21. - Area Effect - the tropics have more area than similar ecosystems at higher latitudes.

  22. V. Biodiversity: Patterns and Processes • The Species-Area Relationship • The Latitudinal Trend in Diversity • The patterns • Potential Causes • a. energy-diversity hypothesis • b. habitat heterogeneity – diversity hypothesis • c. Species – Area Effects • d. Intermediate disturbance hypothesis

  23. Diversity is Maximized at Intermediate Disturbance (Connell, 1978). Diversity Disturbance

  24. - "Disturbance" is removal of biomass... - frequency - intensity - areal extent Diversity Disturbance

  25. - Why is diversity maximized in the middle? Competitive exclusion in very stable habitats Diversity Disturbance

  26. - Why is diversity maximized in the middle? No competitive exclusion because disturbance keeps populations low, but doesn't cause extinctions.... lots of colonists coexist... Diversity Disturbance

  27. - Why is diversity maximized in the middle? Environment is too harsh; only species that can survive the disturbance persist... Diversity Disturbance

  28. V. Biodiversity: Patterns and Processes • The Species-Area Relationship • The Latitudinal Trend in Diversity • The patterns • Potential Causes • a. energy-diversity hypothesis • b. habitat heterogeneity – diversity hypothesis • c. Species – Area Effects • d. Intermediate disturbance hypothesis • e. Environmental stability hypothesis

  29. end of last glacial - 10,000 years ago

  30. So temperate regions have not had enough time to exploit all the available niches opened by glacial retreat.

  31. - BUT.. still a global impact on climate...

  32. V. Biodiversity: Patterns and Processes • The Species-Area Relationship • The Latitudinal Trend in Diversity • The patterns • Potential Causes • a. energy-diversity hypothesis • b. habitat heterogeneity – diversity hypothesis • c. Species – Area Effects • d. Intermediate disturbance hypothesis • e. Environmental stability hypothesis • 3. Cradle or Museum?

  33. Cradle or museum? David Jablonski, Kaustuv Roy, James W. Valentine. 2006. Out of the Tropics: Evolutionary Dynamics of the Latitudinal Diversity Gradient. Science 314: 102-106. Diversity is a function of speciation rate, extinction rate, and immigration rate (range expansion into that region). HIGHER SPECIATION RATE LOWER EXTINCTION RATE

  34. Cradle or museum? David Jablonski, Kaustuv Roy, James W. Valentine. 2006. Out of the Tropics: Evolutionary Dynamics of the Latitudinal Diversity Gradient. Science 314: 102-106. Diversity is a function of speciation rate, extinction rate, and immigration rate (range expansion into that region). "Out of the tropics" model

  35. Cradle or museum? David Jablonski, Kaustuv Roy, James W. Valentine. 2006. Out of the Tropics: Evolutionary Dynamics of the Latitudinal Diversity Gradient. Science 314: 102-106. Looked at the origin of bivalve taxa (genera) in tropics and beyond Genera first appearing in the Pleistocene (2mya)

  36. Cradle or museum? David Jablonski, Kaustuv Roy, James W. Valentine. 2006. Out of the Tropics: Evolutionary Dynamics of the Latitudinal Diversity Gradient. Science 314: 102-106. Looked at the origin of bivalve taxa (genera) in tropics and beyond Genera first appearing in the Pliocene (5 mya)

  37. Cradle or museum? David Jablonski, Kaustuv Roy, James W. Valentine. 2006. Out of the Tropics: Evolutionary Dynamics of the Latitudinal Diversity Gradient. Science 314: 102-106. Looked at the origin of bivalve taxa (genera) in tropics and beyond Genera first appearing in the Miocene (23 mya)

  38. Cradle or museum? David Jablonski, Kaustuv Roy, James W. Valentine. 2006. Out of the Tropics: Evolutionary Dynamics of the Latitudinal Diversity Gradient. Science 314: 102-106. SO: The tropics may be both cradle and museum. And that begs the question regarding divergence rates... could pairs of species in temperate zone with recent common ancestors have a tropical origin?

  39. V. Biodiversity: Patterns and Processes • The Species-Area Relationship • The Latitudinal Trend in Diversity • Trend in Diversity over Geological Time

  40. Geological Time - diversity increases through time - there are periodic mass extinctions, followed by faunal recovery

  41. Geological Time Patterns in Fish Diversity Competitive replacement seems likely, as do adaptive radiations of competitively successful group.

  42. Geological Time Patterns in Tetrapod Diversity

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