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The Ecology of Adaptive Radiation

The Ecology of Adaptive Radiation. QUICK. Think of the First Adaptive Radiation That Comes to Mind. Hawaiian Silverswords. Malagasy Vangids. Andean Espeletia. Ecological Opportunity.

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The Ecology of Adaptive Radiation

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  1. The Ecology of Adaptive Radiation

  2. QUICK Think of the First Adaptive Radiation That Comes to Mind

  3. Hawaiian Silverswords

  4. Malagasy Vangids

  5. Andean Espeletia

  6. Ecological Opportunity “loosely defined as a wealth of evolutionarily accessible resources little used by competing taxa” (Schluter 2000, p.69).

  7. Ecological Opportunity • Does it promote AR? • If so, how? • Is it required for AR? • Is it an operationally useful concept, or just a useful heuristic?

  8. “Evolutionary divergence of members of a single phylogenetic lineageinto a variety of different adaptive forms.” Futuyma, Evolutionary Biology, 1998 Adaptive Radiation

  9. Hawaiian Honeycreepers

  10. AR Definitional Issues • Is pace of diversification part of the definition? In particular, does it have to be explosive? • How are ARs distinguished from non-ARs?

  11. AR

  12. AR Definitional Issues • Is pace of diversification part of the definition? In particular, does it have to be explosive? • How are ARs distinguished from non-ARs? • Does it make sense to categorize a continuously distributed characteristic?

  13. AR

  14. AR Definitional Issues • Is pace of diversification part of the definition? In particular, does it have to be explosive? • How are ARs distinguished from non-ARs? • Does it make sense to categorize a continuously distributed characteristic? • Is the number of species the appropriate metric?

  15. AR Non-Adaptive Non-Radiation Non-Adaptive Radiation

  16. What Prompts AR? • Classic idea (Simpson, Major Features of Evolution, 1954)—AR requires: • Geographical Access • colonization • Physical Access • mass extinction, appearance of new resource • Evolutionary Access • key innovation

  17. “The evolution of a trait that allows a species to interact with the environment in an entirely new way” Key Innovation

  18. “The evolution of a trait that allows a species to interact with the environment in an entirely new way” Key Innovation Note: 1. KI does not necessarily cause AR

  19. “The evolution of a trait that allows a species to interact with the environment in an entirely new way” Key Innovation Note: 1. KI does not necessarily cause AR 2. KI refers to ecological diversity, not number of species

  20. What Is the Evidence that Ecological Opportunity Prompts AR? • Biogeography: AR on islands • Paleontology: AR after mass extinction • Evolution: AR associated with KI • Phylogeny: Decline in diversification as radiation progresses

  21. Mahler et al., Evolution, 2010 Rabosky and Glor, PNAS, 2010

  22. What is the Evidence that Ecological Opportunity Prompts AR? • Biogeography: AR on islands • Paleontology: AR after mass extinction • Evolution: AR associated with KI • Phylogeny: Decline in diversification as radiation progresses • Experimental evolution in lab

  23. Ecological Opportunity • Does it promote AR? • If so, how? • Is it required for AR? • Is it an operational useful concept, or just a useful heuristic?

  24. Adaptive Radiation Requires: • Adaptive Diversification • Speciation

  25. (seed size)

  26. (seed size)

  27. (seed size)

  28. (seed size)

  29. (seed size)

  30. Two Questions: • Is interspecific competition the only ecological interaction that can lead to AR? • Is speciation+diversification a one-step process or a two-step process?

  31. Two Questions: • Is interspecific competition the only ecological interaction that can lead to AR? • Is speciation+diversification a one-step process or a two-step process?

  32. Speciation Adaptive Differentiation 2 Steps

  33. Speciation + Adaptive Differentiation 1 Step

  34. Ecological Speciation Andrew P. Hendry. 2009. Ecological speciation! Or the lack thereof? Canadian Journal of Fisheries and Aquatic Sciences 66: 1383-1398.

  35. Two Flavors of Ecological Speciation • Strong—in the presence of gene flow (sympatric/parapatric speciation) • Weak—divergence driven by natural selection regardless of geographic context

  36. Strong Flavor: Speciation in presence of gene flow Speciation + Adaptive Differentiation 1 Step

  37. Speciation in allopatry Adaptive Differentiation • 2-Step Models: • Does adaptive differentiation occur in allopatry or sympatry?

  38. Why might NS favor different adaptations on different islands?

  39. Nat Sel may be involved in speciation (weak ES); Competition not important Nat selnot part of speciation

  40. Character Displacement Assumption: Body size correlates with resource use

  41. Nat Selpart of speciation; Competition not important Nat selnot part of speciation

  42. Nat Selpart of speciation; Competition not important Nat selnot part of speciation

  43. Two Questions? • Is interspecific competition the only ecological interaction that can lead to AR? • Is speciation-diversification a one-step process or a two-step process?

  44. Other Processes That Could Promote AR • Apparent competition/Competition for predator-free space (predation)

  45. Apparent Competition • In Habitat A, Predator 1 preys on Prey 1 • More Prey 1  more Predator 1 • Predator 1 also opportunistically eats Prey 2 • More Predator 1  fewer Prey 2 • Hence, more Prey 1  fewer Prey 2 • “Apparent” competition • Promotes habitat divergence by Prey 2 to escape Prey 1’s predators

  46. Other Processes That Could Promote AR • Apparent competition/Competition for predator-free space (predation) • Parasitism/Herbivory ecologically the same as above • Mutualism/Coevolution

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