1. Lecture Overview Origins of plant-pollinator interactions Diversification of insects and angiosperms Proving the pollinator-mediated speciation story Empirical evidence for pollinator-mediated selection on floral traits Empirical evidence for pollinator-mediated speciation

3. Margaret Mee (1909 - 1988)

8. Using Experimental Studies To Understand Pollinator-mediated Speciation Angiosperm

9. Lecture Overview Origins of plant-pollinator interactions Diversification of insects and angiosperms Proving the pollinator-mediated speciation story Empirical evidence for pollinator-mediated selection on floral traits Empirical evidence for pollinator-mediated speciation

10. Origins of plant-pollinator interactions Dates back ~ 300 million years to cycads

12. Origins of plant-pollinator interactions Dates back ~ 300 million years to cycads Cycads (gymnosperms) pollinated by weevils

15. Origins of plant-pollinator interactions Dates back ~ 300 million years to cycads Cycads (gymnosperms) pollinated by weevils Male cones thermogenic - emit attractive scent

16. Origins of plant-pollinator interactions Dates back ~ 300 million years to cycads Cycads (gymnosperms) pollinated by weevils Male cones thermogenic - emit attractive scent Weevils, feed, mate, lay eggs in cones

17. Lecture Overview Origins of plant-pollinator interactions Diversification of insects and angiosperms Proving the pollinator-mediated speciation story Empirical evidence for pollinator-mediated selection on floral traits

18. Diversification of insects and angiosperms Earliest angiosperms ~140 mya; exponential  in diversity

21. Diversification of insects and angiosperms Earliest angiosperms ~140 mya; exponential  in diversity Bird and bee radiation occurred simultaneously

22. Diversification of insects and angiosperms Earliest angiosperms ~140 mya; exponential  in diversity Bird and bee radiation occurred simultaneously Angiosperm diversification fastest in animal- pollinated lineages

23. Diversification of insects and angiosperms Earliest angiosperms ~140 mya; exponential  in diversity Bird and bee radiation occurred simultaneously Angiosperm diversification fastest in animal- pollinated lineages Angiosperm diversity driven in part by pollinator- mediated speciation?

28. Lecture Overview Origins of plant-pollinator interactions Diversification of insects and angiosperms Proving the pollinator-mediated speciation story Empirical evidence for pollinator-mediated selection on floral traits Empirical evidence for pollinator-mediated speciation

29. Proving the pollinator-mediated speciation story Demonstrating speciation by pollinators is difficult

30. Proving the pollinator-mediated speciation story Demonstrating speciation by pollinators is difficult –most closely-related taxa don’t interbreed

31. Proving the pollinator-mediated speciation story Demonstrating speciation by pollinators is difficult –most closely-related taxa don’t interbreed Difficult to acquire empirical evidence to satisfy skeptical inquirer

32. Proving the pollinator-mediated speciation story Demonstrating speciation by pollinators is difficult –most closely-related taxa don’t interbreed Difficult to acquire empirical evidence to satisfy skeptical inquirer Can it be demonstrated?

33. Essentials of plant/pollinator interaction Many pollinators seek maximum reward per unit of effort (= optimal foraging)

34. Essentials of plant/pollinator interaction Many pollinators seek maximum reward per unit of effort (= optimal foraging) –short search time –short flower handling time –high reward

35. Essentials of plant/pollinator interaction Many pollinators seek maximum reward per unit of effort (= optimal foraging) –short search time –short flower handling time –high reward Plants benefit from reliable and efficient pollinators

36. Essentials of plant/pollinator interaction Many pollinators seek maximum reward per unit of effort (= optimal foraging) –short search time –short flower handling time –high reward Plants benefit from reliable and efficient pollinators –pollen ends up on conspecific flower = not wasted –pollen properly placed within flower

37. Essentials of plant/pollinator interaction Many pollinators seek maximum reward per unit of effort –short search time –short flower handling time –high reward Plants benefit from reliable and efficient pollinators –pollen ends up on conspecific flower = not wasted –pollen properly placed within flower Design experiments to capitalize on these facts

38. Conceptual Approach to Proving Pollinator-mediated Speciation Step 1 - demonstrate pollinators cause floral trait (e.g. size, color) evolution

39. Conceptual Approach to Proving Pollinator-mediated Speciation Step 1 - demonstrate pollinators cause floral trait (e.g. size, color) evolution Step 2 - demonstrate that differences in floral traits (e.g. morphology, color) lead to reproductive isolation

40. Lecture Overview Origins of plant-pollinator interactions Diversification of insects and angiosperms Proving the pollinator-mediated speciation story Empirical evidence for pollinator-mediated selection on floral traits Empirical evidence for pollinator-mediated speciation

41. Two Important Studies Ipomopsis aggregata (scarlet gilia) and hummingbirds (Campbell et al., 1997)

43. Experiment Results Visits/ flower/ hr. Mean corolla width Visits/ flower/ hr. Optical Density More redLess red Wider Flowers = More Pollen Export

44. Conclusions Take ~ 250 years for a broad, red flower to evolve from a white-tubular flower by pollinator-mediated selection

45. Two Important Studies Ipomopsis aggregata (scarlet gilia) and hummingbirds Polemonium viscosum (alpine skypilot) and bumblebees (Galen, 1996)

47. Timberline 11,000 ft. Alpine - 11,500 ft. Corolla width = 18 mm Corolla width = 16 mm What explains corolla size difference?

48. Timberline 11,000 ft. Alpine - 11,500 ft. Corolla width = 18 mm Corolla width = 16 mm What explains corolla size difference?

49. Conclusions Bumblebees selected for wide corolla Evolution from 16mm to 18 mm corolla ~20 yrs

50. Lecture Overview Origins of plant-pollinator interactions Diversification of insects and angiosperms Proving the pollinator-mediated speciation story Empirical evidence for pollinator-mediated selection on floral traits Empirical evidence for pollinator-mediated speciation

51. Reproductive isolation in columbine Aquilegia pubescens Aquilegia formosa

52. Reproductive isolation in columbine Aquilegia pubescens Aquilegia formosa Note - viable hybrids from hand pollination

53. Aquilegia pubescens Aquilegia formosa

54. Experimental Design (Fulton and Hodges, 1999)

55. Results and Conclusion Hummingbirds almost always visit A. formosa Hawkmoths always visit A. pubescens

56. Results and Conclusion Hummingbirds almost always visit A. formosa Hawkmoths always visit A. pubescens Reproductive isolation achieved through corolla morphology differences

57. 1 problem with this study No hybrids in array - not a complete test of speciation process

58. 1 problem with this study No hybrids in array - not a true test of speciation process Solution - Mimulus cardinalis (hummingbird) and Mimulus lewisii (bumblebee) (Schemske and Bradshaw, 1999)

61. Results % of total visits made by bees

62. Conclusion Pollinator discrimination can select for corolla morphology differences that lead to reproductive isolation

63. Lecture Summary Pollinators are agents of selection on floral traits due to foraging fidelity as agents of gene flow pollinators foster divergence in floral traits different pollinators select in different directions = floral trait evolution floral trait evolution can lead to reproductive isolation = speciation

64. Insect Pollination and Flowering Plant Species Diversification Flowering plant families that are insect-pollinated tend to have high degree of speciation (e.g. orchids) Pollinators likely have been a source of speciation in flowering plant families (e.g. Mimulus)