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Pollinator-mediated Speciation in Angiosperms: What Do We Know?

Pollinator-mediated Speciation in Angiosperms: What Do We Know?. Lecture Overview. Vascular plant diversity Modes of angiosperm speciation Pollination modes and angiosperm diversification Experiments: pollinator-mediated selection on floral traits Conclusions. Lecture Overview.

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Pollinator-mediated Speciation in Angiosperms: What Do We Know?

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  1. Pollinator-mediated Speciation in Angiosperms: What Do We Know?

  2. Lecture Overview • Vascular plant diversity • Modes of angiosperm speciation • Pollination modes and angiosperm diversification • Experiments: pollinator-mediated selection on floral traits • Conclusions

  3. Lecture Overview • Vascular plant diversity • Modes of angiosperm speciation • Pollination modes and angiosperm diversification • Experiments: pollinator-mediated selection on floral traits • Conclusions

  4. Vascular Plant Diversity • 260,000+ species

  5. Vascular Plant Diversity • 260,000+ species ~ 850 gymnosperms (290 mya) ~ 9800 ferns and fern allies (400 mya) ~ 249,000 angiosperms (130 mya)

  6. Rapid diversification of angiosperms: “Abominable mystery”

  7. Rapid diversification of angiosperms: “Abominable mystery” His attempt to identify a single cause: “wretchedly poor”

  8. Lecture Overview • Vascular plant diversity • Modes of angiosperm speciation • Pollination modes and angiosperm diversification • Experiments: pollinator-mediated selection on floral traits • Conclusions

  9. Modes of Angiosperm Speciation(speciation = reproductive isolation)

  10. Modes of Angiosperm Speciation(speciation = reproductive isolation) • Mechanical barriers (e.g., mountain range)

  11. Modes of Angiosperm Speciation(speciation = reproductive isolation) • Mechanical barriers (e.g., mountain range) • Genomic events - polyploidy (e.g., diploid to tetraploid)

  12. Modes of Angiosperm Speciation(speciation = reproductive isolation) • Mechanical barriers (e.g., mountain range) • Genomic events - polyploidy (e.g., diploid to tetraploid) - chromosomal rearrangements

  13. Modes of Angiosperm Speciation(speciation = reproductive isolation) • Mechanical barriers (e.g., mountain range) • Genomic events - polyploidy (e.g., diploid to tetraploid) - chromosomal rearrangements - • Pollinator-mediated reproductive isolation - evolution of different floral morphologies

  14. Lecture Overview • Vascular plant diversity • Modes of angiosperm speciation • Pollination modes and angiosperm diversification • Experiments: pollinator-mediated selection on floral traits • Conclusions

  15. Pollination Mode and Diversification Pollination = transfer of pollen to stigma

  16. Stigma Anther Petal Sepal

  17. Stigma Anther Petal Sepal

  18. Stigma Anther Petal Sepal

  19. Pollination Mode and Diversification Pollination = transfer of pollen to stigma - > 99% of gymnosperm species wind-pollinated

  20. Pollination Mode and Diversification Pollination = transfer of pollen to stigma - > 99% of gymnosperm species wind-pollinated - > 80% of angiosperms are animal-pollinated

  21. Pollinators and angiosperm speciation: correlations • Angiosperm and insect diversification co-occurred

  22. Pollinators and angiosperm speciation: correlations • Angiosperm and insect diversification co-occurred • Animal-pollination correlated with species richness at family level

  23. Correlation ≠ Causation

  24. Correlation ≠ Causation Blood Pressure Income

  25. Lecture Overview • Vascular plant diversity • Modes of angiosperm speciation • Pollination modes and angiosperm diversification • Experiments: pollinator-mediated selection on floral traits • Conclusions

  26. Two Important Studies • Polemonium viscosum (alpine skypilot) and bumblebees (Galen, 1996)

  27. Corolla tube width = 16 mm Timberline 11,000 ft.

  28. Corolla tube width = 18 mm Alpine - 12,000 ft. Corolla tube width = 16 mm Timberline 11,000 ft.

  29. = 11% difference in corolla tube width Corolla tube width = 18 mm Alpine - 12,000 ft. Corolla tube width = 16 mm Timberline 11,000 ft.

  30. What explains corolla tube width difference? = 11% difference in corolla tube width Corolla tube width = 18 mm Alpine - 12,000 ft. Corolla tube width = 16 mm Timberline 11,000 ft.

  31. What explains corolla tube width difference? Solitary bees Corolla tube width = 18 mm Alpine - 12,000 ft. Corolla tube width = 16 mm Timberline 11,000 ft.

  32. What explains corolla tube width difference? Bumble bees Solitary bees Corolla tube width = 18 mm Alpine - 12,000 ft. Corolla tube width = 16 mm Timberline 11,000 ft.

  33. Conclusions • Bumblebees selected for wide corolla • Evolution from 16mm to 18 mm corolla ~20 yrs • Pollinator preference can cause floral trait evolution

  34. Two Important Studies • Polemonium viscosum (alpine skypilot) and bumblebees (Galen, 1996) • Ipomopsis aggregata (scarlet gilia) and hummingbirds (Campbell et al., 1997)

  35. Experiment Results Visits/ flower/ hr. Mean corolla tube width

  36. Experiment Results Visits/ flower/ hr. Mean corolla tube width Wider Flowers = More Pollen Export

  37. Experiment Results Seed set/ flower Visits/ flower/ hr. Mean corolla tube width Optical Density More red Less red Wider Flowers = More Pollen Export

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