Pollination and Flower Specialization

Overview of Pollination

• Pollination: The process when a pollen grain lands on the stigma of a carpel on a flower.
  • Self-pollination: Pollen grain transferred from an anther to a stigma on the same plant, often the same flower.
  • Cross-pollination: Pollen from one plant travels to a stigma on flowers of a different plant, requiring a transport method (e.g., wind or animal).
• Trade-offs: Consider benefits and costs of self-pollination vs. cross-pollination.

Flower Structure and Pollination Likelihood

• Perfect vs. Imperfect Flowers: Cross-pollination likelihood varies.
• Monoecious vs. Dioecious: Influences self-pollination vs. cross-pollination likelihood.
• Maturation Timing: Different maturation times for stamens and carpels to prevent self-pollination.
  • Example: Stamens mature before carpels, promoting cross-pollination by insects.

Self-Incompatibility

• Pollen may not germinate if proteins on stigma and pollen don't match, preventing self-pollination.

Methods of Pollen Transfer

• Wind Pollination:

  • Common in 20% of angiosperms (e.g., grasses).
  • Inefficient, requires large pollen production and close plant proximity.
  • Leads to allergies due to lightweight pollen.
  • Small flowers with reduced petals and no scent.

• Animal Pollination:

  • Majority of angiosperms use this method.
  • Flowers attract specific pollinators through co-evolution.
  • Mutualistic relationship: plants receive pollination, animals receive food (pollen or nectar).

Pollination Syndromes

• Wind Pollination:

  • Small, unscented flowers.
  • Produces large amounts of pollen.

• Animal Pollination:

  • Flowers attract specific pollinators through features like scent, color, and shape.
  • Examples:
    • Bees: Attracted to fragrant, bright-colored flowers (yellow), with UV patterns.
    • Butterflies: Prefer milder scents, bright colors (pink/purple), tubular interiors.
    • Moths: Attracted to strong-smelling, pale flowers (white/yellow).
    • Flies: Attracted to small, pale open flowers during the day; some to meat-mimicking flowers.
    • Birds: Prefer bright red/orange flowers, tubular shape, large nectar amounts.
    • Bats: Prefer large, strongly scented, pale flowers, open at night, with large nectar rewards.

Co-evolution

• The traits of flowers and their pollinators evolve together to increase fitness and efficiency.
  • Example: Long tubular flowers for birds and moths with long tongues or beaks.

Conclusion

• Distinct flower features arise from co-evolution to optimize pollination efficiency by different pollinators.