Lecture on Bird Speciation

Introduction

• Approximately 10,000 known bird species exist.
• Birds-of-Paradise as an example of diverse evolution from a common ancestor.
• Key concept: Speciation

Definition of Species

• Classic definition: Groups of interbreeding natural populations, reproductively isolated from others.

Speciation Process

• Separation and Isolation: Groups become separated in space or behavior, leading to lack of regular mating.
  • Example: Birds colonizing a new volcanic island.
  • Reproductive Isolation: New island populations become isolated from mainland populations.
• Natural and Sexual Selection: Over generations, distinct forms develop with unique genetic fingerprints.

Testing Speciation

• Experiment: Introducing individuals from different populations at intervals:
  • 200 Generations: Still recognize each other, mate.
  • 1000 Generations: Differing songs, but mating occurs.
  • 10,000 Generations: No recognition or interest, speciation complete.

Geographic Speciation

• Habitat Fragmentation: Division leading to speciation.
  • Example: Island with central mountain ridge and valley.
  • Eastern Birds: Evolve specialized mating systems and fancy plumage due to resource abundance.
  • Western Birds: Stable traits due to harsher conditions.
• Isolation Effects: Once isolated populations no longer produce viable offspring when they meet.

Case Study: Birds-of-Paradise

• Originated from a crow-like ancestor.
• New Guinea and surrounding islands: Key geographic area for their evolution.
• Ongoing process shaped by geographic changes and selection pressures.

Conclusion

• Speciation as a constant, ongoing process.
• Contributes to the vast biodiversity from a single bird ancestor.

Summary

• Speciation explains the diversity of bird species from a common ancestor.
• Geographic isolation and selection pressures are crucial.
• Biodiversity is a result of evolutionary processes driving speciation.