Lecture: Evolution and Natural Selection in Rock Pocket Mice

Introduction to the Valley of Fire

• Located in New Mexico's Valley of Fire.
• Dramatic landscape change due to volcanic eruptions 1,000 years ago.
• Resulted in black lava rock disrupting desert sands.

The Rock Pocket Mouse

• Habitat: Adapts to light desert sand and dark lava rocks.
• Predators: Foxes, coyotes, rattlesnakes, owls, hawks (visual predators).

Evolutionary Adaptation

• Camouflage: Light fur on desert sand, dark fur on lava.
• Predation Pressure: Dark fur evolved due to selection pressure from predators.

Mechanism of Color Change

• Mutation: Random mutation leads to dark fur.
• Natural Selection: Predators eliminate mice that stand out.
• Research by Michael Nachman:
  • Collection and study of mice to understand fur color adaptation.
  • DNA analysis to identify genetic mutation responsible for dark coloration.

Genetic Findings

• Difference between dark and light mice attributed to a gene called MC1R.
• MC1R controls dark pigment in mouse hair follicles.
• Even with a small initial advantage, dark fur can quickly dominate a population.
  • Example: A 1% advantage leads to 95% dark mice in 1,000 years.
  • A 10% advantage results in the same in just 100 years.

Implications for Evolutionary Theory

• Natural Selection vs Mutation
  • Mutation is random but natural selection is not.
  • Natural selection sorts traits based on environmental conditions.

Repeated Evolution

• Similar Adaptations in Different Locations:
  • Different genetic mutations can lead to similar adaptations (dark mice).
  • Other lava flows have produced similar dark mice independently.
• Conclusion:
  • Evolution can repeat under similar environmental pressures.

Conclusion

• Rock pocket mice provide a clear example of Darwin's natural selection.
• Demonstrates how species adapt to changing environments.
• Highlights that evolutionary change is a continuous process.