Lecture Notes: Evolution in the Valley of Fire

Introduction

• Speaker: Sean Carroll
• Location: Valley of Fire, New Mexico
• Main Topic: Evolutionary adaptation of rock pocket mice to lava flow environment

The Valley of Fire Environment

• Landscape Features:
  • Golden deserts with patches of black volcanic rock
  • Volcanic eruptions occurred ~1,000 years ago, leaving black rock remnants
• Ecological Challenge:
  • Animals dependent on camouflage face challenges due to the contrasting black rock

Rock Pocket Mice and Camouflage

• Predator-Prey Dynamics:
  • Predators include foxes, coyotes, rattlesnakes, owls, hawks
  • Predators are primarily visual hunters
• Pocket Mice Characteristics:
  • Light colored fur blends with sandy desert
  • Dark colored fur blends with black volcanic rock

Evolutionary Adaptation

• Field Research by Michael Nachman:
  • Dark pocket mice discovered on lava
  • Most mice on lava flows are dark
• Color Change:
  • Beneficial adaptation to evade predators
  • Selection pressure from predators

Genetic Mutation and Fur Color

• Mutation as a Mechanism:
  • Dark mice arise from genetic mutations
  • Mutations are rare and random
• Gene Focus: Mc1r gene
  • Controls dark pigment in hair follicles
  • Mutation in Mc1r results in dark fur

Spread of Dark Fur Trait

• Population Genetics:
  • Rapid spread of dark fur trait due to reproductive advantage
  • Math model: Small advantage compounded leads to widespread trait
• Timeframe: Approximately 1,000 years for significant population change

Natural Selection and Evolution

• Natural Selection:
  • Non-random process that sorts winners and losers
  • Mutation is random, but selection is directional
• Evidence from Other Lava Flows:
  • Different lava flows show similar adaptations
  • Different genetic paths can lead to similar phenotypic outcomes

Conclusion

• Repetition of Evolution:
  • Evolution can repeat itself under similar environmental pressures
• Continuous Evolutionary Process:
  • As environments change, species must adapt and re-adapt
  • Example of Darwin’s natural selection

Key Takeaways

• Evolutionary Biology Insight:
  • Simple ecological systems provide clear examples of evolution
  • Natural selection drives evolutionary change and adaptation
• Rock Pocket Mice as a Model:
  • Perfect illustration of evolutionary principles
  • Provides insight into genetic and environmental interactions