Speciation Mechanisms Quiz

Speciation Mechanisms

• Speciation is the process where populations of the same species diverge, becoming reproductively isolated. This divergence is often driven by geographical separation and genetic differences.

Allopatric Speciation

• Definition: Populations become geographically isolated, preventing gene flow. This isolation leads to independent evolutionary trajectories.
• Vicariant Speciation: A large population is split into smaller groups by a geographic barrier (e.g., Isthmus of Panama, continental drift). This isolates populations, leading to the evolution of new species.
• Peripatric Speciation: A smaller group migrates to a new, isolated area. This small founding population has reduced genetic diversity, which is subject to genetic drift and natural selection. This results in rapid evolutionary changes. (e.g., Hawaiian fruit flies).

Peripatric Speciation

• Definition: A small group of a species colonizes a new, isolated area.
• Key features:
  • Founder Effect: The new population has significantly reduced genetic diversity compared to the original population.
  • Genetic Drift: Random changes in allele frequencies occur due to the small population size.
  • Strong Natural Selection: The new environment often favors different traits, which drive rapid adaptation.
• Examples: Hawaiian fruit flies, Cocos Island Finch.

Parapatric Speciation

• Definition: Populations are adjacent but do not mix freely due to differences in the surrounding environment.
• Clinal Speciation: Populations gradually diverge as they spread across different environments (a continuous change).
• Stepping-Stone Model: Genetic exchange occurs between populations living in isolated patches along a gradient of environmental change.
• Examples: Little Greenbul birds in Africa, lizards on Martinique Island, metal-tolerant plants near mines.
• Evidence: Houseflies bred in different conditions developed mating preferences for their group after generations.