rdmp-lecture-6-macroevolution-rates-dates

Overview of Macroevolution

• Definition: Macroevolution refers to large-scale evolutionary changes that occur over geologic time, leading to the diversification of life forms.

Key Contributors and Topics

• Lecturers:

  • Rod Page: Evolution and Diversity, Evolutionary Trees, Molecular Phylogenies

  • Barbara Mable: Biometrics and Biodiversity

  • Sofie Spatharis: Functional Diversity and Biodiversity Conservation

  • Others: M Llewellyn, S White

• Main Topics Covered:

  1. Introduction to Evolution and Diversity

  2. Evolutionary Trees

  3. Molecular Phylogenies

  4. Reconstructing Ancestors

  5. Measures of Biodiversity (Molecular, Taxonomic, Functional)

  6. Biodiversity and Conservation Practices

  7. Macroevolution: Rates and Dates

  8. Biogeography

Rates and Dates in Evolution

• Key Equation: Amount of Evolution = Rate × Time

  • Examples:

    • Slow rate over a long period can lead to significant evolutionary changes.

    • Fast rate over a short period can also produce large changes.

• Change Types:

  • Continuous Change: Ongoing small changes over time.

  • Episodic Change: Sudden bursts of change typically after significant geological or environmental events.

• Separating Rates from Dates:

  • Addressing whether diversity is due to age or rate of evolution is crucial for understanding evolutionary trees.

Case Study: Hawaiian Honeycreepers

• Diversity & Evolution:

  • Hawaiian honeycreepers showcase significant diversity, their evolutionary history may reflect lengthy adaptation and evolutionary radiation.

• Comparative Analysis:

  • Two alternative hypotheses regarding honeycreepers and thrushes:

    1. Honeycreepers are older than thrushes but evolved at the same rate.

    2. Honeycreepers have evolved more quickly than thrushes, leading to greater biodiversity.

Methodologies in Macroevolution Study

• Fossil Record: Essential for dating evolutionary events but often incomplete.

• Molecular Data: Used to estimate divergence times and evolutionary rates based on genetic differences.

Understanding Rate Estimates

• Assumptions:

  • Fossil records are reasonably complete to provide minimum age estimates for various evolutionary lineages.

• Examples of Evolutionary Lineage:

  • Coelacanths illustrate how certain species show virtually no evolutionary change over millions of years.

Biogeographical Evidence

• Geographic events significantly shape biological events, linking fossils and extant species over time.

Punctuated Equilibrium vs. Gradualism

• Punctuated Equilibrium: Long periods of stasis in species interspersed with short bursts of rapid evolution.

• Gradualism: Slow, continuous change within a species over time.

Conclusion

• Final Notes:

  • Understanding rates of evolution requires solid dates obtained through fossils, biogeography, and other evidentiary associations.

  • The relationship between speciation rates and molecular evolution is an active area of research, highlighting the complexity of evolutionary mechanisms.