Molecular correlates of reproductive isolation

Area of Science:

• Evolutionary biology
• Speciation research
• Population genetics

Background:

• Reproductive isolation is key to speciation in sexual animals, often arising as a byproduct of genetic divergence.
• The relationship between general genetic divergence and the rate of speciation is not well understood.
• Divergent selection in allopatric populations may accelerate speciation, but reproductive isolation itself isn't directly selected for.

Purpose of the Study:

• To investigate the factors linking general genetic divergence to the evolution of reproductive isolation.
• To test whether allozyme (protein) divergence or silent DNA divergence better predicts reproductive isolation in Drosophila.
• To provide evidence for or against a model of selection-mediated allopatric speciation.

Main Methods:

• Analysis of published data on Drosophila species.
• Comparison of genetic divergence measures: allozyme divergence (reflecting protein evolution) and silent DNA divergence.
• Correlation analysis between genetic divergence metrics and measures of pre- and postmating reproductive isolation.

Main Results:

• Pre- and postmating reproductive isolation in Drosophila species showed a stronger correlation with allozyme divergence than with silent DNA divergence.
• Proteins are generally more influenced by natural selection than silent DNA polymorphisms.
• The findings suggest that selection acting on proteins plays a significant role in the speciation process.

Conclusions:

• The results broadly support a model where allopatric speciation is mediated by natural selection.
• Selection on traits, reflected in protein evolution, appears to be a crucial factor driving the accumulation of reproductive isolation.
• This highlights the importance of considering selection's role in understanding the tempo and mode of speciation.