Patterns of postzygotic isolation in Lepidoptera

Area of Science:

• Evolutionary Biology
• Speciation Genetics
• Insect Systematics

Background:

• Intrinsic postzygotic isolation is a key factor in speciation.
• Understanding the tempo and mode of postzygotic isolation evolution is crucial for evolutionary theory.
• Haldane's rule describes a pattern of sex-biased hybrid dysfunction.

Purpose of the Study:

• To characterize the evolutionary patterns of intrinsic postzygotic isolation in Lepidoptera.
• To investigate the time-course of postzygotic isolation and hybrid fitness problems.
• To test the composite theory of Haldane's rule using Lepidoptera data.

Main Methods:

• Literature data analysis on genetic distance, hybrid sterility/inviability, biogeography, and natural hybridization.
• Using genetic distance as a proxy for evolutionary time.
• Comparative analysis with Drosophila data.

Main Results:

• Postzygotic isolation increases gradually with species divergence.
• Hybrid sterility evolves more rapidly than hybrid inviability.
• Haldane's rule is strongly supported in Lepidoptera, with female-biased hybrid problems.
• Haldane's rule for sterility evolves as fast or faster in Lepidoptera compared to Drosophila.
• A significant proportion of sympatric Lepidoptera species hybridize, often with reduced hybrid fitness.

Conclusions:

• Postzygotic isolation accumulates progressively during species divergence in Lepidoptera.
• The findings support and refine theories on the evolution of reproductive isolation and Haldane's rule.
• Natural hybridization occurs frequently in sympatry and can contribute to speciation through reduced hybrid fitness.