The genetics of speciation: are complex incompatibilities easier to evolve?

Area of Science:

• Evolutionary Biology
• Genetics

Background:

• Reproductive isolation is key to speciation.
• Dobzhansky-Muller incompatibilities (DMIs) are genetic incompatibilities that arise between diverging populations.
• DMIs can be complex (multiple loci) and asymmetrical (unequal fitness effects).

Purpose of the Study:

• To investigate whether the ease of DMI evolution, based on the number of evolutionary paths, predicts the delay in divergence.
• To assess the influence of DMI complexity and symmetry on the time to reproductive isolation.

Main Methods:

• Modeling evolutionary divergence in allopatry.
• Calculating delays to divergence caused by different types of DMIs.
• Analyzing the relationship between DMI characteristics and divergence time.

Main Results:

• The number of evolutionary paths is not always a reliable predictor of divergence time.
• Symmetrical DMIs can delay divergence, particularly two-locus cases with no fit intermediates.
• Complex symmetrical DMIs delay divergence only in specific parameter ranges.
• DMI form and presence have minimal impact on divergence times in most scenarios.

Conclusions:

• The 'ease of evolution' hypothesis for complex and asymmetrical DMIs is not well-supported by these models.
• Divergence time is influenced by factors beyond the number of evolutionary paths created by DMIs.
• Further research is needed to fully explain the observed patterns of DMI evolution in experimental crosses.