Three modes of adaptive speciation in spatially structured populations

Area of Science:

• Evolutionary biology
• Speciation research
• Population genetics

Background:

• Adaptive speciation via assortative mating is classically studied under frequency-dependent competition or local adaptation.
• Existing models rarely compare these two speciation drivers directly.

Purpose of the Study:

• To integrate frequency-dependent competition and local adaptation into a single model.
• To investigate the interaction between these two mechanisms in driving speciation.
• To identify novel modes of speciation.

Main Methods:

• Development of a theoretical model incorporating both frequency-dependent competition and local adaptation.
• Analysis of conditions under which each mechanism drives speciation individually.
• Examination of the combined effects and interactions of both mechanisms.

Main Results:

• Individually, frequency-dependent competition and local adaptation operate under distinct conditions with minimal interaction when sufficient alone.
• A novel third mode of speciation emerges when both mechanisms interact.
• This third mode involves initial selection against maladapted migrants followed by within-deme competition, leading to faster speciation.

Conclusions:

• Frequency-dependent competition and local adaptation can act synergistically to drive adaptive speciation.
• This interaction facilitates a rapid speciation process, distinct from classical reinforcement.
• The model predicts successful coexistence of newly formed species in sympatry.