Testing for mating isolation between ecotypes: laboratory experiments with lake, stream and hybrid stickleback

Area of Science:

• Evolutionary Biology
• Speciation Research
• Behavioral Ecology

Background:

• Ecological speciation is often linked to mating isolation.
• The consistency of mating isolation evolving from divergent selection remains unclear.

Purpose of the Study:

• To test for genetically based mating isolation between lake and stream threespine stickleback populations.
• To investigate the role of divergent selection in driving mating isolation.

Main Methods:

• Used second-generation laboratory-reared fish to minimize environmental influences.
• Incorporated male-male competition and included hybrids in mate choice trials.
• Observed male behaviors (aggression, display, nest activities) and mating success.

Main Results:

• Lake and Inlet stickleback males exhibited behavioral differences relevant to mate choice.
• Hybrid males showed intermediate or 'inferior' behaviors compared to pure types.
• No assortative mating was observed between Lake and Inlet fish; hybrids faced no mating disadvantage.

Conclusions:

• Divergent ecological differences between stickleback populations did not lead to mating isolation.
• Mating isolation is not an inevitable consequence of ecological divergence.
• Further research is needed to understand factors influencing ecological speciation progress.