Genetic differentiation and selection against migrants in evolutionarily replicated extreme environments.

Area of Science:

• Evolutionary Biology
• Ecology
• Genetics

Background:

• Livebearing fishes (Poecilia) in sulfidic and nonsulfidic habitats show convergent phenotypic evolution.
• The evolution of reproductive isolation mechanisms in these populations was previously unclear.

Purpose of the Study:

• Investigate the mechanisms of reproductive isolation in Poecilia across different habitats.
• Determine if reproductive isolation mechanisms evolved convergently in replicate drainages.

Main Methods:

• Microsatellite analysis to assess gene flow between populations.
• Reciprocal translocation experiments to evaluate selection against immigrants.
• Mate choice experiments to study assortative mating preferences.

Main Results:

• Strongly reduced gene flow observed between populations in different habitat types.
• Significant selection against immigrants into sulfidic waters, with variation in nonsulfidic waters.
• Assortative mating evolved in females from nonsulfidic habitats, but not sulfidic ones.
• Negative correlation between natural selection (RI(m)) and sexual selection (RI(s)) suggests reinforcement.

Conclusions:

• Local adaptation to sulfide springs repeatedly leads to reproductive isolation and genetic differentiation in Poecilia.
• Mechanisms of reproductive isolation vary across independent evolutionary replicates, showing both convergent and nonconvergent trajectories.