Genome-Wide Allele Frequency Changes Reveal That Dynamic Metapopulations Evolve Differently.

Area of Science:

• Evolutionary Biology
• Population Genetics
• Ecology

Background:

• Metapopulations exhibit unique evolutionary dynamics driven by extinction-recolonization and gene flow, distinct from large, stable populations.
• The propagule model predicts initial intermediate allele frequencies in new subpopulations, shifting towards equilibrium via selection and drift.
• Site frequency spectrum (SFS) distribution is a key indicator of evolutionary processes in populations.

Purpose of the Study:

• To investigate the evolutionary trajectories of site frequency spectra in a natural Daphnia magna metapopulation.
• To assess the applicability of the propagule model to metapopulation dynamics.
• To disentangle the effects of stochastic events and genetic drift on subpopulation divergence and convergence.

Main Methods:

• Longitudinal study of a natural Daphnia magna metapopulation over 5 years.
• Collection of biannual pool-seq samples from 118 ponds with known subpopulation ages.
• Analysis of site frequency spectrum dynamics to infer evolutionary processes.

Main Results:

• Newly founded subpopulations showed SFS trending towards intermediate frequencies, shifting to right-skewed distributions with age, consistent with the propagule model.
• Immigration and hybrid vigor influenced SFS dynamics.
• Stochastic founder and immigration events promoted subpopulation divergence, while genetic drift led to SFS convergence in persistent subpopulations.

Conclusions:

• Site frequency spectrum dynamics provide a powerful tool for understanding metapopulation evolution.
• Metapopulations evolve distinctively due to factors like founder effects and gene flow, differing from classical populations.
• The propagule model effectively explains the observed evolutionary patterns in the Daphnia magna metapopulation.