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Trans-Specific Polymorphisms Between Cryptic Daphnia Species Affect Fitness and Behavior.
Connor S Murray1,2, Madison Karram1, David J Bass1
1Department of Biology, University of Virginia, Charlottesville, Virginia, USA.
Molecular Ecology
|December 24, 2024
Summary
Shared polymorphisms in Daphnia pulex, despite millions of years of divergence, suggest convergent evolution and balancing selection. A blue opsin gene with these polymorphisms impacts behavior and fitness.
Area of Science:
- Evolutionary Biology
- Population Genetics
- Genomics
Background:
- Shared polymorphisms, identical alleles across species, offer insights into evolutionary processes.
- These can result from selection maintaining ancient variation or promoting convergent evolution.
Purpose of the Study:
- To investigate the abundance and distribution of shared polymorphisms between North American and European Daphnia pulex.
- To test hypotheses including balancing selection, hybridization, incomplete lineage sorting, and convergent evolution.
Main Methods:
- Analysis of over 2,000 genomes from six taxa within the Daphnia pulex species group.
- Examination of shared allele prevalence and distribution between North American and European D. pulex.
Main Results:
- North American and European D. pulex diverged over 10 million years ago but retain tens of thousands of shared polymorphisms.
- Shared polymorphisms are largely explained by convergent evolution, with a subset representing ancient trans-specific polymorphisms.
- Balancing selection acts on both convergent and ancient shared mutations.
Conclusions:
- Hybridization and incomplete lineage sorting alone do not account for the observed shared polymorphisms.
- Convergent evolution is a major driver of shared polymorphisms in this species pair.
- A blue wavelength opsin gene exhibits trans-specific polymorphisms influencing behavior and fitness in wild populations.
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