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Geographic Variation in Genomic Signals of Admixture Between Two Closely Related European Sepsid Fly Species
Athene Giesen1, Wolf U Blanckenhorn1, Martin A Schäfer1
1Department of Evolutionary Biology and Environmental Studies, University of Zürich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
Evolutionary Biology
|October 19, 2023
Summary
Interspecific gene flow between dung fly species varies geographically. Selection against hybrids influences species boundaries, with no uniform link between proximity and gene flow.
Area of Science:
- Evolutionary Biology
- Speciation Genetics
- Population Genetics
Background:
- Interspecific gene flow's role in species barrier dynamics is unclear.
- Hybridization can impede adaptive divergence or promote reinforcement.
- Understanding past gene flow patterns is crucial for speciation research.
Purpose of the Study:
- To investigate signals of past interspecific gene flow between *Sepsis cynipsea* and *S. neocynipsea*.
- To compare gene flow patterns in allopatric versus sympatric populations.
- To assess the influence of eco-geographic context on species boundaries.
Main Methods:
- Microsatellite genotyping to infer demographic history via Approximate Bayesian Computation.
- Genomic analysis of pooled DNA using ABBA-BABA tests (D-statistic) for interspecific gene flow.
- Comparison of gene flow signals with contemporary geographic distribution (allopatric/sympatric).
Main Results:
- An excess of past interspecific gene flow was detected at one French site.
- Lower gene flow signals were observed in sympatric Swiss populations compared to allopatric ones.
- Contrasting patterns suggest context-dependent species boundaries.
Conclusions:
- Species boundaries between *S. cynipsea* and *S. neocynipsea* are influenced by past and present eco-geographic factors.
- No consistent relationship exists between contemporary geographic proximity and historical interspecific gene flow.
- Eco-geographic context plays a significant role in shaping species divergence and gene flow dynamics.
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