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Asymmetric Gene Flow Maintains Range Edges in a Marine Invertebrate
Zachary B Hancock1,2, Nicole E Adams2, Perry L Wood2
1Department of Biological Sciences, Augusta University, Augusta, Georgia 30912.
The American Naturalist
|July 23, 2026
Summary
Range edge evolution is explained by migration limitation, not gene swamping. Genomic data for the Canadian shovel bug (Haustorius canadensis) reveals reduced gene flow to the periphery, supporting this hypothesis.
Area of Science:
- Evolutionary Biology
- Population Genetics
- Marine Biology
Background:
- Species ranges are limited, and adaptation at periphery is often poor.
- Hypotheses for range edge persistence include gene swamping and dispersal limitation.
- Assessing these hypotheses is challenging due to range complexity.
Purpose of the Study:
- Investigate the evolutionary mechanisms maintaining range edges.
- Test the gene swamping versus dispersal limitation hypotheses.
- Utilize genomic data in an empirical system, *Haustorius canadensis*.
Main Methods:
- Range-wide genomic sequencing of *Haustorius canadensis*.
- Analysis of genetic drift, inbreeding, and migration patterns.
- Inference of dispersal based on genomic signatures and environmental factors.
Main Results:
- Increased genetic drift and inbreeding observed at range edges.
- Detected asymmetric migration patterns, directed towards the range center.
- Migration directionality aligns with North Atlantic current regimes.
Conclusions:
- Findings support the migration limitation hypothesis for range edge persistence.
- Anisotropic dispersal limits peripheral population replenishment.
- This generates the ecological pattern of an 'abundant center'.
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