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Riverscape genetics of the orangethroat darter complex
John T Belcik1,2, Mary V Ashley1
1Department of Biological Sciences, University of Illinois at Chicago, Chicago, Illinois, USA.
Journal of Fish Biology
|November 16, 2023
Summary
Orangethroat darters (Ceasia) in the US show surprising genetic structure in glaciated areas, with two distinct clusters in Etheostoma spectabile. Unglaciated regions exhibited less genetic differentiation, suggesting complex post-glacial gene flow.
Area of Science:
- Ichthyology
- Evolutionary Biology
- Conservation Genetics
Background:
- The orangethroat darter species complex (Ceasia) is widespread across the Central and Southern United States.
- This complex includes up to 15 species, with varying distributions in glaciated and unglaciated regions.
- Species diversity and endemism are notably higher in the unglaciated Central Highlands.
Purpose of the Study:
- To evaluate genetic diversity and structure within the Ceasia complex.
- To investigate pre- and post-glacial range dynamics.
- To test the hypothesis of stronger genetic differentiation in unglaciated areas.
Main Methods:
- Microsatellite genotyping of 384 darters from 52 sites.
- Analysis of genetic diversity and population structure.
- Comparison of genetic data with geographical distribution and species identification.
Main Results:
- Two distinct genetic clusters of Etheostoma spectabile were identified in glaciated regions (Illinois River basin and Wabash/Great Lakes tributaries).
- These clusters suggest expansion from two isolated glacial refugia with limited post-glacial gene flow.
- Fish from unglaciated regions showed less genetic differentiation, with some species (E. burri, E. uniporum) not genetically distinct from E. spectabile.
Conclusions:
- Glaciated regions exhibit stronger genetic differentiation than anticipated, indicating isolation from distinct glacial refugia.
- Hybridization and introgression in the Central Highlands may complicate species delineation in this high-diversity area.
- Further research is needed to clarify species boundaries and evolutionary history within the Ceasia complex.
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