Genetic data reveal fine-scale ecological segregation between larval plethodontid salamanders in replicate contact zones

Abstract

Contact zones present unique opportunities to investigate ecological divergence, reproductive barriers, and gene flow between species. The two-lined salamander (Eurycea bislineata) species complex is a group of semiaquatic plethodontid salamanders with a reticulate evolutionary history that reflects the reorganization of river drainage basins. Although evidence for widespread, ancient introgression suggests an absence of reproductive isolating mechanisms in the early evolutionary history of the group, modern contact zones reveal a broader diversity of outcomes—with some putative species pairs occurring in sympatry and others exhibiting narrow hybrid zones. Here, we used RADcap data to investigate gene flow and ecological divergence in replicate contact zones between two species in the Appalachian foothills. Our results demonstrate that gene flow between these species is absent or rare, and larvae show strong, fine-scale ecological segregation among riffles, runs, and pools in streams. These results reinforce the more ambiguous conclusions of previous studies that suggested the evolutionary distinctiveness of these two species and underscore the importance of ecological factors in shaping local distributions.

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Availability of data and material

All sequence reads are available from the NCBI SRA (PRJNA630450), and all other data files and results from analyses are available from the Dryad Digital Repository (https://doi.org/10.5061/dryad.brv15dv6s).

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Acknowledgements

We thank Ken Kozak for aiding with the initial sample collection for the design of RADcap loci and for general guidance throughout this research. We thank Natalia Bayona-Vásquez, Joel Corush, Allison Devault, Travis Glenn, and Troy Kieran for aid in experimental design and laboratory assistance. We thank Natalia Bayona-Vásquez, Cyndi Carter, Troy Kieran, and Alexander Miele for aid in the field.

Funding

Funding was provided by the North Carolina Herpetological Society and the University of Tennessee Knoxville’s Department of Ecology and Evolutionary Biology Research Funds, and TWP was supported by a National Science Foundation Graduate Research Fellowship (DGE-1452154).

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All authors conceived of and designed the study and analyses. TWP and CDC collected data in the field. TWP conducted all laboratory work, analyzed data, and wrote the manuscript. All authors edited the manuscript and approved the final version.

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Correspondence to Todd W. Pierson.

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The authors declare no conflicts of interest or competing interests.

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This research was approved under an animal use protocol from the University of Tennessee Knoxville IACUC (#2482-0916), and collections were permitted by the Chattahoochee National Forest and in compliance with all local, state, and federal wildlife laws and regulations. The authors declare no conflicts of interest.

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Pierson, T.W., Fitzpatrick, B.M. & Camp, C.D. Genetic data reveal fine-scale ecological segregation between larval plethodontid salamanders in replicate contact zones. Evol Ecol (2021). https://doi.org/10.1007/s10682-020-10099-1

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Keywords

  • Eurycea
  • Hybridization
  • Sympatry
  • Two-lined salamander