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Discerning structure versus speciation in phylogeographic analysis of Seepage Salamanders (Desmognathus aeneus) using demography, environment, geography, and phenotype
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  • Alex Pyron,
  • Anvith Kakkera,
  • David Beamer,
  • Kyle O'Connell
Alex Pyron
The George Washington University

Corresponding Author:[email protected]

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Anvith Kakkera
Thomas Jefferson High School for Science and Technology
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David Beamer
East Carolina University
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Kyle O'Connell
Deloitte LLP
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Numerous mechanisms drive ecological speciation, including isolation by adaptation, barrier, distance, environment, hierarchy, and resistance. These promote genetic and phenotypic differentiation of local populations, formation of phylogeographic lineages, and ultimately, completed speciation via reinforcement. In contrast, it is possible that similar mechanisms might lead to lineage cohesion through stabilizing rather than diversifying ecomorphological selection and the long-term persistence of population structure within species. Processes that drive the formation and maintenance of geographic genetic diversity while facilitating high rates of migration and limiting phenotypic divergence may thereby result in population structure that is not accompanied by divergence towards reproductive isolation. We suggest that this framework can be applied more broadly to address the classic dilemma of “structure versus speciation” when evaluating phylogeographic diversity, unifying population genetics, species delimitation, and the underlying study of speciation. We demonstrate one such instance in the Seepage Salamander (Desmognathus aeneus) from the southeastern United States. Recent studies estimated up to 6.3% mitochondrial divergence and 4 phylogenomic lineages with broad admixture across geographic hybrid zones, which could potentially represent distinct species. However, while limited dispersal promotes substantial isolation by distance, extreme microhabitat specificity appears to yield stabilizing selection on ecologically mediated phenotypes. As a result, climatic cycles promote recurrent contact between lineages that are not adaptively differentiated and therefore experience repeated bouts of high migration and introgression through time. This leads to a unified, single species with deeply divergent phylogeographic lineages that nonetheless do not appear to represent incipient species.
04 Aug 2023Submitted to Molecular Ecology
07 Aug 2023Submission Checks Completed
07 Aug 2023Assigned to Editor
07 Aug 2023Review(s) Completed, Editorial Evaluation Pending
13 Aug 2023Reviewer(s) Assigned
18 Sep 2023Editorial Decision: Revise Minor
26 Oct 20231st Revision Received
27 Oct 2023Submission Checks Completed
27 Oct 2023Assigned to Editor
27 Oct 2023Review(s) Completed, Editorial Evaluation Pending
13 Nov 2023Editorial Decision: Accept