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Abstract Species interactions drive diverse evolutionary outcomes. Speciation by cascade reinforcement represents one example of how species interactions can contribute to the proliferation of species. This process occurs when the divergence of mating traits in response to selection against interspecific hybridization incidentally leads to reproductive isolation among populations of the same species. Here, we investigated the population genetic outcomes of cascade reinforcement in North American chorus frogs (Hylidae:Pseudacris). Specifically, we estimated the frequency of hybridization among three taxa, assessed genetic structure within the focal species,P.feriarum, and ascertained the directionality of gene flow withinP.feriarumacross replicated contact zones via coalescent modeling. Through field observations and preliminary experimental crosses, we assessed whether hybridization is possible under natural and laboratory conditions. We found that hybridization occurs amongP.feriarumand two conspecifics at a low rate in multiple contact zones, and that gene flow within the former species is unidirectional from allopatry into sympatry with these other species in three of four contact zones studied. We found evidence of substantial genetic structuring withinP.feriarumincluding a divergent western allopatric cluster, a behaviorally‐distinct sympatric South Carolina cluster, and several genetically‐overlapping clusters from the remainder of the distribution. Furthermore, we found sub‐structuring between reinforced and nonreinforced populations in the two most intensely‐sampled contact zones. Our literature review indicated thatP.feriarumhybridizes with at least five heterospecifics at the periphery of its range providing a mechanism for further intraspecific diversification. This work strengthens the evidence for cascade reinforcement in this clade, revealing the geographic and genetic landscape upon which this process can contribute to the proliferation of species.
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Phylogeography and paleoclimatic range dynamics explain variable outcomes to contact across a species' range
Abstract Replicability of divergence after contact is a poorly characterized process, particularly in the contexts of phylogeography and postglacial range dynamics within species. Using contact zones located at the leading‐, mid‐ and rear‐edges of a species' range, we examined variation in outcomes to contact between divergent lineages ofCampanula americana. We investigated whether contact zones vary in quantity and directionality of gene flow, how phylogeographic structure differs between contact zones, and how historic range dynamics may affect outcomes to contact. We found that all contact zones formed at similar times via primary contact yet detected significant admixture in only the rear‐edge (RE) contact zone. In the northern leading‐edge contact zone and the mid‐range Virginia contact zone, gene flow was minimal and asymmetric. In the southern RE contact zone, gene flow was strong and symmetric. Asymmetric admixture in the leading‐edge and Virginia contact zones matches the directionality of a known cosmopolitan cytonuclear incompatibility between lineages ofC. americana. Our results emphasize the dependence of speciation processes on phylogeographic structure, evolutionary history and range dynamics.
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- Award ID(s):
- 2021791
- PAR ID:
- 10561353
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Molecular Ecology
- Volume:
- 33
- Issue:
- 15
- ISSN:
- 0962-1083
- Subject(s) / Keyword(s):
- contact zones, phylogeography, range dynamics, speciation
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1111/mec.17450
