1
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Garner AG, Goulet-Scott BE, Hopkins R. Phylogenomic analyses re-examine the evolution of reinforcement and hypothesized hybrid speciation in Phlox wildflowers. THE NEW PHYTOLOGIST 2024; 243:451-465. [PMID: 38764373 DOI: 10.1111/nph.19802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Accepted: 03/22/2024] [Indexed: 05/21/2024]
Abstract
The tree of life is riddled with reticulate evolutionary histories, and some clades, such as the eastern standing Phlox, appear to be hotspots of hybridization. In this group, there are two cases of reinforcement and nine hypothesized hybrid species. Given their historical importance in our understanding of plant speciation, the relationships between these taxa and the role of hybridization in their diversification require genomic validation. Using phylogenomic analyses, we resolve the evolutionary relationships of the eastern standing Phlox and evaluate hypotheses about whether and how hybridization and gene flow played a role in their diversification. Our results provide novel resolution of the phylogenetic relationships in this group, including paraphyly across some taxa. We identify gene flow during one case of reinforcement and find genomic support for a hybrid lineage underlying one of the five hypothesized homoploid hybrid speciation events. Additionally, we estimate the ancestries of four allotetraploid hybrid species. Our results are consistent with hybridization contributing to diverse evolutionary outcomes within this group; although, not as extensively as previously hypothesized. This study demonstrates the importance of phylogenomics in evaluating hypothesized evolutionary histories of non-model systems and adds to the growing support of interspecific genetic exchange in the generation of biodiversity.
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Affiliation(s)
- Austin G Garner
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA
- The Arnold Arboretum, Harvard University, Boston, MA, 02131, USA
| | - Benjamin E Goulet-Scott
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA
- The Arnold Arboretum, Harvard University, Boston, MA, 02131, USA
| | - Robin Hopkins
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA
- The Arnold Arboretum, Harvard University, Boston, MA, 02131, USA
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2
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Carscadden KA, Batstone RT, Hauser FE. Origins and evolution of biological novelty. Biol Rev Camb Philos Soc 2023; 98:1472-1491. [PMID: 37056155 DOI: 10.1111/brv.12963] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 03/30/2023] [Accepted: 04/03/2023] [Indexed: 04/15/2023]
Abstract
Understanding the origins and impacts of novel traits has been a perennial interest in many realms of ecology and evolutionary biology. Here, we build on previous evolutionary and philosophical treatments of this subject to encompass novelties across biological scales and eco-evolutionary perspectives. By defining novelties as new features at one biological scale that have emergent effects at other biological scales, we incorporate many forms of novelty that have previously been treated in isolation (such as novelty from genetic mutations, new developmental pathways, new morphological features, and new species). Our perspective is based on the fundamental idea that the emergence of a novelty, at any biological scale, depends on its environmental and genetic context. Through this lens, we outline a broad array of generative mechanisms underlying novelty and highlight how genomic tools are transforming our understanding of the origins of novelty. Lastly, we present several case studies to illustrate how novelties across biological scales and systems can be understood based on common mechanisms of change and their environmental and genetic contexts. Specifically, we highlight how gene duplication contributes to the evolution of new complex structures in visual systems; how genetic exchange in symbiosis alters functions of both host and symbiont, resulting in a novel organism; and how hybridisation between species can generate new species with new niches.
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Affiliation(s)
- Kelly A Carscadden
- Department of Ecology and Evolutionary Biology, University of Colorado Boulder, 1900 Pleasant St, Boulder, CO, 80309, USA
| | - Rebecca T Batstone
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 West Gregory Drive, Urbana, IL, 61801, USA
| | - Frances E Hauser
- Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, Ontario, M1C 1A4, Canada
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3
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Anderson CB, Ospina O, Beerli P, Lemmon AR, Banker SE, Hassinger AB, Dye M, Kortyna ML, Lemmon EM. The population genetics of speciation by cascade reinforcement. Ecol Evol 2023; 13:e9773. [PMID: 36789346 PMCID: PMC9905665 DOI: 10.1002/ece3.9773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Revised: 12/22/2022] [Accepted: 01/09/2023] [Indexed: 02/10/2023] Open
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 within P. feriarum across 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 among P. feriarum and 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 within P. feriarum including 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 that P. feriarum hybridizes 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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Affiliation(s)
- Carlie B. Anderson
- Department of Biological ScienceFlorida State UniversityTallahasseeFloridaUSA
| | - Oscar Ospina
- Department of Biostatistics and BioinformaticsMoffitt Cancer CenterTampaFloridaUSA
| | - Peter Beerli
- Department of Scientific ComputingFlorida State UniversityTallahasseeFloridaUSA
| | - Alan R. Lemmon
- Department of Scientific ComputingFlorida State UniversityTallahasseeFloridaUSA
| | - Sarah E. Banker
- Department of Biological ScienceFlorida State UniversityTallahasseeFloridaUSA,Pfizer Clinical Pharmacogenomics GroupGrotonConnecticutUSA
| | - Alyssa Bigelow Hassinger
- Department of Biological ScienceFlorida State UniversityTallahasseeFloridaUSA,Varigen BiosciencesMiddletonWisconsinUSA
| | - Mysia Dye
- Department of Biological ScienceFlorida State UniversityTallahasseeFloridaUSA
| | - Michelle L. Kortyna
- Department of Biological ScienceFlorida State UniversityTallahasseeFloridaUSA
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4
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Iwaoka Y, Watanabe T, Satoh SS, Nambu H, Yamazaki Y. Hybridization of Two Species of Japanese Toads, Bufo torrenticola and Bufo japonicus formosus, in the Central Part of Japan. Zoolog Sci 2021; 38:506-512. [PMID: 34854282 DOI: 10.2108/zs210023] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Accepted: 08/17/2021] [Indexed: 11/17/2022]
Abstract
Interspecific hybridization between two species of Japanese toads, Bufo torrenticola (Bt) and Bufo japonicus formosus (Bjf), was not thought to have occurred due to the differences in their spawning habitats, although their hybridization was reported by previous research in a limited area. Such hybridization could have pivotal effects, such as genetic admixture, on Bt, which has a limited distribution and habitat. In this study, to clarify the details of hybridization, a total of 192 individuals were collected from multiple parapatric regions and an only Bjf allopatric region and analyzed based on morphology, mtDNA sequences, and nuclear DNA microsatellite loci. Each individual was identified based on morphological type and mtDNA lineage, and two mismatched combinations, Bt or an intermediate morphological type and the Bjf mtDNA lineage, were detected. In particular, the combination of Bt type and Bjf lineage was dominant in parapatric regions, and it was considered that asymmetric hybridization in which Bjf became a matriline had occurred. In addition, a Bayesian clustering method based on the microsatellite loci was conducted to detect a genetic admixture of the two toad species. Individuals representing a combination of the Bt type and Bjf lineage in the parapatric regions were largely assigned to the Bt cluster or equally to both clusters. These results indicate that backcross with Bt has been repeated, and therefore the traits of Bt might be maintained in this study.
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Affiliation(s)
- Yuma Iwaoka
- University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan,
| | | | - Shin S Satoh
- University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan.,FASMAC Co. Ltd., 3088 Okada, Atsugi, Kanagawa 243-0021, Japan
| | | | - Yuji Yamazaki
- University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan
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5
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Calabrese GM, Pfennig KS. Reinforcement and the Proliferation of Species. J Hered 2021; 111:138-146. [PMID: 31850499 DOI: 10.1093/jhered/esz073] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Accepted: 11/23/2019] [Indexed: 12/20/2022] Open
Abstract
Adaptive radiations are characterized by the rapid proliferation of species. Explaining how adaptive radiations occur therefore depends, in part, on identifying how populations become reproductively isolated-and ultimately become different species. Such reproductive isolation could arise when populations adapting to novel niches experience selection to avoid interbreeding and, consequently, evolve mating traits that minimize such hybridization via the process of reinforcement. Here, we highlight that a downstream consequence of reinforcement is divergence of conspecific populations, and this further divergence can instigate species proliferation. Moreover, we evaluate when reinforcement will-and will not-promote species proliferation. Finally, we discuss empirical approaches to test what role, if any, reinforcement plays in species proliferation and, consequently, in adaptive radiation. To date, reinforcement's downstream effects on species proliferation remain largely unknown and speculative. Because the ecological and evolutionary contexts in which adaptive radiations occur are conducive to reinforcement and its downstream consequences, adaptive radiations provide an ideal framework in which to evaluate reinforcement's role in diversification.
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Affiliation(s)
- Gina M Calabrese
- Department of Biology, University of North Carolina, Chapel Hill, NC
| | - Karin S Pfennig
- Department of Biology, University of North Carolina, Chapel Hill, NC
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6
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Hsiao YW, Tseng HY, Nguyen HN, Lin SM. Asymmetric acoustic signal recognition led to asymmetric gene flow between two parapatric frogs. Zool J Linn Soc 2021. [DOI: 10.1093/zoolinnean/zlaa114] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Abstract
Correct discrimination between courtship signals could help to maintain genetic integrity between closely related species. However, asymmetric usage of signals might cause asymmetric gene flow across the contact zone. Buergeria choui and B. otai are sibling-species with a parapatric distribution pattern in Taiwan, having two narrow contact zones on the east and west sides of the island. Combining behavioural experiments with genome-wide RAD-seq analyses, we test whether the ability of signal recognition influences genetic introgression across their species boundary. The playback experiments show that all B. choui populations respond strongest to their own ‘cricket’ trills, while the western population of B. otai have evolved a strong level of reproductive character displacement by showing the inclusive usage of the unique ‘chicken’ signals. In contrast, the eastern B. otai population uses both ‘chicken’ and ‘cricket’ trills, and has a stronger preference for the latter. The weak reproductive character displacement in the eastern population has led to asymmetry genetic introgression from B. choui toward B. otai. Our results support the prediction that a more specialized signal-user, compared to its sibling, generalized signal-user, might have a higher probability of maintaining their genetic integrity in the secondary contact region.
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Affiliation(s)
- Yu-Wei Hsiao
- School of Life Science, National Taiwan Normal University, Taiwan
| | - Hui-Yun Tseng
- Department of Entomology, National Taiwan University, Taiwan
| | - Hung Ngoc Nguyen
- School of Life Science, National Taiwan Normal University, Taiwan
- Department of Zoology, Southern Institute of Ecology, Vietnam Academy of Science and Technology, Ho Chi Minh City, Vietnam
| | - Si-Min Lin
- School of Life Science, National Taiwan Normal University, Taiwan
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7
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Banker SE, Lemmon AR, Hassinger AB, Dye M, Holland SD, Kortyna ML, Ospina OE, Ralicki H, Lemmon EM. Hierarchical Hybrid Enrichment: Multitiered Genomic Data Collection Across Evolutionary Scales, With Application to Chorus Frogs (Pseudacris). Syst Biol 2021; 69:756-773. [PMID: 31886503 PMCID: PMC7302053 DOI: 10.1093/sysbio/syz074] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2018] [Revised: 10/26/2019] [Accepted: 11/04/2019] [Indexed: 01/25/2023] Open
Abstract
Determining the optimal targets of genomic subsampling for phylogenomics, phylogeography, and population genomics remains a challenge for evolutionary biologists. Of the available methods for subsampling the genome, hybrid enrichment (sequence capture) has become one of the primary means of data collection for systematics, due to the flexibility and cost efficiency of this approach. Despite the utility of this method, information is lacking as to what genomic targets are most appropriate for addressing questions at different evolutionary scales. In this study, first, we compare the benefits of target loci developed for deep- and shallow scales by comparing these loci at each of three taxonomic levels: within a genus (phylogenetics), within a species (phylogeography), and within a hybrid zone (population genomics). Specifically, we target evolutionarily conserved loci that are appropriate for deeper phylogenetic scales and more rapidly evolving loci that are informative for phylogeographic and population genomic scales. Second, we assess the efficacy of targeting multiple-locus sets for different taxonomic levels in the same hybrid enrichment reaction, an approach we term hierarchical hybrid enrichment. Third, we apply this approach to the North American chorus frog genus Pseudacris to answer key evolutionary questions across taxonomic and temporal scales. We demonstrate that in this system the type of genomic target that produces the most resolved gene trees differs depending on the taxonomic level, although the potential for error is substantially lower for the deep-scale loci at all levels. We successfully recover data for the two different locus sets with high efficiency. Using hierarchical data targeting deep and shallow levels: we 1) resolve the phylogeny of the genus Pseudacris and introduce a novel visual and hypothesis testing method that uses nodal heat maps to examine the robustness of branch support values to the removal of sites and loci; 2) estimate the phylogeographic history of Pseudacris feriarum, which reveals up to five independent invasions leading to sympatry with congener Pseudacris nigrita to form replicated reinforcement contact zones with ongoing gene flow into sympatry; and 3) quantify with high confidence the frequency of hybridization in one of these zones between P. feriarum and P. nigrita, which is lower than microsatellite-based estimates. We find that the hierarchical hybrid enrichment approach offers an efficient, multitiered data collection method for simultaneously addressing questions spanning multiple evolutionary scales. [Anchored hybrid enrichment; heat map; hybridization; phylogenetics; phylogeography; population genomics; reinforcement; reproductive character displacement.].
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Affiliation(s)
- Sarah E Banker
- Department of Biological Science, Florida State University, 319 Stadium Drive, Tallahassee, FL 32306, USA.,Department of Integrative Biology, University of California, Berkeley, #3160 Berkeley, CA 94720-3160, USA
| | - Alan R Lemmon
- Department of Scientific Computing, Florida State University 400 Dirac Science Library, Tallahassee, FL 32306, USA
| | - Alyssa Bigelow Hassinger
- Department of Biological Science, Florida State University, 319 Stadium Drive, Tallahassee, FL 32306, USA.,Department of Evolution, Ecology, and Organismal Biology, Ohio State University, 318 W. 12th Avenue, 300 Aronoff Laboratory, Columbus, OH 43210, USA
| | - Mysia Dye
- Department of Biological Science, Florida State University, 319 Stadium Drive, Tallahassee, FL 32306, USA
| | - Sean D Holland
- Department of Biological Science, Florida State University, 319 Stadium Drive, Tallahassee, FL 32306, USA
| | - Michelle L Kortyna
- Department of Biological Science, Florida State University, 319 Stadium Drive, Tallahassee, FL 32306, USA
| | - Oscar E Ospina
- Department of Biological Science, Florida State University, 319 Stadium Drive, Tallahassee, FL 32306, USA
| | - Hannah Ralicki
- Department of Biological Science, Florida State University, 319 Stadium Drive, Tallahassee, FL 32306, USA.,Department of Biological Science, University of Connecticut, 91 North Eagleville Road, Storrs, CT 06268, USA
| | - Emily Moriarty Lemmon
- Department of Biological Science, Florida State University, 319 Stadium Drive, Tallahassee, FL 32306, USA
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8
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Tonzo V, Papadopoulou A, Ortego J. Genomic footprints of an old affair: Single nucleotide polymorphism data reveal historical hybridization and the subsequent evolution of reproductive barriers in two recently diverged grasshoppers with partly overlapping distributions. Mol Ecol 2020; 29:2254-2268. [DOI: 10.1111/mec.15475] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 05/10/2020] [Accepted: 05/11/2020] [Indexed: 12/17/2022]
Affiliation(s)
- Vanina Tonzo
- Department of Integrative Ecology Estación Biológica de Doñana (EBD‐CSIC) Seville Spain
| | - Anna Papadopoulou
- Department of Biological Sciences University of Cyprus Nicosia Cyprus
| | - Joaquín Ortego
- Department of Integrative Ecology Estación Biológica de Doñana (EBD‐CSIC) Seville Spain
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9
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Wollenberg Valero KC, Marshall JC, Bastiaans E, Caccone A, Camargo A, Morando M, Niemiller ML, Pabijan M, Russello MA, Sinervo B, Werneck FP, Sites JW, Wiens JJ, Steinfartz S. Patterns, Mechanisms and Genetics of Speciation in Reptiles and Amphibians. Genes (Basel) 2019; 10:genes10090646. [PMID: 31455040 PMCID: PMC6769790 DOI: 10.3390/genes10090646] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Revised: 07/21/2019] [Accepted: 08/05/2019] [Indexed: 12/22/2022] Open
Abstract
In this contribution, the aspects of reptile and amphibian speciation that emerged from research performed over the past decade are reviewed. First, this study assesses how patterns and processes of speciation depend on knowing the taxonomy of the group in question, and discuss how integrative taxonomy has contributed to speciation research in these groups. This study then reviews the research on different aspects of speciation in reptiles and amphibians, including biogeography and climatic niches, ecological speciation, the relationship between speciation rates and phenotypic traits, and genetics and genomics. Further, several case studies of speciation in reptiles and amphibians that exemplify many of these themes are discussed. These include studies of integrative taxonomy and biogeography in South American lizards, ecological speciation in European salamanders, speciation and phenotypic evolution in frogs and lizards. The final case study combines genomics and biogeography in tortoises. The field of amphibian and reptile speciation research has steadily moved forward from the assessment of geographic and ecological aspects, to incorporating other dimensions of speciation, such as genetic mechanisms and evolutionary forces. A higher degree of integration among all these dimensions emerges as a goal for future research.
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Affiliation(s)
| | - Jonathon C Marshall
- Department of Zoology, Weber State University, 1415 Edvalson Street, Dept. 2505, Ogden, UT 84401, USA
| | - Elizabeth Bastiaans
- Department of Biology, State University of New York, College at Oneonta, Oneonta, NY 13820, USA
| | - Adalgisa Caccone
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06520, USA
| | - Arley Camargo
- Centro Universitario de Rivera, Universidad de la República, Ituzaingó 667, Rivera 40000, Uruguay
| | - Mariana Morando
- Instituto Patagónico para el Estudio de los Ecosistemas Continentales (IPEEC, CENPAT-CONICET) Bv. Brown 2915, Puerto Madryn U9120ACD, Argentina
| | - Matthew L Niemiller
- Department of Biological Sciences, The University of Alabama in Huntsville, Huntsville, AL 35899, USA
| | - Maciej Pabijan
- Department of Comparative Anatomy, Institute of Zoology and Biomedical Research, Jagiellonian University, ul. Gronostajowa 9, 30-387 Kraków, Poland
| | - Michael A Russello
- Department of Biology, University of British Columbia, Okanagan Campus, 3247 University Way, Kelowna, BC V1V 1V7, Canada
| | - Barry Sinervo
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Coastal Biology Building, 130 McAllister Way, Santa Cruz, CA 95060, USA
| | - Fernanda P Werneck
- Programa de Coleções Científicas Biológicas, Coordenação de Biodiversidade, Instituto Nacional de Pesquisas da Amazônia, Manaus 69060-000, Brazil
| | - Jack W Sites
- Department of Biological and Marine Sciences, University of Hull, Cottingham Road, Hull HU6 7RX, UK
| | - John J Wiens
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721, USA
| | - Sebastian Steinfartz
- Molecular Evolution and Systematics of Animals, Institute of Biology, University of Leipzig, Talstrasse 33, 04103 Leipzig, Germany
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10
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Genetic rescue insights from population- and family-level hybridization effects in brook trout. CONSERV GENET 2019. [DOI: 10.1007/s10592-019-01179-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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11
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Drillon O, Dufresnes G, Perrin N, Crochet PA, Dufresnes C. Reaching the edge of the speciation continuum: hybridization between three sympatric species of Hyla tree frogs. Biol J Linn Soc Lond 2019. [DOI: 10.1093/biolinnean/bly198] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Affiliation(s)
- Olivier Drillon
- Agence Française pour la Biodiversité, Service Départemental de la Charente, Champniers, France
| | | | - Nicolas Perrin
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
| | - Pierre-André Crochet
- CEFE, CNRS, University of Montpellier, University Paul Valéry Montpellier, EPHE, IRD, Montpellier, France
| | - Christophe Dufresnes
- Department of Animal and Plant Sciences, Alfred Denny Building, University of Sheffield, Sheffield, UK
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12
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Dyer KA, Bewick ER, White BE, Bray MJ, Humphreys DP. Fine-scale geographic patterns of gene flow and reproductive character displacement in Drosophila subquinaria and Drosophila recens. Mol Ecol 2018; 27:10.1111/mec.14825. [PMID: 30074656 PMCID: PMC6360132 DOI: 10.1111/mec.14825] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2018] [Revised: 07/13/2018] [Accepted: 07/14/2018] [Indexed: 12/12/2022]
Abstract
When two species are incompletely isolated, strengthening premating isolation barriers in response to the production of low fitness hybrids may complete the speciation process. Here, we use the sister species Drosophila subquinaria and Drosophila recens to study the conditions under which this reinforcement of species boundaries occurs in natural populations. We first extend the region of known sympatry between these species, and then we conduct a fine-scale geographic survey of mate discrimination coupled with estimates of gene flow within and admixture between species. Within D. subquinaria, reinforcement is extremely effective: we find variation in mate discrimination both against D. recens males and against conspecific allopatric males on the scale of a few kilometres and in the face of gene flow both from conspecific populations and introgression from D. recens. In D. recens, we do not find evidence for increased mate discrimination in sympatry, even where D. recens is rare, consistent with substantial gene flow throughout the species' range. Finally, we find that introgression between species is asymmetric, with more from D. recens into D. subquinaria than vice versa. Within each species, admixture is highest in the geographic region where it is rare relative to the other species, suggesting that when hybrids are produced they are of low fitness. In sum, reinforcement within D. subquinaria is effective at maintaining species boundaries, but even when reinforcing selection is strong it may not always result in a pattern of strong reproductive character displacement due to variation in the frequency of hybridization and gene flow from neighbouring populations.
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Affiliation(s)
- Kelly A. Dyer
- Department of Genetics; University of Georgia; Athens, GA 30602; USA
| | | | - Brooke E. White
- Department of Genetics; University of Georgia; Athens, GA 30602; USA
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13
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Advancing Understanding of Amphibian Evolution, Ecology, Behavior, and Conservation with Massively Parallel Sequencing. POPULATION GENOMICS 2018. [DOI: 10.1007/13836_2018_61] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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14
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Lemmon EM, Juenger TE. Geographic variation in hybridization across a reinforcement contact zone of chorus frogs ( Pseudacris). Ecol Evol 2017; 7:9485-9502. [PMID: 29187984 PMCID: PMC5696400 DOI: 10.1002/ece3.3443] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 08/02/2017] [Accepted: 08/31/2017] [Indexed: 12/11/2022] Open
Abstract
Reinforcement contact zones, which are secondary contact zones where species are diverging in reproductive behaviors due to selection against hybridization, represent natural laboratories for studying speciation‐in‐action. Here, we examined replicate localities across the entire reinforcement contact zone between North American chorus frogs Pseudacris feriarum and P. nigrita to investigate geographic variation in hybridization frequencies and to assess whether reinforcement may have contributed to increased genetic divergence within species. Previous work indicated these species have undergone reproductive character displacement (RCD) in male acoustic signals and female preferences due to reinforcement. We also examined acoustic signal variation across the contact zone to assess whether signal characteristics reliably predict hybrid index and to elucidate whether the degree of RCD predicts hybridization rate. Using microsatellites, mitochondrial sequences, and acoustic signal information from >1,000 individuals across >50 localities and ten sympatric focal regions, we demonstrate: (1) hybridization occurs and (2) varies substantially across the geographic range of the contact zone, (3) hybridization is asymmetric and in the direction predicted from observed patterns of asymmetric RCD, (4) in one species, genetic distance is higher between conspecific localities where one or both have been reinforced than between nonreinforced localities, after controlling for geographic distance, (5) acoustic signal characters strongly predict hybrid index, and (6) the degree of RCD does not strongly predict admixture levels. By showing that hybridization occurs in all sympatric localities, this study provides the fifth and final line of evidence that reproductive character displacement is due to reinforcement in the chorus frog contact zone. Furthermore, this work suggests that the dual action of cascade reinforcement and partial geographic isolation is promoting genetic diversification within one of the reinforced species.
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Affiliation(s)
| | - Thomas E Juenger
- Department of Integrative Biology University of Texas, Austin Austin TX USA
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