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Firneno TJ, Semenov G, Dopman EB, Taylor SA, Larson EL, Gompert Z. Quantitative Analyses of Coupling in Hybrid Zones. Cold Spring Harb Perspect Biol 2023; 15:a041434. [PMID: 37739809 PMCID: PMC10691479 DOI: 10.1101/cshperspect.a041434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/24/2023]
Abstract
In hybrid zones, whether barrier loci experience selection mostly independently or as a unit depends on the ratio of selection to recombination as captured by the coupling coefficient. Theory predicts a sharper transition between an uncoupled and coupled system when more loci affect hybrid fitness. However, the extent of coupling in hybrid zones has rarely been quantified. Here, we use simulations to characterize the relationship between the coupling coefficient and variance in clines across genetic loci. We then reanalyze 25 hybrid zone data sets and find that cline variances and estimated coupling coefficients form a smooth continuum from high variance and weak coupling to low variance and strong coupling. Our results are consistent with low rates of hybridization and a strong genome-wide barrier to gene flow when the coupling coefficient is much greater than 1, but also suggest that this boundary might be approached gradually and at a near constant rate over time.
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Affiliation(s)
- Thomas J Firneno
- Department of Biology, University of Denver, Denver, Colorado 80208, USA
| | - Georgy Semenov
- Department of Ecology and Evolutionary Biology, University of Colorado Boulder, Boulder, Colorado 80211, USA
| | - Erik B Dopman
- Department of Biology, Tufts University, Medford, Massachusetts 02155, USA
| | - Scott A Taylor
- Department of Ecology and Evolutionary Biology, University of Colorado Boulder, Boulder, Colorado 80211, USA
| | - Erica L Larson
- Department of Biology, University of Denver, Denver, Colorado 80208, USA
| | - Zachariah Gompert
- Department of Biology, Utah State University, Logan, Utah 84321, USA
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Pascal FJM, Vega A, Akopyan M, Hoke KL, Robertson JM. Sexual signal evolution and patterns of assortative mating across an intraspecific contact zone. J Evol Biol 2023; 36:1077-1089. [PMID: 37306282 DOI: 10.1111/jeb.14186] [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: 11/02/2022] [Revised: 03/10/2023] [Accepted: 04/04/2023] [Indexed: 06/13/2023]
Abstract
Contact zones provide important insights into the evolutionary processes that underlie lineage divergence and speciation. Here, we use a contact zone to ascertain speciation potential in the red-eyed treefrog (Agalychnis callidryas), a brightly coloured and polymorphic frog that exhibits unusually high levels of intraspecific variation. Populations of A. callidryas differ in a number of traits, several of which are known sexual signals that mediate premating reproductive isolation in allopatric populations. Along the Caribbean coast of Costa Rica, a ~100 km contact zone, situated between two phenotypically and genetically divergent parent populations, contains multiple colour pattern phenotypes and late-generation hybrids. This contact zone provides the opportunity to examine processes that are important in the earliest stages of lineage divergence. We performed analyses of colour pattern variation in five contact zone sites and six parental sites and found complex, continuous colour variation along the contact zone. We found discordance between the geographic distribution of colour pattern and previously described genomic population structure. We then used a parental site and contact zone site to measure assortative mating and directional selection from naturally-occurring amplectant mating pairs. We found assortative mating in a parental population, but no assortative mating in the contact zone. Furthermore, we uncovered evidence of directional preference towards the adjacent parental phenotype in the contact zone population, but no directional preference in the parent population. Combined, these data provide insights into potential dynamics at the contact zone borders and indicate that incipient speciation between parent populations will be slowed.
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Affiliation(s)
- Florine J M Pascal
- Department of Biology, California State University, Northridge, Northridge, California, USA
| | | | - Maria Akopyan
- Department of Biology, California State University, Northridge, Northridge, California, USA
- Department of Ecology and Evolutionary Biology, Cornell University, New York, New York, USA
| | - Kim L Hoke
- Department of Biology, Colorado State University, Fort Collins, Colorado, USA
| | - Jeanne M Robertson
- Department of Biology, California State University, Northridge, Northridge, California, USA
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Dougherty RP, Pulica RM, Caldwell MS. Multi‐night territorial behavior, chorus attendance, and mating success in red‐eyed treefrogs. Ethology 2022. [DOI: 10.1111/eth.13321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ryan P. Dougherty
- Yale School of the Environment Yale University New Haven Connecticut USA
| | - Rachael M. Pulica
- Gettysburg College Gettysburg Pennsylvania USA
- School of Graduate Studies, New Jersey Medical School Rutgers Biomedical and Health Sciences Newark New Jersey USA
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Robertson JM, Bell RC, Loew ER. Vision in dim light and the evolution of color pattern in a crepuscular/nocturnal frog. Evol Ecol 2022. [DOI: 10.1007/s10682-022-10173-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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Clark MI, Bradburd GS, Akopyan M, Vega A, Rosenblum EB, Robertson JM. Genetic isolation by distance underlies colour pattern divergence in red-eyed treefrogs (Agalychnis callidryas). Mol Ecol 2022; 31:1666-1681. [PMID: 35034406 PMCID: PMC8923152 DOI: 10.1111/mec.16350] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2021] [Revised: 10/21/2021] [Accepted: 01/04/2022] [Indexed: 10/19/2022]
Abstract
Investigating the spatial distribution of genetic and phenotypic variation can provide insights into the evolutionary processes that shape diversity in natural systems. We characterized patterns of genetic and phenotypic diversity to learn about drivers of colour-pattern diversification in red-eyed treefrogs (Agalychnis callidryas) in Costa Rica. Along the Pacific coast, red-eyed treefrogs have conspicuous leg colour patterning that transitions from orange in the north to purple in the south. We measured phenotypic variation of frogs, with increased sampling at sites where the orange-to-purple transition occurs. At the transition zone, we discovered the co-occurrence of multiple colour-pattern morphs. To explore possible causes of this variation, we generated a single nucleotide polymorphism data set to analyse population genetic structure, measure genetic diversity and infer the processes that mediate genotype-phenotype dynamics. We investigated how patterns of genetic relatedness correspond to individual measures of colour pattern along the coast, including testing for the role of hybridization in geographic regions where orange and purple phenotypic groups co-occur. We found no evidence that colour-pattern polymorphism in the transition zone arose through recent hybridization. Instead, a strong pattern of genetic isolation by distance indicates that colour-pattern variation was either retained through other processes such as ancestral colour polymorphisms or ancient secondary contact, or else it was generated by novel mutations. We found that phenotype changes along the Pacific coast more than would be expected based on genetic divergence and geographic distance alone. Combined, our results suggest the possibility of selective pressures acting on colour pattern at a small geographic scale.
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Affiliation(s)
- Meaghan I. Clark
- Department of Biology, California State University Northridge, Northridge, California, USA,Department of integrative Biology, Ecology, Evolution and Behavior Program, Michigan State University, East Lansing, Michigan, USA,W.K. Kellogg Biological Station, Michigan State University, Hickory Corners, Michigan, USA
| | - Gideon S. Bradburd
- Department of integrative Biology, Ecology, Evolution and Behavior Program, Michigan State University, East Lansing, Michigan, USA
| | - Maria Akopyan
- Department of Biology, California State University Northridge, Northridge, California, USA,Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, New York, USA
| | | | - Erica Bree Rosenblum
- Department of Environmental Science, Policy, and Management, University of California Berkeley, Berkeley, California, USA,Museum of Vertebrate Zoology, University of California Berkeley, Berkeley, California, USA
| | - Jeanne M. Robertson
- Department of Biology, California State University Northridge, Northridge, California, USA,Department of Herpetology, Natural History Museum of Los Angeles County, Los Angeles, California, USA
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6
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Blackburn DC, Nielsen SV, Ghose SL, Burger M, Gonwouo LN, Greenbaum E, Gvoždík V, Hirschfeld M, Kouete MT, Kusamba C, Lawson D, McLaughlin PJ, Zassi-Boulou AG, Rödel MO. Phylogeny of African Long-Fingered Frogs (Arthroleptidae: Cardioglossa) Reveals Recent Allopatric Divergences in Coloration. ICHTHYOLOGY & HERPETOLOGY 2021. [DOI: 10.1643/h2020165] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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7
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Jahner JP, Parchman TL, Matocq MD. Multigenerational backcrossing and introgression between two woodrat species at an abrupt ecological transition. Mol Ecol 2021; 30:4245-4258. [PMID: 34219316 DOI: 10.1111/mec.16056] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 06/28/2021] [Indexed: 12/27/2022]
Abstract
When organisms experience secondary contact after allopatric divergence, genomic regions can introgress differentially depending on their relationships with adaptation, reproductive isolation, recombination, and drift. Analyses of genome-wide patterns of divergence and introgression could provide insight into the outcomes of hybridization and the potential relationship between allopatric divergence and reproductive isolation. Here, we generate population genetic data (26,262 SNPs; 353 individuals) using a reduced-representation sequencing approach to quantify patterns of ancestry, differentiation, and introgression between a pair of ecologically distinct mammals-the desert woodrat (N. lepida) and Bryant's woodrat (N. bryanti)-that hybridize at a sharp ecotone in southern California. Individual ancestry estimates confirmed that hybrids were rare in this bimodal hybrid zone, and entirely consisted of a few F1 individuals and a broad range of multigenerational backcrosses. Genomic cline analyses indicated more than half of loci had elevated introgression from one genomic background into the other. However, introgression was not associated with relative or absolute measures of divergence, and loci with extreme values for both were not typically found near detoxification enzymes previously implicated in dietary specialization for woodrats. The decoupling of differentiation and introgression suggests that processes other than adaptation, such as drift, may underlie the extreme clines at this contact zone.
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Affiliation(s)
- Joshua P Jahner
- Department of Biology, University of Nevada, Reno, Nevada, USA.,Department of Botany, University of Wyoming, Laramie, Wyoming, USA
| | - Thomas L Parchman
- Department of Biology, University of Nevada, Reno, Nevada, USA.,Program in Ecology, Evolution, and Conservation Biology, University of Nevada, Reno, Nevada, USA
| | - Marjorie D Matocq
- Program in Ecology, Evolution, and Conservation Biology, University of Nevada, Reno, Nevada, USA.,Department of Natural Resources and Environmental Science, University of Nevada, Reno, Nevada, USA
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Broder ED, Elias DO, Rodríguez RL, Rosenthal GG, Seymoure BM, Tinghitella RM. Evolutionary novelty in communication between the sexes. Biol Lett 2021; 17:20200733. [PMID: 33529546 PMCID: PMC8086948 DOI: 10.1098/rsbl.2020.0733] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Accepted: 01/11/2021] [Indexed: 12/18/2022] Open
Abstract
The diversity of signalling traits within and across taxa is vast and striking, prompting us to consider how novelty evolves in the context of animal communication. Sexual selection contributes to diversification, and here we endeavour to understand the initial conditions that facilitate the maintenance or elimination of new sexual signals and receiver features. New sender and receiver variants can occur through mutation, plasticity, hybridization and cultural innovation, and the initial conditions of the sender, the receiver and the environment then dictate whether a novel cue becomes a signal. New features may arise in the sender, the receiver or both simultaneously. We contend that it may be easier than assumed to evolve new sexual signals because sexual signals may be arbitrary, sexual conflict is common and receivers are capable of perceiving much more of the world than just existing sexual signals. Additionally, changes in the signalling environment can approximate both signal and receiver changes through a change in transmission characteristics of a given environment or the use of new environments. The Anthropocene has led to wide-scale disruption of the environment and may thus generate opportunity to directly observe the evolution of new signals to address questions that are beyond the reach of phylogenetic approaches.
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Affiliation(s)
- E. Dale Broder
- Department of Biology, St Ambrose University, Davenport, IA 52803, USA
| | - Damian O. Elias
- Department of Environmental Science, Policy and Management, UC Berkeley, Berkeley, CA 94720, USA
| | - Rafael L. Rodríguez
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA
| | - Gil G. Rosenthal
- Department of Biology, Texas A&M, College Station, TX 77843, USA
| | - Brett M. Seymoure
- Living Earth Collaborative, Washington University in St. Louis, St. Louis, MO 63130, USA
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