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Thompson KA, Brandvain Y, Coughlan JM, Delmore KE, Justen H, Linnen CR, Ortiz-Barrientos D, Rushworth CA, Schneemann H, Schumer M, Stelkens R. The Ecology of Hybrid Incompatibilities. Cold Spring Harb Perspect Biol 2024; 16:a041440. [PMID: 38151331 PMCID: PMC11368197 DOI: 10.1101/cshperspect.a041440] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2023]
Abstract
Ecologically mediated selection against hybrids, caused by hybrid phenotypes fitting poorly into available niches, is typically viewed as distinct from selection caused by epistatic Dobzhansky-Muller hybrid incompatibilities. Here, we show how selection against transgressive phenotypes in hybrids manifests as incompatibility. After outlining our logic, we summarize current approaches for studying ecology-based selection on hybrids. We then quantitatively review QTL-mapping studies and find traits differing between parent taxa are typically polygenic. Next, we describe how verbal models of selection on hybrids translate to phenotypic and genetic fitness landscapes, highlighting emerging approaches for detecting polygenic incompatibilities. Finally, in a synthesis of published data, we report that trait transgression-and thus possibly extrinsic hybrid incompatibility in hybrids-escalates with the phenotypic divergence between parents. We discuss conceptual implications and conclude that studying the ecological basis of hybrid incompatibility will facilitate new discoveries about mechanisms of speciation.
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Affiliation(s)
- Ken A Thompson
- Department of Biology, Stanford University, Stanford, California 94305, USA
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305, USA
| | - Yaniv Brandvain
- Department of Plant and Microbial Biology, University of Minnesota - Twin Cities, St Paul, Minnesota 55108, USA
| | - Jenn M Coughlan
- Department of Ecology & Evolutionary Biology, Yale University, New Haven, Connecticut 06511, USA
| | - Kira E Delmore
- Department of Biology, Texas A&M University, College Station, Texas 77843, USA
| | - Hannah Justen
- Department of Biology, Texas A&M University, College Station, Texas 77843, USA
| | - Catherine R Linnen
- Department of Biology, University of Kentucky, Lexington, Kentucky 40506, USA
| | - Daniel Ortiz-Barrientos
- School of Biological Sciences, The University of Queensland, Centre of Excellence for Plant Success in Nature and Agriculture, St Lucia, Queensland 4072, Australia
| | - Catherine A Rushworth
- Department of Biology and Ecology Center, Utah State University, Logan, Utah 84322, USA
| | - Hilde Schneemann
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, United Kingdom
| | - Molly Schumer
- Department of Biology, Stanford University, Stanford, California 94305, USA
- Centro de Investigaciones Científicas de las Huastecas "Aguazarca," A.C., Calnali 43240, Mexico
- Hanna H. Gray Fellow, Howard Hughes Medical Institute, Chevy Chase, Maryland 20815, USA
| | - Rike Stelkens
- Division of Population Genetics, Department of Zoology, Stockholm University, 106 91 Stockholm, Sweden
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2
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Weir JT, Aleixo A, Pulido-Santacruz P. Amazonian rivers are leaky barriers to gene flow in forest understory birds. Proc Biol Sci 2024; 291:20240795. [PMID: 39226930 DOI: 10.1098/rspb.2024.0795] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 05/28/2024] [Accepted: 05/29/2024] [Indexed: 09/05/2024] Open
Abstract
Ever since Alfred Russel Wallace's nineteenth-century observation that related terrestrial species are often separated on opposing riverbanks, major Amazonian rivers have been recognized as key drivers of speciation. However, rivers are dynamic entities whose widths and courses may vary through time. It thus remains unknown how effective rivers are at reducing gene flow and promoting speciation over long timescales. We fit demographic models to genomic sequences to reconstruct the history of gene flow in three pairs of avian taxa fully separated by different Amazonian rivers, and whose geographic ranges do not make contact in headwater regions where rivers may cease to be barriers. Models with gene flow were best fit but still supported an initial period without any gene flow, which ranged from 187 000 to over 959 000 years, suggesting that rivers are capable of initiating speciation through long stretches of allopatric divergence. Allopatry was followed by either bursts or prolonged episodes of gene flow that retarded genomic differentiation but did not fully homogenize populations. Our results support Amazonian rivers as key barriers that promoted speciation and the build-up of species richness, but they also suggest that river barriers are often leaky, with genomic divergence accumulating slowly owing to episodes of substantial gene flow.
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Affiliation(s)
- Jason T Weir
- Department of Ecology and Evolutionary Biology, University of Toronto , Toronto, Ontario M5S 3B2, Canada
- Department of Biological Sciences, University of Toronto Scarborough , Toronto, Ontario M1C 1A4, Canada
- Department of Ornithology, Royal Ontario Museum , Toronto, Ontario M5S 2C6, Canada
| | - Alexandre Aleixo
- Pós-graduação em Biodiversidade e Evolução, Museu Paraense Emílio Goeldi , Belém 66040-170, Brazil
- Vale Technology Institute-Sustainable Development (ITV-DS) , Belém 66055-090, Brazil
| | - Paola Pulido-Santacruz
- Department of Ecology and Evolutionary Biology, University of Toronto , Toronto, Ontario M5S 3B2, Canada
- Department of Biology, Faculty of Natural Sciences, Universidad del Rosario , Bogotá 111221, Colombia
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3
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Anderson SAS, López-Fernández H, Weir JT. Ecology and the origin of non-ephemeral species. Am Nat 2022; 201:619-638. [PMID: 37130236 DOI: 10.1086/723763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
AbstractResearch over the past three decades has shown that ecology-based extrinsic reproductive barriers can rapidly arise to generate incipient species-but such barriers can also rapidly dissolve when environments change, resulting in incipient species collapse. Understanding the evolution of unconditional, "intrinsic" reproductive barriers is therefore important for understanding the longer-term buildup of biodiversity. In this article, we consider ecology's role in the evolution of intrinsic reproductive isolation. We suggest that this topic has fallen into a gap between disciplines: while evolutionary ecologists have traditionally focused on the rapid evolution of extrinsic isolation between co-occurring ecotypes, speciation geneticists studying intrinsic isolation in other taxa have devoted little attention to the ecological context in which it evolves. We argue that for evolutionary ecology to close this gap, the field will have to expand its focus beyond rapid adaptation and its traditional model systems. Synthesizing data from several subfields, we present circumstantial evidence for and against different forms of ecological adaptation as promoters of intrinsic isolation and discuss alternative forces that may be significant. We conclude by outlining complementary approaches that can better address the role of ecology in the evolution of nonephemeral reproductive barriers and, by extension, less ephemeral species.
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4
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Non-parallel morphological divergence following colonization of a new host plant. Evol Ecol 2022. [DOI: 10.1007/s10682-022-10189-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
AbstractAdaptation to new ecological niches is known to spur population diversification and may lead to speciation if gene flow is ceased. While adaptation to the same ecological niche is expected to be parallel, it is more difficult to predict whether selection against maladaptive hybridization in secondary sympatry results in parallel divergence also in traits that are not directly related to the ecological niches. Such parallelisms in response to selection for reproductive isolation can be identified through estimating parallelism in reproductive character displacement across different zones of secondary contact. Here, we use a host shift in the phytophagous peacock fly Tephritis conura, with both host races represented in two geographically separate areas East and West of the Baltic Sea to investigate convergence in morphological adaptations. We asked (i) if there are consistent morphological adaptations to a host plant shift and (ii) if the response to secondary sympatry with the alternate host race is parallel across contact zones. We found surprisingly low and variable, albeit significant, divergence between host races. Only one trait, the length of the female ovipositor, which serves an important function in the interaction with the hosts, was consistently different between host races. Instead, co-existence with the other host race significantly affected the degree of morphological divergence, but the divergence was largely driven by different traits in different contact zones. Thus, local stochastic fixation or reinforcement could generate trait divergence, and additional evidence is needed to conclude whether divergence is locally adaptive.
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5
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Barrera-Guzmán AO, Aleixo A, Faccio M, de Melo Dantas S, Weir JT. Gene flow, genomic homogenization and the timeline to speciation in Amazonian manakins. Mol Ecol 2022; 31:4050-4066. [PMID: 35665558 DOI: 10.1111/mec.16562] [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: 10/29/2021] [Revised: 02/28/2022] [Accepted: 05/12/2022] [Indexed: 11/26/2022]
Abstract
Phylogeographic studies of the most species rich region of the planet - the Amazon basin - repeatedly uncover genetically distinctive, allopatric lineages within currently named species, but understanding whether such lineages are reproductively isolated species is challenging. Here we harness the power of genome-wide datasets together with detailed phylogeographic sampling to both characterize the number of unique lineages and infer levels of reproductive isolation for three parapatric manakin species that make up the genus Pipra. The mitochondrial and nuclear genomes both support six distinctive lineages. The youngest lineages are now highly admixed with each other across major portions of their geographic ranges with one lineage now extinct in a genomically unadmixed state. In contrast, the oldest sets of lineages - dated to 1.4 million years - exhibit narrow hybrid zones. By fitting demographic models to parapatric lineage pairs we found that levels of gene flow and genomic homogenization decline with increasing evolutionary age. Only lineages descending from the 1.4 Ma basal node in the genus experience negligible gene flow, possess genomes resistant to homogenization and are separated by narrow hybrid zones. We conclude that a million years or more were required for Pipra manakins to become reproductively isolated. We suggest the six lineages be reclassified as two or three reproductively isolated species. Our unique approach to quantifying reproductive isolation in parapatric lineages could be applied broadly to other phylogeographic studies and would help determine species classification of the plethora of newly identified lineages in the Amazon basin and other regions.
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Affiliation(s)
- Alfredo O Barrera-Guzmán
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada.,Department of Biological Sciences, University of Toronto Scarborough, Toronto, Ontario, Canada.,Departamento de Biología Marina, Campus de Ciencias biológicas y Agropecuarias, Universidad Autónoma de Yucatán
| | - Alexandre Aleixo
- Pós-graduação em Biodiversidade e Evolução, Museu Paraense Emílio Goeldi, Belém, Brazil.,Finnish Museum of Natural History, University of Helsinki, Helsinki, Finland
| | - Maya Faccio
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada.,Department of Biological Sciences, University of Toronto Scarborough, Toronto, Ontario, Canada
| | - Sidnei de Melo Dantas
- Pós-graduação em Biodiversidade e Evolução, Museu Paraense Emílio Goeldi, Belém, Brazil
| | - Jason T Weir
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada.,Department of Biological Sciences, University of Toronto Scarborough, Toronto, Ontario, Canada.,Department of ornithology, Royal Ontario Museum, Toronto, Ontario, Canada
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6
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Irwin D, Schluter D. Hybridization and the Coexistence of Species. Am Nat 2022; 200:E93-E109. [DOI: 10.1086/720365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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7
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Musher LJ, Giakoumis M, Albert J, Del-Rio G, Rego M, Thom G, Aleixo A, Ribas CC, Brumfield RT, Smith BT, Cracraft J. River network rearrangements promote speciation in lowland Amazonian birds. SCIENCE ADVANCES 2022; 8:eabn1099. [PMID: 35394835 PMCID: PMC8993111 DOI: 10.1126/sciadv.abn1099] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Large Amazonian rivers impede dispersal for many species, but lowland river networks frequently rearrange, thereby altering the location and effectiveness of river barriers through time. These rearrangements may promote biotic diversification by facilitating episodic allopatry and secondary contact among populations. We sequenced genome-wide markers to evaluate the histories of divergence and introgression in six Amazonian avian species complexes. We first tested the assumption that rivers are barriers for these taxa and found that even relatively small rivers facilitate divergence. We then tested whether species diverged with gene flow and recovered reticulate histories for all species, including one potential case of hybrid speciation. Our results support the hypothesis that river rearrangements promote speciation and reveal that many rainforest taxa are micro-endemic, unrecognized, and thus threatened with imminent extinction. We propose that Amazonian hyper-diversity originates partly from fine-scale barrier displacement processes-including river dynamics-which allow small populations to differentiate and disperse into secondary contact.
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Affiliation(s)
- Lukas J. Musher
- Department of Ornithology, The Academy of Natural
Sciences of Drexel University, Philadelphia, PA 19103, USA
- Department of Ornithology, American Museum of Natural
History, New York, NY 10028, USA
- Corresponding author.
| | - Melina Giakoumis
- Department of Biology, City College of New York, New
York, NY 10031, USA
- Graduate Center, City University of New York, New
York, NY 10016, USA
| | - James Albert
- Department of Biology, University of Louisiana at
Lafayette, Lafayette, LA 70503, USA
| | - Glaucia Del-Rio
- Department of Biological Sciences, Louisiana State
University, Baton Rouge, LA 70803, USA
- Museum of Natural Science, Louisiana State
University, Baton Rouge, LA 70803, USA
| | - Marco Rego
- Department of Biological Sciences, Louisiana State
University, Baton Rouge, LA 70803, USA
- Museum of Natural Science, Louisiana State
University, Baton Rouge, LA 70803, USA
| | - Gregory Thom
- Department of Ornithology, American Museum of Natural
History, New York, NY 10028, USA
| | - Alexandre Aleixo
- Finnish Museum of Natural History of Helsinki,
University of Helsinki, Helsinki, Finland
- Museu Paraense Emílio Goeldi, Belém,
Brazil
- Instituto Tecnológico Vale, Belém,
Brazil
| | - Camila C. Ribas
- Instituto Nacional de Pesquisas da
Amazônia, INPA, Manaus, Brazil
| | - Robb T. Brumfield
- Department of Biological Sciences, Louisiana State
University, Baton Rouge, LA 70803, USA
- Museum of Natural Science, Louisiana State
University, Baton Rouge, LA 70803, USA
| | - Brian Tilston Smith
- Department of Ornithology, American Museum of Natural
History, New York, NY 10028, USA
| | - Joel Cracraft
- Department of Ornithology, American Museum of Natural
History, New York, NY 10028, USA
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8
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9
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Tang Q, Burri R, Liu Y, Suh A, Sundev G, Heckel G, Schweizer M. Seasonal migration patterns and the maintenance of evolutionary diversity in a cryptic bird radiation. Mol Ecol 2021; 31:632-645. [PMID: 34674334 PMCID: PMC9298432 DOI: 10.1111/mec.16241] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2021] [Revised: 10/07/2021] [Accepted: 10/12/2021] [Indexed: 02/03/2023]
Abstract
Morphological differentiation associated with evolutionary diversification is often explained with adaptive benefits but the processes and mechanisms maintaining cryptic diversity are still poorly understood. Using genome‐wide data, we show here that the pale sand martin Riparia diluta in Central and East Asia consists of three genetically deeply differentiated lineages which vary only gradually in morphology but broadly reflect traditional taxonomy. We detected no signs of gene flow along the eastern edge of the Qinghai‐Tibetan plateau between lowland south‐eastern Chinese R. d. fohkienensis and high‐altitude R. d. tibetana. Largely different breeding and migration timing between these low and high altitude populations as indicated by phenology data suggests that allochrony might act as prezygotic isolation mechanism in the area where their ranges abut. Mongolian populations of R. d. tibetana, however, displayed signs of limited mixed ancestries with Central Asian R. d. diluta. Their ranges meet in the area of a well‐known avian migratory divide, where western lineages take a western migration route around the Qinghai‐Tibetan plateau to winter quarters in South Asia, and eastern lineages take an eastern route to Southeast Asia. This might also be the case between western R. d. diluta and eastern R. d. tibetana as indicated by differing wintering grounds. We hypothesize that hybrids might have nonoptimal intermediate migration routes and selection against them might restrict gene flow. Although further potential isolation mechanisms might exist in the pale sand martin, our study points towards contrasting migration behaviour as an important factor in maintaining evolutionary diversity under morphological stasis.
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Affiliation(s)
- Qindong Tang
- Institute of Ecology and Evolution, University of Bern, Bern, Switzerland.,Natural History Museum, Bern, Switzerland
| | - Reto Burri
- Schweizerische Vogelwarte, Sempach, Switzerland
| | - Yang Liu
- State Key Laboratory of Biocontrol, College of Ecology School of Life Science, Sun Yat-sen University, Guangzhou, China
| | - Alexander Suh
- School of Biological Sciences-Organisms and the Environment, University of East Anglia, Norwich, UK.,Department of Organismal Biology - Systematic Biology, Evolutionary Biology Centre (EBC), Uppsala University, Uppsala, Sweden
| | - Gombobaatar Sundev
- National University of Mongolia and Mongolian Ornithological Society, Ulaanbaatar, Mongolia
| | - Gerald Heckel
- Institute of Ecology and Evolution, University of Bern, Bern, Switzerland
| | - Manuel Schweizer
- Institute of Ecology and Evolution, University of Bern, Bern, Switzerland.,Natural History Museum, Bern, Switzerland
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10
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Freeman BG, Pennell MW. The latitudinal taxonomy gradient. Trends Ecol Evol 2021; 36:778-786. [PMID: 34074540 DOI: 10.1016/j.tree.2021.05.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 05/03/2021] [Accepted: 05/06/2021] [Indexed: 10/21/2022]
Abstract
Emerging large-scale datasets coupled with statistical advances have provided new insights into the processes that generate the latitudinal diversity gradient (LDG). But many of these studies run into an old, if often underappreciated, problem: The interpretation of the data critically depends on the consistent application of criteria to define what constitutes a species. This is particularly pernicious for the LDG because good species have been easier to recognize in temperate than in tropical regions. We provide evidence that this latitudinal taxonomy gradient exists, discuss how this potentially impacts inferences about latitudinal variation in ecoevolutionary processes such as population differentiation and speciation, and provide a roadmap for how to mitigate taxonomic biases in the study of biodiversity patterns.
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Affiliation(s)
- Benjamin G Freeman
- Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada, V6T1Z4; Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada.
| | - Matthew W Pennell
- Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada, V6T1Z4; Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
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11
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Buainain N, Maximiano MFA, Ferreira M, Aleixo A, Faircloth BC, Brumfield RT, Cracraft J, Ribas CC. Multiple species and deep genomic divergences despite little phenotypic differentiation in an ancient Neotropical songbird, Tunchiornis ochraceiceps (Sclater, 1860) (Aves: Vireonidae). Mol Phylogenet Evol 2021; 162:107206. [PMID: 34015447 DOI: 10.1016/j.ympev.2021.107206] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 05/04/2021] [Accepted: 05/11/2021] [Indexed: 11/20/2022]
Abstract
Several bird taxa have been recently described or elevated to full species and almost twice as many bird species than are currently recognized may exist. Defining species is one of the most basic and important issues in biological science because unknown or poorly defined species hamper subsequent studies. Here, we evaluate the species limits and evolutionary history of Tunchiornis ochraceiceps-a widespread forest songbird that occurs in the lowlands of Central America, Chocó and Amazonia-using an integrative approach that includes plumage coloration, morphometrics, vocalization and genomic data. The species has a relatively old crown age (~9 Ma) and comprises several lineages with little, if any, evidence of gene flow among them. We propose a taxonomic arrangement composed of four species, three with a plumage coloration diagnosis and one deeply divergent cryptic species. Most of the remaining lineages have variable but unfixed phenotypic characters despite their relatively old origin. This decoupling of genomic and phenotypic differentiation reveals a remarkable case of phenotypic conservatism, possibly due to strict habitat association. Lineages are geographically delimited by the main Amazonian rivers and the Andes, a pattern observed in studies of other understory upland forest Neotropical birds, although phylogenetic relationships and divergence times among populations are idiosyncratic.
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Affiliation(s)
- Nelson Buainain
- Instituto Nacional de Pesquisas da Amazônia (INPA), Programa de Pós-Graduação em Ecologia, Av. André Araújo, 2936, Petrópolis, Manaus, AM 69067-375, Brazil.
| | - Marina F A Maximiano
- Instituto Nacional de Pesquisas da Amazônia (INPA), Programa de Pós-Graduação em Ecologia, Av. André Araújo, 2936, Petrópolis, Manaus, AM 69067-375, Brazil
| | - Mateus Ferreira
- Centro de Estudos da Biodiversidade, Universidade Federal de Roraima, Av. Cap. Ene Garcez, 2413, Boa Vista, Roraima, RR 69304-000, Brazil
| | - Alexandre Aleixo
- Finnish Museum of Natural History, University of Helsinki, Helsinki, Finland
| | - Brant C Faircloth
- Louisiana State University, Department of Biological Sciences, Baton Rouge, LA 70803, USA; Museum of Natural Science and Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Robb T Brumfield
- Louisiana State University, Department of Biological Sciences, Baton Rouge, LA 70803, USA; Museum of Natural Science and Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Joel Cracraft
- American Museum of Natural History, Department of Ornithology, New York, NY, USA
| | - Camila C Ribas
- Instituto Nacional de Pesquisas da Amazônia, Coordenação de Biodiversidade, Av. André Araújo, 2936, Manaus, AM 69067-375, Brazil
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12
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Lopez KA, McDiarmid CS, Griffith SC, Lovette IJ, Hooper DM. Evaluating evidence of mitonuclear incompatibilities with the sex chromosomes in an avian hybrid zone. Evolution 2021; 75:1395-1414. [PMID: 33908624 DOI: 10.1111/evo.14243] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Revised: 02/15/2021] [Accepted: 04/11/2021] [Indexed: 12/13/2022]
Abstract
The exploration of hybrid zones and the intergenomic conflicts exposed through hybridization provide windows into the processes of divergence and speciation. Sex chromosomes and mitonuclear incompatibilities have strong associations with the genetics of hybrid dysfunction. In ZW sex-determining systems, maternal co-inheritance of the mitochondrial and W chromosomes immediately exposes incompatibilities between these maternal contributions of one species and the Z chromosome of another. We analyze mitochondrial and Z chromosome admixture in the long-tailed finch (Poephila acuticauda) of Australia, where hybridizing subspecies differ prominently in Z chromosome genotype and in bill color, yet the respective centers of geographic admixture for these two traits are offset by 350 km. We report two well-defined mitochondrial clades that diverged ∼0.5 million years ago. Mitochondrial contact is geographically co-located within a hybrid zone of Z chromosome admixture and is displaced from bill color admixture by nearly 400 km. Consistent with Haldane's rule expectations, hybrid zone females are significantly less likely than males to carry an admixed Z chromosome or have mismatched Z-mitochondrial genotypes. Furthermore, there are significantly fewer than expected mitonuclear mismatches in hybrid zone females and paternal backcross males. Results suggest a potential for mitonuclear/sex chromosome incompatibilities in the emergence of reproductive isolation in this system.
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Affiliation(s)
- Kelsie A Lopez
- Cornell Lab of Ornithology, Cornell University, Ithaca, NY, 14850, USA
| | - Callum S McDiarmid
- Department of Biological Sciences, Macquarie University, Sydney, NSW, Australia
| | - Simon C Griffith
- Department of Biological Sciences, Macquarie University, Sydney, NSW, Australia
| | - Irby J Lovette
- Cornell Lab of Ornithology, Cornell University, Ithaca, NY, 14850, USA
| | - Daniel M Hooper
- Cornell Lab of Ornithology, Cornell University, Ithaca, NY, 14850, USA.,Department of Biological Sciences, Columbia University, New York, NY, 10027, USA
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