1
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Johannesson K, Faria R, Le Moan A, Rafajlović M, Westram AM, Butlin RK, Stankowski S. Diverse pathways to speciation revealed by marine snails. Trends Genet 2024; 40:337-351. [PMID: 38395682 DOI: 10.1016/j.tig.2024.01.002] [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: 09/30/2023] [Revised: 01/06/2024] [Accepted: 01/10/2024] [Indexed: 02/25/2024]
Abstract
Speciation is a key evolutionary process that is not yet fully understood. Combining population genomic and ecological data from multiple diverging pairs of marine snails (Littorina) supports the search for speciation mechanisms. Placing pairs on a one-dimensional speciation continuum, from undifferentiated populations to species, obscured the complexity of speciation. Adding multiple axes helped to describe either speciation routes or reproductive isolation in the snails. Divergent ecological selection repeatedly generated barriers between ecotypes, but appeared less important in completing speciation while genetic incompatibilities played a key role. Chromosomal inversions contributed to genomic barriers, but with variable impact. A multidimensional (hypercube) approach supported framing of questions and identification of knowledge gaps and can be useful to understand speciation in many other systems.
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Affiliation(s)
- Kerstin Johannesson
- Department of Marine Sciences, University of Gothenburg, Tjärnö Marine Laboratory, SE 45296 Strömstad, Sweden; The Linnaeus Centre for Marine Evolutionary Biology, University of Gothenburg, Gothenburg, Sweden.
| | - Rui Faria
- The Linnaeus Centre for Marine Evolutionary Biology, University of Gothenburg, Gothenburg, Sweden; CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, InBIO, Laboratório Associado, Universidade do Porto, Vairão, Portugal; BIOPOLIS Program in Genomics, Biodiversity and Land Planning, CIBIO, Campus de Vairão, 4485-661 Vairão, Portugal
| | - Alan Le Moan
- The Linnaeus Centre for Marine Evolutionary Biology, University of Gothenburg, Gothenburg, Sweden; CNRS & Sorbonne Université, Station Biologique de Roscoff, Roscoff, France
| | - Marina Rafajlović
- The Linnaeus Centre for Marine Evolutionary Biology, University of Gothenburg, Gothenburg, Sweden; Department of Marine Sciences, University of Gothenburg, SE 41390 Gothenburg, Sweden; Gothenburg Global Biodiversity Centre, University of Gothenburg, Gothenburg, Sweden
| | - Anja Marie Westram
- Department of Marine Sciences, University of Gothenburg, Tjärnö Marine Laboratory, SE 45296 Strömstad, Sweden; The Linnaeus Centre for Marine Evolutionary Biology, University of Gothenburg, Gothenburg, Sweden; Faculty of Biosciences and Aquaculture, Nord University, Bodø, Norway
| | - Roger K Butlin
- Department of Marine Sciences, University of Gothenburg, Tjärnö Marine Laboratory, SE 45296 Strömstad, Sweden; The Linnaeus Centre for Marine Evolutionary Biology, University of Gothenburg, Gothenburg, Sweden; Ecology and Evolutionary Biology, School of Biosciences, The University of Sheffield, Sheffield, UK
| | - Sean Stankowski
- The Linnaeus Centre for Marine Evolutionary Biology, University of Gothenburg, Gothenburg, Sweden; Institute of Science and Technology Austria, Klosterneuburg, Austria; Department of Ecology and Evolution, University of Sussex, Brighton, UK
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2
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Grupstra CGB, Gómez-Corrales M, Fifer JE, Aichelman HE, Meyer-Kaiser KS, Prada C, Davies SW. Integrating cryptic diversity into coral evolution, symbiosis and conservation. Nat Ecol Evol 2024; 8:622-636. [PMID: 38351091 DOI: 10.1038/s41559-023-02319-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Accepted: 12/12/2023] [Indexed: 04/13/2024]
Abstract
Understanding how diversity evolves and is maintained is critical to predicting the future trajectories of ecosystems under climate change; however, our understanding of these processes is limited in marine systems. Corals, which engineer reef ecosystems, are critically threatened by climate change, and global efforts are underway to conserve and restore populations as attempts to mitigate ocean warming continue. Recently, sequencing efforts have uncovered widespread undescribed coral diversity, including 'cryptic lineages'-genetically distinct but morphologically similar coral taxa. Such cryptic lineages have been identified in at least 24 coral genera spanning the anthozoan phylogeny and across ocean basins. These cryptic lineages co-occur in many reef systems, but their distributions often differ among habitats. Research suggests that cryptic lineages are ecologically specialized and several examples demonstrate differences in thermal tolerance, highlighting the critical implications of this diversity for predicting coral responses to future warming. Here, we draw attention to recent discoveries, discuss how cryptic diversity affects the study of coral adaptation and acclimation to future environments, explore how it shapes symbiotic partnerships, and highlight challenges and opportunities for conservation and restoration efforts.
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Affiliation(s)
| | | | - James E Fifer
- Department of Biology, Boston University, Boston, MA, USA
| | | | | | - Carlos Prada
- Department of Biological Sciences, University of Rhode Island, Kingston, RI, USA
| | - Sarah W Davies
- Department of Biology, Boston University, Boston, MA, USA.
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3
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Reifová R, Ament-Velásquez SL, Bourgeois Y, Coughlan J, Kulmuni J, Lipinska AP, Okude G, Stevison L, Yoshida K, Kitano J. Mechanisms of Intrinsic Postzygotic Isolation: From Traditional Genic and Chromosomal Views to Genomic and Epigenetic Perspectives. Cold Spring Harb Perspect Biol 2023; 15:a041607. [PMID: 37696577 PMCID: PMC10547394 DOI: 10.1101/cshperspect.a041607] [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: 09/13/2023]
Abstract
Intrinsic postzygotic isolation typically appears as reduced viability or fertility of interspecific hybrids caused by genetic incompatibilities between diverged parental genomes. Dobzhansky-Muller interactions among individual genes, and chromosomal rearrangements causing problems with chromosome synapsis and recombination in meiosis, have both long been considered as major mechanisms behind intrinsic postzygotic isolation. Recent research has, however, suggested that the genetic basis of intrinsic postzygotic isolation can be more complex and involves, for example, overall divergence of the DNA sequence or epigenetic changes. Here, we review the mechanisms of intrinsic postzygotic isolation from genic, chromosomal, genomic, and epigenetic perspectives across diverse taxa. We provide empirical evidence for these mechanisms, discuss their importance in the speciation process, and highlight questions that remain unanswered.
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Affiliation(s)
- Radka Reifová
- Department of Zoology, Faculty of Science, Charles University, 128 00 Prague, Czech Republic
| | | | - Yann Bourgeois
- DIADE, University of Montpellier, CIRAD, IRD, 34090 Montpellier, France
| | - Jenn Coughlan
- Department of Ecology & Evolutionary Biology, Yale University, New Haven, Connecticut 06520, USA
| | - Jonna Kulmuni
- Institute for Biodiversity and Ecosystem Dynamics, Department of Evolutionary and Population Biology, University of Amsterdam, 1012 Amsterdam, The Netherlands
- Organismal & Evolutionary Biology Research Programme, University of Helsinki, 00100 Helsinki, Finland
| | - Agnieszka P Lipinska
- Department of Algal Development and Evolution, Max Planck Institute for Biology, 72076 Tuebingen, Germany
- CNRS, UMR 8227, Integrative Biology of Marine Models, Sorbonne Université, Station Biologique de Roscoff, 29680 Roscoff, France
| | - Genta Okude
- Department of Genomics and Evolutionary Biology, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
| | - Laurie Stevison
- Department of Biological Sciences, Auburn University, Auburn, Alabama 36849, USA
| | - Kohta Yoshida
- Department of Genomics and Evolutionary Biology, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
| | - Jun Kitano
- Department of Genomics and Evolutionary Biology, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
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4
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Cutter AD. Speciation and development. Evol Dev 2023; 25:289-327. [PMID: 37545126 DOI: 10.1111/ede.12454] [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: 03/07/2023] [Revised: 06/13/2023] [Accepted: 07/20/2023] [Indexed: 08/08/2023]
Abstract
Understanding general principles about the origin of species remains one of the foundational challenges in evolutionary biology. The genomic divergence between groups of individuals can spawn hybrid inviability and hybrid sterility, which presents a tantalizing developmental problem. Divergent developmental programs may yield either conserved or divergent phenotypes relative to ancestral traits, both of which can be responsible for reproductive isolation during the speciation process. The genetic mechanisms of developmental evolution involve cis- and trans-acting gene regulatory change, protein-protein interactions, genetic network structures, dosage, and epigenetic regulation, all of which also have roots in population genetic and molecular evolutionary processes. Toward the goal of demystifying Darwin's "mystery of mysteries," this review integrates microevolutionary concepts of genetic change with principles of organismal development, establishing explicit links between population genetic process and developmental mechanisms in the production of macroevolutionary pattern. This integration aims to establish a more unified view of speciation that binds process and mechanism.
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Affiliation(s)
- Asher D Cutter
- Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada
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5
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Stankowski S, Chase MA, McIntosh H, Streisfeld MA. Integrating top-down and bottom-up approaches to understand the genetic architecture of speciation across a monkeyflower hybrid zone. Mol Ecol 2023; 32:2041-2054. [PMID: 36651268 DOI: 10.1111/mec.16849] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 01/04/2023] [Accepted: 01/12/2023] [Indexed: 01/19/2023]
Abstract
Understanding the phenotypic and genetic architecture of reproductive isolation is a long-standing goal of speciation research. In several systems, large-effect loci contributing to barrier phenotypes have been characterized, but such causal connections are rarely known for more complex genetic architectures. In this study, we combine "top-down" and "bottom-up" approaches with demographic modelling toward an integrated understanding of speciation across a monkeyflower hybrid zone. Previous work suggests that pollinator visitation acts as a primary barrier to gene flow between two divergent red- and yellow-flowered ecotypes of Mimulus aurantiacus. Several candidate isolating traits and anonymous single nucleotide polymorphism loci under divergent selection have been identified, but their genomic positions remain unknown. Here, we report findings from demographic analyses that indicate this hybrid zone formed by secondary contact, but that subsequent gene flow was restricted by widespread barrier loci across the genome. Using a novel, geographic cline-based genome scan, we demonstrate that candidate barrier loci are broadly distributed across the genome, rather than mapping to one or a few "islands of speciation." Quantitative trait locus (QTL) mapping reveals that most floral traits are highly polygenic, with little evidence that QTL colocalize, indicating that most traits are genetically independent. Finally, we find little evidence that QTL and candidate barrier loci overlap, suggesting that some loci contribute to other forms of reproductive isolation. Our findings highlight the challenges of understanding the genetic architecture of reproductive isolation and reveal that barriers to gene flow other than pollinator isolation may play an important role in this system.
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Affiliation(s)
- Sean Stankowski
- Institute of Ecology and Evolution, University of Oregon, Eugene, Oregon, USA
| | - Madeline A Chase
- Institute of Ecology and Evolution, University of Oregon, Eugene, Oregon, USA
| | - Hanna McIntosh
- Institute of Ecology and Evolution, University of Oregon, Eugene, Oregon, USA
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6
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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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7
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Augustijnen H, Patsiou T, Lucek K. Secondary contact rather than coexistence-Erebia butterflies in the Alps. Evolution 2022; 76:2669-2686. [PMID: 36117267 PMCID: PMC9828779 DOI: 10.1111/evo.14615] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Revised: 08/05/2022] [Accepted: 08/30/2022] [Indexed: 01/22/2023]
Abstract
Secondary contact zones are ideal systems to study the processes that govern the evolution of reproductive barriers, especially at advanced stages of the speciation process. An increase in reproductive isolation resulting from selection against maladaptive hybrids is thought to contribute to reproductive barrier buildup in secondary contact zones. Although such processes have been invoked for many systems, it remains unclear to which extent they influence contact zone dynamics in nature. Here, we study a very narrow contact zone between the butterfly species Erebia cassioides and Erebia tyndarus in the Swiss Alps. We quantified phenotypic traits related to wing shape and reproduction as well as ecology to compare the degree of intra- and interspecific differentiation. Even though only very few first-generation hybrids occur, we find no strong indications for current reinforcing selection, suggesting that if reinforcement occurred in our system, it likely operated in the past. Additionally, we show that both species differ less in their ecological niche at the contact zone than elsewhere, which could explain why coexistence between these butterflies may currently not be possible.
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Affiliation(s)
- Hannah Augustijnen
- Department of Environmental SciencesUniversity of BaselBaselCH‐4056Switzerland
| | - Theofania Patsiou
- Institute of Plant SciencesUniversity of BernBernCH‐3013Switzerland,Department of BiologyUniversity of FribourgFribourgCH‐1700Switzerland
| | - Kay Lucek
- Department of Environmental SciencesUniversity of BaselBaselCH‐4056Switzerland
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8
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Patton AH, Richards EJ, Gould KJ, Buie LK, Martin CH. Hybridization alters the shape of the genotypic fitness landscape, increasing access to novel fitness peaks during adaptive radiation. eLife 2022; 11:e72905. [PMID: 35616528 PMCID: PMC9135402 DOI: 10.7554/elife.72905] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Accepted: 04/14/2022] [Indexed: 12/30/2022] Open
Abstract
Estimating the complex relationship between fitness and genotype or phenotype (i.e. the adaptive landscape) is one of the central goals of evolutionary biology. However, adaptive walks connecting genotypes to organismal fitness, speciation, and novel ecological niches are still poorly understood and processes for surmounting fitness valleys remain controversial. One outstanding system for addressing these connections is a recent adaptive radiation of ecologically and morphologically novel pupfishes (a generalist, molluscivore, and scale-eater) endemic to San Salvador Island, Bahamas. We leveraged whole-genome sequencing of 139 hybrids from two independent field fitness experiments to identify the genomic basis of fitness, estimate genotypic fitness networks, and measure the accessibility of adaptive walks on the fitness landscape. We identified 132 single nucleotide polymorphisms (SNPs) that were significantly associated with fitness in field enclosures. Six out of the 13 regions most strongly associated with fitness contained differentially expressed genes and fixed SNPs between trophic specialists; one gene (mettl21e) was also misexpressed in lab-reared hybrids, suggesting a potential intrinsic genetic incompatibility. We then constructed genotypic fitness networks from adaptive alleles and show that scale-eating specialists are the most isolated of the three species on these networks. Intriguingly, introgressed and de novo variants reduced fitness landscape ruggedness as compared to standing variation, increasing the accessibility of genotypic fitness paths from generalist to specialists. Our results suggest that adaptive introgression and de novo mutations alter the shape of the fitness landscape, providing key connections in adaptive walks circumventing fitness valleys and triggering the evolution of novelty during adaptive radiation.
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Affiliation(s)
- Austin H Patton
- Department of Integrative Biology, University of California, BerkeleyBerkeleyUnited States
- Museum of Vertebrate Zoology, University of California, BerkeleyBerkeleyUnited States
| | - Emilie J Richards
- Department of Integrative Biology, University of California, BerkeleyBerkeleyUnited States
- Museum of Vertebrate Zoology, University of California, BerkeleyBerkeleyUnited States
| | - Katelyn J Gould
- Department of Biology, University of North CarolinaChapel HillUnited States
| | - Logan K Buie
- Department of Biology, University of North CarolinaChapel HillUnited States
| | - Christopher H Martin
- Department of Integrative Biology, University of California, BerkeleyBerkeleyUnited States
- Museum of Vertebrate Zoology, University of California, BerkeleyBerkeleyUnited States
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9
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Payne C, Bovio R, Powell DL, Gunn TR, Banerjee SM, Grant V, Rosenthal GG, Schumer M. Genomic insights into variation in thermotolerance between hybridizing swordtail fishes. Mol Ecol 2022. [PMID: 35510780 DOI: 10.1111/mec.16489] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Revised: 02/22/2022] [Accepted: 04/19/2022] [Indexed: 11/30/2022]
Abstract
Understanding how organisms adapt to changing environments is a core focus of research in evolutionary biology. One common mechanism is adaptive introgression, which has received increasing attention as a potential route to rapid adaptation in populations struggling in the face of ecological change, particularly global climate change. However, hybridization can also result in deleterious genetic interactions that may limit the benefits of adaptive introgression. Here, we used a combination of genome-wide quantitative trait locus mapping and differential gene expression analyses between the swordtail fish species Xiphophorus malinche and X. birchmanni to study the consequences of hybridization on thermotolerance. While these two species are adapted to different thermal environments, we document a complicated architecture of thermotolerance in hybrids. We identify a region of the genome that contributes to reduced thermotolerance in individuals heterozygous for X. malinche and X. birchmanni ancestry, as well as widespread misexpression in hybrids of genes that respond to thermal stress in the parental species, particularly in the circadian clock pathway. We also show that a previously mapped hybrid incompatibility between X. malinche and X. birchmanni contributes to reduced thermotolerance in hybrids. Together, our results highlight the challenges of understanding the impact of hybridization on complex ecological traits and its potential impact on adaptive introgression.
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Affiliation(s)
- Cheyenne Payne
- Department of Biology, Stanford University, Stanford, California, USA
- Centro de Investigaciones Científicas de las Huastecas "Aguazarca", A.C., Calnali, Hidalgo, México
| | - Richard Bovio
- Centro de Investigaciones Científicas de las Huastecas "Aguazarca", A.C., Calnali, Hidalgo, México
- Department of Biology, Texas A&M University, College Station, Texas, USA
| | - Daniel L Powell
- Department of Biology, Stanford University, Stanford, California, USA
- Centro de Investigaciones Científicas de las Huastecas "Aguazarca", A.C., Calnali, Hidalgo, México
| | - Theresa R Gunn
- Department of Biology, Stanford University, Stanford, California, USA
- Centro de Investigaciones Científicas de las Huastecas "Aguazarca", A.C., Calnali, Hidalgo, México
| | - Shreya M Banerjee
- Department of Biology, Stanford University, Stanford, California, USA
- Centro de Investigaciones Científicas de las Huastecas "Aguazarca", A.C., Calnali, Hidalgo, México
| | - Victoria Grant
- Department of Biology, Stanford University, Stanford, California, USA
- Centro de Investigaciones Científicas de las Huastecas "Aguazarca", A.C., Calnali, Hidalgo, México
| | - Gil G Rosenthal
- Centro de Investigaciones Científicas de las Huastecas "Aguazarca", A.C., Calnali, Hidalgo, México
- Department of Biology, Texas A&M University, College Station, Texas, USA
- Department of Biology, University of Padua, Italy
| | - Molly Schumer
- Department of Biology, Stanford University, Stanford, California, USA
- Centro de Investigaciones Científicas de las Huastecas "Aguazarca", A.C., Calnali, Hidalgo, México
- Department of Biology, University of Padua, Italy
- Hanna H. Gray Fellow, Howard Hughes Medical Institute, Stanford, California, USA
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10
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Meza‐Lázaro RN, Peña‐Carrillo KI, Poteaux C, Lorenzi MC, Wetterer JK, Zaldívar‐Riverón A. Genome and cuticular hydrocarbon-based species delimitation shed light on potential drivers of speciation in a Neotropical ant species complex. Ecol Evol 2022; 12:e8704. [PMID: 35342602 PMCID: PMC8928884 DOI: 10.1002/ece3.8704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Revised: 02/02/2022] [Accepted: 02/18/2022] [Indexed: 12/03/2022] Open
Abstract
Geographic separation that leads to the evolution of reproductive isolation between populations generally is considered the most common form of speciation. However, speciation may also occur in the absence of geographic barriers due to phenotypic and genotypic factors such as chemical cue divergence, mating signal divergence, and mitonuclear conflict. Here, we performed an integrative study based on two genome-wide techniques (3RAD and ultraconserved elements) coupled with cuticular hydrocarbon (CHC) and mitochondrial (mt) DNA sequence data, to assess the species limits within the Ectatomma ruidum species complex, a widespread and conspicuous group of Neotropical ants for which heteroplasmy (i.e., presence of multiple mtDNA variants in an individual) has been recently discovered in some populations from southeast Mexico. Our analyses indicate the existence of at least five distinct species in this complex: two widely distributed across the Neotropics, and three that are restricted to southeast Mexico and that apparently have high levels of heteroplasmy. We found that species boundaries in the complex did not coincide with geographic barriers. We therefore consider possible roles of alternative drivers that may have promoted the observed patterns of speciation, including mitonuclear incompatibility, CHC differentiation, and colony structure. Our study highlights the importance of simultaneously assessing different sources of evidence to disentangle the species limits of taxa with complicated evolutionary histories.
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Affiliation(s)
- Rubi N. Meza‐Lázaro
- Colección Nacional de InsectosInstituto de BiologíaUniversidad Nacional Autónoma de MéxicoCiudad de MéxicoMéxico
| | - Kenzy I. Peña‐Carrillo
- Laboratoire d’Ethologie Expérimentale et ComparéeUR 4443LEECUniversité Sorbonne Paris NordClémentFrance
- INIFAPCampo Experimental General TeránGeneral TeránMexico
| | - Chantal Poteaux
- Laboratoire d’Ethologie Expérimentale et ComparéeUR 4443LEECUniversité Sorbonne Paris NordClémentFrance
| | - Maria Cristina Lorenzi
- Laboratoire d’Ethologie Expérimentale et ComparéeUR 4443LEECUniversité Sorbonne Paris NordClémentFrance
| | - James K. Wetterer
- Harriet L. Wilkes Honors CollegeFlorida Atlantic UniversityJupiterFloridaUSA
| | - Alejandro Zaldívar‐Riverón
- Colección Nacional de InsectosInstituto de BiologíaUniversidad Nacional Autónoma de MéxicoCiudad de MéxicoMéxico
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11
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Shi Y, Bouska KL, McKinney GJ, Dokai W, Bartels A, McPhee MV, Larson WA. Gene flow influences the genomic architecture of local adaptation in six riverine fish species. Mol Ecol 2021; 32:1549-1566. [PMID: 34878685 DOI: 10.1111/mec.16317] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 11/15/2021] [Accepted: 12/01/2021] [Indexed: 11/30/2022]
Abstract
Understanding how gene flow influences adaptive divergence is important for predicting adaptive responses. Theoretical studies suggest that when gene flow is high, clustering of adaptive genes in fewer genomic regions would protect adaptive alleles from recombination and thus be selected for, but few studies have tested it with empirical data. Here, we used restriction site-associated sequencing to generate genomic data for six fish species with contrasting life histories from six reaches of the Upper Mississippi River System, USA. We used four differentiation-based outlier tests and three genotype-environment association analyses to define neutral single nucleotide polymorphisms (SNPs) and outlier SNPs that were putatively under selection. We then examined the distribution of outlier SNPs along the genome and investigated whether these SNPs were found in genomic islands of differentiation and inversions. We found that gene flow varied among species, and outlier SNPs were clustered more tightly in species with higher gene flow. The two species with the highest overall FST (0.0303-0.0720) and therefore lowest gene flow showed little evidence of clusters of outlier SNPs, with outlier SNPs in these species spreading uniformly across the genome. In contrast, nearly all outlier SNPs in the species with the lowest FST (0.0003) were found in a single large putative inversion. Two other species with intermediate gene flow (FST ~ 0.0025-0.0050) also showed clustered genomic architectures, with most islands of differentiation clustered on a few chromosomes. Our results provide important empirical evidence to support the hypothesis that increasingly clustered architecture of local adaptation is associated with high gene flow.
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Affiliation(s)
- Yue Shi
- College of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Juneau, Alaska, USA.,Wisconsin Cooperative Fishery Research Unit, College of Natural Resources, University of Wisconsin-Stevens Point, Stevens Point, Wisconsin, USA
| | - Kristen L Bouska
- U.S. Geological Survey, Upper Midwest Environmental Sciences Center, La Crosse, Wisconsin, USA
| | - Garrett J McKinney
- NRC Research Associateship Program, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Seattle, Washington, USA
| | - William Dokai
- College of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Juneau, Alaska, USA.,Wisconsin Cooperative Fishery Research Unit, College of Natural Resources, University of Wisconsin-Stevens Point, Stevens Point, Wisconsin, USA
| | - Andrew Bartels
- Long Term Resource Monitoring Program, Wisconsin Department of Natural Resources, La Crosse, Wisconsin, USA
| | - Megan V McPhee
- College of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Juneau, Alaska, USA
| | - Wesley A Larson
- National Oceanographic and Atmospheric Administration, Auke Bay Laboratories, National Marine Fisheries Service, Alaska Fisheries Science Center, Juneau, Alaska, USA.,U.S. Geological Survey, Wisconsin Cooperative Fishery Research Unit, College of Natural Resources, University of Wisconsin-Stevens Point, Stevens Point, Wisconsin, USA
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12
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Martin CH, Gould KJ. Surprising spatiotemporal stability of a multi-peak fitness landscape revealed by independent field experiments measuring hybrid fitness. Evol Lett 2020; 4:530-544. [PMID: 33312688 PMCID: PMC7719547 DOI: 10.1002/evl3.195] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Revised: 07/23/2020] [Accepted: 09/14/2020] [Indexed: 12/14/2022] Open
Abstract
The effect of the environment on fitness in natural populations is a fundamental question in evolutionary biology. However, experimental manipulations of both environment and phenotype at the same time are rare. Thus, the relative importance of the competitive environment versus intrinsic organismal performance in shaping the location, height, and fluidity of fitness peaks and valleys remains largely unknown. Here, we experimentally tested the effect of competitor frequency on the complex fitness landscape driving adaptive radiation of a generalist and two trophic specialist pupfishes, a scale-eater and molluscivore, endemic to hypersaline lakes on San Salvador Island (SSI), Bahamas. We manipulated phenotypes, by generating 3407 F4/F5 lab-reared hybrids, and competitive environment, by altering the frequency of rare transgressive hybrids between field enclosures in two independent lake populations. We then tracked hybrid survival and growth rates across these four field enclosures for 3-11 months. In contrast to competitive speciation theory, we found no evidence that the frequency of hybrid phenotypes affected their survival. Instead, we observed a strikingly similar fitness landscape to a previous independent field experiment, each supporting multiple fitness peaks for generalist and molluscivore phenotypes and a large fitness valley isolating the divergent scale-eater phenotype. These features of the fitness landscape were stable across manipulated competitive environments, multivariate trait axes, and spatiotemporal heterogeneity. We suggest that absolute performance constraints and divergent gene regulatory networks shape macroevolutionary (interspecific) fitness landscapes in addition to microevolutionary (intraspecific) competitive dynamics. This interplay between organism and environment underlies static and dynamic features of the adaptive landscape.
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Affiliation(s)
- Christopher H. Martin
- Department of Integrative BiologyUniversity of California, BerkeleyBerkeleyCalifornia94720
- Museum of Vertebrate ZoologyUniversity of California, BerkeleyBerkeleyCalifornia94720
| | - Katelyn J. Gould
- Department of BiologyUniversity of North Carolina at Chapel HillChapel HillNorth Carolina27515
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13
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Kulmuni J, Nouhaud P, Pluckrose L, Satokangas I, Dhaygude K, Butlin RK. Instability of natural selection at candidate barrier loci underlying speciation in wood ants. Mol Ecol 2020; 29:3988-3999. [PMID: 32854139 DOI: 10.1111/mec.15606] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 08/12/2020] [Accepted: 08/13/2020] [Indexed: 12/11/2022]
Abstract
Speciation underlies the generation of novel biodiversity. Yet, there is much to learn about how natural selection shapes genomes during speciation. Selection is assumed to act against gene flow at barrier loci, promoting reproductive isolation. However, evidence for gene flow and selection is often indirect and we know very little about the temporal stability of barrier loci. Here we utilize haplodiploidy to identify candidate male barrier loci in hybrids between two wood ant species. As ant males are haploid, they are expected to reveal recessive barrier loci, which can be masked in diploid females if heterozygous. We then test for barrier stability in a sample collected 10 years later and use survival analysis to provide a direct measure of natural selection acting on candidate male barrier loci. We find multiple candidate male barrier loci scattered throughout the genome. Surprisingly, a proportion of them are not stable after 10 years, natural selection apparently switching from acting against to favouring introgression in the later sample. Instability of the barrier effect and natural selection for introgressed alleles could be due to environment-dependent selection, emphasizing the need to consider temporal variation in the strength of natural selection and the stability of the barrier effect at putative barrier loci in future speciation work.
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Affiliation(s)
- Jonna Kulmuni
- Organismal & Evolutionary Biology Research Programme, University of Helsinki, Helsinki, Finland.,Tvärminne Zoological Station, University of Helsinki, Hanko, Finland
| | - Pierre Nouhaud
- Organismal & Evolutionary Biology Research Programme, University of Helsinki, Helsinki, Finland
| | - Lucy Pluckrose
- Organismal & Evolutionary Biology Research Programme, University of Helsinki, Helsinki, Finland
| | - Ina Satokangas
- Organismal & Evolutionary Biology Research Programme, University of Helsinki, Helsinki, Finland
| | - Kishor Dhaygude
- Organismal & Evolutionary Biology Research Programme, University of Helsinki, Helsinki, Finland
| | - Roger K Butlin
- Department of Animal and Plant Sciences, Alfred Denny Building, University of Sheffield, Sheffield, UK.,Department of Marine Science, University of Gothenburg, Gothenburg, Sweden
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14
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Rometsch SJ, Torres-Dowdall J, Meyer A. Evolutionary dynamics of pre- and postzygotic reproductive isolation in cichlid fishes. Philos Trans R Soc Lond B Biol Sci 2020; 375:20190535. [PMID: 32654645 DOI: 10.1098/rstb.2019.0535] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Cichlid fishes are exceptionally species-rich, speciated at explosive rates and, hence, are a model system in speciation research. Yet, their reproductive isolating barriers have, so far, not been comprehensively studied. Here, we review current knowledge on pre- and postzygotic mechanisms in cichlids. While premating isolation is the norm in cichlids, its strength varies across lineages and with the geographical setting. Moreover, manipulations of ambient conditions tended to reduce assortative mating among closely related species, suggesting that premating isolation in cichlids is often fragile and context dependent. The observed lack of complete reproductive isolation is supported by past and present hybridization events that have contributed to diversity by creating novel allelic combinations. On the other hand, our meta-analysis highlights that intrinsic postzygotic isolation might accumulate faster than assumed. Mild forms of genetic incompatibilities, such as sex ratio distortion, can already be observed among closely related species. Therefore, cessation of gene flow by strong reproductive isolation in cichlids requires a combination of premating prezygotic isolation supplemented with intrinsic and extrinsic postzygotic barriers. Further, we suggest crucial next steps to improve our knowledge about reproductive barriers in cichlids to understand the evolutionary dynamics of pre- and postzygotic isolation mechanisms during adaptive radiations. This article is part of the theme issue 'Towards the completion of speciation: the evolution of reproductive isolation beyond the first barriers'.
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Affiliation(s)
- Sina J Rometsch
- Department of Biology, University of Konstanz, Universitätsstraße 10, 78457 Konstanz, Germany
| | - Julián Torres-Dowdall
- Department of Biology, University of Konstanz, Universitätsstraße 10, 78457 Konstanz, Germany
| | - Axel Meyer
- Department of Biology, University of Konstanz, Universitätsstraße 10, 78457 Konstanz, Germany
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15
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Coughlan JM, Matute DR. The importance of intrinsic postzygotic barriers throughout the speciation process. Philos Trans R Soc Lond B Biol Sci 2020; 375:20190533. [PMID: 32654642 DOI: 10.1098/rstb.2019.0533] [Citation(s) in RCA: 70] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Intrinsic postzygotic barriers can play an important and multifaceted role in speciation, but their contribution is often thought to be reserved to the final stages of the speciation process. Here, we review how intrinsic postzygotic barriers can contribute to speciation, and how this role may change through time. We outline three major contributions of intrinsic postzygotic barriers to speciation. (i) reduction of gene flow: intrinsic postzygotic barriers can effectively reduce gene exchange between sympatric species pairs. We discuss the factors that influence how effective incompatibilities are in limiting gene flow. (ii) early onset of species boundaries via rapid evolution: intrinsic postzygotic barriers can evolve between recently diverged populations or incipient species, thereby influencing speciation relatively early in the process. We discuss why the early origination of incompatibilities is expected under some biological models, and detail how other (and often less obvious) incompatibilities may also serve as important barriers early on in speciation. (iii) reinforcement: intrinsic postzygotic barriers can promote the evolution of subsequent reproductive isolation through processes such as reinforcement, even between relatively recently diverged species pairs. We incorporate classic and recent empirical and theoretical work to explore these three facets of intrinsic postzygotic barriers, and provide our thoughts on recent challenges and areas in the field in which progress can be made. This article is part of the theme issue 'Towards the completion of speciation: the evolution of reproductive isolation beyond the first barriers'.
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Affiliation(s)
- Jenn M Coughlan
- Department of Biology, University of North Carolina, 120 South Road, Coker Hall, Chapel Hill, NC 27599, USA
| | - Daniel R Matute
- Department of Biology, University of North Carolina, 120 South Road, Coker Hall, Chapel Hill, NC 27599, USA
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16
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Blanckaert A, Bank C, Hermisson J. The limits to parapatric speciation 3: evolution of strong reproductive isolation in presence of gene flow despite limited ecological differentiation. Philos Trans R Soc Lond B Biol Sci 2020; 375:20190532. [PMID: 32654650 PMCID: PMC7423268 DOI: 10.1098/rstb.2019.0532] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Gene flow tends to impede the accumulation of genetic divergence. Here, we determine the limits for the evolution of postzygotic reproductive isolation in a model of two populations that are connected by gene flow. We consider two selective mechanisms for the creation and maintenance of a genetic barrier: local adaptation leads to divergence among incipient species due to selection against migrants, and Dobzhansky–Muller incompatibilities (DMIs) reinforce the genetic barrier through selection against hybrids. In particular, we are interested in the maximum strength of the barrier under a limited amount of local adaptation, a challenge that many incipient species may initially face. We first confirm that with classical two-locus DMIs, the maximum amount of local adaptation is indeed a limit to the strength of a genetic barrier. However, with three or more loci and cryptic epistasis, this limit holds no longer. In particular, we identify a minimal configuration of three epistatically interacting mutations that is sufficient to confer strong reproductive isolation. This article is part of the theme issue ‘Towards the completion of speciation: the evolution of reproductive isolation beyond the first barriers’.
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Affiliation(s)
- Alexandre Blanckaert
- Department of Mathematics, University of Vienna, 1090 Vienna, Austria.,Instituto Gulbenkian de Ciência, 2780-156 Oeiras, Portugal
| | - Claudia Bank
- Instituto Gulbenkian de Ciência, 2780-156 Oeiras, Portugal
| | - Joachim Hermisson
- Department of Mathematics, University of Vienna, 1090 Vienna, Austria.,Mathematics and Biosciences Group, Max Perutz Lab, 1030 Vienna, Austria
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17
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McGirr JA, Martin CH. Ecological divergence in sympatry causes gene misexpression in hybrids. Mol Ecol 2020; 29:2707-2721. [PMID: 32557903 DOI: 10.1111/mec.15512] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 05/21/2020] [Accepted: 06/01/2020] [Indexed: 12/17/2022]
Abstract
Ecological speciation occurs when reproductive isolation evolves as a byproduct of adaptive divergence between populations. Selection favouring gene regulatory divergence between species could result in transgressive levels of gene expression in F1 hybrids that may lower hybrid fitness. We combined 58 resequenced genomes with 124 transcriptomes to identify patterns of hybrid gene misexpression that may be driven by adaptive regulatory divergence within a young radiation of Cyprinodon pupfishes, which consists of a dietary generalist and two trophic specialists-a molluscivore and a scale-eater. We found more differential gene expression between closely related sympatric specialists than between allopatric generalist populations separated by 1,000 km. Intriguingly, 9.6% of genes that were differentially expressed between sympatric species were also misexpressed in F1 hybrids. A subset of these genes were in highly differentiated genomic regions and enriched for functions important for trophic specialization, including head, muscle and brain development. These regions also included genes that showed evidence of hard selective sweeps and were significantly associated with oral jaw length-the most rapidly diversifying skeletal trait in this radiation. Our results indicate that divergent ecological selection in sympatry can contribute to hybrid gene misexpression which may act as a reproductive barrier between nascent species.
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Affiliation(s)
- Joseph A McGirr
- Department of Biology, University of North Carolina, Chapel Hill, NC
| | - Christopher H Martin
- Department of Biology, University of North Carolina, Chapel Hill, NC.,Department of Integrative Biology and Museum of Vertebrate Zoology, University of California, Berkeley, CA
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18
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Capblancq T, Després L, Mavárez J. Genetic, morphological and ecological variation across a sharp hybrid zone between two alpine butterfly species. Evol Appl 2020; 13:1435-1450. [PMID: 32684968 PMCID: PMC7359832 DOI: 10.1111/eva.12925] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Revised: 12/02/2019] [Accepted: 12/09/2019] [Indexed: 11/26/2022] Open
Abstract
Identifying the mechanisms involved in the formation and maintenance of species is a central question in evolutionary biology, and distinguishing the selective drivers of populations' divergence from demographic processes is of particular interest to better understand the speciation process. Hybrid zones are recognized to provide ideal places to investigate the genetic architecture of speciation and to identify the mechanisms allowing diverging species to maintain their integrity in the face of gene flow. Here, we studied two alpine butterfly species, Coenonympha macromma and C. gardetta, which can be found flying together and hybridizing in narrow contact zones in the southern French Alps. We characterized the genomic composition of individuals, their morphology and their local habitat requirements, within and around a hybrid zone. Genetic diversity analysis at 794 SNPs revealed that all individuals within the hybrid zone were highly admixed, which was not the case outside the hybrid zone. Cline analysis showed that, despite ongoing hybridization, 56 out of 122 loci differentially fixed or nearly so between the two species were impermeable to introgression across the sharp hybrid zone (9 km wide). We also found concordance in cline position and width among genetic, morphological and environmental variation, suggesting a coupling of different reproductive barriers. Habitat characteristics such as the presence of trees and shrubs and the start of the growing season were strongly associated with the genetic variation, and we found evidence of divergence at genetic markers associated with morphology and physiology, putatively involved in visual or environmental reproductive isolation. We discuss the various behavioural and ecological factors that might interplay to maintain current levels of divergence and gene flow between this species pair.
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Affiliation(s)
- Thibaut Capblancq
- Laboratoire d’Écologie AlpineUMR UGA‐USMB‐CNRS 5553Université Grenoble AlpesGrenobleFrance
- Department of Plant BiologyUniversity of VermontBurlingtonVTUSA
| | - Laurence Després
- Laboratoire d’Écologie AlpineUMR UGA‐USMB‐CNRS 5553Université Grenoble AlpesGrenobleFrance
| | - Jesús Mavárez
- Laboratoire d’Écologie AlpineUMR UGA‐USMB‐CNRS 5553Université Grenoble AlpesGrenobleFrance
- Departamento de Ciencias Biológicas y AmbientalesUniversidad Jorge Tadeo LozanoBogotáColombia
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19
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Tobler M, Barts N, Greenway R. Mitochondria and the Origin of Species: Bridging Genetic and Ecological Perspectives on Speciation Processes. Integr Comp Biol 2020; 59:900-911. [PMID: 31004483 DOI: 10.1093/icb/icz025] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Mitochondria have been known to be involved in speciation through the generation of Dobzhansky-Muller incompatibilities, where functionally neutral co-evolution between mitochondrial and nuclear genomes can cause dysfunction when alleles are recombined in hybrids. We propose that adaptive mitochondrial divergence between populations can not only produce intrinsic (Dobzhansky-Muller) incompatibilities, but could also contribute to reproductive isolation through natural and sexual selection against migrants, post-mating prezygotic isolation, as well as by causing extrinsic reductions in hybrid fitness. We describe how these reproductive isolating barriers can potentially arise through adaptive divergence of mitochondrial function in the absence of mito-nuclear coevolution, a departure from more established views. While a role for mitochondria in the speciation process appears promising, we also highlight critical gaps of knowledge: (1) many systems with a potential for mitochondrially-mediated reproductive isolation lack crucial evidence directly linking reproductive isolation and mitochondrial function; (2) it often remains to be seen if mitochondrial barriers are a driver or a consequence of reproductive isolation; (3) the presence of substantial gene flow in the presence of mito-nuclear incompatibilities raises questions whether such incompatibilities are strong enough to drive speciation to completion; and (4) it remains to be tested how mitochondrial effects on reproductive isolation compare when multiple mechanisms of reproductive isolation coincide. We hope this perspective and the proposed research plans help to inform future studies of mitochondrial adaptation in a manner that links genotypic changes to phenotypic adaptations, fitness, and reproductive isolation in natural systems, helping to clarify the importance of mitochondria in the formation and maintenance of biological diversity.
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Affiliation(s)
- M Tobler
- Division of Biology, Kansas State University, Manhattan, KS 66506, USA
| | - N Barts
- Division of Biology, Kansas State University, Manhattan, KS 66506, USA
| | - R Greenway
- Division of Biology, Kansas State University, Manhattan, KS 66506, USA
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20
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Johannesson K, Zagrodzka Z, Faria R, Marie Westram A, Butlin RK. Is embryo abortion a post-zygotic barrier to gene flow between Littorina ecotypes? J Evol Biol 2019; 33:342-351. [PMID: 31724256 PMCID: PMC7079066 DOI: 10.1111/jeb.13570] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Revised: 11/07/2019] [Accepted: 11/12/2019] [Indexed: 11/25/2022]
Abstract
Genetic incompatibilities contribute to reproductive isolation between many diverging populations, but it is still unclear to what extent they play a role if divergence happens with gene flow. In contact zones between the "Crab" and "Wave" ecotypes of the snail Littorina saxatilis, divergent selection forms strong barriers to gene flow, while the role of post‐zygotic barriers due to selection against hybrids remains unclear. High embryo abortion rates in this species could indicate the presence of such barriers. Post‐zygotic barriers might include genetic incompatibilities (e.g. Dobzhansky–Muller incompatibilities) but also maladaptation, both expected to be most pronounced in contact zones. In addition, embryo abortion might reflect physiological stress on females and embryos independent of any genetic stress. We examined all embryos of >500 females sampled outside and inside contact zones of three populations in Sweden. Females' clutch size ranged from 0 to 1,011 embryos (mean 130 ± 123), and abortion rates varied between 0% and 100% (mean 12%). We described female genotypes by using a hybrid index based on hundreds of SNPs differentiated between ecotypes with which we characterized female genotypes. We also calculated female SNP heterozygosity and inversion karyotype. Clutch size did not vary with female hybrid index, and abortion rates were only weakly related to hybrid index in two sites but not at all in a third site. No additional variation in abortion rate was explained by female SNP heterozygosity, but increased female inversion heterozygosity added slightly to increased abortion. Our results show only weak and probably biologically insignificant post‐zygotic barriers contributing to ecotype divergence, and the high and variable abortion rates were marginally, if at all, explained by hybrid index of females.
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Affiliation(s)
- Kerstin Johannesson
- Department of Marine Sciences at Tjärnö, University of Gothenburg, Strömstad, Sweden
| | - Zuzanna Zagrodzka
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield, UK
| | - Rui Faria
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield, UK.,CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, InBIO, Laboratório Associado, Universidade do Porto, Vairão, Portugal
| | | | - Roger K Butlin
- Department of Marine Sciences at Tjärnö, University of Gothenburg, Strömstad, Sweden.,Department of Animal and Plant Sciences, University of Sheffield, Sheffield, UK
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21
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Barth JMI, Villegas-Ríos D, Freitas C, Moland E, Star B, André C, Knutsen H, Bradbury I, Dierking J, Petereit C, Righton D, Metcalfe J, Jakobsen KS, Olsen EM, Jentoft S. Disentangling structural genomic and behavioural barriers in a sea of connectivity. Mol Ecol 2019; 28:1394-1411. [PMID: 30633410 PMCID: PMC6518941 DOI: 10.1111/mec.15010] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Revised: 12/21/2018] [Accepted: 12/27/2018] [Indexed: 12/17/2022]
Abstract
Genetic divergence among populations arises through natural selection or drift and is counteracted by connectivity and gene flow. In sympatric populations, isolating mechanisms are thus needed to limit the homogenizing effects of gene flow to allow for adaptation and speciation. Chromosomal inversions act as an important mechanism maintaining isolating barriers, yet their role in sympatric populations and divergence with gene flow is not entirely understood. Here, we revisit the question of whether inversions play a role in the divergence of connected populations of the marine fish Atlantic cod (Gadus morhua), by exploring a unique data set combining whole‐genome sequencing data and behavioural data obtained with acoustic telemetry. Within a confined fjord environment, we find three genetically differentiated Atlantic cod types belonging to the oceanic North Sea population, the western Baltic population and a local fjord‐type cod. Continuous behavioural tracking over 4 year revealed temporally stable sympatry of these types within the fjord. Despite overall weak genetic differentiation consistent with high levels of gene flow, we detected significant frequency shifts of three previously identified inversions, indicating an adaptive barrier to gene flow. In addition, behavioural data indicated that North Sea cod and individuals homozygous for the LG12 inversion had lower fitness in the fjord environment. However, North Sea and fjord‐type cod also occupy different depths, possibly contributing to prezygotic reproductive isolation and representing a behavioural barrier to gene flow. Our results provide the first insights into a complex interplay of genomic and behavioural isolating barriers in Atlantic cod and establish a new model system towards an understanding of the role of genomic structural variants in adaptation and diversification.
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Affiliation(s)
- Julia M I Barth
- Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, Oslo, Norway.,Zoological Institute, University of Basel, Basel, Switzerland
| | - David Villegas-Ríos
- Department of Ecology and Marine Resources, Mediterranean Institute for Advanced Studies, IMEDEA CSIC-UIB, Esporles, Spain.,Department of Ecology and Marine Resources, Institute of Marine Research, (IIM CSIC), Vigo, Spain
| | - Carla Freitas
- Institute for Marine Research, Flødevigen, Norway.,Centre for Coastal Research, University of Agder, Agder, Norway.,Oceanic Observatory of Madeira, Funchal, Portugal
| | - Even Moland
- Institute for Marine Research, Flødevigen, Norway.,Centre for Coastal Research, University of Agder, Agder, Norway
| | - Bastiaan Star
- Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, Oslo, Norway
| | - Carl André
- Department of Marine Sciences - Tjärnö, University of Gothenburg, Gothenburg, Sweden
| | - Halvor Knutsen
- Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, Oslo, Norway.,Institute for Marine Research, Flødevigen, Norway.,Centre for Coastal Research, University of Agder, Agder, Norway
| | - Ian Bradbury
- Science Branch, Fisheries and Oceans Canada, St. John's, Newfoundland and Labrador, Canada
| | - Jan Dierking
- GEOMAR Helmholtz Centre for Ocean Research, Kiel, Germany
| | | | - David Righton
- Centre for Environment, Fisheries and Aquaculture Science (CEFAS), Lowestoft, UK
| | - Julian Metcalfe
- Centre for Environment, Fisheries and Aquaculture Science (CEFAS), Lowestoft, UK
| | - Kjetill S Jakobsen
- Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, Oslo, Norway
| | - Esben M Olsen
- Institute for Marine Research, Flødevigen, Norway.,Centre for Coastal Research, University of Agder, Agder, Norway
| | - Sissel Jentoft
- Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, Oslo, Norway
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22
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Riquet F, Liautard-Haag C, Woodall L, Bouza C, Louisy P, Hamer B, Otero-Ferrer F, Aublanc P, Béduneau V, Briard O, El Ayari T, Hochscheid S, Belkhir K, Arnaud-Haond S, Gagnaire PA, Bierne N. Parallel pattern of differentiation at a genomic island shared between clinal and mosaic hybrid zones in a complex of cryptic seahorse lineages. Evolution 2019; 73:817-835. [PMID: 30854632 DOI: 10.1111/evo.13696] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Revised: 01/19/2019] [Accepted: 01/24/2019] [Indexed: 01/02/2023]
Abstract
Diverging semi-isolated lineages either meet in narrow clinal hybrid zones, or have a mosaic distribution associated with environmental variation. Intrinsic reproductive isolation is often emphasized in the former and local adaptation in the latter, although both reduce gene flow between groups. Rarely are these two patterns of spatial distribution reported in the same study system. Here, we report that the long-snouted seahorse Hippocampus guttulatus is subdivided into discrete panmictic entities by both types of hybrid zones. Along the European Atlantic coasts, a northern and a southern lineage meet in the southwest of France where they coexist in sympatry-i.e., in the same geographical zone-with little hybridization. In the Mediterranean Sea, two lineages have a mosaic distribution, associated with lagoon-like and marine habitats. A fifth lineage was identified in the Black Sea. Genetic homogeneity over large spatial scales contrasts with isolation maintained in sympatry or close parapatry at a fine scale. A high variation in locus-specific introgression rates provides additional evidence that partial reproductive isolation must be maintaining the divergence. We find that fixed differences between lagoon and marine populations in the Mediterranean Sea belong to the most differentiated SNPs between the two Atlantic lineages, against the genome-wide pattern of structure that mostly follow geography. These parallel outlier SNPs cluster on a single chromosome-wide island of differentiation. Since Atlantic lineages do not map to lagoon-sea habitat variation, genetic parallelism at the genomic island suggests a shared genetic barrier contributes to reproductive isolation in contrasting contexts-i.e., spatial versus ecological. We discuss how a genomic hotspot of parallel differentiation could have evolved and become associated both with space and with a patchy environment in a single study system.
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Affiliation(s)
- Florentine Riquet
- Institut des Sciences de l'Evolution de Montpellier, Université Montpellier, Montpellier, France.,CNRS Institut des Sciences de l'Evolution, UMR5554 UM-CNRS-IRD-EPHE, Sète, France
| | - Cathy Liautard-Haag
- Institut des Sciences de l'Evolution de Montpellier, Université Montpellier, Montpellier, France.,CNRS Institut des Sciences de l'Evolution, UMR5554 UM-CNRS-IRD-EPHE, Sète, France
| | - Lucy Woodall
- Department of Zoology, University of Oxford, Wytham, OX2 8QJ, United Kingdom.,Natural History Museum, London, SW7 5BD, United Kingdom
| | - Carmen Bouza
- Department of Genetics, Faculty of Veterinary Science, Universidade de Santiago de Compostela, Lugo, Spain
| | - Patrick Louisy
- ECOMERS Laboratory, University of Nice Sophia Antipolis, Faculty of Sciences, Parc Valrose, Nice, France.,Association Peau-Bleue, 46 rue des Escais, Agde, France
| | - Bojan Hamer
- Center for Marine Research, Ruder Boskovic Institute, Giordano Paliaga 5, 52210, Rovinj, Croatia
| | - Francisco Otero-Ferrer
- Grupo en Biodiversidad y Conservación, IU-ECOAQUA, Universidad de Las Palmas de Gran Canaria, Crta. Taliarte s/n, 35214, Telde, Spain
| | - Philippe Aublanc
- Institut océanographique Paul Ricard, Ile des Embiez, Six-Fours-les-Plages, France
| | - Vickie Béduneau
- Océarium du Croisic, Avenue de Saint Goustan, Le Croisic, France
| | - Olivier Briard
- Aquarium de Biarritz, Biarritz Océan, Plateau de l'Atalaye, Biarritz, France
| | - Tahani El Ayari
- Institut des Sciences de l'Evolution de Montpellier, Université Montpellier, Montpellier, France.,CNRS Institut des Sciences de l'Evolution, UMR5554 UM-CNRS-IRD-EPHE, Sète, France
| | - Sandra Hochscheid
- Stazione Zoologica Anton Dohrn, Department Research Infrastructures for Marine Biological Resources, Aquarium Unit, Napoli, Italy
| | - Khalid Belkhir
- Institut des Sciences de l'Evolution de Montpellier, Université Montpellier, Montpellier, France.,CNRS Institut des Sciences de l'Evolution, UMR5554 UM-CNRS-IRD-EPHE, Sète, France
| | - Sophie Arnaud-Haond
- Institut des Sciences de l'Evolution de Montpellier, Université Montpellier, Montpellier, France.,Ifremer-MARine Biodiversity, Exploitation and Conservation, UMR 9190 IRD-IFREMER-UM-CNRS, Sète, France
| | - Pierre-Alexandre Gagnaire
- Institut des Sciences de l'Evolution de Montpellier, Université Montpellier, Montpellier, France.,CNRS Institut des Sciences de l'Evolution, UMR5554 UM-CNRS-IRD-EPHE, Sète, France
| | - Nicolas Bierne
- Institut des Sciences de l'Evolution de Montpellier, Université Montpellier, Montpellier, France.,CNRS Institut des Sciences de l'Evolution, UMR5554 UM-CNRS-IRD-EPHE, Sète, France
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23
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Underwood JN, Travers MJ, Snow M, Puotinen M, Gouws G. Cryptic lineages in the Wolf Cardinalfish living in sympatry on remote coral atolls. Mol Phylogenet Evol 2018; 132:183-193. [PMID: 30528081 DOI: 10.1016/j.ympev.2018.12.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Revised: 10/11/2018] [Accepted: 12/04/2018] [Indexed: 10/27/2022]
Abstract
Coral reef health and biodiversity is under threat worldwide due to rapid climate change. However, much of the inter- and intra-specific diversity of coral reefs are undescribed even in well studied taxa such as fish. Delimiting previously unrecognised diversity is important for understanding the processes that generate and sustain biodiversity in coral reef ecosystems and informing strategies for their conservation and management. Many taxa that inhabit geographically isolated coral reefs rely on self-recruitment for population persistence, providing the opportunity for the evolution of unique genetic lineages through divergent selection and reproductive isolation. Many such lineages in corals and fish are morphologically similar or indistinguishable. Here, we report the discovery and characterisation of cryptic lineages of the Wolf Cardinalfish, Cheilodipterus artus, from the coral atolls of northwest Australia using multiple molecular markers from mitochondrial (CO1 and D-loop) and nuclear (microsatellites) DNA. Concordant results from all markers identified two highly divergent lineages that are morphologically cryptic and reproductively isolated. These lineages co-occurred at daytime resting sites, but the relative abundance of each lineage was strongly correlated with wave exposure. It appears, therefore, that fish from each lineage are better adapted to different microhabitats. Such cryptic and ecologically based diversity appears to be common in these atolls and may well aid resilience of these systems. Our results also highlight that underwater surveys based on visual identification clearly underestimate biodiversity, and that a taxonomic revision of the Cheilodipterus genus is necessary.
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Affiliation(s)
- Jim N Underwood
- Australian Institute of Marine Science, Indian Oceans Marine Research Centre, Crawley, WA 6009, Australia.
| | - Michael J Travers
- Australian Institute of Marine Science, Indian Oceans Marine Research Centre, Crawley, WA 6009, Australia; Western Australian Fisheries and Marine Research Laboratories, Department of Primary Industries and Regional Development, Government of Western Australia, PO Box 20, North Beach, Western Australia 6920, Australia
| | - Michael Snow
- Western Australian Fisheries and Marine Research Laboratories, Department of Primary Industries and Regional Development, Government of Western Australia, PO Box 20, North Beach, Western Australia 6920, Australia
| | - Marji Puotinen
- Australian Institute of Marine Science, Indian Oceans Marine Research Centre, Crawley, WA 6009, Australia
| | - Gavin Gouws
- National Research Foundation - South African Institute for Aquatic Biodiversity, Private Bag 1015, Grahamstown 6140, South Africa
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24
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Underwood JN, Richards ZT, Miller KJ, Puotinen ML, Gilmour JP. Genetic signatures through space, time and multiple disturbances in a ubiquitous brooding coral. Mol Ecol 2018; 27:1586-1602. [DOI: 10.1111/mec.14559] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Revised: 02/22/2018] [Accepted: 02/24/2018] [Indexed: 12/17/2022]
Affiliation(s)
- Jim N. Underwood
- Indian Oceans Marine Research Centre Australian Institute of Marine Science Crawley WA Australia
| | - Zoe T. Richards
- Trace and Environmental DNA Laboratory School of Molecular and Life Sciences Curtin University Bentley WA Australia
- Department of Aquatic Zoology Western Australian Museum Perth WA Australia
| | - Karen J. Miller
- Indian Oceans Marine Research Centre Australian Institute of Marine Science Crawley WA Australia
| | - Marji L. Puotinen
- Indian Oceans Marine Research Centre Australian Institute of Marine Science Crawley WA Australia
| | - James P. Gilmour
- Indian Oceans Marine Research Centre Australian Institute of Marine Science Crawley WA Australia
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25
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Evolutionary Mechanisms of Varying Chromosome Numbers in the Radiation of Erebia Butterflies. Genes (Basel) 2018; 9:genes9030166. [PMID: 29547586 PMCID: PMC5867887 DOI: 10.3390/genes9030166] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2017] [Revised: 03/14/2018] [Accepted: 03/14/2018] [Indexed: 02/03/2023] Open
Abstract
The evolution of intrinsic barriers to gene flow is a crucial step in the process of speciation. Chromosomal changes caused by fusion and fission events are one such barrier and are common in several groups of Lepidoptera. However, it remains unclear if and how chromosomal changes have contributed to speciation in this group. I tested for a phylogenetic signal of varying chromosome numbers in Erebia butterflies by combining existing sequence data with karyological information. I also compared different models of trait evolution in order to infer the underlying evolutionary mechanisms. Overall, I found significant phylogenetic signals that are consistent with non-neutral trait evolution only when parts of the mitochondrial genome were included, suggesting cytonuclear discordances. The adaptive evolutionary model tested in this study consistently outperformed the neutral model of trait evolution. Taken together, these results suggest that, unlike other Lepidoptera groups, changes in chromosome numbers may have played a role in the diversification of Erebia butterflies.
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Menon M, Bagley JC, Friedline CJ, Whipple AV, Schoettle AW, Leal‐Sàenz A, Wehenkel C, Molina‐Freaner F, Flores‐Rentería L, Gonzalez‐Elizondo MS, Sniezko RA, Cushman SA, Waring KM, Eckert AJ. The role of hybridization during ecological divergence of southwestern white pine (
Pinus strobiformis
) and limber pine (
P. flexilis
). Mol Ecol 2018; 27:1245-1260. [DOI: 10.1111/mec.14505] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Revised: 12/19/2017] [Accepted: 12/21/2017] [Indexed: 12/11/2022]
Affiliation(s)
- Mitra Menon
- Integrative Life Sciences Virginia Commonwealth University Richmond VA USA
- Department of Biology Virginia Commonwealth University Richmond VA USA
| | - Justin C. Bagley
- Department of Biology Virginia Commonwealth University Richmond VA USA
- Departamento de Zoologia Universidade de Brasília Brasília DF Brazil
| | | | - Amy V. Whipple
- Department of Biological Sciences and Merriam Powel Center for Environmental Research Northern Arizona University Flagstaff AZ USA
| | - Anna W. Schoettle
- Rocky Mountain Research Station USDA Forest Service Ft. Collins CO USA
| | - Alejandro Leal‐Sàenz
- Programa Institucional de Doctorado en Ciencias Agropecuarias y Forestales Universidad Juárez del Estado de Durango Durango Mexico
| | - Christian Wehenkel
- Instituto de Silvicultura e Industria de la Madera Universidad Juarez del Estado de Durango Durango Mexico
| | - Francisco Molina‐Freaner
- Institutos de Geologia y Ecologia Universidad Nacional Autónoma de Mexico, Estación Regional del Noroeste Hermosillo Sonora Mexico
| | | | | | | | - Samuel A. Cushman
- Rocky Mountain Research Station USDA Forest Service Flagstaff AZ USA
| | | | - Andrew J. Eckert
- Department of Biology Virginia Commonwealth University Richmond VA USA
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27
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The Limits to Parapatric Speciation II: Strengthening a Preexisting Genetic Barrier to Gene Flow in Parapatry. Genetics 2018; 209:241-254. [PMID: 29496748 PMCID: PMC5937195 DOI: 10.1534/genetics.117.300652] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Accepted: 02/27/2018] [Indexed: 11/25/2022] Open
Abstract
By encompassing the whole continuum between allopatric and sympatric scenarios, parapatric speciation includes many potential scenarios for the evolution of new species. Here, we investigate how a genetic barrier to gene flow, that relies on a single postzygotic genetic incompatibility, may further evolve under ongoing migration. We consider a continent island model with three loci involved in pairwise Dobzhansky–Muller incompatibilities (DMIs). Using an analytic approach, we derive the conditions for invasion of a new mutation and its consequences for the strength and stability of the initial genetic barrier. Our results show that the accumulation of genetic incompatibilities in the presence of gene flow is under strong selective constraints. In particular, preexisting incompatibilities do not always facilitate the invasion of further barrier genes. If new mutations do invade, they will often weaken or destroy the barrier rather than strengthening it. We conclude that migration is highly effective at disrupting the so-called “snowball effect”, the accelerated accumulation of DMIs that has been described for allopatric populations en route to reproductive isolation.
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28
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Ghenu AH, Blanckaert A, Butlin RK, Kulmuni J, Bank C. Conflict between heterozygote advantage and hybrid incompatibility in haplodiploids (and sex chromosomes). Mol Ecol 2018; 27:3935-3949. [PMID: 29328538 DOI: 10.1111/mec.14482] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2017] [Revised: 12/19/2017] [Accepted: 12/22/2017] [Indexed: 01/08/2023]
Abstract
In many diploid species, the sex chromosomes play a special role in mediating reproductive isolation. In haplodiploids, where females are diploid and males haploid, the whole genome behaves similarly to the X/Z chromosomes of diploids. Therefore, haplodiploid systems can serve as a model for the role of sex chromosomes in speciation and hybridization. A previously described population of Finnish Formica wood ants displays genome-wide signs of ploidally and sexually antagonistic selection resulting from hybridization. Here, hybrid females have increased survivorship but hybrid males are inviable. To understand how the unusual hybrid population may be maintained, we developed a mathematical model with hybrid incompatibility, female heterozygote advantage, recombination and assortative mating. The rugged fitness landscape resulting from the co-occurrence of heterozygote advantage and hybrid incompatibility results in a sexual conflict in haplodiploids, which is caused by the ploidy difference. Thus, whereas heterozygote advantage always promotes long-term polymorphism in diploids, we find various outcomes in haplodiploids in which the population stabilizes either in favour of males, females or via maximizing the number of introgressed individuals. We discuss these outcomes with respect to the potential long-term fate of the Finnish wood ant population and provide approximations for the extension of the model to multiple incompatibilities. Moreover, we highlight the general implications of our results for speciation and hybridization in haplodiploids versus diploids and how the described fitness relationships could contribute to the outstanding role of sex chromosomes as hotspots of sexual antagonism and genes involved in speciation.
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Affiliation(s)
| | | | - Roger K Butlin
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield, UK.,Department of Marine Sciences, University of Gothenburg, Gothenburg, Sweden
| | - Jonna Kulmuni
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield, UK.,Centre of Excellence in Biological Interactions, Department of Biosciences, University of Helsinki, Helsinki, Finland
| | - Claudia Bank
- Instituto Gulbenkian de Ciência, Oeiras, Portugal.,Kavli Institute for Theoretical Physics, University of California at Santa Barbara, Santa Barbara, CA, USA
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29
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Gélin P, Fauvelot C, Bigot L, Baly J, Magalon H. From population connectivity to the art of striping Russian dolls: the lessons from Pocillopora corals. Ecol Evol 2018; 8:1411-1426. [PMID: 29375807 PMCID: PMC5773318 DOI: 10.1002/ece3.3747] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Revised: 10/25/2017] [Accepted: 10/27/2017] [Indexed: 01/01/2023] Open
Abstract
Here, we examined the genetic variability in the coral genus Pocillopora, in particular within the Primary Species Hypothesis PSH09, identified by Gélin, Postaire, Fauvelot and Magalon (2017) using species delimitation methods [also named Pocillopora eydouxi/meandrina complex sensu, Schmidt-Roach, Miller, Lundgren, & Andreakis (2014)] and which was found to split into three secondary species hypotheses (SSH09a, SSH09b, and SSH09c) according to assignment tests using multi-locus genotypes (13 microsatellites). From a large sampling (2,507 colonies) achieved in three marine provinces [Western Indian Ocean (WIO), Tropical Southwestern Pacific (TSP), and Southeast Polynesia (SEP)], genetic structuring analysis conducted with two clustering analyses (structure and DAPC) using 13 microsatellites revealed that SSH09a was restricted to the WIO while SSH09b and SSH09c were almost exclusively in the TSP and SEP. More surprisingly, each SSH split into two to three genetically differentiated clusters, found in sympatry at the reef scale, leading to a pattern of nested hierarchical levels (PSH > SSH > cluster), each level hiding highly differentiated genetic groups. Thus, rather than structured populations within a single species, these three SSHs, and even the eight clusters, likely represent distinct genetic lineages engaged in a speciation process or real species. The issue is now to understand which hierarchical level (SSH, cluster, or even below) corresponds to the species one. Several hypotheses are discussed on the processes leading to this pattern of mixed clusters in sympatry, evoking formation of reproductive barriers, either by allopatric speciation or habitat selection.
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Affiliation(s)
- Pauline Gélin
- UMR ENTROPIE (Université de La Réunion, IRD, CNRS)Université de La RéunionSt DenisLa Réunion
- Laboratoire d'excellence‐CORAILPerpignanFrance
| | - Cécile Fauvelot
- Laboratoire d'excellence‐CORAILPerpignanFrance
- UMR ENTROPIE (IRD, Université de La Réunion, CNRS)Centre IRD de NouméaNoumeaNew Caledonia
- Present address:
Université Côte d'AzurCNRSNiceFrance
| | - Lionel Bigot
- UMR ENTROPIE (Université de La Réunion, IRD, CNRS)Université de La RéunionSt DenisLa Réunion
- Laboratoire d'excellence‐CORAILPerpignanFrance
| | - Joseph Baly
- Laboratoire d'excellence‐CORAILPerpignanFrance
- UMR ENTROPIE (IRD, Université de La Réunion, CNRS)Centre IRD de NouméaNoumeaNew Caledonia
| | - Hélène Magalon
- UMR ENTROPIE (Université de La Réunion, IRD, CNRS)Université de La RéunionSt DenisLa Réunion
- Laboratoire d'excellence‐CORAILPerpignanFrance
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31
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Johannesson K. A life-cycle approach to species barriers. Mol Ecol 2017; 26:3321-3323. [PMID: 28632344 DOI: 10.1111/mec.14168] [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: 03/27/2017] [Revised: 04/12/2017] [Accepted: 05/01/2017] [Indexed: 11/27/2022]
Abstract
What maintains reproductive barriers between closely related species is, of course, of fundamental interest to a closer understanding of the mechanisms that generate new biodiversity. One important dichotomy is to separate barriers evolved from divergent selection over environmental gradients (extrinsic barriers) from barriers caused by incompatibilities between different genetic arrangements that may have evolved in isolation (intrinsic barriers). This dichotomy also reflects an important applied consequence. As the extrinsic barriers are associated with specific environmental contexts, they may be partly or completely erased if the environment changes. In contrast, intrinsic barriers are inert to the environmental context and resistant to environmental changes. From a conservation biology perspective, it may thus be important to be able to separate extrinsic and intrinsic species barriers, but this may in many organisms be a complex matter. In this issue of Molecular Ecology, Montecinos et al. () found a tractable approach that works for species with life cycles that include two reproductive but ecologically similar generations, one haploid and the other diploid. What they demonstrate is that using a life-cycle approach offers a unique possibility to separate between prezygotic and postzygotic barriers. Indeed, in the case of an isomorphic life cycle, there is even a possibility to suggest whether postzygotic barriers are more likely to be intrinsic or extrinsic. In this way, their approach may be useful both to increase our understanding of the basic mechanisms of speciation and to single out when species barriers will better resist environmental changes.
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Affiliation(s)
- Kerstin Johannesson
- Department of Marine Sciences, University of Gothenburg, Tjärnö, Strömstad, Sweden
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Johannesson K, Butlin RK, Panova M, Westram AM. Mechanisms of Adaptive Divergence and Speciation in Littorina saxatilis: Integrating Knowledge from Ecology and Genetics with New Data Emerging from Genomic Studies. POPULATION GENOMICS 2017. [DOI: 10.1007/13836_2017_6] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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