1
|
Souza FHS, Perez MF, Ferreira PHN, Bertollo LAC, Ezaz T, Charlesworth D, Cioffi MB. Multiple karyotype differences between populations of the Hoplias malabaricus (Teleostei; Characiformes), a species complex in the gray area of the speciation process. Heredity (Edinb) 2024:10.1038/s41437-024-00707-z. [PMID: 39039117 DOI: 10.1038/s41437-024-00707-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Revised: 07/15/2024] [Accepted: 07/16/2024] [Indexed: 07/24/2024] Open
Abstract
Neotropical fishes exhibit remarkable karyotype diversity, whose evolution is poorly understood. Here, we studied genetic differences in 60 individuals, from 11 localities of one species, the wolf fish Hoplias malabaricus, from populations that include six different "karyomorphs". These differ in Y-X chromosome differentiation, and, in several cases, by fusions with autosomes that have resulted in multiple sex chromosomes. Other differences are also observed in diploid chromosome numbers and morphologies. In an attempt to start understanding how this diversity was generated, we analyzed within- and between-population differences in a genome-wide sequence data set. We detect clear genotype differences between karyomorphs. Even in sympatry, samples with different karyomorphs differ more in sequence than samples from allopatric populations of the same karyomorph, suggesting that they represent populations that are to some degree reproductively isolated. However, sequence divergence between populations with different karyomorphs is remarkably low, suggesting that chromosome rearrangements may have evolved during a brief evolutionary time. We suggest that the karyotypic differences probably evolved in allopatry, in small populations that would have allowed rapid fixation of rearrangements, and that they became sympatric after their differentiation. Further studies are needed to test whether the karyotype differences contribute to reproductive isolation detected between some H. malabaricus karyomorphs.
Collapse
Affiliation(s)
- Fernando H S Souza
- Laboratory of Evolutionary Cytogenetics, Department of Genetics and Evolution, Federal University of São Carlos, São Carlos, SP, Brazil
| | - Manolo F Perez
- Laboratory of Evolutionary Cytogenetics, Department of Genetics and Evolution, Federal University of São Carlos, São Carlos, SP, Brazil
| | - Pedro H N Ferreira
- Laboratory of Evolutionary Cytogenetics, Department of Genetics and Evolution, Federal University of São Carlos, São Carlos, SP, Brazil
| | - Luiz A C Bertollo
- Laboratory of Evolutionary Cytogenetics, Department of Genetics and Evolution, Federal University of São Carlos, São Carlos, SP, Brazil
| | - Tariq Ezaz
- Institute for Applied Ecology, University of Canberra, Canberra, NSW, Australia
| | - Deborah Charlesworth
- Institute for Evolutionary Biology, Ashworth Laboratories, King's Buildings, University of Edinburgh, Edinburgh, UK
| | - Marcelo B Cioffi
- Laboratory of Evolutionary Cytogenetics, Department of Genetics and Evolution, Federal University of São Carlos, São Carlos, SP, Brazil.
| |
Collapse
|
2
|
Innes PA, Goebl AM, Smith CCR, Rosenberger K, Kane NC. Gene expression and alternative splicing contribute to adaptive divergence of ecotypes. Heredity (Edinb) 2024; 132:120-132. [PMID: 38071268 PMCID: PMC10924094 DOI: 10.1038/s41437-023-00665-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 11/23/2023] [Accepted: 11/24/2023] [Indexed: 03/10/2024] Open
Abstract
Regulation of gene expression is a critical link between genotype and phenotype explaining substantial heritable variation within species. However, we are only beginning to understand the ways that specific gene regulatory mechanisms contribute to adaptive divergence of populations. In plants, the post-transcriptional regulatory mechanism of alternative splicing (AS) plays an important role in both development and abiotic stress response, making it a compelling potential target of natural selection. AS allows organisms to generate multiple different transcripts/proteins from a single gene and thus may provide a source of evolutionary novelty. Here, we examine whether variation in alternative splicing and gene expression levels might contribute to adaptation and incipient speciation of dune-adapted prairie sunflowers in Great Sand Dunes National Park, Colorado, USA. We conducted a common garden experiment to assess transcriptomic variation among ecotypes and analyzed differential expression, differential splicing, and gene coexpression. We show that individual genes are strongly differentiated for both transcript level and alternative isoform proportions, even when grown in a common environment, and that gene coexpression networks are disrupted between ecotypes. Furthermore, we examined how genome-wide patterns of sequence divergence correspond to divergence in transcript levels and isoform proportions and find evidence for both cis and trans-regulation. Together, our results emphasize that alternative splicing has been an underappreciated mechanism providing source material for natural selection at short evolutionary time scales.
Collapse
Affiliation(s)
- Peter A Innes
- Ecology and Evolutionary Biology Department, University of Colorado, Boulder, CO, USA.
| | - April M Goebl
- Ecology and Evolutionary Biology Department, University of Colorado, Boulder, CO, USA
- Research and Conservation Department, Denver Botanic Gardens, Denver, CO, USA
| | - Chris C R Smith
- Ecology and Evolutionary Biology Department, University of Colorado, Boulder, CO, USA
- Institute of Ecology and Evolution, University of Oregon, Eugene, OR, USA
| | - Kaylee Rosenberger
- Ecology and Evolutionary Biology Department, University of Colorado, Boulder, CO, USA
| | - Nolan C Kane
- Ecology and Evolutionary Biology Department, University of Colorado, Boulder, CO, USA
| |
Collapse
|
3
|
Goebl AM, Kane NC, Doak DF, Rieseberg LH, Ostevik KL. Adaptation to distinct habitats is maintained by contrasting selection at different life stages in sunflower ecotypes. Mol Ecol 2024; 33:e16785. [PMID: 36374153 DOI: 10.1111/mec.16785] [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: 07/12/2022] [Revised: 10/20/2022] [Accepted: 11/02/2022] [Indexed: 11/16/2022]
Abstract
Conspecific populations living in adjacent but contrasting microenvironments represent excellent systems for studying natural selection. These systems are valuable because gene flow is expected to force genetic homogeneity except at loci experiencing divergent selection. A history of reciprocal transplant and common garden studies in such systems, and a growing number of genomic studies, have contributed to understanding how selection operates in natural populations. While selection can vary across different fitness components and life stages, few studies have investigated how this ultimately affects allele frequencies and the maintenance of divergence between populations. Here, we study two sunflower ecotypes in distinct, adjacent habitats by combining demographic models with genome-wide sequence data to estimate fitness and allele frequency change at multiple life stages. This framework allows us to estimate that only local ecotypes are likely to experience positive population growth (λ > 1) and that the maintenance of divergent adaptation appears to be mediated via habitat- and life stage-specific selection. We identify genetic variation, significantly driven by loci in chromosomal inversions, associated with different life history strategies in neighbouring ecotypes that optimize different fitness components and may contribute to the maintenance of distinct ecotypes.
Collapse
Affiliation(s)
- April M Goebl
- Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, Colorado, USA
| | - Nolan C Kane
- Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, Colorado, USA
| | - Daniel F Doak
- Environmental Studies Programme, University of Colorado, Boulder, Colorado, USA
| | - Loren H Rieseberg
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
| | - Kate L Ostevik
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Evolution, Ecology and Organismal Biology, University of California Riverside, Riverside, California, USA
| |
Collapse
|
4
|
James ME, Ortiz-Barrientos D. The genomic consequences of selection across development. Mol Ecol 2024; 33:e17280. [PMID: 38247305 DOI: 10.1111/mec.17280] [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: 09/25/2023] [Revised: 01/01/2024] [Accepted: 01/12/2024] [Indexed: 01/23/2024]
Abstract
Understanding how natural selection drives diversification in nature has been at the forefront of biological research for over a century. The main idea is simple: natural selection favours individuals best suited to pass on their genes. However, the journey from birth to reproduction is complex as organisms experience multiple developmental stages, each influenced by genetic and environmental factors (Orr, 2009). These complexities compound even further as each stage of development might be governed by a unique underlying set of alleles and genes. In this issue of Molecular Ecology, Goebl et al. (2022) examine the role of natural selection in driving ecotypic divergence across different life history stages of the prairie sunflower Helianthus petiolaris. The authors used reciprocal transplant experiments, demographic models, and genomic sequencing to explore fitness variation across developmental stages. They show how natural selection impacts population divergence across multiple life history stages and evaluate the resulting allele frequency changes. Goebl et al. link these results to the role of chromosomal inversions, thus furthering our understanding of how ecological divergence proceeds in the face of gene flow. Below, we explore these results in detail and complement their interpretation by considering the evolution of genetic correlations amongst traits governing fitness.
Collapse
Affiliation(s)
- Maddie E James
- School of the Environment, The University of Queensland, St Lucia, QLD, Australia
- Australian Research Council Centre of Excellence for Plant Success in Nature and Agriculture, St Lucia, QLD, Australia
| | - Daniel Ortiz-Barrientos
- School of the Environment, The University of Queensland, St Lucia, QLD, Australia
- Australian Research Council Centre of Excellence for Plant Success in Nature and Agriculture, St Lucia, QLD, Australia
| |
Collapse
|
5
|
Soudi S, Jahani M, Todesco M, Owens GL, Bercovich N, Rieseberg LH, Yeaman S. Repeatability of adaptation in sunflowers reveals that genomic regions harbouring inversions also drive adaptation in species lacking an inversion. eLife 2023; 12:RP88604. [PMID: 38095362 PMCID: PMC10721221 DOI: 10.7554/elife.88604] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2023] Open
Abstract
Local adaptation commonly involves alleles of large effect, which experience fitness advantages when in positive linkage disequilibrium (LD). Because segregating inversions suppress recombination and facilitate the maintenance of LD between locally adapted loci, they are also commonly found to be associated with adaptive divergence. However, it is unclear what fraction of an adaptive response can be attributed to inversions and alleles of large effect, and whether the loci within an inversion could still drive adaptation in the absence of its recombination-suppressing effect. Here, we use genome-wide association studies to explore patterns of local adaptation in three species of sunflower: Helianthus annuus, Helianthus argophyllus, and Helianthus petiolaris, which each harbour a large number of species-specific inversions. We find evidence of significant genome-wide repeatability in signatures of association to phenotypes and environments, which are particularly enriched within regions of the genome harbouring an inversion in one species. This shows that while inversions may facilitate local adaptation, at least some of the loci can still harbour mutations that make substantial contributions without the benefit of recombination suppression in species lacking a segregating inversion. While a large number of genomic regions show evidence of repeated adaptation, most of the strongest signatures of association still tend to be species-specific, indicating substantial genotypic redundancy for local adaptation in these species.
Collapse
Affiliation(s)
- Shaghayegh Soudi
- Department of Biological Sciences, University of CalgaryCalgaryCanada
| | - Mojtaba Jahani
- Department of Biological Sciences, University of CalgaryCalgaryCanada
- Department of Botany, University of British ColumbiaVancouverCanada
| | - Marco Todesco
- Department of Botany, University of British ColumbiaVancouverCanada
- Michael Smith Laboratories, University of British ColumbiaVancouverCanada
- Irving K. Barber Faculty of Science, University of British Columbia OkanaganKelownaCanada
| | | | | | | | - Sam Yeaman
- Department of Biological Sciences, University of CalgaryCalgaryCanada
| |
Collapse
|
6
|
Bock DG, Cai Z, Elphinstone C, González-Segovia E, Hirabayashi K, Huang K, Keais GL, Kim A, Owens GL, Rieseberg LH. Genomics of plant speciation. PLANT COMMUNICATIONS 2023; 4:100599. [PMID: 37050879 PMCID: PMC10504567 DOI: 10.1016/j.xplc.2023.100599] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 03/21/2023] [Accepted: 04/06/2023] [Indexed: 06/19/2023]
Abstract
Studies of plants have been instrumental for revealing how new species originate. For several decades, botanical research has complemented and, in some cases, challenged concepts on speciation developed via the study of other organisms while also revealing additional ways in which species can form. Now, the ability to sequence genomes at an unprecedented pace and scale has allowed biologists to settle decades-long debates and tackle other emerging challenges in speciation research. Here, we review these recent genome-enabled developments in plant speciation. We discuss complications related to identification of reproductive isolation (RI) loci using analyses of the landscape of genomic divergence and highlight the important role that structural variants have in speciation, as increasingly revealed by new sequencing technologies. Further, we review how genomics has advanced what we know of some routes to new species formation, like hybridization or whole-genome duplication, while casting doubt on others, like population bottlenecks and genetic drift. While genomics can fast-track identification of genes and mutations that confer RI, we emphasize that follow-up molecular and field experiments remain critical. Nonetheless, genomics has clarified the outsized role of ancient variants rather than new mutations, particularly early during speciation. We conclude by highlighting promising avenues of future study. These include expanding what we know so far about the role of epigenetic and structural changes during speciation, broadening the scope and taxonomic breadth of plant speciation genomics studies, and synthesizing information from extensive genomic data that have already been generated by the plant speciation community.
Collapse
Affiliation(s)
- Dan G Bock
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Zhe Cai
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Cassandra Elphinstone
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Eric González-Segovia
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | | | - Kaichi Huang
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Graeme L Keais
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Amy Kim
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Gregory L Owens
- Department of Biology, University of Victoria, Victoria, BC, Canada
| | - Loren H Rieseberg
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada.
| |
Collapse
|
7
|
Gonçalves-Dias J, Singh A, Graf C, Stetter MG. Genetic Incompatibilities and Evolutionary Rescue by Wild Relatives Shaped Grain Amaranth Domestication. Mol Biol Evol 2023; 40:msad177. [PMID: 37552934 PMCID: PMC10439364 DOI: 10.1093/molbev/msad177] [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: 04/25/2023] [Revised: 07/20/2023] [Accepted: 08/02/2023] [Indexed: 08/10/2023] Open
Abstract
Crop domestication and the subsequent expansion of crops have long been thought of as a linear process from a wild ancestor to a domesticate. However, evidence of gene flow from locally adapted wild relatives that provided adaptive alleles into crops has been identified in multiple species. Yet, little is known about the evolutionary consequences of gene flow during domestication and the interaction of gene flow and genetic load in crop populations. We study the pseudo-cereal grain amaranth that has been domesticated three times in different geographic regions of the Americas. We quantify the amount and distribution of gene flow and genetic load along the genome of the three grain amaranth species and their two wild relatives. Our results show ample gene flow between crop species and between crops and their wild relatives. Gene flow from wild relatives decreased genetic load in the three crop species. This suggests that wild relatives could provide evolutionary rescue by replacing deleterious alleles in crops. We assess experimental hybrids between the three crop species and found genetic incompatibilities between one Central American grain amaranth and the other two crop species. These incompatibilities might have created recent reproductive barriers and maintained species integrity today. Together, our results show that gene flow played an important role in the domestication and expansion of grain amaranth, despite genetic species barriers. The domestication of plants was likely not linear and created a genomic mosaic by multiple contributors with varying fitness effects for today's crops.
Collapse
Affiliation(s)
| | - Akanksha Singh
- Institute for Plant Sciences, University of Cologne, Cologne, Germany
| | - Corbinian Graf
- Institute for Plant Sciences, University of Cologne, Cologne, Germany
| | - Markus G Stetter
- Institute for Plant Sciences, University of Cologne, Cologne, Germany
- Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, Cologne, Germany
| |
Collapse
|
8
|
Owens GL, Huang K, Todesco M, Rieseberg LH. Re-evaluating Homoploid Reticulate Evolution in Helianthus Sunflowers. Mol Biol Evol 2023; 40:6989481. [PMID: 36648104 PMCID: PMC9907532 DOI: 10.1093/molbev/msad013] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Revised: 01/03/2023] [Accepted: 01/11/2023] [Indexed: 01/18/2023] Open
Abstract
Sunflowers of the genus Helianthus are models for hybridization research and contain three of the best-studied examples of homoploid hybrid speciation. To understand a broader picture of hybridization within the annual sunflowers, we used whole-genome resequencing to conduct a phylogenomic analysis and test for gene flow between lineages. We find that all annual sunflower species tested have evidence of admixture, suggesting hybridization was common during the radiation of the genus. Support for the major species tree decreases with increasing recombination rate, consistent with hybridization and introgression contributing to discordant topologies. Admixture graphs found hybridization to be associated with the origins of the three putative hybrid species (Helianthus anomalus, Helianthus deserticola, and Helianthus paradoxus). However, the hybridization events are more ancient than suggested by previous work. Furthermore, H. anomalus and H. deserticola appear to have arisen from a single hybridization event involving an unexpected donor, rather than through multiple independent events as previously proposed. This means our results are consistent with, but not definitive proof of, two ancient independent homoploid hybrid speciation events in the genus. Using a broader data set that covers the whole Helianthus genus, including perennial species, we find that signals of introgression span the genus and beyond, suggesting highly divergent introgression and/or the sorting of ancient haplotypes. Thus, Helianthus can be viewed as a syngameon in which largely reproductively isolated species are linked together by occasional or frequent gene flow.
Collapse
Affiliation(s)
| | - Kaichi Huang
- Department of Botany and Beaty Biodiversity Center, University of British Columbia, Vancouver, BC, Canada
| | - Marco Todesco
- Department of Botany and Beaty Biodiversity Center, University of British Columbia, Vancouver, BC, Canada
| | - Loren H Rieseberg
- Department of Botany and Beaty Biodiversity Center, University of British Columbia, Vancouver, BC, Canada
| |
Collapse
|
9
|
Kiemel K, Gurke M, Paraskevopoulou S, Havenstein K, Weithoff G, Tiedemann R. Variation in heat shock protein 40 kDa relates to divergence in thermotolerance among cryptic rotifer species. Sci Rep 2022; 12:22626. [PMID: 36587065 PMCID: PMC9805463 DOI: 10.1038/s41598-022-27137-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Accepted: 12/26/2022] [Indexed: 01/01/2023] Open
Abstract
Genetic divergence and the frequency of hybridization are central for defining species delimitations, especially among cryptic species where morphological differences are merely absent. Rotifers are known for their high cryptic diversity and therefore are ideal model organisms to investigate such patterns. Here, we used the recently resolved Brachionus calyciflorus species complex to investigate whether previously observed between species differences in thermotolerance and gene expression are also reflected in their genomic footprint. We identified a Heat Shock Protein gene (HSP 40 kDa) which exhibits cross species pronounced sequence variation. This gene exhibits species-specific fixed sites, alleles, and sites putatively under positive selection. These sites are located in protein binding regions involved in chaperoning and may therefore reflect adaptive diversification. By comparing three genetic markers (ITS, COI, HSP 40 kDa), we revealed hybridization events between the cryptic species. The low frequency of introgressive haplotypes/alleles suggest a tight, but not fully impermeable boundary between the cryptic species.
Collapse
Affiliation(s)
- K. Kiemel
- grid.11348.3f0000 0001 0942 1117Unit of Evolutionary Biology/Systematic Zoology, Institute for Biochemistry and Biology, University of Potsdam, Karl-Liebknecht Straße 24-25, 14476 Potsdam, Germany
| | - M. Gurke
- grid.422371.10000 0001 2293 9957Museum für Naturkunde – Leibniz Institute for Evolution and Biodiversity Science, Invalidenstraße 43, 10115 Berlin, Germany ,grid.7468.d0000 0001 2248 7639Department of Biology, Humboldt-University, Invalidenstraße 42, 10115 Berlin, Germany
| | - S. Paraskevopoulou
- grid.4514.40000 0001 0930 2361Department of Biology, Lund University, Microbiology Group, Sölvegatan 35, 223 62 Lund, Sweden
| | - K. Havenstein
- grid.11348.3f0000 0001 0942 1117Unit of Evolutionary Biology/Systematic Zoology, Institute for Biochemistry and Biology, University of Potsdam, Karl-Liebknecht Straße 24-25, 14476 Potsdam, Germany
| | - G. Weithoff
- grid.11348.3f0000 0001 0942 1117Unit of Ecology and Ecosystem Modelling, Institute for Biochemistry and Biology, University of Potsdam, Am Neuen Palais 10, 14469 Potsdam, Germany
| | - R. Tiedemann
- grid.11348.3f0000 0001 0942 1117Unit of Evolutionary Biology/Systematic Zoology, Institute for Biochemistry and Biology, University of Potsdam, Karl-Liebknecht Straße 24-25, 14476 Potsdam, Germany
| |
Collapse
|
10
|
Osmolovsky I, Shifrin M, Gamliel I, Belmaker J, Sapir Y. Eco-Geography and Phenology Are the Major Drivers of Reproductive Isolation in the Royal Irises, a Species Complex in the Course of Speciation. PLANTS (BASEL, SWITZERLAND) 2022; 11:3306. [PMID: 36501345 PMCID: PMC9739335 DOI: 10.3390/plants11233306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Revised: 10/30/2022] [Accepted: 11/25/2022] [Indexed: 06/17/2023]
Abstract
The continuous nature of speciation implies that different species are found at different stages of divergence, from no- to complete reproductive isolation. This process and its underlying mechanisms are best viewed in incipient species. Moreover, the species complex can offer unique insight into how reproductive isolation (RI) has evolved. The royal irises (Iris section Oncocyclus) are a young group of species in the course of speciation, providing an ideal system for speciation study. We quantified pre- and post-zygotic reproductive barriers between the eight Israeli species of this complex and estimated the total RI among them. We tested for both pre-pollination and post-pollination reproductive barriers. Pre-pollination barriers, i.e., eco-geographic divergence and phenological differentiation were the major contributors to RI among the Iris species. On the other hand, post-pollination barriers, namely pollen-stigma interactions, fruit set, and seed viability had negligible contributions to total RI. The strength of RI was not uniform across the species complex, suggesting that species may have diverged at different rates. Overall, this study in a young, recently diverged group of species provides insight into the first steps of speciation, suggesting a crucial role of the pre-zygotic barriers.
Collapse
Affiliation(s)
- Inna Osmolovsky
- The Botanical Garden, School of Plant Science and Food Security, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Mariana Shifrin
- The Botanical Garden, School of Plant Science and Food Security, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Inbal Gamliel
- School of Zoology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Jonathan Belmaker
- School of Zoology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Yuval Sapir
- The Botanical Garden, School of Plant Science and Food Security, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| |
Collapse
|
11
|
Christie K, Fraser LS, Lowry DB. The strength of reproductive isolating barriers in seed plants: Insights from studies quantifying premating and postmating reproductive barriers over the past 15 years. Evolution 2022; 76:2228-2243. [PMID: 35838076 PMCID: PMC9796645 DOI: 10.1111/evo.14565] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2021] [Revised: 06/23/2022] [Accepted: 06/30/2022] [Indexed: 01/22/2023]
Abstract
Speciation is driven by the evolution of reproductive isolating barriers that reduce, and ultimately prevent, substantial gene flow between lineages. Despite its central role in evolutionary biology, the process can be difficult to study because it proceeds differently among groups and may occur over long timescales. Due to this complexity, we typically rely on generalizations of empirical data to describe and understand the process. Previous reviews of reproductive isolation (RI) in flowering plants have suggested that prezygotic or extrinsic barriers generally have a stronger effect on reducing gene flow compared to postzygotic or intrinsic barriers. Past conclusions have rested on relatively few empirical estimates of RI; however, RI data have become increasingly abundant over the past 15 years. We analyzed data from recent studies quantifying multiple pre- and postmating barriers in plants and compared the strengths of isolating barriers across 89 taxa pairs using standardized RI metrics. Individual prezygotic barriers were on average stronger than individual postzygotic barriers, and the total strength of prezygotic RI was approximately twice that of postzygotic RI. These findings corroborate that ecological divergence and extrinsic factors, as opposed to solely the accumulation of genetic incompatibilities, are important to speciation and the maintenance of species boundaries in plants. Despite an emphasis in the literature on asymmetric postmating and postzygotic RI, we found that prezygotic barriers acted equally asymmetrically. Overall, substantial variability in the strengths of 12 isolating barriers highlights the great diversity of mechanisms that contribute to plant diversification.
Collapse
Affiliation(s)
- Kyle Christie
- Department of Plant BiologyMichigan State UniversityEast LansingMichigan48824,Department of Biological SciencesNorthern Arizona UniversityFlagstaffArizona86011
| | - Linnea S. Fraser
- Department of Plant BiologyMichigan State UniversityEast LansingMichigan48824
| | - David B. Lowry
- Department of Plant BiologyMichigan State UniversityEast LansingMichigan48824
| |
Collapse
|
12
|
Jalali T, Rosinger HS, Hodgins KA, Fournier‐Level AJ. Pollen competition in hybridizing Cakile species: How does a latecomer win the race? AMERICAN JOURNAL OF BOTANY 2022; 109:1290-1304. [PMID: 35844035 PMCID: PMC9544311 DOI: 10.1002/ajb2.16035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 06/10/2022] [Accepted: 06/14/2022] [Indexed: 06/15/2023]
Abstract
PREMISE Hybridization between cross-compatible species depends on the extent of competition between alternative mates. Even if stigmatic compatibility allows for hybridization, hybridization requires the heterospecific pollen to be competitive. Here, we determined whether conspecific pollen has an advantage in the race to fertilize ovules and the potential handicap to be overcome by heterospecific pollen in invasive Cakile species. METHODS We used fluorescence microscopy to measure pollen tube growth after conspecific and heterospecific hand-pollination treatments. We then determined siring success in the progeny relative to the timing of heterospecific pollen arrival on the stigma using CAPS markers. RESULTS In the absence of pollen competition, pollination time and pollen recipient species had a significant effect on the ratio of pollen tube growth. In long-styled C. maritima (outcrosser), pollen tubes grew similarly in both directions. In short-styled C. edentula (selfer), conspecific and heterospecific pollen tubes grew differently. Cakile edentula pollen produced more pollen tubes, revealing the potential for a mating asymmetry whereby C. edentula pollen had an advantage relative to C. maritima. In the presence of pollen competition, siring success was equivalent when pollen deposition was synchronous. However, a moderate 1-h advantage in the timing of conspecific pollination resulted in almost complete assortative mating, while an equivalent delay in conspecific pollination resulted in substantial hybrid formation. CONCLUSIONS Hybridization can aid the establishment of invasive species through the transfer of adaptive alleles from cross-compatible species, but also lead to extinction through demographic or genetic swamping. Time of pollen arrival on the stigma substantially affected hybridization rate, pointing to the importance of pollination timing in driving introgression and genetic swamping.
Collapse
Affiliation(s)
- Tara Jalali
- School of BiosciencesThe University of MelbourneParkvilleVictoria3010Australia
| | - Hanna S. Rosinger
- School of Biological SciencesMonash UniversityClaytonVictoria3800Australia
| | - Kathryn A. Hodgins
- School of Biological SciencesMonash UniversityClaytonVictoria3800Australia
| | | |
Collapse
|
13
|
Abstract
Speciation is the process by which barriers to gene flow evolve between populations. Although we now know that speciation is largely driven by natural selection, knowledge of the agents of selection and the genetic and genomic mechanisms that facilitate divergence is required for a satisfactory theory of speciation. In this essay, we highlight three advances/problems in our understanding of speciation that have arisen from studies of the genes and genomic regions that underlie the evolution of reproductive isolation. First, we describe how the identification of “speciation” genes makes it possible to identify the agents of selection causing the evolution of reproductive isolation, while also noting that the link between the genetics of phenotypic divergence and intrinsic postzygotic reproductive barriers remains tenuous. Second, we discuss the important role of recombination suppressors in facilitating speciation with gene flow, but point out that the means and timing by which reproductive barriers become associated with recombination cold spots remains uncertain. Third, we establish the importance of ancient genetic variation in speciation, although we argue that the focus of speciation studies on evolutionarily young groups may bias conclusions in favor of ancient variation relative to new mutations.
Collapse
|
14
|
Huang K, Ostevik KL, Elphinstone C, Todesco M, Bercovich N, Owens GL, Rieseberg LH. Mutation load in sunflower inversions is negatively correlated with inversion heterozygosity. Mol Biol Evol 2022; 39:6583099. [PMID: 35535689 PMCID: PMC9127631 DOI: 10.1093/molbev/msac101] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Recombination is critical both for accelerating adaptation and purging deleterious mutations. Chromosomal inversions can act as recombination modifiers that suppress local recombination in heterozygotes and thus, under some conditions, are predicted to accumulate such mutations. In this study, we investigated patterns of recombination, transposable element abundance and coding sequence evolution across the genomes of 1,445 individuals from three sunflower species, as well as within nine inversions segregating within species. We also analyzed the effects of inversion genotypes on 87 phenotypic traits to test for overdominance. We found significant negative correlations of long terminal repeat retrotransposon abundance and deleterious mutations with recombination rates across the genome in all three species. However, we failed to detect an increase in these features in the inversions, except for a modest increase in the proportion of stop codon mutations in several very large or rare inversions. Consistent with this finding, there was little evidence of overdominance of inversions in phenotypes that may relate to fitness. On the other hand, significantly greater load was observed for inversions in populations polymorphic for a given inversion compared to populations monomorphic for one of the arrangements, suggesting that the local state of inversion polymorphism affects deleterious load. These seemingly contradictory results can be explained by the low frequency of inversion heterozygotes in wild sunflower populations, apparently due to divergent selection and associated geographic structure. Inversions contributing to local adaptation represent ideal recombination modifiers, acting to facilitate adaptive divergence with gene flow, while largely escaping the accumulation of deleterious mutations.
Collapse
Affiliation(s)
- Kaichi Huang
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Kate L Ostevik
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada.,Department of Evolution, Ecology, and Organismal Biology, University of California, Riverside, CA, USA
| | - Cassandra Elphinstone
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Marco Todesco
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Natalia Bercovich
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Gregory L Owens
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada.,Department of Biology, University of Victoria, Victoria, BC, Canada
| | - Loren H Rieseberg
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| |
Collapse
|
15
|
Innes P, Gossweiler A, Jensen S, Tilley D, St. John L, Jones T, Kitchen S, Hulke BS. Assessment of biogeographic variation in traits of Lewis flax ( Linum lewisii) for use in restoration and agriculture. AOB PLANTS 2022; 14:plac005. [PMID: 35273788 PMCID: PMC8906388 DOI: 10.1093/aobpla/plac005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Accepted: 01/31/2022] [Indexed: 06/14/2023]
Abstract
Lewis flax (Linum lewisii) is widely distributed across western North America and is currently used in native ecosystem restoration. There is also growing interest in de novo domestication of Lewis flax as a perennial oilseed crop. To better understand this species and facilitate both restoration and domestication, we used common gardens to assess biogeographical variation in a variety of seed and growth traits from 37 flax accessions, consisting of 35 wild populations from the Intermountain West region, the pre-variety germplasm Maple Grove (L. lewisii) and the cultivar 'Appar' (L. perenne) and related this variation to collection site geography and climate. Results from linear mixed models suggest there is extensive phenotypic variation among populations of Lewis flax within the Intermountain West. Using a multivariate approach, we identify a key suite of traits that are related to latitude and climate and may facilitate adaptation, including flowering indeterminacy, seed mass and stem number. These traits should be taken into account when considering the release of new germplasm for restoration efforts. We also find that Lewis flax seed contains desirably high amounts of alpha-linolenic acid and is otherwise mostly indistinguishable in fatty acid composition from oil-type varieties of domesticated flax (L. usitatissimum), making it a strong candidate for domestication. This study provides fundamental knowledge for future research into the ecology and evolution of Lewis flax, which will inform its use in both restoration and agriculture.
Collapse
Affiliation(s)
- Peter Innes
- Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309, USA
| | - André Gossweiler
- Department of Plant Sciences, North Dakota State University, Fargo, ND 58108, USA
| | - Scott Jensen
- Rocky Mountain Research Station, United States Department of Agriculture – Forest Service, Provo, UT 84606, USA
| | - Derek Tilley
- Aberdeen Plant Materials Center, United States Department of Agriculture – Natural Resources Conservation Service, Aberdeen, ID 83210, USA
| | - Loren St. John
- Aberdeen Plant Materials Center, United States Department of Agriculture – Natural Resources Conservation Service, Aberdeen, ID 83210, USA
| | - Thomas Jones
- Forage and Range Research Laboratory, United States Department of Agriculture – Agricultural Research Service, Logan, UT 84322, USA
| | - Stanley Kitchen
- Rocky Mountain Research Station, United States Department of Agriculture – Forest Service, Provo, UT 84606, USA
| | - Brent S Hulke
- Edward T. Schafer Agricultural Research Center, United States Department of Agriculture – Agricultural Research Service, Fargo, ND 58102, USA
| |
Collapse
|
16
|
Singhal S, Colli GR, Grundler MR, Costa GC, Prates I, Rabosky DL. No link between population isolation and speciation rate in squamate reptiles. Proc Natl Acad Sci U S A 2022; 119:e2113388119. [PMID: 35058358 PMCID: PMC8795558 DOI: 10.1073/pnas.2113388119] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Accepted: 11/19/2021] [Indexed: 11/26/2022] Open
Abstract
Rates of species formation vary widely across the tree of life and contribute to massive disparities in species richness among clades. This variation can emerge from differences in metapopulation-level processes that affect the rates at which lineages diverge, persist, and evolve reproductive barriers and ecological differentiation. For example, populations that evolve reproductive barriers quickly should form new species at faster rates than populations that acquire reproductive barriers more slowly. This expectation implicitly links microevolutionary processes (the evolution of populations) and macroevolutionary patterns (the profound disparity in speciation rate across taxa). Here, leveraging extensive field sampling from the Neotropical Cerrado biome in a biogeographically controlled natural experiment, we test the role of an important microevolutionary process-the propensity for population isolation-as a control on speciation rate in lizards and snakes. By quantifying population genomic structure across a set of codistributed taxa with extensive and phylogenetically independent variation in speciation rate, we show that broad-scale patterns of species formation are decoupled from demographic and genetic processes that promote the formation of population isolates. Population isolation is likely a critical stage of speciation for many taxa, but our results suggest that interspecific variability in the propensity for isolation has little influence on speciation rates. These results suggest that other stages of speciation-including the rate at which reproductive barriers evolve and the extent to which newly formed populations persist-are likely to play a larger role than population isolation in controlling speciation rate variation in squamates.
Collapse
Affiliation(s)
- Sonal Singhal
- Department of Biology, California State University, Dominguez Hills, Carson, CA 90747;
| | - Guarino R Colli
- Departamento de Zoologia, Universidade de Brasília, Brasília, Distrito Federal 70910-900, Brazil
| | - Maggie R Grundler
- Department of Environmental Science, Policy, & Management, University of California, Berkeley, CA 94720
- Museum of Vertebrate Zoology, University of California, Berkeley, CA 94720
| | - Gabriel C Costa
- Department of Biology and Environmental Sciences, Auburn University at Montgomery, Montgomery, AL 36117
| | - Ivan Prates
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109
- Museum of Zoology, University of Michigan, Ann Arbor, MI 48109
| | - Daniel L Rabosky
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109;
- Museum of Zoology, University of Michigan, Ann Arbor, MI 48109
| |
Collapse
|
17
|
Sandstedt GD, Wu CA, Sweigart AL. Evolution of multiple postzygotic barriers between species of the Mimulus tilingii complex. Evolution 2021; 75:600-613. [PMID: 33044006 PMCID: PMC7987689 DOI: 10.1111/evo.14105] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 09/04/2020] [Accepted: 09/21/2020] [Indexed: 12/17/2022]
Abstract
Species are often defined by their ability to interbreed (i.e., Biological Species Concept), but determining how and why reproductive isolation arises between new species can be challenging. In the Mimulus tilingii species complex, three species (M. caespitosa, M. minor, and M. tilingii) are largely allopatric and grow exclusively at high elevations (>2000 m). The extent to which geographic separation has shaped patterns of divergence among the species is not well understood. In this study, we determined that the three species are morphologically and genetically distinct, yet recently diverged. Additionally, we performed reciprocal crosses within and between the species and identified several strong postzygotic reproductive barriers, including hybrid seed inviability, F1 hybrid necrosis, and F1 hybrid male and female sterility. In this study, such postzygotic barriers are so strong that a cross between any species pair in the M. tilingii complex would cause nearly complete reproductive isolation. We consider how geographical and topographical patterns may have facilitated the evolution of several postzygotic barriers and contributed to speciation of closely related members within the M. tilingii species complex.
Collapse
Affiliation(s)
| | - Carrie A. Wu
- Department of Biology, University of Richmond, Richmond, Virginia 23173
| | | |
Collapse
|
18
|
Rushworth CA, Mitchell-Olds T. The Evolution of Sex is Tempered by Costly Hybridization in Boechera (Rock Cress). J Hered 2020; 112:67-77. [PMID: 33211850 DOI: 10.1093/jhered/esaa041] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Accepted: 10/03/2020] [Indexed: 12/17/2022] Open
Abstract
Despite decades of research, the evolution of sex remains an enigma in evolutionary biology. Typically, research addresses the costs of sex and asexuality to characterize the circumstances favoring one reproductive mode. Surprisingly few studies address the influence of common traits that are, in many organisms, obligately correlated with asexuality, including hybridization and polyploidy. These characteristics have substantial impacts on traits under selection. In particular, the fitness consequences of hybridization (i.e., reduced fitness due to interspecific reproductive isolation) will influence the evolution of sex. This may comprise a cost of either sex or asexuality due to the link between hybridity and asexuality. We examined reproductive isolation in the formation of de novo hybrid lineages between 2 widespread species in the ecological model system Boechera. Seventeen percent of 664 crosses produced F1 fruits, and only 10% of these were viable, suggesting that postmating prezygotic and postzygotic barriers inhibit hybrid success in this system. The postmating prezygotic barrier was asymmetrical, with 110 of 115 total F1 fruits produced when Boechera stricta acted as maternal parent. This asymmetry was confirmed in wild-collected lineages, using a chloroplast phylogeny of wild-collected B. stricta, Boechera retrofracta, and hybrids. We next compared fitness of F2 hybrids and selfed parental B. stricta lines, finding that F2 fitness was reduced by substantial hybrid sterility. Multiple reproductively isolating barriers influence the formation and fitness of hybrid lineages in the wild, and the costs of hybridization likely have profound impacts on the evolution of sex in the natural environment.
Collapse
Affiliation(s)
- Catherine A Rushworth
- Department of Evolution and Ecology, Storer Hall, University of California Davis, Davis, CA.,Department of Plant and Microbial Biology, University of Minnesota, St. Paul, MN.,University and Jepson Herbaria, University of California Berkeley, Berkeley, CA.,Department of Biology and Center for Genomic and Computational Biology, Duke University, Box, Durham, NC
| | - Tom Mitchell-Olds
- Department of Biology and Center for Genomic and Computational Biology, Duke University, Box, Durham, NC
| |
Collapse
|
19
|
Divergence in flowering time is a major component contributing to reproductive isolation between two wild rice species (Oryza rufipogon and O. nivara). SCIENCE CHINA. LIFE SCIENCES 2020; 63:1714-1724. [PMID: 32318909 DOI: 10.1007/s11427-019-1678-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2019] [Accepted: 03/12/2020] [Indexed: 10/24/2022]
Abstract
It is of critical importance for our understanding of speciation process to determine the forms of reproductive isolation and their relative importance in species divergence. Oryza nivara and O. rufipogon are direct ancestors of Asian cultivated rice and a progenitor-daughter species pair. Investigating the reproductive isolation between them provides insights into plant speciation and helps understanding of the rice domestication. Here, we quantitatively measured the major components of reproductive isolation between the two species based on common garden and crossing experiments for three pairs of sympatric populations in Nepal, Cambodia and Laos. We revealed significant differences in the flowering times between species pairs, with O. nivara flowering much earlier than O. rufipogon. A very weak reduction in seed set but no reduction in F1 viability and fertility were detected for the crosses between species relative to those within species. Moreover, we detected asymmetrical compatibility between species and found that emasculation significantly decreased pollination success in O. nivara but not in O. rufipogon. Our study demonstrates that the divergence between O. nivara and O. rufipogon is maintained almost entirely by the difference in flowering times and suggests that differential flowering times contribute to both habitat preferences and reproductive isolation between species.
Collapse
|
20
|
Singh P, Ballmer DN, Laubscher M, Schärer L. Successful mating and hybridisation in two closely related flatworm species despite significant differences in reproductive morphology and behaviour. Sci Rep 2020; 10:12830. [PMID: 32732887 PMCID: PMC7393371 DOI: 10.1038/s41598-020-69767-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Accepted: 07/20/2020] [Indexed: 12/16/2022] Open
Abstract
Reproductive traits are some of the fastest diverging characters and can serve as reproductive barriers. The free-living flatworm Macrostomum lignano, and its congener M. janickei are closely related, but differ substantially in their male intromittent organ (stylet) morphology. Here, we examine whether these morphological differences are accompanied by differences in behavioural traits, and whether these could represent barriers to successful mating and hybridization between the two species. Our data shows that the two species differ in many aspects of their mating behaviour. Despite these differences, the species mate readily with each other in heterospecific pairings. Although both species have similar fecundity in conspecific pairings, the heterospecific pairings revealed clear postmating barriers, as few heterospecific pairings produced F1 hybrids. These hybrids had a stylet morphology that was intermediate between that of the parental species, and they were fertile. Finally, using a mate choice experiment, we show that the nearly two-fold higher mating rate of M. lignano caused it to mate more with conspecifics, leading to assortative mating, while M. janickei ended up mating more with heterospecifics. Thus, while the two species can hybridize, the mating rate differences could possibly lead to higher fitness costs for M. janickei compared to M. lignano.
Collapse
Affiliation(s)
- Pragya Singh
- Department of Environmental Sciences, Zoological Institute, University of Basel, Vesalgasse 1, 4051, Basel, Switzerland.
| | - Daniel N Ballmer
- Department of Environmental Sciences, Zoological Institute, University of Basel, Vesalgasse 1, 4051, Basel, Switzerland.,Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - Max Laubscher
- Department of Environmental Sciences, Zoological Institute, University of Basel, Vesalgasse 1, 4051, Basel, Switzerland
| | - Lukas Schärer
- Department of Environmental Sciences, Zoological Institute, University of Basel, Vesalgasse 1, 4051, Basel, Switzerland
| |
Collapse
|
21
|
Massive haplotypes underlie ecotypic differentiation in sunflowers. Nature 2020; 584:602-607. [PMID: 32641831 DOI: 10.1038/s41586-020-2467-6] [Citation(s) in RCA: 177] [Impact Index Per Article: 44.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2019] [Accepted: 04/16/2020] [Indexed: 12/22/2022]
Abstract
Species often include multiple ecotypes that are adapted to different environments1. However, it is unclear how ecotypes arise and how their distinctive combinations of adaptive alleles are maintained despite hybridization with non-adapted populations2-4. Here, by resequencing 1,506 wild sunflowers from 3 species (Helianthus annuus, Helianthus petiolaris and Helianthus argophyllus), we identify 37 large (1-100 Mbp in size), non-recombining haplotype blocks that are associated with numerous ecologically relevant traits, as well as soil and climate characteristics. Limited recombination in these haplotype blocks keeps adaptive alleles together, and these regions differentiate sunflower ecotypes. For example, haplotype blocks control a 77-day difference in flowering between ecotypes of the silverleaf sunflower H. argophyllus (probably through deletion of a homologue of FLOWERING LOCUS T (FT)), and are associated with seed size, flowering time and soil fertility in dune-adapted sunflowers. These haplotypes are highly divergent, frequently associated with structural variants and often appear to represent introgressions from other-possibly now-extinct-congeners. These results highlight a pervasive role of structural variation in ecotypic adaptation.
Collapse
|
22
|
Huang K, Andrew RL, Owens GL, Ostevik KL, Rieseberg LH. Multiple chromosomal inversions contribute to adaptive divergence of a dune sunflower ecotype. Mol Ecol 2020; 29:2535-2549. [PMID: 32246540 DOI: 10.1111/mec.15428] [Citation(s) in RCA: 71] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2019] [Accepted: 03/19/2020] [Indexed: 12/19/2022]
Abstract
Both models and case studies suggest that chromosomal inversions can facilitate adaptation and speciation in the presence of gene flow by suppressing recombination between locally adapted alleles. Until recently, however, it has been laborious and time-consuming to identify and genotype inversions in natural populations. Here we apply RAD sequencing data and newly developed population genomic approaches to identify putative inversions that differentiate a sand dune ecotype of the prairie sunflower (Helianthus petiolaris) from populations found on the adjacent sand sheet. We detected seven large genomic regions that exhibit a different population structure than the rest of the genome and that vary in frequency between dune and nondune populations. These regions also show high linkage disequilibrium and high heterozygosity between, but not within, arrangements, consistent with the behaviour of large inversions, an inference subsequently validated in part by comparative genetic mapping. Genome-environment association analyses show that key environmental variables, including vegetation cover and soil nitrogen, are significantly associated with inversions. The inversions colocate with previously described "islands of differentiation," and appear to play an important role in adaptive divergence and incipient speciation within H. petiolaris.
Collapse
Affiliation(s)
- Kaichi Huang
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Rose L Andrew
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada.,School of Environmental and Rural Science, University of New England, Armidale, NSW, Australia
| | - Gregory L Owens
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada.,Department of Integrative Biology, University of California, Berkeley, CA, USA
| | - Kate L Ostevik
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada.,Department of Biology, Duke University, Durham, NC, USA
| | - Loren H Rieseberg
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| |
Collapse
|
23
|
Huang K, Rieseberg LH. Frequency, Origins, and Evolutionary Role of Chromosomal Inversions in Plants. FRONTIERS IN PLANT SCIENCE 2020; 11:296. [PMID: 32256515 DOI: 10.3389/fpls.2020.00296/full] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Accepted: 02/27/2020] [Indexed: 05/24/2023]
Abstract
Chromosomal inversions have the potential to play an important role in evolution by reducing recombination between favorable combinations of alleles. Until recently, however, most evidence for their likely importance derived from dipteran flies, whose giant larval salivary chromosomes aided early cytogenetic studies. The widespread application of new genomic technologies has revealed that inversions are ubiquitous across much of the plant and animal kingdoms. Here we review the rapidly accumulating literature on inversions in the plant kingdom and discuss what we have learned about their establishment and likely evolutionary role. We show that inversions are prevalent across a wide range of plant groups. We find that inversions are often associated with locally favored traits, as well as with traits that contribute to assortative mating, suggesting that they may be key to adaptation and speciation in the face of gene flow. We also discuss the role of inversions in sex chromosome formation, and explore possible parallels with inversion establishment on autosomes. The identification of inversion origins, as well as the causal variants within them, will advance our understanding of chromosomal evolution in plants.
Collapse
Affiliation(s)
- Kaichi Huang
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Loren H Rieseberg
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| |
Collapse
|
24
|
Huang K, Rieseberg LH. Frequency, Origins, and Evolutionary Role of Chromosomal Inversions in Plants. FRONTIERS IN PLANT SCIENCE 2020; 11:296. [PMID: 32256515 PMCID: PMC7093584 DOI: 10.3389/fpls.2020.00296] [Citation(s) in RCA: 66] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Accepted: 02/27/2020] [Indexed: 05/11/2023]
Abstract
Chromosomal inversions have the potential to play an important role in evolution by reducing recombination between favorable combinations of alleles. Until recently, however, most evidence for their likely importance derived from dipteran flies, whose giant larval salivary chromosomes aided early cytogenetic studies. The widespread application of new genomic technologies has revealed that inversions are ubiquitous across much of the plant and animal kingdoms. Here we review the rapidly accumulating literature on inversions in the plant kingdom and discuss what we have learned about their establishment and likely evolutionary role. We show that inversions are prevalent across a wide range of plant groups. We find that inversions are often associated with locally favored traits, as well as with traits that contribute to assortative mating, suggesting that they may be key to adaptation and speciation in the face of gene flow. We also discuss the role of inversions in sex chromosome formation, and explore possible parallels with inversion establishment on autosomes. The identification of inversion origins, as well as the causal variants within them, will advance our understanding of chromosomal evolution in plants.
Collapse
Affiliation(s)
- Kaichi Huang
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Loren H. Rieseberg
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| |
Collapse
|
25
|
Babiychuk E, Teixeira JG, Tyski L, Guimaraes JTF, Romeiro LA, da Silva EF, Dos Santos JF, Vasconcelos S, da Silva DF, Castilho A, Siqueira JO, Fonseca VLI, Kushnir S. Geography is essential for reproductive isolation between florally diversified morning glory species from Amazon canga savannahs. Sci Rep 2019; 9:18052. [PMID: 31792228 PMCID: PMC6889514 DOI: 10.1038/s41598-019-53853-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Accepted: 11/06/2019] [Indexed: 11/29/2022] Open
Abstract
The variety, relative importance and eco-evolutionary stability of reproductive barriers are critical to understanding the processes of speciation and species persistence. Here we evaluated the strength of the biotic prezygotic and postzygotic isolation barriers between closely related morning glory species from Amazon canga savannahs. The flower geometry and flower visitor assemblage analyses supported pollination by the bees in lavender-flowered Ipomoea marabaensis and recruitment of hummingbirds as pollinators in red-flowered Ipomoea cavalcantei. Nevertheless, native bee species and alien honeybees foraged on flowers of both species. Real-time interspecific hybridization underscored functionality of the overlap in flower visitor assemblages, questioning the strength of prezygotic isolation underpinned by diversification in flower colour and geometry. Interspecific hybrids were fertile and produced offspring in nature. No significant asymmetry in interspecific hybridization and hybrid incompatibilities among offspring were found, indicating weak postmating and postzygotic isolation. The results suggested that despite floral diversification, the insular-type geographic isolation remains a major barrier to gene flow. Findings set a framework for the future analysis of contemporary evolution of plant-pollinator networks at the population, community, and ecosystem levels in tropical ecosystems that are known to be distinct from the more familiar temperate climate models.
Collapse
Affiliation(s)
- Elena Babiychuk
- Instituto Tecnológico Vale, Rua Boaventura da Silva 955, CEP 66055-090, Belém, Pará, Brazil.
| | | | - Lourival Tyski
- Parque Zoobotânico Vale, VALE S.A., Rod. Raimundo Mascarenhas, Km 26, S/N., Núcleo Urbano de Carajás, CEP 68516-000, Parauapebas, Pará, Brazil
| | | | - Luiza Araújo Romeiro
- Instituto Tecnológico Vale, Rua Boaventura da Silva 955, CEP 66055-090, Belém, Pará, Brazil
| | | | | | - Santelmo Vasconcelos
- Instituto Tecnológico Vale, Rua Boaventura da Silva 955, CEP 66055-090, Belém, Pará, Brazil
| | - Delmo Fonseca da Silva
- Parque Zoobotânico Vale, VALE S.A., Rod. Raimundo Mascarenhas, Km 26, S/N., Núcleo Urbano de Carajás, CEP 68516-000, Parauapebas, Pará, Brazil
| | - Alexandre Castilho
- Gerência de Meio Ambiente, Departamento de Ferrosos Corredor Norte, Vale S.A., Rua Guamá n 60, Núcleo Urbano, CEP 68516-000, Parauapebas, Pará, Brazil
| | - José Oswaldo Siqueira
- Instituto Tecnológico Vale, Rua Boaventura da Silva 955, CEP 66055-090, Belém, Pará, Brazil
| | | | - Sergei Kushnir
- Unaffiliated, Belém, Pará, Brazil.,Teagasc, Crop Science Department, Oak Park, Carlow, R93 XE12, Ireland
| |
Collapse
|
26
|
Moreira-Hernández JI, Muchhala N. Importance of Pollinator-Mediated Interspecific Pollen Transfer for Angiosperm Evolution. ANNUAL REVIEW OF ECOLOGY EVOLUTION AND SYSTEMATICS 2019. [DOI: 10.1146/annurev-ecolsys-110218-024804] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Understanding how pollen moves between species is critical to understanding speciation, diversification, and evolution of flowering plants. For co-flowering species that share pollinators, competition through interspecific pollen transfer (IPT) can profoundly impact floral evolution, decreasing female fitness via heterospecific pollen deposition on stigmas and male fitness via pollen misplacement during visits to heterospecific flowers. The pollination literature demonstrates that such reproductive interference frequently selects for reproductive character displacement in floral traits linked to pollinator attraction, pollen placement, and mating systems and has also revealed that IPT between given pairs of species is typically asymmetric. More recent work is starting to elucidate its importance to the speciation process, clarifying the link between IPT and current and historical patterns of hybridization, the evolution of phenotypic novelty through adaptive introgression, and the rise of reproductive isolation. Our review aims to stimulate further research on IPT as a ubiquitous mechanism that plays a central role in angiosperm diversification.
Collapse
Affiliation(s)
- Juan Isaac Moreira-Hernández
- Department of Biology and Whitney R. Harris World Ecology Center, University of Missouri–St. Louis, St. Louis, Missouri 63121, USA;,
| | - Nathan Muchhala
- Department of Biology and Whitney R. Harris World Ecology Center, University of Missouri–St. Louis, St. Louis, Missouri 63121, USA;,
| |
Collapse
|
27
|
Zhang JQ, Imerovski I, Borkowski K, Huang K, Burge D, Rieseberg LH. Intraspecific genetic divergence within Helianthus niveus and the status of two new morphotypes from Mexico. AMERICAN JOURNAL OF BOTANY 2019; 106:1229-1239. [PMID: 31461165 DOI: 10.1002/ajb2.1349] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Accepted: 07/17/2019] [Indexed: 05/12/2023]
Abstract
PREMISE Collecting and characterizing the genetic diversity of wild relatives of crops can contribute importantly to sustainable crop production and food security. Wild sunflower, Helianthus niveus, occurs in arid regions in western North America and is partially cross-compatible with the cultivated sunflower (H. annuus). We assessed phylogenetic relationships and patterns of genetic divergence among three previously described subspecies (subsp. niveus, subsp. canescens, and subsp. tephrodes) as well as two new morphotypes of H. niveus recently discovered in extreme drought and dune habitats in Baja California, Mexico. METHODS We measured 50 plants growing in a common garden for 27 morphological traits and conducted principal component analysis to assess patterns of phenotypic variation. Genome size of each accession was determined using flow cytometry. Pollen viability of first generation hybrids between taxa was tested to infer the strength of intrinsic postzygotic reproductive barriers. Finally, genotyping-by-sequencing data were used to investigate the genetic structure and phylogenetic relationships among the previously described subspecies and new morphotypes. RESULTS The intraspecific genetic and phenotypic divergence of H. niveus populations closely tracks their geographical distribution. Subspecies niveus is phenotypically, genetically, and reproductively distinct from the other two subspecies and has a larger genome. Therefore, H. niveus as currently circumscribed should be considered to contain two distinct species, H. niveus and H. tephrodes. ABBA-BABA tests revealed substantial introgression between subsp. canescens and its sympatric congener H. petiolaris, which might contribute to their morphological similarities. The two new morphotypes collected in Mexico represent local ecotypes of subsp. niveus that occur in extreme drought and dune environments. Mantel tests showed a strong positive correlation between genetic and geographic distances. CONCLUSIONS We conclude that geographic isolation is primarily responsible for intraspecific genomic divergence within H. niveus, while patterns of phenotypic variation appear to have been shaped by ecological selection and interspecific introgression.
Collapse
Affiliation(s)
- Jian-Qiang Zhang
- College of Life Sciences, Shaanxi Normal University, Xi'an, 710119, China
- Department of Botany, University of British Columbia, Vancouver, British Columbia, V6T1Z4, Canada
| | - Ivana Imerovski
- Department of Botany, University of British Columbia, Vancouver, British Columbia, V6T1Z4, Canada
| | - Kelly Borkowski
- Department of Botany, University of British Columbia, Vancouver, British Columbia, V6T1Z4, Canada
| | - Kaichi Huang
- Department of Botany, University of British Columbia, Vancouver, British Columbia, V6T1Z4, Canada
| | - Dylan Burge
- Department of Botany, University of British Columbia, Vancouver, British Columbia, V6T1Z4, Canada
| | - Loren H Rieseberg
- Department of Botany, University of British Columbia, Vancouver, British Columbia, V6T1Z4, Canada
| |
Collapse
|
28
|
Christie K, Strauss SY. Reproductive isolation and the maintenance of species boundaries in two serpentine endemic Jewelflowers. Evolution 2019; 73:1375-1391. [PMID: 31152435 DOI: 10.1111/evo.13767] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Revised: 04/28/2019] [Accepted: 05/03/2019] [Indexed: 12/30/2022]
Abstract
Speciation occurs when reproductive barriers substantially reduce gene flow between lineages. Understanding how specific barriers contribute to reproductive isolation offers insight into the initial forces driving divergence and the evolutionary and ecological processes responsible for maintaining diversity. Here, we quantified multiple pre- and post-pollination isolating barriers in a pair of closely related California Jewelflowers (Streptanthus, Brassicaceae) living in an area of sympatry. S. breweri and S. hesperidis are restricted to similar serpentine habitats; however, populations are spatially isolated at fine-scales and rarely co-occur in intermixed stands. Several intrinsic postzygotic barriers were among the strongest we quantified, yet, postzygotic barriers currently contribute little to overall reproductive isolation due to the cumulative strength of earlier-acting extrinsic barriers, including spatial isolation, and flowering time and pollinator differences. Data from multiple years suggest that pre-pollination barriers may have different strengths depending on annual environmental conditions. Similarly, crossing data suggest that the strength of intrinsic isolation may vary among different population pairs. Estimates of total reproductive isolation in S. breweri and S. hesperidis are robust to uncertainty and variability in individual barrier strength estimates, demonstrating how multiple barriers can act redundantly to prevent gene flow between close relatives living in sympatry.
Collapse
Affiliation(s)
- Kyle Christie
- UC Davis Department of Evolution and Ecology, and Center for Population Biology, University of California, One Shields Avenue, Davis, California, 95616
| | - Sharon Y Strauss
- UC Davis Department of Evolution and Ecology, and Center for Population Biology, University of California, One Shields Avenue, Davis, California, 95616
| |
Collapse
|
29
|
Spriggs EL, Schlutius C, Eaton DA, Park B, Sweeney PW, Edwards EJ, Donoghue MJ. Differences in flowering time maintain species boundaries in a continental radiation of Viburnum. AMERICAN JOURNAL OF BOTANY 2019; 106:833-849. [PMID: 31124135 DOI: 10.1002/ajb2.1292] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 03/19/2019] [Indexed: 05/21/2023]
Abstract
PREMISE We take an integrative approach in assessing how introgression and Pleistocene climate fluctuations have shaped the diversification of the core Lentago clade of Viburnum, a group of five interfertile species with broad areas of sympatry. We specifically tested whether flowering time plays a role in maintaining species isolation. METHODS RAD-seq data for 103 individuals were used to infer the species relationships and the genetic structure within each species. Flowering times were compared among species on the basis of historical flowering dates documented by herbarium specimens. RESULTS Within each species, we found a strong relationship between flowering date and latitude, such that southern populations flower earlier than northern ones. In areas of sympatry, the species flower in sequence rather than simultaneously, with flowering dates offset by ≥9 d for all species pairs. In two cases it appears that the offset in flowering times is an incidental consequence of adaptation to differing climates, but in the recently diverged sister species V. prunifolium and V. rufidulum, we find evidence that reinforcement led to reproductive character displacement. Long-term trends suggest that the two northern-most species are flowering earlier in response to recent climate change. CONCLUSIONS We argue that speciation in the Lentago clade has primarily occurred through ecological divergence of allopatric populations, but differences in flowering time were essential to maintain separation of incipient species when they came into secondary contact. This combination of factors may underlie diversification in many other plant clades.
Collapse
Affiliation(s)
- Elizabeth L Spriggs
- Department of Ecology and Evolutionary Biology, Yale University, P.O. Box 208106, New Haven, Connecticut, 06520, USA
| | - Caroline Schlutius
- Department of Ecology and Evolutionary Biology, Yale University, P.O. Box 208106, New Haven, Connecticut, 06520, USA
| | - Deren A Eaton
- Department of Ecology, Evolution, and Environmental Biology, Columbia University, New York, New York, 10027, USA
| | - Brian Park
- Department of Ecology and Evolutionary Biology, Yale University, P.O. Box 208106, New Haven, Connecticut, 06520, USA
| | - Patrick W Sweeney
- Division of Botany, Peabody Museum of Natural History, Yale University, P.O. Box 208118, New Haven, Connecticut, 06520, USA
| | - Erika J Edwards
- Department of Ecology and Evolutionary Biology, Yale University, P.O. Box 208106, New Haven, Connecticut, 06520, USA
- Division of Botany, Peabody Museum of Natural History, Yale University, P.O. Box 208118, New Haven, Connecticut, 06520, USA
| | - Michael J Donoghue
- Department of Ecology and Evolutionary Biology, Yale University, P.O. Box 208106, New Haven, Connecticut, 06520, USA
- Division of Botany, Peabody Museum of Natural History, Yale University, P.O. Box 208118, New Haven, Connecticut, 06520, USA
| |
Collapse
|
30
|
Yan LJ, Burgess KS, Zheng W, Tao ZB, Li DZ, Gao LM. Incomplete reproductive isolation between Rhododendron taxa enables hybrid formation and persistence. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2019; 61:433-448. [PMID: 30192058 DOI: 10.1111/jipb.12718] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2018] [Accepted: 09/06/2018] [Indexed: 06/08/2023]
Abstract
The evolutionary consequences of hybridization ultimately depend on the magnitude of reproductive isolation between hybrids and their parents. We evaluated the relative contributions of pre- and post-zygotic barriers to reproduction for hybrid formation, hybrid persistence and potential for reproductive isolation of hybrids formed between two Rhododendron species, R. spiciferum and R. spinuliferum. Our study established that incomplete reproductive isolation promotes hybrid formation and persistence and delays hybrid speciation. All pre-zygotic barriers to reproduction leading to hybrid formation are incomplete: parental species have overlapping flowering; they share the same pollinators; reciprocal assessments of pollen tube germination and growth do not differ among parents. The absence of post-zygotic barriers between parental taxa indicates that the persistence of hybrids is likely. Reproductive isolation was incomplete between hybrids and parents in all cases studied, although asymmetric differences in reproductive fitness were prevalent and possibly explain the genetic structure of natural hybrid swarms where hybridization is known to be bidirectional but asymmetric. Introgression, rather than speciation, is a probable evolutionary outcome of hybridization between the two Rhododendron taxa. Our study provides insights into understanding the evolutionary implications of natural hybridization in woody plants.
Collapse
Affiliation(s)
- Li-Jun Yan
- Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, the Chinese Academy of Sciences, Kunming 650201, China
- Germplasm Bank of Wild Species, Kunming Institute of Botany, the Chinese Academy of Sciences, Kunming 650201, China
- Kunming College of Life Science, University of the Chinese Academy of Sciences, Kunming 650201, China
- College of Vocational and Technical Education, Yunnan Normal University, Kunming 650092, China
| | - Kevin S Burgess
- Department of Biology, College of Letters & Sciences, Columbus State University, University System of Georgia, 31907-5645 Columbus, GA, USA
| | - Wei Zheng
- Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, the Chinese Academy of Sciences, Kunming 650201, China
- Kunming College of Life Science, University of the Chinese Academy of Sciences, Kunming 650201, China
| | - Zhi-Bin Tao
- Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, the Chinese Academy of Sciences, Kunming 650201, China
- Kunming College of Life Science, University of the Chinese Academy of Sciences, Kunming 650201, China
| | - De-Zhu Li
- Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, the Chinese Academy of Sciences, Kunming 650201, China
- Germplasm Bank of Wild Species, Kunming Institute of Botany, the Chinese Academy of Sciences, Kunming 650201, China
- Kunming College of Life Science, University of the Chinese Academy of Sciences, Kunming 650201, China
| | - Lian-Ming Gao
- Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, the Chinese Academy of Sciences, Kunming 650201, China
| |
Collapse
|
31
|
Karrenberg S, Liu X, Hallander E, Favre A, Herforth-Rahmé J, Widmer A. Ecological divergence plays an important role in strong but complex reproductive isolation in campions (Silene). Evolution 2018; 73:245-261. [PMID: 30499144 DOI: 10.1111/evo.13652] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 11/13/2018] [Accepted: 01/16/2018] [Indexed: 12/27/2022]
Abstract
New species arise through the evolution of reproductive barriers between formerly interbreeding lineages. Yet, comprehensive assessments of potential reproductive barriers, which are needed to make inferences on processes driving speciation, are only available for a limited number of systems. In this study, we estimated individual and cumulative strengths of seven prezygotic and six postzygotic reproductive barriers between the recently diverged taxa Silene dioica (L.) Clairv. and S. latifolia Poiret using both published and new data. A combination of multiple partial reproductive barriers resulted in near-complete reproductive isolation between S. dioica and S. latifolia, consistent with earlier estimates of gene flow between the taxa. Extrinsic barriers associated with adaptive ecological divergence were most important, while intrinsic postzygotic barriers had moderate individual strength but contributed only little to total reproductive isolation. These findings are in line with ecological divergence as driver of speciation. We further found extensive variation in extrinsic reproductive isolation, ranging from sites with very strong selection against migrants and hybrids to intermediate sites where substantial hybridization is possible. This situation may allow for, or even promote, heterogeneous genetic divergence.
Collapse
Affiliation(s)
- Sophie Karrenberg
- Department of Ecology and Genetics, Uppsala University, Norbyvägen 18 D, 75236, Uppsala, Sweden
| | - Xiaodong Liu
- Department of Ecology and Genetics, Uppsala University, Norbyvägen 18 D, 75236, Uppsala, Sweden
| | - Emelie Hallander
- Department of Ecology and Genetics, Uppsala University, Norbyvägen 18 D, 75236, Uppsala, Sweden.,Current Address: Swedish Board of Agriculture, Vallgatan 8, 551 82, Jönköping, Sweden
| | - Adrien Favre
- Department of Diversity and Evolution of Higher Plants, Institute of Ecology, Evolution and Diversity, Goethe-University, 60439, Frankfurt am Main, Germany.,Senckenberg Research Institute and Natural History Museum, Senckenberganlage 25, 60325, Frankfurt am Main, Germany
| | - Joelle Herforth-Rahmé
- ETH Zurich, Institute of Integrative Biology, Universitätstrasse 16, 8092, Zürich, Switzerland.,Current Address: Research Institute of Organic Agriculture FiBL, Department of Soil Sciences, Ackerstrasse 113, Box 219, 5070, Frick, Switzerland
| | - Alex Widmer
- ETH Zurich, Institute of Integrative Biology, Universitätstrasse 16, 8092, Zürich, Switzerland
| |
Collapse
|
32
|
Quantification of Reproductive Isolating Barriers Between Two Naturally Hybridizing Killifish Species. Evol Biol 2018. [DOI: 10.1007/s11692-018-9460-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
|
33
|
Cahenzli F, Bonetti C, Erhardt A. Divergent strategies in pre- and postzygotic reproductive isolation between two closely related Dianthus species. Evolution 2018; 72:1851-1862. [PMID: 30003537 DOI: 10.1111/evo.13556] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Accepted: 07/02/2018] [Indexed: 10/28/2022]
Abstract
Quantifying the relative contribution of multiple isolation barriers to gene flow between recently diverged species is essential for understanding speciation processes. In parapatric populations, local adaptation is thought to be a major contributor to the evolution of reproductive isolation. However, extrinsic postzygotic barriers assessed in reciprocal transplant experiments are often neglected in empirical assessments of multiple isolation barriers. We analyzed multiple isolation barriers between two closely related species of the plant genus Dianthus, a genus characterized by the most rapid species diversification in plants reported so far. Although D. carthusianorum L. and D. sylvestris Wulf. can easily be hybridized in crossing experiments, natural hybrids are rare. We found that in parapatry, pollinator-mediated prezygotic reproductive isolation barriers are important for both D. carthusianorum (0.761) and D. sylvestris (0.468). In contrast to D. carthusianorum, high hybrid viability in D. sylvestris (-0.491) was counteracted by strong extrinsic postzygotic isolation (0.900). Our study highlights the importance of including reciprocal transplant experiments for documenting extrinsic postzygotic isolation and demonstrates clearly divergent strategies and hence asymmetric pre- and postzygotic reproductive isolation between closely related species. It also suggests that pollinator-mediated and ecological isolation could have interacted in synergistic ways, further stimulating rapid speciation in Dianthus.
Collapse
Affiliation(s)
- Fabian Cahenzli
- Forschungsinstitut für biologischen Landbau (FiBL), Department of crop Sciences, Ackerstrasse 113, CH-5070, Frick, Switzerland
| | - Christophe Bonetti
- Department of Environmental Sciences, Section Conservation Biology (NLU), University of Basel, St. Johanns-Vorstadt 10, CH-4056, Basel, Switzerland
| | - Andreas Erhardt
- Department of Environmental Sciences, Botany, University of Basel, Schönbeinstrasse 6, CH-4056, Basel, Switzerland
| |
Collapse
|
34
|
Spasojevic MJ, Catano CP, LaManna JA, Myers JA. Integrating species traits into species pools. Ecology 2018; 99:1265-1276. [DOI: 10.1002/ecy.2220] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Accepted: 03/02/2018] [Indexed: 12/29/2022]
Affiliation(s)
- Marko J. Spasojevic
- Department of Evolution, Ecology, and Organismal Biology University of California Riverside Riverside California 92521 USA
| | - Christopher P. Catano
- Department of Biology and Tyson Research Center Washington University in St. Louis St. Louis Missouri 63130 USA
| | - Joseph A. LaManna
- Department of Biology and Tyson Research Center Washington University in St. Louis St. Louis Missouri 63130 USA
| | - Jonathan A. Myers
- Department of Biology and Tyson Research Center Washington University in St. Louis St. Louis Missouri 63130 USA
| |
Collapse
|
35
|
Christie K, Strauss SY. Along the speciation continuum: Quantifying intrinsic and extrinsic isolating barriers across five million years of evolutionary divergence in California jewelflowers. Evolution 2018; 72:1063-1079. [DOI: 10.1111/evo.13477] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2017] [Accepted: 02/27/2018] [Indexed: 12/11/2022]
Affiliation(s)
- Kyle Christie
- Department of Evolution and Ecology and Center for Population Biology University of California One Shields Avenue Davis California 95616
| | - Sharon Y. Strauss
- Department of Evolution and Ecology and Center for Population Biology University of California One Shields Avenue Davis California 95616
| |
Collapse
|
36
|
Moving Character Displacement beyond Characters Using Contemporary Coexistence Theory. Trends Ecol Evol 2017; 33:74-84. [PMID: 29180041 DOI: 10.1016/j.tree.2017.11.002] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Revised: 11/02/2017] [Accepted: 11/06/2017] [Indexed: 11/20/2022]
Abstract
Character displacement is one of the most studied phenomena in evolutionary biology, yet research has narrowly focused on demonstrating whether or not displacement has occurred. We propose a new experimental approach, adopted from the coexistence literature, that directly measures interspecific competition among sympatric and allopatric populations of species. Doing so allows increased ability to (i) test predictions of character displacement without biases inherent to character-centric tests, (ii) quantify its effect on the stability of coexistence, (iii) resolve the phenotypic pathways through which competitive divergence is achieved, and (iv) perform comparative tests. Our approach extends research to forms of character displacement not readily identified by past methods and will lead to a broader understanding of its consequences for community structure.
Collapse
|
37
|
Brothers AN, Delph LF. Divergence in style length and pollen size leads to a postmating-prezygotic reproductive barrier among populations of Silene latifolia. Evolution 2017; 71:1532-1540. [PMID: 28394403 DOI: 10.1111/evo.13248] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2016] [Accepted: 03/27/2017] [Indexed: 12/25/2022]
Abstract
A central tenet of speciation research is the need to identify reproductive isolating barriers. One approach to this line of research is to identify the phenotypes that lead to reproductive isolation. Several studies on flowering plants have shown that differences in style length contribute to reproductive isolation between species, leading us to consider whether style length could act as a reproductive barrier among populations of a single species. This could occur if style length varied sufficiently and pollen size covaried with style length. Populations of Silene latifolia exhibit variation in flower size, including style length, that is negatively correlated with annual precipitation. We show that this divergence in style length has a genetic basis and acts as a reproductive barrier: males from small-flowered populations produced relatively small pollen grains that were poor at fertilizing ovules when crossed to females from large-flowered populations, leading to a significant reduction in seed production. Manipulating the distance pollen tubes had to travel revealed that this failure was purely mechanical and not the result of other incompatibilities. These results show that style length acts as a postmating-prezygotic reproductive barrier and indicate a potential link between ecotypic differentiation and reproductive isolation within a species.
Collapse
Affiliation(s)
- Amanda N Brothers
- Department of Biology, Indiana University, Bloomington, Indiana, 47405
| | - Lynda F Delph
- Department of Biology, Indiana University, Bloomington, Indiana, 47405
| |
Collapse
|