1
|
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 Commun 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] [What about the content of this article? (0)] [Affiliation(s)] [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
|
2
|
Wong ELY, Filatov DA. The role of recombination landscape in species hybridisation and speciation. Front Plant Sci 2023; 14:1223148. [PMID: 37484464 PMCID: PMC10361763 DOI: 10.3389/fpls.2023.1223148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Accepted: 06/13/2023] [Indexed: 07/25/2023]
Abstract
It is now well recognised that closely related species can hybridize and exchange genetic material, which may promote or oppose adaptation and speciation. In some cases, interspecific hybridisation is very common, making it surprising that species identity is preserved despite active gene exchange. The genomes of most eukaryotic species are highly heterogeneous with regard to gene density, abundance of repetitive DNA, chromatin compactisation etc, which can make certain genomic regions more prone or more resistant to introgression of genetic material from other species. Heterogeneity in local recombination rate underpins many of the observed patterns across the genome (e.g. actively recombining regions are typically gene rich and depleted for repetitive DNA) and it can strongly affect the permeability of genomic regions to interspecific introgression. The larger the region lacking recombination, the higher the chance for the presence of species incompatibility gene(s) in that region, making the entire non- or rarely recombining block impermeable to interspecific introgression. Large plant genomes tend to have highly heterogeneous recombination landscape, with recombination frequently occurring at the ends of the chromosomes and central regions lacking recombination. In this paper we review the relationship between recombination and introgression in plants and argue that large rarely recombining regions likely play a major role in preserving species identity in actively hybridising plant species.
Collapse
Affiliation(s)
- Edgar L. Y. Wong
- Department of Biology, University of Oxford, Oxford, United Kingdom
- Senckenberg Biodiversity and Climate Research Centre, Frankfurt am Main, Germany
| | | |
Collapse
|
3
|
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: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [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
|
4
|
Roesti M, Gilbert KJ, Samuk K. Chromosomal inversions can limit adaptation to new environments. Mol Ecol 2022; 31:4435-4439. [PMID: 35810344 DOI: 10.1111/mec.16609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Revised: 07/04/2022] [Accepted: 07/05/2022] [Indexed: 11/29/2022]
Abstract
Chromosomal inversions are often thought to facilitate local adaptation and population divergence because they can link multiple adaptive alleles into non-recombining genomic blocks. Selection should thus be more efficient in driving inversion-linked adaptive alleles to high frequency in a population, particularly in the face of maladaptive gene flow. But what if ecological conditions and hence selection on inversion-linked alleles change? Reduced recombination within inversions could then constrain the formation of optimal combinations of pre-existing alleles under these new ecological conditions. Here, we outline this idea of inversions limiting adaptation and divergence when ecological conditions change across time or space. We reason and use simulations to illustrate that the benefit of inversions for local adaptation and divergence under one set of ecological conditions can come with a concomitant constraint for adaptation to novel sets of ecological conditions. This limitation of inversions to adaptation may contribute to the maintenance of polymorphism within species.
Collapse
Affiliation(s)
- Marius Roesti
- Division of Evolutionary Ecology, Institute of Ecology and Evolution, University of Bern, Bern, Switzerland
| | | | - Kieran Samuk
- Department of Evolution, Ecology, and Organismal Biology, University of California, Riverside, California, USA
| |
Collapse
|
5
|
Mitchell N, Luu H, Owens GL, Rieseberg LH, Whitney KD. Hybrid evolution repeats itself across environmental contexts in Texas sunflowers (Helianthus). Evolution 2022; 76:1512-1528. [PMID: 35665925 PMCID: PMC9544064 DOI: 10.1111/evo.14536] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 05/05/2022] [Accepted: 05/09/2022] [Indexed: 01/22/2023]
Abstract
To what extent is evolution repeatable? Little is known about whether the evolution of hybrids is more (or less) repeatable than that of nonhybrids. We used field experimental evolution in annual sunflowers (Helianthus) in Texas to ask the extent to which hybrid evolution is repeatable across environments compared to nonhybrid controls. We created hybrids between Helianthus annuus (L.) and H. debilis (Nutt.) and grew plots of both hybrids and nonhybrid controls through eight generations at three sites in Texas. We collected seeds from each generation and grew each generation × treatment × home site combination at two final common gardens. We estimated the strength and direction of evolution in terms of fitness and 24 traits, tested for repeated versus nonrepeated evolution, and assessed overall phenotypic evolution across lineages and in relation to a locally adapted phenotype. Hybrids consistently evolved higher fitness over time, while controls did not, although trait evolution varied in strength across home sites. Repeated evolution was more evident in hybrids versus nonhybrid controls, and hybrid evolution was often in the direction of the locally adapted phenotype. Our findings have implications for both the nature of repeatability in evolution and the contribution of hybridization to evolution across environmental contexts.
Collapse
Affiliation(s)
- Nora Mitchell
- Department of BiologyUniversity of New MexicoAlbuquerqueNew MexicoUSA,Department of BiologyUniversity of Wisconsin – Eau ClaireEau ClaireWisconsinUSA
| | - Hoang Luu
- Department of Environmental and Plant BiologyOhio UniversityAthensOhioUSA
| | - Gregory L. Owens
- Department of BiologyUniversity of VictoriaVictoriaBritish ColumbiaCanada
| | - Loren H. Rieseberg
- Department of Botany and Biodiversity Research CentreUniversity of British ColumbiaBritish ColumbiaCanada
| | | |
Collapse
|
6
|
Todesco M, Bercovich N, Kim A, Imerovski I, Owens GL, Dorado Ruiz Ó, Holalu SV, Madilao LL, Jahani M, Légaré JS, Blackman BK, Rieseberg LH. Genetic basis and dual adaptive role of floral pigmentation in sunflowers. eLife 2022; 11:72072. [PMID: 35040432 PMCID: PMC8765750 DOI: 10.7554/elife.72072] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Accepted: 11/28/2021] [Indexed: 12/25/2022] Open
Abstract
Variation in floral displays, both between and within species, has been long known to be shaped by the mutualistic interactions that plants establish with their pollinators. However, increasing evidence suggests that abiotic selection pressures influence floral diversity as well. Here, we analyse the genetic and environmental factors that underlie patterns of floral pigmentation in wild sunflowers. While sunflower inflorescences appear invariably yellow to the human eye, they display extreme diversity for patterns of ultraviolet pigmentation, which are visible to most pollinators. We show that this diversity is largely controlled by cis-regulatory variation affecting a single MYB transcription factor, HaMYB111, through accumulation of ultraviolet (UV)-absorbing flavonol glycosides in ligules (the ‘petals’ of sunflower inflorescences). Different patterns of ultraviolet pigments in flowers are strongly correlated with pollinator preferences. Furthermore, variation for floral ultraviolet patterns is associated with environmental variables, especially relative humidity, across populations of wild sunflowers. Ligules with larger ultraviolet patterns, which are found in drier environments, show increased resistance to desiccation, suggesting a role in reducing water loss. The dual role of floral UV patterns in pollinator attraction and abiotic response reveals the complex adaptive balance underlying the evolution of floral traits. Flowers are an important part of how many plants reproduce. Their distinctive colours, shapes and patterns attract specific pollinators, but they can also help to protect the plant from predators and environmental stresses. Many flowers contain pigments that absorb ultraviolet (UV) light to display distinct UV patterns – although invisible to the human eye, most pollinators are able to see them. For example, when seen in UV, sunflowers feature a ‘bullseye’ with a dark centre surrounded by a reflective outer ring. The sizes and thicknesses of these rings vary a lot within and between flower species, and so far, it has been unclear what causes this variation and how it affects the plants. To find out more, Todesco et al. studied the UV patterns in various wild sunflowers across North America by considering the ecology and molecular biology of different plants. This revealed great variation between the UV patterns of the different sunflower populations. Moreover, Todesco et al. found that a gene called HaMYB111 is responsible for the diverse UV patterns in the sunflowers. This gene controls how plants make chemicals called flavonols that absorb UV light. Flavonols also help to protect plants from damage caused by droughts and extreme temperatures. Todesco et al. showed that plants with larger bullseyes had more flavonols, attracted more pollinators, and were better at conserving water. Accordingly, these plants were found in drier locations. This study suggests that, at least in sunflowers, UV patterns help both to attract pollinators and to control water loss. These insights could help to improve pollination – and consequently yield – in cultivated plants, and to develop plants with better resistance to extreme weather. This work also highlights the importance of combining biology on small and large scales to understand complex processes, such as adaptation and evolution.
Collapse
Affiliation(s)
- Marco Todesco
- Department of Botany and Biodiversity Research Centre, University of British Columbia
| | - Natalia Bercovich
- Department of Botany and Biodiversity Research Centre, University of British Columbia
| | - Amy Kim
- Department of Botany and Biodiversity Research Centre, University of British Columbia
| | - Ivana Imerovski
- Department of Botany and Biodiversity Research Centre, University of British Columbia
| | - Gregory L Owens
- Department of Botany and Biodiversity Research Centre, University of British Columbia
- Department of Biology, University of Victoria
| | - Óscar Dorado Ruiz
- Department of Botany and Biodiversity Research Centre, University of British Columbia
| | | | - Lufiani L Madilao
- Michael Smith Laboratory and Wine Research Centre, University of British Columbia
| | - Mojtaba Jahani
- Department of Botany and Biodiversity Research Centre, University of British Columbia
| | - Jean-Sébastien Légaré
- Department of Botany and Biodiversity Research Centre, University of British Columbia
| | | | - Loren H Rieseberg
- Department of Botany and Biodiversity Research Centre, University of British Columbia
| |
Collapse
|
7
|
Rieseberg L, Warschefsky E, O'Boyle B, Taberlet P, Ortiz-Barrientos D, Kane NC, Sibbett B. Editorial 2022. Mol Ecol 2021; 31:1-30. [PMID: 34957606 DOI: 10.1111/mec.16328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Accepted: 12/10/2021] [Indexed: 11/30/2022]
Affiliation(s)
- Loren Rieseberg
- Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada
| | | | | | - Pierre Taberlet
- Laboratoire d'Ecologie Alpine, CNRS UMR 5553, Université Univ. Grenoble Alpes, Grenoble Cedex 9, France
| | - Daniel Ortiz-Barrientos
- School of Biological Sciences, The University of Queenland, St. Lucia, Queensland, Australia
| | - Nolan C Kane
- University of Colorado at Boulder, Boulder, Colorado, USA
| | | |
Collapse
|
8
|
Taylor RS, Jensen EL, Coltman DW, Foote AD, Lamichhaney S. Seeing the whole picture: What molecular ecology is gaining from whole genomes. Mol Ecol 2021; 30:5917-5922. [PMID: 34845797 DOI: 10.1111/mec.16282] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 11/12/2021] [Accepted: 11/15/2021] [Indexed: 12/12/2022]
Affiliation(s)
- Rebecca S Taylor
- Biology Department, Trent University, Peterborough, Ontario, Canada
| | - Evelyn L Jensen
- School of Natural and Environmental Sciences, Newcastle University, Newcastle Upon Tyne, UK
| | - David W Coltman
- Department of Biological Sciences, University of Alberta, Edmonton, Canada.,Biology Department, Western University, London, Ontario, Canada
| | - Andrew D Foote
- Department of Natural History, NTNU University Museum, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
| | | |
Collapse
|