1
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Brown MR, Abbott RJ, Twyford AD. The emerging importance of cross-ploidy hybridisation and introgression. Mol Ecol 2024; 33:e17315. [PMID: 38501394 DOI: 10.1111/mec.17315] [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] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Revised: 02/21/2024] [Accepted: 02/23/2024] [Indexed: 03/20/2024]
Abstract
Natural hybridisation is now recognised as pervasive in its occurrence across the Tree of Life. Resurgent interest in natural hybridisation fuelled by developments in genomics has led to an improved understanding of the genetic factors that promote or prevent species cross-mating. Despite this body of work overturning many widely held assumptions about the genetic barriers to hybridisation, it is still widely thought that ploidy differences between species will be an absolute barrier to hybridisation and introgression. Here, we revisit this assumption, reviewing findings from surveys of polyploidy and hybridisation in the wild. In a case study in the British flora, 203 hybrids representing 35% of hybrids with suitable data have formed via cross-ploidy matings, while a wider literature search revealed 59 studies (56 in plants and 3 in animals) in which cross-ploidy hybridisation has been confirmed with genetic data. These results show cross-ploidy hybridisation is readily overlooked, and potentially common in some groups. General findings from these studies include strong directionality of hybridisation, with introgression usually towards the higher ploidy parent, and cross-ploidy hybridisation being more likely to involve allopolyploids than autopolyploids. Evidence for adaptive introgression across a ploidy barrier and cases of cross-ploidy hybrid speciation shows the potential for important evolutionary outcomes.
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Affiliation(s)
- Max R Brown
- Institute of Ecology and Evolution, University of Edinburgh, Edinburgh, UK
- School of Life Sciences, Anglia Ruskin University, Cambridge, UK
| | - Richard J Abbott
- School of Biology, University of St Andrews, St Andrews, Fife, UK
| | - Alex D Twyford
- Institute of Ecology and Evolution, University of Edinburgh, Edinburgh, UK
- Royal Botanical Garden Edinburgh, Edinburgh, UK
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2
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Fu PC, Twyford AD, Hao YT, Zhang Y, Chen SL, Sun SS. Hybridization and divergent climatic preferences drive divergence of two allopatric Gentiana species on the Qinghai-Tibet Plateau. Ann Bot 2023; 132:1271-1288. [PMID: 37963010 PMCID: PMC10902892 DOI: 10.1093/aob/mcad179] [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] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Revised: 10/19/2023] [Accepted: 11/13/2023] [Indexed: 11/16/2023]
Abstract
BACKGROUND AND AIMS Exploring how species diverge is vital for understanding the drivers of speciation. Factors such as geographical separation and ecological selection, hybridization, polyploidization and shifts in mating system are all major mechanisms of plant speciation, but their contributions to divergence are rarely well understood. Here we test these mechanisms in two plant species, Gentiana lhassica and G. hoae, with the goal of understanding recent allopatric species divergence on the Qinghai-Tibet Plateau (QTP). METHODS We performed Bayesian clustering, phylogenetic analysis and estimates of hybridization using 561 302 nuclear genomic single nucleotide polymorphisms (SNPs). We performed redundancy analysis, and identified and annotated species-specific SNPs (ssSNPs) to explore the association between climatic preference and genetic divergence. We also estimated genome sizes using flow cytometry to test for overlooked polyploidy. KEY RESULTS Genomic evidence confirms that G. lhassica and G. hoae are closely related but distinct species, while genome size estimates show divergence occurred without polyploidy. Gentiana hoae has significantly higher average FIS values than G. lhassica. Population clustering based on genomic SNPs shows no signature of recent hybridization, but each species is characterized by a distinct history of hybridization with congeners that has shaped genome-wide variation. Gentiana lhassica has captured the chloroplast and experienced introgression with a divergent gentian species, while G. hoae has experienced recurrent hybridization with related taxa. Species distribution modelling suggested range overlap in the Last Interglacial Period, while redundancy analysis showed that precipitation and temperature are the major climatic differences explaining the separation of the species. The species differ by 2993 ssSNPs, with genome annotation showing missense variants in genes involved in stress resistance. CONCLUSIONS This study suggests that the distinctiveness of these species on the QTP is driven by a combination of hybridization, geographical isolation, mating system differences and evolution of divergent climatic preferences.
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Affiliation(s)
- Peng-Cheng Fu
- School of Life Science, Luoyang Normal University, 6 Jiqing Road, Luoyang 471934, P. R. China
| | - Alex D Twyford
- Institute of Ecology and Evolution, The University of Edinburgh, Edinburgh, EH9 3FL, UK
- Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh, EH3 5LR, UK
| | - Yu-Tong Hao
- School of Life Science, Luoyang Normal University, 6 Jiqing Road, Luoyang 471934, P. R. China
| | - Yue Zhang
- School of Life Science, Luoyang Normal University, 6 Jiqing Road, Luoyang 471934, P. R. China
| | - Shi-Long Chen
- Key Laboratory of Adaptation and Evolution of Plateau Biota, Northwest Institute of Plateau Biology, Chinese Academy of Sciences, 810001 Xining, P. R. China
| | - Shan-Shan Sun
- School of Life Science, Luoyang Normal University, 6 Jiqing Road, Luoyang 471934, P. R. China
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3
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Boyle JH, Strickler S, Twyford AD, Ricono A, Powell A, Zhang J, Xu H, Smith R, Dalgleish HJ, Jander G, Agrawal AA, Puzey JR. Temporal matches between monarch butterfly and milkweed population changes over the past 25,000 years. Curr Biol 2023; 33:3702-3710.e5. [PMID: 37607548 DOI: 10.1016/j.cub.2023.07.057] [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] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Revised: 04/13/2023] [Accepted: 07/26/2023] [Indexed: 08/24/2023]
Abstract
In intimate ecological interactions, the interdependency of species may result in correlated demographic histories. For species of conservation concern, understanding the long-term dynamics of such interactions may shed light on the drivers of population decline. Here, we address the demographic history of the monarch butterfly, Danaus plexippus, and its dominant host plant, the common milkweed Asclepias syriaca (A. syriaca), using broad-scale sampling and genomic inference. Because genetic resources for milkweed have lagged behind those for monarchs, we first release a chromosome-level genome assembly and annotation for common milkweed. Next, we show that despite its enormous geographic range across eastern North America, A. syriaca is best characterized as a single, roughly panmictic population. Using approximate Bayesian computation with random forests (ABC-RF), a machine learning method for reconstructing demographic histories, we show that both monarchs and milkweed experienced population expansion during the most recent recession of North American glaciers 10,000-20,000 years ago. Our data also identify concurrent population expansions in both species during the large-scale clearing of eastern forests (∼200 years ago). Finally, we find no evidence that either species experienced a reduction in effective population size over the past 75 years. Thus, the well-documented decline of monarch abundance over the past 40 years is not visible in our genomic dataset, reflecting a possible mismatch of the overwintering census population to effective population size in this species.
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Affiliation(s)
- John H Boyle
- Biology Department, College of William & Mary, 540 Landrum Dr., Williamsburg, VA 23185, USA; Biology Department, University of Mary, 7500 University Dr., Bismarck, ND 58504, USA
| | - Susan Strickler
- Boyce Thompson Institute, 533 Tower Rd., Ithaca, NY 14853, USA; Chicago Botanic Garden, Plant Science and Conservation, 1000 Lake Cook Rd., Glencoe, IL 60022, USA; Northwestern University, Plant Biology and Conservation Program, 2145 Sheridan Rd., Evanston, IL 60208, USA
| | - Alex D Twyford
- Institute of Ecology and Evolution, University of Edinburgh, Charlotte Auerbach Rd., Edinburgh EH9 3FL, UK; Royal Botanic Garden Edinburgh, Edinburgh EH3 5NZ, UK
| | - Angela Ricono
- Biology Department, College of William & Mary, 540 Landrum Dr., Williamsburg, VA 23185, USA
| | - Adrian Powell
- Boyce Thompson Institute, 533 Tower Rd., Ithaca, NY 14853, USA
| | - Jing Zhang
- Boyce Thompson Institute, 533 Tower Rd., Ithaca, NY 14853, USA
| | - Hongxing Xu
- Boyce Thompson Institute, 533 Tower Rd., Ithaca, NY 14853, USA; College of Life Sciences, Shaanxi Normal University, South Chang'an Rd., Xi'an 710062, China
| | - Ronald Smith
- Data Science Program, College of William & Mary, 540 Landrum Dr., Williamsburg, VA 23185, USA
| | - Harmony J Dalgleish
- Biology Department, College of William & Mary, 540 Landrum Dr., Williamsburg, VA 23185, USA
| | - Georg Jander
- Boyce Thompson Institute, 533 Tower Rd., Ithaca, NY 14853, USA
| | - Anurag A Agrawal
- Department of Ecology and Evolutionary Biology, Cornell University, Corson Hall, Ithaca, NY 14853, USA
| | - Joshua R Puzey
- Biology Department, College of William & Mary, 540 Landrum Dr., Williamsburg, VA 23185, USA.
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4
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Christenhusz MJM, Bell D, Twyford AD. The genome sequence of common ivy, Hedera helix L., 1753. Wellcome Open Res 2023; 8:325. [PMID: 38046190 PMCID: PMC10690035 DOI: 10.12688/wellcomeopenres.19662.1] [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] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/03/2023] [Indexed: 12/05/2023] Open
Abstract
We present a genome assembly from a specimen of Hedera helix (common ivy; Streptophyta; Magnoliopsida; Apiales; Araliaceae). The genome sequence is 1,199.4 megabases in span. Most of the assembly is scaffolded into 24 chromosomal pseudomolecules. The mitochondrial and plastid genomes have also been assembled and are 609.2 and 162.2 kilobases in length respectively.
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Affiliation(s)
| | - David Bell
- Royal Botanic Garden Edinburgh, Edinburgh, Scotland, UK
| | - Alex D. Twyford
- Royal Botanic Garden Edinburgh, Edinburgh, Scotland, UK
- The University of Edinburgh, Edinburgh, Scotland, UK
| | | | | | - Plant Genome Sizing collective
- Royal Botanic Gardens Kew, Richmond, England, UK
- Royal Botanic Garden Edinburgh, Edinburgh, Scotland, UK
- The University of Edinburgh, Edinburgh, Scotland, UK
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5
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Brown MR, Hollingsworth PM, Forrest LL, Hart ML, Leitch IJ, Jones L, Ford C, de Vere N, Twyford AD. Genetic factors predict hybrid formation in the British flora. Proc Natl Acad Sci U S A 2023; 120:e2220261120. [PMID: 37040419 PMCID: PMC10120012 DOI: 10.1073/pnas.2220261120] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/12/2023] Open
Abstract
Natural hybridization can have a profound evolutionary impact, with consequences ranging from the extinction of rare taxa to the origin of new species. Natural hybridization is particularly common in plants; however, our understanding of the general factors that promote or prevent hybridization is hampered by the highly variable outcomes in different lineages. Here, we quantify the influence of different predictors on hybrid formation across species from an entire flora. We combine estimates of hybridization with ecological attributes and a new species-level phylogeny for over 1,100 UK flowering plant species. Our results show that genetic factors, particularly parental genetic distance, as well as phylogenetic position and ploidy, are key determinants of hybrid formation, whereas many other factors such as range overlap and genus size explain much less variation in hybrid formation. Overall, intrinsic genetic factors shape the evolutionary and ecological consequences of natural hybridization across species in a flora.
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Affiliation(s)
- Max R Brown
- Institute of Ecology and Evolution, University of Edinburgh, Edinburgh EH9 3FL, United Kingdom
- Tree of Life, Wellcome Trust Genome Campus, Hinxton CB10 1RQ, United Kingdom
| | | | - Laura L Forrest
- Royal Botanical Garden Edinburgh, Edinburgh EH3 5LR, United Kingdom
| | - Michelle L Hart
- Royal Botanical Garden Edinburgh, Edinburgh EH3 5LR, United Kingdom
| | - Ilia J Leitch
- Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AB, United Kingdom
| | - Laura Jones
- Conservation and Research Department, National Botanic Garden of Wales, Llanarthne, Carmarthenshire SA32 8HG, United Kingdom
| | - Col Ford
- Spirent Communications, Positioning Technology, Crawley, West Sussex RH10 1BD, United Kingdom
| | - Natasha de Vere
- Natural History Museum of Denmark, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Alex D Twyford
- Institute of Ecology and Evolution, University of Edinburgh, Edinburgh EH9 3FL, United Kingdom
- Royal Botanical Garden Edinburgh, Edinburgh EH3 5LR, United Kingdom
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6
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Christenhusz MJ, Twyford AD, Hudson A. The genome sequence of thale cress, Arabidopsis thaliana (Heynh., 1842). Wellcome Open Res 2023. [DOI: 10.12688/wellcomeopenres.18665.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
We present a genome assembly of an Arabidopsis thaliana specimen (thale cress; Streptophyta; Magnoliopsida; Brassicales; Brassicaceae). The genome sequence spans 138 megabases. Most of the assembly (98.76%) is scaffolded into five chromosomal pseudomolecules. The mitochondrial and plastid genomes were also assembled and are 368.8 and 154.5 kilobases in length respectively.
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7
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Brown MR, Becher H, Williams S, Twyford AD. Is there hybridization between diploid and tetraploid Euphrasia in a secondary contact zone? Am J Bot 2023; 110:e16100. [PMID: 36371731 PMCID: PMC10107515 DOI: 10.1002/ajb2.16100] [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] [Figures] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Revised: 10/21/2022] [Accepted: 10/21/2022] [Indexed: 06/16/2023]
Abstract
PREMISE Strong postzygotic reproductive isolating barriers are usually expected to limit the extent of natural hybridization between species with contrasting ploidy. However, genomic sequencing has revealed previously overlooked examples of natural cross-ploidy hybridization in some flowering plant genera, suggesting that the phenomenon may be more common than once thought. We investigated potential cross-ploidy hybridization in British eyebrights (Euphrasia, Orobanchaceae), a group from which 13 putative cross-ploidy hybrid combinations have been reported based on morphology. METHODS We analyzed a contact zone between diploid Euphrasia rostkoviana and tetraploid E. arctica in Wales. We sequenced part of the internal transcribed spacer (ITS) of nuclear ribosomal DNA and used genotyping by sequencing (GBS) to look for evidence of cross-ploidy hybridization and introgression. RESULTS Common variant sites in the ITS region were fixed between diploids and tetraploids, indicating a strong barrier to hybridization. Clustering analyses of 356 single-nucleotide polymorphisms (SNPs) generated using GBS clearly separated samples by ploidy and revealed strong genetic structure (FST = 0.44). However, the FST distribution across all SNPs was bimodal, indicating potential differential selection on loci between diploids and tetraploids. Demographic inference suggested potential gene flow, limited to around one or fewer migrants per generation. CONCLUSIONS Our results suggest that recent cross-ploidy hybridization is rare or absent in a site of secondary contact in Euphrasia. While a strong ploidy barrier prevents hybridization over ecological timescales, such hybrids may form in stable populations over evolutionary timescales, potentially allowing cross-ploidy introgression to take place.
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Affiliation(s)
- Max R. Brown
- Institute of Ecology and EvolutionUniversity of Edinburgh, Ashworth Laboratories, Charlotte Auerbach RoadEdinburghEH9 3FLUK
- Wellcome Sanger InstituteWellcome Genome Campus, HinxtonCambridgeCB10 1SAUK
| | - Hannes Becher
- Institute of Ecology and EvolutionUniversity of Edinburgh, Ashworth Laboratories, Charlotte Auerbach RoadEdinburghEH9 3FLUK
| | - Sebastian Williams
- Institute of Ecology and EvolutionUniversity of Edinburgh, Ashworth Laboratories, Charlotte Auerbach RoadEdinburghEH9 3FLUK
| | - Alex D. Twyford
- Institute of Ecology and EvolutionUniversity of Edinburgh, Ashworth Laboratories, Charlotte Auerbach RoadEdinburghEH9 3FLUK
- Royal Botanic Garden Edinburgh, 20a Inverleith RowEdinburghEH3 5LRUK
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8
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Fu PC, Sun SS, Hollingsworth PM, Chen SL, Favre A, Twyford AD. Population genomics reveal deep divergence and strong geographical structure in gentians in the Hengduan Mountains. Front Plant Sci 2022; 13:936761. [PMID: 36092450 PMCID: PMC9453878 DOI: 10.3389/fpls.2022.936761] [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: 05/05/2022] [Accepted: 07/28/2022] [Indexed: 06/15/2023]
Abstract
Understanding the evolutionary and ecological processes driving population differentiation and speciation can provide critical insights into the formation of biodiversity. Here, we examine the link between population genetic processes and biogeographic history underlying the generation of diversity in the Hengduan Mountains (HM), a region harboring a rich and dynamic flora. We used restriction site-associated DNA sequencing to generate 1,907 single-nucleotide polymorphisms (SNPs) and four-kb of plastid sequence in species of the Gentiana hexaphylla complex (Gentianaceae). We performed genetic clustering with spatial and non-spatial models, phylogenetic reconstructions, and ancestral range estimation, with the aim of addressing the processes influencing diversification of G. hexaphylla in the HM. We find the G. hexaphylla complex is characterized by geographic genetic structure with clusters corresponding to the South, North and the central HM. Phylogenetic reconstruction and pairwise F ST analyses showed deep differentiation between Southern and Northern populations in the HM. The population in Mount Taibai exhibited the highest genetic similarity to the North HM. Ancestral range estimation indicated that the G. hexaphylla complex originated in the central HM and then diverged in the Pliocene and the Early Pleistocene, before dispersing widely, resulting in the current distinct lineages. Overall, we found deep genomic differentiation in the G. hexaphylla complex corresponds to geographic barriers to dispersal in the HM and highlights a critical role of the uplift of the Daxue Mountains and subsequent climatic fluctuations underlying diversification. The colonization of G. hexaphylla in the Mount Taibai region suggests directional dispersal between the alpine flora of the Qinling Mountains and the HM.
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Affiliation(s)
- Peng-Cheng Fu
- School of Life Science, Luoyang Normal University, Luoyang, China
| | - Shan-Shan Sun
- School of Life Science, Luoyang Normal University, Luoyang, China
| | | | - Shi-Long Chen
- Key Laboratory of Adaptation and Evolution of Plateau Biota, Northwest Institute of Plateau Biology, Chinese Academy of Sciences, Xining, China
| | - Adrien Favre
- Senckenberg Research Institute and Natural History Museum, Frankfurt, Germany
| | - Alex D. Twyford
- Royal Botanic Garden Edinburgh, Edinburgh, United Kingdom
- Ashworth Laboratories, Institute of Evolutionary Biology, The University of Edinburgh, Edinburgh, United Kingdom
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9
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Becher H, Sampson J, Twyford AD. Measuring the Invisible: The Sequences Causal of Genome Size Differences in Eyebrights ( Euphrasia) Revealed by k-mers. Front Plant Sci 2022; 13:818410. [PMID: 35968114 PMCID: PMC9372453 DOI: 10.3389/fpls.2022.818410] [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] [Figures] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Accepted: 06/20/2022] [Indexed: 06/15/2023]
Abstract
Genome size variation within plant taxa is due to presence/absence variation, which may affect low-copy sequences or genomic repeats of various frequency classes. However, identifying the sequences underpinning genome size variation is challenging because genome assemblies commonly contain collapsed representations of repetitive sequences and because genome skimming studies by design miss low-copy number sequences. Here, we take a novel approach based on k-mers, short sub-sequences of equal length k, generated from whole-genome sequencing data of diploid eyebrights (Euphrasia), a group of plants that have considerable genome size variation within a ploidy level. We compare k-mer inventories within and between closely related species, and quantify the contribution of different copy number classes to genome size differences. We further match high-copy number k-mers to specific repeat types as retrieved from the RepeatExplorer2 pipeline. We find genome size differences of up to 230Mbp, equivalent to more than 20% genome size variation. The largest contributions to these differences come from rDNA sequences, a 145-nt genomic satellite and a repeat associated with an Angela transposable element. We also find size differences in the low-copy number class (copy number ≤ 10×) of up to 27 Mbp, possibly indicating differences in gene space between our samples. We demonstrate that it is possible to pinpoint the sequences causing genome size variation within species without the use of a reference genome. Such sequences can serve as targets for future cytogenetic studies. We also show that studies of genome size variation should go beyond repeats if they aim to characterise the full range of genomic variants. To allow future work with other taxonomic groups, we share our k-mer analysis pipeline, which is straightforward to run, relying largely on standard GNU command line tools.
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Affiliation(s)
- Hannes Becher
- School of Biological Sciences, Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, United Kingdom
| | - Jacob Sampson
- School of Biological Sciences, Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, United Kingdom
| | - Alex D. Twyford
- School of Biological Sciences, Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, United Kingdom
- Royal Botanic Garden Edinburgh, Edinburgh, United Kingdom
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10
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Garrett P, Becher H, Gussarova G, dePamphilis CW, Ness RW, Gopalakrishnan S, Twyford AD. Pervasive Phylogenomic Incongruence Underlies Evolutionary Relationships in Eyebrights ( Euphrasia, Orobanchaceae). Front Plant Sci 2022; 13:869583. [PMID: 35720561 PMCID: PMC9197813 DOI: 10.3389/fpls.2022.869583] [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: 02/04/2022] [Accepted: 04/19/2022] [Indexed: 06/15/2023]
Abstract
Disentangling the phylogenetic relationships of taxonomically complex plant groups is often mired by challenges associated with recent speciation, hybridization, complex mating systems, and polyploidy. Here, we perform a phylogenomic analysis of eyebrights (Euphrasia), a group renowned for taxonomic complexity, with the aim of documenting the extent of phylogenetic discordance at both deep and at shallow phylogenetic scales. We generate whole-genome sequencing data and integrate this with prior genomic data to perform a comprehensive analysis of nuclear genomic, nuclear ribosomal (nrDNA), and complete plastid genomes from 57 individuals representing 36 Euphrasia species. The species tree analysis of 3,454 conserved nuclear scaffolds (46 Mb) reveals that at shallow phylogenetic scales postglacial colonization of North Western Europe occurred in multiple waves from discrete source populations, with most species not being monophyletic, and instead combining genomic variants from across clades. At a deeper phylogenetic scale, the Euphrasia phylogeny is structured by geography and ploidy, and partially by taxonomy. Comparative analyses show Southern Hemisphere tetraploids include a distinct subgenome indicative of independent polyploidy events from Northern Hemisphere taxa. In contrast to the nuclear genome analyses, the plastid genome phylogeny reveals limited geographic structure, while the nrDNA phylogeny is informative of some geographic and taxonomic affinities but more thorough phylogenetic inference is impeded by the retention of ancestral polymorphisms in the polyploids. Overall our results reveal extensive phylogenetic discordance at both deeper and shallower nodes, with broad-scale geographic structure of genomic variation but a lack of definitive taxonomic signal. This suggests that Euphrasia species either have polytopic origins or are maintained by narrow genomic regions in the face of extensive homogenizing gene flow. Moreover, these results suggest genome skimming will not be an effective extended barcode to identify species in groups such as Euphrasia, or many other postglacial species groups.
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Affiliation(s)
- Phen Garrett
- GLOBE Institute, University of Copenhagen, Copenhagen, Denmark
| | - Hannes Becher
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Galina Gussarova
- Natural History Museum, University of Oslo, Oslo, Norway
- Botany Department, Faculty of Biology and Soil Science, St Petersburg State University, St Petersburg, Russia
- Tromsø University Museum, University of Tromsø, Tromsø, Norway
| | - Claude W. dePamphilis
- Department of Biology and Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA, United States
| | - Rob W. Ness
- Department of Biology, University of Toronto Mississauga, Mississauga, ON, Canada
| | | | - Alex D. Twyford
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
- Royal Botanic Garden Edinburgh, Edinburgh, United Kingdom
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11
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Soza VL, Kriebel R, Ramage E, Hall BD, Twyford AD. The symmetry spectrum in a hybridising, tropical group of rhododendrons. New Phytol 2022; 234:1491-1506. [PMID: 35274743 PMCID: PMC9313591 DOI: 10.1111/nph.18083] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Accepted: 01/23/2022] [Indexed: 06/14/2023]
Abstract
Many diverse plant clades possess bilaterally symmetrical flowers and specialised pollination syndromes, suggesting that these traits may promote diversification. We examined the evolution of diverse floral morphologies in a species-rich tropical radiation of Rhododendron. We used restriction-site associated DNA sequencing on 114 taxa from Rhododendron sect. Schistanthe to reconstruct phylogenetic relationships and examine hybridisation. We then captured and quantified floral variation using geometric morphometric analyses, which we interpreted in a phylogenetic context. We uncovered phylogenetic conflict and uncertainty caused by introgression within and between clades. Morphometric analyses revealed flower symmetry to be a morphological continuum without clear transitions between radial and bilateral symmetry. Tropical Rhododendron species that began diversifying into New Guinea c. 6 million years ago expanded into novel floral morphological space. Our results showed that the evolution of tropical Rhododendron is characterised by recent speciation, recurrent hybridisation and the origin of floral novelty. Floral variation evolved via changes to multiple components of the corolla that are only recognised in geometric morphometrics with both front and side views of flowers.
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Affiliation(s)
- Valerie L. Soza
- Department of BiologyUniversity of WashingtonSeattleWA98115USA
| | - Ricardo Kriebel
- Department of BotanyUniversity of Wisconsin‐MadisonMadisonWI53706USA
| | | | | | - Alex D. Twyford
- Institute of Evolutionary BiologySchool of Biological SciencesUniversity of EdinburghCharlotte Auerbach RoadEdinburghEH9 3FLUK
- Royal Botanic Garden Edinburgh20A Inverleith RowEdinburghEH3 5LRUK
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12
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Nishii K, Hart M, Kelso N, Barber S, Chen Y, Thomson M, Trivedi U, Twyford AD, Möller M. The first genome for the Cape Primrose Streptocarpus rexii (Gesneriaceae), a model plant for studying meristem-driven shoot diversity. Plant Direct 2022; 6:e388. [PMID: 35388373 PMCID: PMC8977575 DOI: 10.1002/pld3.388] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Revised: 01/26/2022] [Accepted: 01/30/2022] [Indexed: 05/16/2023]
Abstract
Cape Primroses (Streptocarpus, Gesneriaceae) are an ideal study system for investigating the genetics underlying species diversity in angiosperms. Streptocarpus rexii has served as a model species for plant developmental research for over five decades due to its unusual extended meristem activity present in the leaves. In this study, we sequenced and assembled the complete nuclear, chloroplast, and mitochondrial genomes of S. rexii using Oxford Nanopore Technologies long read sequencing. Two flow cells of PromethION sequencing resulted in 32 billion reads and were sufficient to generate a draft assembly including the chloroplast, mitochondrial and nuclear genomes, spanning 776 Mbp. The final nuclear genome assembly contained 5,855 contigs, spanning 766 Mbp of the 929-Mbp haploid genome with an N50 of 3.7 Mbp and an L50 of 57 contigs. Over 70% of the draft genome was identified as repeats. A genome repeat library of Gesneriaceae was generated and used for genome annotation, with a total of 45,045 genes annotated in the S. rexii genome. Ks plots of the paranomes suggested a recent whole genome duplication event, shared between S. rexii and Primulina huaijiensis. A new chloroplast and mitochondrial genome assembly method, based on contig coverage and identification, was developed, and successfully used to assemble both organellar genomes of S. rexii. This method was developed into a pipeline and proved widely applicable. The nuclear genome of S. rexii and other datasets generated and reported here will be invaluable resources for further research to aid in the identification of genes involved in morphological variation underpinning plant diversification.
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Affiliation(s)
- Kanae Nishii
- Royal Botanic Garden EdinburghEdinburghUK
- Kanagawa UniversityHiratsukaJapan
| | | | | | | | - Yun‐Yu Chen
- Royal Botanic Garden EdinburghEdinburghUK
- Institute of Molecular Plant SciencesThe University of EdinburghEdinburghUK
| | - Marian Thomson
- Edinburgh Genomics, Ashworth LaboratoriesThe University of EdinburghEdinburghUK
| | - Urmi Trivedi
- Edinburgh Genomics, Ashworth LaboratoriesThe University of EdinburghEdinburghUK
| | - Alex D. Twyford
- Royal Botanic Garden EdinburghEdinburghUK
- Institute of Evolutionary Biology, Ashworth LaboratoriesThe University of EdinburghEdinburghUK
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13
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Durán-Castillo M, Hudson A, Wilson Y, Field DL, Twyford AD. A phylogeny of Antirrhinum reveals parallel evolution of alpine morphology. New Phytol 2022; 233:1426-1439. [PMID: 34170548 DOI: 10.1111/nph.17581] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Accepted: 06/20/2021] [Indexed: 06/13/2023]
Abstract
Parallel evolution of similar morphologies in closely related lineages provides insight into the repeatability and predictability of evolution. In the genus Antirrhinum (snapdragons), as in other plants, a suite of morphological characters are associated with adaptation to alpine environments. We tested for parallel trait evolution in Antirrhinum by investigating phylogenetic relationships using restriction-site associated DNA (RAD) sequencing. We then associated phenotypic information to our phylogeny to reconstruct the patterns of morphological evolution and related this to evidence for hybridisation between emergent lineages. Phylogenetic analyses showed that the alpine character syndrome is present in multiple groups, suggesting that Antirrhinum has repeatedly colonised alpine habitats. Dispersal to novel environments happened in the presence of intraspecific and interspecific gene flow. We found support for a model of parallel evolution in Antirrhinum. Hybridisation in natural populations, and a complex genetic architecture underlying the alpine morphology syndrome, support an important role of natural selection in maintaining species divergence in the face of gene flow.
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Affiliation(s)
- Mario Durán-Castillo
- Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, EH9 3FL, UK
| | - Andrew Hudson
- Institute of Molecular Plant Sciences, University of Edinburgh, Edinburgh, EH9 3BF, UK
| | - Yvette Wilson
- Institute of Molecular Plant Sciences, University of Edinburgh, Edinburgh, EH9 3BF, UK
| | - David L Field
- School of Science, Edith Cowan University, 270 Joondalup Drive, Joondalup, 6027, Australia
| | - Alex D Twyford
- Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, EH9 3FL, UK
- Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh, EH3 5LR, UK
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14
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Henniges MC, Powell RF, Mian S, Stace CA, Walker KJ, Gornall RJ, Christenhusz MJM, Brown MR, Twyford AD, Hollingsworth PM, Jones L, de Vere N, Antonelli A, Leitch AR, Leitch IJ. A taxonomic, genetic and ecological data resource for the vascular plants of Britain and Ireland. Sci Data 2022; 9:1. [PMID: 35013360 PMCID: PMC8748506 DOI: 10.1038/s41597-021-01104-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Accepted: 11/12/2021] [Indexed: 11/15/2022] Open
Abstract
The vascular flora of Britain and Ireland is among the most extensively studied in the world, but the current knowledge base is fragmentary, with taxonomic, ecological and genetic information scattered across different resources. Here we present the first comprehensive data repository of native and alien species optimized for fast and easy online access for ecological, evolutionary and conservation analyses. The inventory is based on the most recent reference flora of Britain and Ireland, with taxon names linked to unique Kew taxon identifiers and DNA barcode data. Our data resource for 3,227 species and 26 traits includes existing and unpublished genome sizes, chromosome numbers and life strategy and life-form assessments, along with existing data on functional traits, species distribution metrics, hybrid propensity, associated biomes, realized niche description, native status and geographic origin of alien species. This resource will facilitate both fundamental and applied research and enhance our understanding of the flora's composition and temporal changes to inform conservation efforts in the face of ongoing climate change and biodiversity loss.
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Affiliation(s)
- Marie C Henniges
- Royal Botanic Gardens, Kew, Richmond, TW9 3AE, UK.
- School of Biological and Behavioural Sciences, Queen Mary University of London, London, E1 4NS, UK.
| | | | - Sahr Mian
- Royal Botanic Gardens, Kew, Richmond, TW9 3AE, UK
| | - Clive A Stace
- Appletree House, Larters Lane, Middlewood Green, Suffolk, IP14 5HB, UK
| | - Kevin J Walker
- Botanical Society of Britain and Ireland, Harrogate, HG1 1SS, UK
| | | | | | - Max R Brown
- University of Edinburgh, Edinburgh, EH8 9YL, UK
| | - Alex D Twyford
- University of Edinburgh, Edinburgh, EH8 9YL, UK
- Royal Botanic Garden Edinburgh, Edinburgh, EH3 5NZ, UK
| | | | - Laura Jones
- National Botanic Garden of Wales, Llanarthne, SA32 8HN, UK
| | - Natasha de Vere
- Natural History Museum of Denmark, University of Copenhagen, DK-2100, Copenhagen, Denmark
| | - Alexandre Antonelli
- Royal Botanic Gardens, Kew, Richmond, TW9 3AE, UK
- Gothenburg Global Biodiversity Centre, Department of Biological and Environmental Sciences, University of Gothenburg, 405 30, Gothenburg, Sweden
- Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB, UK
| | - Andrew R Leitch
- School of Biological and Behavioural Sciences, Queen Mary University of London, London, E1 4NS, UK.
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15
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Brown MR, Moore PGP, Twyford AD. Performance of generalist hemiparasitic Euphrasia across a phylogenetically diverse host spectrum. New Phytol 2021; 232:2165-2174. [PMID: 34555197 DOI: 10.1111/nph.17752] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Accepted: 09/11/2021] [Indexed: 05/14/2023]
Abstract
Generalist hemiparasites may attach to many different host species and experience complex parasite-host interactions. How these parasite-host interactions impact on the fitness of hemiparasitic plants remain largely unknown. We used experimentally tractable eyebrights (Euphrasia, Orobanchaceae) to understand parasite-host species interactions affecting the performance of a generalist hemiparasitic plant. Common garden experiments were carried out measuring Euphrasia performance across 45 diverse hosts and in different parasite-host combinations. We show that variation in hemiparasite performance can be attributed mainly to host species and host phylogenetic relationships (λ = 0.82; 0.17-1.00 CI). When variation in performance is considered temporally, annual host species cause earlier flowering, and lead to poorer performance late in the season. While Euphrasia species typically perform similarly on a given host species, some eyebrights show more specialized parasite-host species interactions. Our results show that generalist hemiparasites only benefit from attaching to a limited, but phylogenetically divergent, subset of hosts. The conserved responses of divergent Euphrasia species suggest hemiparasite performance is affected by common host attributes. However, evidence for more complex parasite-host species interactions show that a generalist hemiparasite can potentially respond to individual host selection pressures and may adapt to local host communities.
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Affiliation(s)
- Max R Brown
- Institute of Evolutionary Biology, University of Edinburgh, Charlotte Auerbach Road, Edinburgh, EH9 3FL, UK
| | | | - Alex D Twyford
- Institute of Evolutionary Biology, University of Edinburgh, Charlotte Auerbach Road, Edinburgh, EH9 3FL, UK
- Royal Botanical Garden Edinburgh, 20A Inverleith Row, Edinburgh, EH3 5LR, UK
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16
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Becher H, Powell RF, Brown MR, Metherell C, Pellicer J, Leitch IJ, Twyford AD. The nature of intraspecific and interspecific genome size variation in taxonomically complex eyebrights. Ann Bot 2021; 128:639-651. [PMID: 34318876 PMCID: PMC8422891 DOI: 10.1093/aob/mcab102] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Accepted: 07/27/2021] [Indexed: 06/13/2023]
Abstract
BACKGROUND AND AIMS Genome size varies considerably across the diversity of plant life. Although genome size is, by definition, affected by genetic presence/absence variants, which are ubiquitous in population sequencing studies, genome size is often treated as an intrinsic property of a species. Here, we studied intra- and interspecific genome size variation in taxonomically complex British eyebrights (Euphrasia, Orobanchaceae). Our aim is to document genome size diversity and investigate underlying evolutionary processes shaping variation between individuals, populations and species. METHODS We generated genome size data for 192 individuals of diploid and tetraploid Euphrasia and analysed genome size variation in relation to ploidy, taxonomy, population affiliation and geography. We further compared the genomic repeat content of 30 samples. KEY RESULTS We found considerable intraspecific genome size variation, and observed isolation-by-distance for genome size in outcrossing diploids. Tetraploid Euphrasia showed contrasting patterns, with genome size increasing with latitude in outcrossing Euphrasia arctica, but with little genome size variation in the highly selfing Euphrasia micrantha. Interspecific differences in genome size and the genomic proportions of repeat sequences were small. CONCLUSIONS We show the utility of treating genome size as the outcome of polygenic variation. Like other types of genetic variation, such as single nucleotide polymorphisms, genome size variation may be affected by ongoing hybridization and the extent of population subdivision. In addition to selection on associated traits, genome size is predicted to be affected indirectly by selection due to pleiotropy of the underlying presence/absence variants.
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Affiliation(s)
- Hannes Becher
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
| | | | - Max R Brown
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
- Wellcome Trust Genome Campus, Hinxton, Saffron Walden, UK
| | - Chris Metherell
- Botanical Society of Britain and Ireland, Harpenden, Hertfordshire, UK
| | - Jaume Pellicer
- Royal Botanic Gardens, Kew, Richmond, Surrey, UK
- Institut Botànic de Barcelona (IBB, CSIC-Ajuntament de Barcelona), Barcelona, Spain
| | | | - Alex D Twyford
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
- Royal Botanic Garden Edinburgh, Edinburgh, UK
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17
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Ranavat S, Becher H, Newman MF, Gowda V, Twyford AD. A Draft Genome of the Ginger Species Alpinia nigra and New Insights into the Genetic Basis of Flexistyly. Genes (Basel) 2021; 12:1297. [PMID: 34573279 PMCID: PMC8468202 DOI: 10.3390/genes12091297] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 08/18/2021] [Accepted: 08/20/2021] [Indexed: 11/17/2022] Open
Abstract
Angiosperms possess various strategies to ensure reproductive success, such as stylar polymorphisms that encourage outcrossing. Here, we investigate the genetic basis of one such dimorphism that combines both temporal and spatial separation of sexual function, termed flexistyly. It is a floral strategy characterised by the presence of two morphs that differ in the timing of stylar movement. We performed a de novo assembly of the genome of Alpinia nigra using high-depth genomic sequencing. We then used Pool-seq to identify candidate regions for flexistyly based on allele frequency or coverage differences between pools of anaflexistylous and cataflexistylous morphs. The final genome assembly size was 2 Gb, and showed no evidence of recent polyploidy. The Pool-seq did not reveal large regions with high FST values, suggesting large structural chromosomal polymorphisms are unlikely to underlie differences between morphs. Similarly, no region had a 1:2 mapping depth ratio which would be indicative of hemizygosity. We propose that flexistyly is governed by a small genomic region that might be difficult to detect with Pool-seq, or a complex genomic region that proved difficult to assemble. Our genome will be a valuable resource for future studies of gingers, and provides the first steps towards characterising this complex floral phenotype.
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Affiliation(s)
- Surabhi Ranavat
- Institute of Evolutionary Biology, University of Edinburgh, Charlotte Auerbach Road, Edinburgh EH9 3FL, UK; (H.B.); (A.D.T.)
- Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh EH3 5LR, UK;
| | - Hannes Becher
- Institute of Evolutionary Biology, University of Edinburgh, Charlotte Auerbach Road, Edinburgh EH9 3FL, UK; (H.B.); (A.D.T.)
| | - Mark F. Newman
- Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh EH3 5LR, UK;
| | - Vinita Gowda
- Department of Biological Sciences, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Road, Bhauri, Bhopal 462 066, Madhya Pradesh, India;
| | - Alex D. Twyford
- Institute of Evolutionary Biology, University of Edinburgh, Charlotte Auerbach Road, Edinburgh EH9 3FL, UK; (H.B.); (A.D.T.)
- Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh EH3 5LR, UK;
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18
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Jones L, Twyford AD, Ford CR, Rich TCG, Davies H, Forrest LL, Hart ML, McHaffie H, Brown MR, Hollingsworth PM, de Vere N. Barcode UK: A complete DNA barcoding resource for the flowering plants and conifers of the United Kingdom. Mol Ecol Resour 2021; 21:2050-2062. [PMID: 33749162 DOI: 10.1111/1755-0998.13388] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 01/09/2021] [Accepted: 03/12/2021] [Indexed: 11/29/2022]
Abstract
DNA barcoding and metabarcoding provide new avenues for investigating biological systems. These techniques require well-curated reference libraries with extensive coverage. Generating an exhaustive national DNA barcode reference library can open up new avenues of research in ecology, evolution and conservation, yet few studies to date have created such a resource. In plant DNA barcoding, herbarium collections provide taxonomically robust material but also pose challenges in lab processing. Here, we present a national DNA barcoding resource covering all of the native flowering plants and conifers of the United Kingdom. This represents 1,482 plant species, with the majority of specimens (81%) sourced from herbaria. Using Sanger sequencing of the plant DNA barcode markers, rbcL, matK, and ITS2, at least one DNA barcode was retrieved from 98% of the UK flora. We sampled from multiple individuals, resulting in a species coverage for rbcL of 96% (4,477 sequences), 90% for matK (3,259 sequences) and 75% for ITS2 (2,585 sequences). Sequence recovery was lower for herbarium material compared to fresh collections, with the age of the specimen having a significant effect on the success of sequence recovery. Species level discrimination was highest with ITS2, however, the ability to successfully retrieve a sequence was lowest for this region. Analyses of the genetic distinctiveness of species across a complete flora showed DNA barcoding to be informative for all but the most taxonomically complex groups. The UK flora DNA barcode reference library provides an important resource for many applications that require plant identification from DNA.
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Affiliation(s)
- Laura Jones
- National Botanic Garden of Wales, Llanarthne, UK
| | - Alex D Twyford
- Royal Botanic Garden Edinburgh, Edinburgh, UK.,School of Biological Sciences, Institute of Evolutionary Biology, Edinburgh, UK
| | - Col R Ford
- National Botanic Garden of Wales, Llanarthne, UK
| | | | | | | | | | | | - Max R Brown
- School of Biological Sciences, Institute of Evolutionary Biology, Edinburgh, UK
| | | | - Natasha de Vere
- National Botanic Garden of Wales, Llanarthne, UK.,Institute of Biological, Environmental and Rural Sciences, Aberystwyth University, Aberystwyth, UK
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19
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Fu P, Sun S, Twyford AD, Li B, Zhou R, Chen S, Gao Q, Favre A. Lineage-specific plastid degradation in subtribe Gentianinae (Gentianaceae). Ecol Evol 2021; 11:3286-3299. [PMID: 33841784 PMCID: PMC8019047 DOI: 10.1002/ece3.7281] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2020] [Revised: 12/24/2020] [Accepted: 01/04/2021] [Indexed: 01/03/2023] Open
Abstract
The structure and sequence of plastid genomes is highly conserved across most land plants, except for a minority of lineages that show gene loss and genome degradation. Understanding the early stages of plastome degradation may provide crucial insights into the repeatability and predictability of genomic evolutionary trends. We investigated these trends in subtribe Gentianinae of the Gentianaceae, which encompasses ca. 450 species distributed around the world, particularly in alpine and subalpine environments. We sequenced, assembled, and annotated the plastomes of 41 species, representing all six genera in subtribe Gentianinae and all main sections of the species-rich genus Gentiana L. We reconstructed the phylogeny, estimated divergence times, investigated the phylogenetic distribution of putative gene losses, and related these to substitution rate shifts and species' habitats. We obtained a strongly supported topology consistent with earlier studies, with all six genera in Gentianinae recovered as monophyletic and all main sections of Gentiana having full support. While closely related species have very similar plastomes in terms of size and structure, independent gene losses, particularly of the ndh complex, have occurred in multiple clades across the phylogeny. Gene loss was usually associated with a shift in the boundaries of the small single-copy and inverted repeat regions. Substitution rates were variable between clades, with evidence for both elevated and decelerated rate shifts. Independent lineage-specific loss of ndh genes occurred at a wide range of times, from Eocene to Pliocene. Our study illustrates that diverse degradation patterns shape the evolution of the plastid in this species-rich plant group.
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Affiliation(s)
- Peng‐Cheng Fu
- School of Life ScienceLuoyang Normal UniversityLuoyangChina
| | - Shan‐Shan Sun
- School of Life ScienceLuoyang Normal UniversityLuoyangChina
| | - Alex D. Twyford
- Ashworth LaboratoriesInstitute of Evolutionary BiologyThe University of EdinburghEdinburghUK
- Royal Botanic Garden EdinburghEdinburghUK
| | - Bei‐Bei Li
- School of Life ScienceLuoyang Normal UniversityLuoyangChina
| | - Rui‐Qi Zhou
- School of Life ScienceLuoyang Normal UniversityLuoyangChina
| | - Shi‐Long Chen
- Key Laboratory of Adaptation and Evolution of Plateau BiotaNorthwest Institute of Plateau BiologyChinese Academy of SciencesXiningChina
- Qinghai Provincial Key Laboratory of Crop Molecular BreedingXiningChina
| | - Qing‐Bo Gao
- Key Laboratory of Adaptation and Evolution of Plateau BiotaNorthwest Institute of Plateau BiologyChinese Academy of SciencesXiningChina
- Qinghai Provincial Key Laboratory of Crop Molecular BreedingXiningChina
| | - Adrien Favre
- Senckenberg Research Institute and Natural History MuseumFrankfurt am MainGermany
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20
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Joffard N, Silva WTAF, Twyford AD. Digest: The role of postzygotic isolation in Mimulus speciation. Evolution 2021; 75:756-758. [PMID: 33469918 DOI: 10.1111/evo.14175] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Accepted: 12/30/2020] [Indexed: 01/08/2023]
Abstract
Recently diverged species often show incomplete reproductive isolation and subsequently experience hybridization and introgression. The plant genus Mimulus includes many such examples of closely related taxa that prove useful for studying incipient speciation. However, Sandstedt et al. show that in contrast to other Mimulus species, species of the M. tilingii complex are characterized by strong postzygotic isolation mediated by multiple barriers. This finding highlights the diverse speciation histories of related plant groups.
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Affiliation(s)
- Nina Joffard
- Evolutionary Biology Centre, Department of Ecology and Genetics, Plant Ecology and Evolution Program, Uppsala University, Uppsala, Sweden
| | - Willian T A F Silva
- Centre for Environmental and Climate Research, Lund University, Lund, Sweden
| | - Alex D Twyford
- Ashworth Laboratories, Institute of Evolutionary Biology, The University of Edinburgh, Edinburgh, UK.,Royal Botanic Garden Edinburgh, Edinburgh, UK
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21
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Fu PC, Twyford AD, Sun SS, Wang HY, Xia MZ, Tan CX, Zhou XJ, Chen SL. Recurrent hybridization underlies the evolution of novelty in Gentiana (Gentianaceae) in the Qinghai-Tibetan Plateau. AoB Plants 2021; 13:plaa068. [PMID: 33510891 PMCID: PMC7821390 DOI: 10.1093/aobpla/plaa068] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2020] [Accepted: 11/30/2020] [Indexed: 05/31/2023]
Abstract
The Qinghai-Tibetan Plateau (QTP) and adjacent areas are centres of diversity for several alpine groups. Although it is known that the QTP acted as a source area for diversification of the alpine genus Gentiana, the evolutionary processes underlying diversity in this genus, especially the formation of narrow endemics, are still poorly understood. Hybridization has been proposed as a driver of plant endemism in the QTP but few cases have been documented with genetic data. Here, we describe a new endemic species in Gentiana section Cruciata as G. hoae sp. nov., and explore its evolutionary history with complete plastid genomes and nuclear ribosomal internal transcribed spacer sequence data. Genetic divergence within G. hoae ~3 million years ago was followed by postglacial expansion on the QTP, suggesting Pleistocene glaciations as a key factor shaping the population history of G. hoae. Furthermore, a mismatch between plastid and nuclear data suggest that G. hoae participated in historical hybridization, while population sequencing show this species continues to hybridize with the co-occurring congener G. straminea in three locations. Our results indicate that hybridization may be a common process in the evolution of Gentiana and may be widespread among recently diverged taxa of the QTP.
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Affiliation(s)
- Peng-Cheng Fu
- School of Life Science, Luoyang Normal University, Luoyang, P.R. China
| | - Alex D Twyford
- Ashworth Laboratories, Institute of Evolutionary Biology, The University of Edinburgh, Edinburgh, UK
- Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh, UK
| | - Shan-Shan Sun
- School of Life Science, Luoyang Normal University, Luoyang, P.R. China
| | - Hong-Yu Wang
- School of Life Science, Luoyang Normal University, Luoyang, P.R. China
| | - Ming-Ze Xia
- Key Laboratory of Adaptation and Evolution of Plateau Biota, Northwest Institute of Plateau Biology, Chinese Academy of Sciences, Xining, P.R. China
- University of Chinese Academy of Sciences, Beijing, P.R. China
| | - Cheng-Xi Tan
- School of Life Science, Luoyang Normal University, Luoyang, P.R. China
| | - Xiao-Jun Zhou
- School of Life Science, Luoyang Normal University, Luoyang, P.R. China
| | - Shi-Long Chen
- Key Laboratory of Adaptation and Evolution of Plateau Biota, Northwest Institute of Plateau Biology, Chinese Academy of Sciences, Xining, P.R. China
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22
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Becher H, Brown MR, Powell G, Metherell C, Riddiford NJ, Twyford AD. Maintenance of Species Differences in Closely Related Tetraploid Parasitic Euphrasia (Orobanchaceae) on an Isolated Island. Plant Commun 2020; 1:100105. [PMID: 33367265 PMCID: PMC7748025 DOI: 10.1016/j.xplc.2020.100105] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [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: 04/28/2020] [Revised: 07/24/2020] [Accepted: 08/27/2020] [Indexed: 05/02/2023]
Abstract
Polyploidy is pervasive in angiosperm evolution and plays important roles in adaptation and speciation. However, polyploid groups are understudied due to complex sequence homology, challenging genome assembly, and taxonomic complexity. Here, we study adaptive divergence in taxonomically complex eyebrights (Euphrasia), where recent divergence, phenotypic plasticity, and hybridization blur species boundaries. We focus on three closely related tetraploid species with contrasting ecological preferences that are sympatric on Fair Isle, a small isolated island in the British Isles. Using a common garden experiment, we show a genetic component to the morphological differences present between these species. Using whole-genome sequencing and a novel k-mer approach we call "Tetmer", we demonstrate that the species are of allopolyploid origin, with a sub-genome divergence of approximately 5%. Using ∼2 million SNPs, we show sub-genome homology across species, with a very low sequence divergence characteristic of recent speciation. This genetic variation is broadly structured by species, with clear divergence of Fair Isle heathland Euphrasia micrantha, while grassland Euphrasia arctica and coastal Euphrasia foulaensis are more closely related. Overall, we show that tetraploid Euphrasia is a system of allopolyploids of postglacial species divergence, where adaptation to novel environments may be conferred by old variants rearranged into new genetic lineages.
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Affiliation(s)
- Hannes Becher
- University of Edinburgh, School of Biological Sciences, Institute of Evolutionary Biology, Charlotte Auerbach Road, Edinburgh EH9 3FL, UK
- Corresponding author
| | - Max R. Brown
- University of Edinburgh, School of Biological Sciences, Institute of Evolutionary Biology, Charlotte Auerbach Road, Edinburgh EH9 3FL, UK
| | - Gavin Powell
- Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh EH3 5LR, UK
| | - Chris Metherell
- Botanical Society of Britain and Ireland, 4 High Firs Crescent, Harpenden, Hertfordshire AL5 1NA, UK
| | | | - Alex D. Twyford
- University of Edinburgh, School of Biological Sciences, Institute of Evolutionary Biology, Charlotte Auerbach Road, Edinburgh EH9 3FL, UK
- Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh EH3 5LR, UK
- Corresponding author
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Brown MR, Frachon N, Wong ELY, Metherell C, Twyford AD. Life history evolution, species differences, and phenotypic plasticity in hemiparasitic eyebrights (Euphrasia). Am J Bot 2020; 107:456-465. [PMID: 32133624 DOI: 10.1002/ajb2.1445] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Accepted: 12/04/2019] [Indexed: 05/14/2023]
Abstract
PREMISE Species delimitation in parasitic organisms is challenging because traits used to identify species are often plastic and vary depending on the host. Here, we use species from a recent radiation of generalist hemiparasitic Euphrasia to investigate trait variation and trait plasticity. We tested whether Euphrasia species show reliable trait differences, investigated whether these differences correspond to life history trade-offs between growth and reproduction, and quantified plasticity in response to host species. METHODS Common garden experiments were used to evaluate trait differences between 11 Euphrasia taxa grown on a common host, document phenotypic plasticity when a single Euphrasia species is grown on eight different hosts, and relate observations to trait differences recorded in the wild. RESULTS Euphrasia exhibited variation in life history strategies; some individuals transitioned rapidly to flowering at the expense of early season growth, while others invested in vegetative growth and delayed flowering. Life history differences were present between some species, though many related taxa lacked clear trait differences. Species differences were further blurred by phenotypic plasticity-many traits were plastic and changed with host type or between environments. CONCLUSIONS Phenotypic plasticity in response to host and environment confounds species delimitation in Euphrasia. When grown in a common garden environment, some morphologically distinct taxa can be identified, though others represent morphologically similar shallow segregates. Trait differences present between some species and populations demonstrate the rapid evolution of distinct life history strategies in response to local ecological conditions.
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Affiliation(s)
- Max R Brown
- University of Edinburgh, Institute of Evolutionary Biology, Charlotte Auerbach Road, Edinburgh, EH9 3FL, UK
| | - Natacha Frachon
- Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh, EH3 5LR, UK
| | - Edgar L Y Wong
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
| | - Chris Metherell
- Botanical Society of Britain and Ireland, 4 High Firs Crescent, Harpenden, Hertfordshire, AL5 1NA, UK
| | - Alex D Twyford
- University of Edinburgh, Institute of Evolutionary Biology, Charlotte Auerbach Road, Edinburgh, EH9 3FL, UK
- Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh, EH3 5LR, UK
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Abstract
In this quick guide, Twyford introduces the reader to parasitic plants, explaining how they steal nutrients from host plants and how this lifestyle has evolved multiple times in plants.
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Affiliation(s)
- Alex D Twyford
- Institute of Evolutionary Biology, The University of Edinburgh, Ashworth Laboratories, Charlotte Auerbach Road, Edinburgh, EH9 3FL, UK.
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Wang X, Gussarova G, Ruhsam M, de Vere N, Metherell C, Hollingsworth PM, Twyford AD. DNA barcoding a taxonomically complex hemiparasitic genus reveals deep divergence between ploidy levels but lack of species-level resolution. AoB Plants 2018; 10:ply026. [PMID: 29765588 PMCID: PMC5941139 DOI: 10.1093/aobpla/ply026] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Accepted: 04/20/2018] [Indexed: 05/18/2023]
Abstract
DNA barcoding is emerging as a useful tool not only for species identification but also for studying evolutionary and ecological processes. Although plant DNA barcodes do not always provide species-level resolution, the generation of large DNA barcode data sets can provide insights into the mechanisms underlying the generation of species diversity. Here, we study evolutionary processes in taxonomically complex British Euphrasia (Orobanchaceae), a group with multiple ploidy levels, frequent self-fertilization, young species divergence and widespread hybridization. We use a phylogenetic approach to investigate the colonization history of British Euphrasia, followed by a DNA barcoding survey and population genetic analyses to reveal the causes of shared sequence variation. Phylogenetic analysis shows Euphrasia have colonized Britain from mainland Europe on multiple occasions. DNA barcoding reveals that no British Euphrasia species has a consistent diagnostic sequence profile, and instead, plastid haplotypes are either widespread across species, or are population specific. The partitioning of nuclear genetic variation suggests differences in ploidy act as a barrier to gene exchange, while the divergence between diploid and tetraploid ITS sequences supports the polyploids being allotetraploid in origin. Overall, these results show that even when lacking species-level resolution, analyses of DNA barcoding data can reveal evolutionary patterns in taxonomically complex genera.
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Affiliation(s)
- Xumei Wang
- School of Pharmacy, Xi’an Jiaotong University, Xi’an, P.R. China
| | - Galina Gussarova
- Tromsø University Museum, UiT The Arctic University of Norway, Langnes, Tromsø, Norway
- CEES-Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, Blindern, Oslo, Norway
- Department of Botany, Faculty of Biology, St Petersburg State University, Universitetskaya nab., Russia
| | | | - Natasha de Vere
- National Botanic Garden of Wales, Llanarthne, Carmarthenshire, UK
- Institute of Biological, Environmental & Rural Sciences (IBERS), Aberystwyth University, Penglais, Aberystwyth, Ceredigion, UK
| | | | | | - Alex D Twyford
- University of Edinburgh, Institute of Evolutionary Biology, Edinburgh, UK
- Corresponding author’s e-mail address:
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26
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Affiliation(s)
- Alex D Twyford
- University of Edinburgh, Institute of Evolutionary Biology, Edinburgh, UK.
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Twyford AD, Caola AM, Choudhary P, Raina R, Friedman J. Loss of Color Pigmentation Is Maintained at High Frequency in a Monkey Flower Population. Am Nat 2018; 191:135-145. [DOI: 10.1086/694853] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Abstract
Parasitic plants demonstrate a diversity of growth strategies, life histories, and developmental and physiological characteristics. Most research to date has focused on a narrow range of parasitic taxa, particularly in the Orobanchaceae, while the other independent origins of parasitism have largely gone unstudied. One type of parasite that has received relatively little attention are the endophytic parasites, which have a fascinating growth strategy where the parasite is embedded within the host tissue, with the flower the only externally visibly plant part. Endophytic growth makes it challenging to understand basic aspects of species biology, such as the size of a given parasite, the number of parasites per host, and the genetic diversity of populations. Recent studies by Barkman et al. (2017) and Pelser et al. (2017) have used microsatellite genotyping to investigate the population biology of endoparasitic Rafflesiaceae species in Asia. They show the potential for extensive parasite spread within a host vine and the strong partitioning of genetic diversity by host. These species are also shown to have an outcrossing mating system. However, these studies suggest different reproductive strategies, one supporting monoecy and one suggesting dioecy. Overall, these studies partly "lift the lid" on the cryptic biology of Rafflesia and the Rafflesiaceae and open the door for future comparative studies between endophytic and free-living parasitic plants.
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Affiliation(s)
- Alex D Twyford
- Institute of Evolutionary Biology, The University of Edinburgh, Ashworth Laboratories, Charlotte Auerbach Road, Edinburgh, EH9 3FL, UK
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29
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Abstract
Plastid sequencing is an essential tool in the study of plant evolution. This high-copy organelle is one of the most technically accessible regions of the genome, and its sequence conservation makes it a valuable region for comparative genome evolution, phylogenetic analysis and population studies. Here, we discuss recent innovations and approaches for de novo plastid assembly that harness genomic tools. We focus on technical developments including low-cost sequence library preparation approaches for genome skimming, enrichment via hybrid baits and methylation-sensitive capture, sequence platforms with higher read outputs and longer read lengths, and automated tools for assembly. These developments allow for a much more streamlined assembly than via conventional short-range PCR. Although newer methods make complete plastid sequencing possible for any land plant or green alga, there are still challenges for producing finished plastomes particularly from herbarium material or from structurally divergent plastids such as those of parasitic plants.
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Affiliation(s)
- Alex D. Twyford
- Institute of Evolutionary BiologyAshworth LaboratoriesUniversity of EdinburghEdinburghEH9 3FLUK
| | - Rob W. Ness
- Department of BiologyUniversity of Toronto MississaugaMississaugaONCanada
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Dexter KG, Lavin M, Torke BM, Twyford AD, Kursar TA, Coley PD, Drake C, Hollands R, Pennington RT. Dispersal assembly of rain forest tree communities across the Amazon basin. Proc Natl Acad Sci U S A 2017; 114:2645-2650. [PMID: 28213498 PMCID: PMC5347625 DOI: 10.1073/pnas.1613655114] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We investigate patterns of historical assembly of tree communities across Amazonia using a newly developed phylogeny for the species-rich neotropical tree genus Inga We compare our results with those for three other ecologically important, diverse, and abundant Amazonian tree lineages, Swartzia, Protieae, and Guatteria Our analyses using phylogenetic diversity metrics demonstrate a clear lack of geographic phylogenetic structure, and show that local communities of Inga and regional communities of all four lineages are assembled by dispersal across Amazonia. The importance of dispersal in the biogeography of Inga and other tree genera in Amazonian and Guianan rain forests suggests that speciation is not driven by vicariance, and that allopatric isolation following dispersal may be involved in the speciation process. A clear implication of these results is that over evolutionary timescales, the metacommunity for any local or regional tree community in the Amazon is the entire Amazon basin.
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Affiliation(s)
- Kyle G Dexter
- School of GeoSciences, University of Edinburgh, Edinburgh EH9 3FF, United Kingdom;
- Royal Botanic Garden Edinburgh, Edinburgh EH3 5LR, United Kingdom
| | - Mathew Lavin
- Department of Plant Sciences and Plant Pathology, Montana State University, Bozeman, MT 59717
| | - Benjamin M Torke
- Institute of Systematic Botany, New York Botanical Garden, Bronx, NY 10458
| | - Alex D Twyford
- Institute of Evolutionary Biology, University of Edinburgh, Edinburgh EH9 3FL, United Kingdom
| | - Thomas A Kursar
- Biology Department, University of Utah, Salt Lake City, UT 84112
- Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancon, Panama
| | - Phyllis D Coley
- Biology Department, University of Utah, Salt Lake City, UT 84112
- Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancon, Panama
| | - Camila Drake
- Royal Botanic Garden Edinburgh, Edinburgh EH3 5LR, United Kingdom
| | - Ruth Hollands
- Royal Botanic Garden Edinburgh, Edinburgh EH3 5LR, United Kingdom
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Abstract
Land plants underpin a multitude of ecosystem functions, support human livelihoods and represent a critically important component of terrestrial biodiversity-yet many tens of thousands of species await discovery, and plant identification remains a substantial challenge, especially where material is juvenile, fragmented or processed. In this opinion article, we tackle two main topics. Firstly, we provide a short summary of the strengths and limitations of plant DNA barcoding for addressing these issues. Secondly, we discuss options for enhancing current plant barcodes, focusing on increasing discriminatory power via either gene capture of nuclear markers or genome skimming. The former has the advantage of establishing a defined set of target loci maximizing efficiency of sequencing effort, data storage and analysis. The challenge is developing a probe set for large numbers of nuclear markers that works over sufficient phylogenetic breadth. Genome skimming has the advantage of using existing protocols and being backward compatible with existing barcodes; and the depth of sequence coverage can be increased as sequencing costs fall. Its non-targeted nature does, however, present a major informatics challenge for upscaling to large sample sets.This article is part of the themed issue 'From DNA barcodes to biomes'.
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Affiliation(s)
| | - De-Zhu Li
- Germplasm Bank of Wild Species, Kunming Institute of Botany, Chinese Academy of Sciences, 132 Lanhei Road, Heilongtan, Kunming, Yunnan 650201, People's Republic of China
| | - Michelle van der Bank
- Department of Botany and Plant Biotechnology, University of Johannesburg, Auckland park, Johannesburg PO Box 524, South Africa
| | - Alex D Twyford
- Ashworth Laboratories, Institute of Evolutionary Biology, University of Edinburgh, Edinburgh EH9 3FL, UK
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Twyford AD. Will Benchtop Sequencers Resolve the Sequencing Trade-off in Plant Genetics? Front Plant Sci 2016; 7:433. [PMID: 27092154 PMCID: PMC4822345 DOI: 10.3389/fpls.2016.00433] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Accepted: 03/21/2016] [Indexed: 06/05/2023]
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Twyford AD, Kidner CA, Ennos RA. Maintenance of species boundaries in a Neotropical radiation of Begonia. Mol Ecol 2016; 24:4982-93. [PMID: 26301313 PMCID: PMC4600226 DOI: 10.1111/mec.13355] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [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: 01/21/2015] [Revised: 08/18/2015] [Accepted: 08/19/2015] [Indexed: 01/04/2023]
Abstract
A major goal of evolutionary biology is to determine the mechanisms generating biodiversity. In Begonia, one of the largest plant genera (1900+ species), it has been postulated that the high number of endemic species is a by-product of low gene flow among populations, which predisposes the group to speciation. However, this model of divergence requires that reproductive barriers accumulate rapidly among diverging species that overlap in their geographic ranges, otherwise speciation will be opposed by homogenizing gene flow in zones of secondary contact. Here, we test the outcomes of secondary contact in Begonia by genotyping multiple sympatric sites with 12 nuclear and seven plastid loci. We show that three sites of secondary contact between B. heracleifolia and B. nelumbiifolia are highly structured, mostly containing parental genotypes, with few F1 hybrids. A sympatric site between B. heracleifolia and B. sericoneura contains a higher proportion of F1s, but little evidence of introgression. The lack of later-generation hybrids contrasts with that documented in many other plant taxa, where introgression is extensive. Our results, in conjunction with previous genetic work, show that Begonia demonstrate properties making them exceptionally prone to speciation, at multiple stages along the divergence continuum. Not only are populations weakly connected by gene flow, promoting allopatric speciation, but species often show strong reproductive barriers in secondary contact. Whether similar mechanisms contribute to diversification in other large genera remains to be tested.
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Affiliation(s)
- Alex D Twyford
- Ashworth Laboratories, Institute of Evolutionary Biology, The University of Edinburgh, Charlotte Auerbach Road, Edinburgh, EH9 3FL, UK.,Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh, EH3 5LR, UK.,Institute of Molecular Plant Sciences, School of Biological Sciences, University of Edinburgh, Edinburgh, EH9 3JH, UK
| | - Catherine A Kidner
- Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh, EH3 5LR, UK.,Institute of Molecular Plant Sciences, School of Biological Sciences, University of Edinburgh, Edinburgh, EH9 3JH, UK
| | - Richard A Ennos
- Ashworth Laboratories, Institute of Evolutionary Biology, The University of Edinburgh, Charlotte Auerbach Road, Edinburgh, EH9 3FL, UK
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Twyford AD, Friedman J. Adaptive divergence in the monkey flower Mimulus guttatus is maintained by a chromosomal inversion. Evolution 2015; 69:1476-1486. [PMID: 25879251 PMCID: PMC5029580 DOI: 10.1111/evo.12663] [Citation(s) in RCA: 109] [Impact Index Per Article: 12.1] [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: 09/29/2014] [Accepted: 04/01/2015] [Indexed: 12/15/2022]
Abstract
Organisms exhibit an incredible diversity of life history strategies as adaptive responses to environmental variation. The establishment of novel life history strategies involves multilocus polymorphisms, which will be challenging to establish in the face of gene flow and recombination. Theory predicts that adaptive allelic combinations may be maintained and spread if they occur in genomic regions of reduced recombination, such as chromosomal inversion polymorphisms, yet empirical support for this prediction is lacking. Here, we use genomic data to investigate the evolution of divergent adaptive ecotypes of the yellow monkey flower Mimulus guttatus. We show that a large chromosomal inversion polymorphism is the major region of divergence between geographically widespread annual and perennial ecotypes. In contrast, ∼40,000 single nucleotide polymorphisms in collinear regions of the genome show no signal of life history, revealing genomic patterns of diversity have been shaped by localized homogenizing gene flow and large-scale Pleistocene range expansion. Our results provide evidence for an inversion capturing and protecting loci involved in local adaptation, while also explaining how adaptive divergence can occur with gene flow.
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Affiliation(s)
- Alex D Twyford
- Ashworth Laboratories, Institute of Evolutionary Biology, The University of Edinburgh, Charlotte Auerbach Road, Edinburgh, EH9 3FL, United Kingdom.,Department of Biology, Syracuse University, 107 College Place, Syracuse, New York, 13244
| | - Jannice Friedman
- Department of Biology, Syracuse University, 107 College Place, Syracuse, New York, 13244
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Twyford AD, Streisfeld MA, Lowry DB, Friedman J. Genomic studies on the nature of species: adaptation and speciation inMimulus. Mol Ecol 2015; 24:2601-9. [DOI: 10.1111/mec.13190] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2015] [Revised: 03/25/2015] [Accepted: 03/27/2015] [Indexed: 12/27/2022]
Affiliation(s)
- Alex D. Twyford
- Ashworth Laboratories; Institute of Evolutionary Biology; The University of Edinburgh; Charlotte Auerbach Road Edinburgh EH9 3FL UK
- Department of Biology; Syracuse University; 107 College Place Syracuse NY 13244 USA
| | | | - David B. Lowry
- Plant Biology Laboratories; Department of Plant Biology; Michigan State University; 612 Wilson Road Room 166 East Lansing MI 48824 USA
| | - Jannice Friedman
- Department of Biology; Syracuse University; 107 College Place Syracuse NY 13244 USA
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Friedman J, Twyford AD, Willis JH, Blackman BK. The extent and genetic basis of phenotypic divergence in life history traits in Mimulus guttatus. Mol Ecol 2014; 24:111-22. [PMID: 25403267 PMCID: PMC4657477 DOI: 10.1111/mec.13004] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [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: 07/30/2014] [Revised: 10/26/2014] [Accepted: 11/06/2014] [Indexed: 12/13/2022]
Abstract
Differential natural selection acting on populations in contrasting environments often results in adaptive divergence in multivariate phenotypes. Multivariate trait divergence across populations could be caused by selection on pleiotropic alleles or through many independent loci with trait-specific effects. Here, we assess patterns of association between a suite of traits contributing to life history divergence in the common monkey flower, Mimulus guttatus, and examine the genetic architecture underlying these correlations. A common garden survey of 74 populations representing annual and perennial strategies from across the native range revealed strong correlations between vegetative and reproductive traits. To determine whether these multitrait patterns arise from pleiotropic or independent loci, we mapped QTLs using an approach combining high-throughput sequencing with bulk segregant analysis on a cross between populations with divergent life histories. We find extensive pleiotropy for QTLs related to flowering time and stolon production, a key feature of the perennial strategy. Candidate genes related to axillary meristem development colocalize with the QTLs in a manner consistent with either pleiotropic or independent QTL effects. Further, these results are analogous to previous work showing pleiotropy-mediated genetic correlations within a single population of M. guttatus experiencing heterogeneous selection. Our findings of strong multivariate trait associations and pleiotropic QTLs suggest that patterns of genetic variation may determine the trajectory of adaptive divergence.
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Affiliation(s)
- Jannice Friedman
- Department of Biology, Syracuse University, 110 College Place, Syracuse, NY, 13244, USA
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Twyford AD. Testing evolutionary hypotheses for DNA barcoding failure in willows. Mol Ecol 2014; 23:4674-6. [PMID: 25263402 DOI: 10.1111/mec.12892] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [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: 06/27/2014] [Revised: 08/03/2014] [Accepted: 08/18/2014] [Indexed: 12/26/2022]
Abstract
The goal of DNA barcoding is to enable the rapid identification of taxa from short diagnostic DNA sequence profiles. But how feasible is this objective when many evolutionary processes, such as hybridization and selective sweeps, cause alleles to be shared among related taxa? In this issue of Molecular Ecology, Percy et al. (2014) test the full suite of seven candidate plant barcoding loci in a broad geographic sample of willow species. They show exceptional plastid haplotype sharing between species across continents, with most taxa not possessing a unique barcode sequence. Using population genetic and molecular dating analyses, they implicate hybridization and selective sweeps, but not incomplete lineage sorting, as the historical processes causing widespread haplotype sharing among willow taxa. This study represents an exceptional case of how poorly barcoding can perform, and highlights methodological issues using universal organellar regions for species identification.
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Affiliation(s)
- Alex D Twyford
- Department of Biology, Syracuse University, 107 College Place, Syracuse, NY, 13244, USA; Institute of Evolutionary Biology, Ashworth Laboratories, The University of Edinburgh, Kings Buildings, West Mains Road, Edinburgh EH9 3JT, UK
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Twyford AD, Ennos RA, White CD, Ali MS, Kidner CA. The evolution of sex ratio differences and inflorescence architectures in Begonia (Begoniaceae). Am J Bot 2014; 101:308-317. [PMID: 24491344 DOI: 10.3732/ajb.1300090] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
PREMISE OF THE STUDY A major benefit conferred by monoecy is the ability to alter floral sex ratio in response to selection. In monoecious species that produce flowers of a given sex at set positions on the inflorescence, floral sex ratio may be related to inflorescence architecture. We studied the loci underlying differences in inflorescence architecture between two monoecious Begonia species and related this to floral sex ratios. METHODS We performed trait comparisons and quantitative trait locus (QTL) mapping in a segregating backcross population between Central American Begonia plebeja and B. conchifolia. We focused on traits related to inflorescence architecture, sex ratios, and other reproductive traits. KEY RESULTS The inflorescence branching pattern of B. conchifolia was more asymmetric than B. plebeja, which in turn affects the floral sex ratio. Colocalizing QTLs of moderate effect influenced both the number of male flowers and the fate decisions of axillary meristems, demonstrating the close link between inflorescence architecture and sex ratio. Additional QTLs were found for stamen number (30% variance explained, VE) and pollen sterility (12.3% VE). CONCLUSIONS One way in which Begonia species develop different floral sex ratios is through modifications of their inflorescence architecture. The potential pleiotropic action of QTL on inflorescence branching and floral sex ratios may have major implications for trait evolution and responses to selection. The presence of a single QTL of large effect on stamen number may allow rapid divergence for this key floral trait. We propose candidate loci for stamen number and inflorescence branching for future characterization.
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Affiliation(s)
- Alex D Twyford
- Department of Biology, Syracuse University, 107 College Place, Room 110 LSC, Syracuse, New York 13244 USA
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Twyford AD, Ennos RA, Kidner CA. Development and characterization of microsatellite markers for Central American Begonia sect. Gireoudia (Begoniaceae). Appl Plant Sci 2013; 1:apps1200499. [PMID: 25202548 PMCID: PMC4105041 DOI: 10.3732/apps.1200499] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2012] [Accepted: 11/10/2012] [Indexed: 06/03/2023]
Abstract
PREMISE OF THE STUDY Transcriptome sequence data were used to design microsatellite primers for two widespread Central American Begonia species, B. heracleifolia and B. nelumbiifolia, to investigate population structure and hybridization. • METHODS AND RESULTS The transcriptome from vegetative meristem tissue from the related B. plebeja was mined for microsatellite loci, and 31 primer pairs amplified in the target species. Fifteen primer pairs were combined in two multiplex PCR reactions, which amplified an average of four alleles per locus. • CONCLUSIONS The markers developed will be a valuable genetic resource for medium-throughput genotyping of Central American species of Begonia sect. Gireoudia. A subset of these markers have perfect sequence matches to Asian B. venusta, and are promising for studies in other Begonia sections.
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Affiliation(s)
- Alex D. Twyford
- Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh EH3 5LR, United Kingdom
- Institute of Molecular Plant Sciences, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JH, United Kingdom
| | - Richard A. Ennos
- Institute of Evolutionary Biology, School of Biological Sciences, Ashworth Laboratories, University of Edinburgh, Edinburgh EH9 3JT, United Kingdom
| | - Catherine A. Kidner
- Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh EH3 5LR, United Kingdom
- Institute of Molecular Plant Sciences, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JH, United Kingdom
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Abstract
Hybridization has a major role in evolution-from the introgression of important phenotypic traits between species, to the creation of new species through hybrid speciation. Molecular studies of hybridization aim to understand the class of hybrids and the frequency of introgression, detect the signature of ancient hybridization, and understand the behaviour of introgressed loci in their new genomic background. This often involves a large investment in the design and application of molecular markers, leading to a compromise between the depth and breadth of genomic data. New techniques designed to assay a large sub-section of the genome, in association with next-generation sequencing (NGS) technologies, will allow genome-wide hybridization and introgression studies in organisms with no prior sequence data. These detailed genotypic data will unite the breadth of sampling of loci characteristic of population genetics with the depth of sequence information associated with molecular phylogenetics. In this review, we assess the theoretical and methodological constraints that limit our understanding of natural hybridization, and promote the use of NGS for detecting hybridization and introgression between non-model organisms. We also make recommendations for the ways in which emerging techniques, such as pooled barcoded amplicon sequencing and restriction site-associated DNA tags, should be used to overcome current limitations, and enhance our understanding of this evolutionary significant process.
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