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Paetzold C, Barke BH, Hörandl E. Evolution of Transcriptomes in Early-Generation Hybrids of the Apomictic Ranunculus auricomus Complex ( Ranunculaceae). Int J Mol Sci 2022; 23:ijms232213881. [PMID: 36430360 PMCID: PMC9697309 DOI: 10.3390/ijms232213881] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Revised: 11/03/2022] [Accepted: 11/09/2022] [Indexed: 11/12/2022] Open
Abstract
Hybridisation in plants may cause a shift from sexual to asexual seed formation (apomixis). Indeed, natural apomictic plants are usually hybrids, but it is still unclear how hybridisation could trigger the shift to apomixis. The genome evolution of older apomictic lineages is influenced by diverse processes such as polyploidy, mutation accumulation, and allelic sequence divergence. To disentangle the effects of hybridisation from these other factors, we analysed the transcriptomes of flowering buds from artificially produced, diploid F2 hybrids of the Ranunculus auricomus complex. The hybrids exhibited unreduced embryo sac formation (apospory) as one important component of apomixis, whereas their parental species were sexual. We revealed 2915 annotated single-copy genes that were mostly under purifying selection according to dN/dS ratios. However, pairwise comparisons revealed, after rigorous filtering, 79 genes under diversifying selection between hybrids and parents, whereby gene annotation assigned ten of them to reproductive processes. Four genes belong to the meiosis-sporogenesis phase (ASY1, APC1, MSP1, and XRI1) and represent, according to literature records, candidate genes for apospory. We conclude that hybridisation could combine novel (or existing) mutations in key developmental genes in certain hybrid lineages, and establish (together with altered gene expression profiles, as observed in other studies) a heritable regulatory mechanism for aposporous development.
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Affiliation(s)
- Claudia Paetzold
- Department of Botany and Molecular Evolution, Senckenberg Research Institute, 60325 Frankfurt am Main, Germany
| | - Birthe H. Barke
- Department of Systematics, Biodiversity and Evolution of Plants (with Herbarium), University of Goettingen, 37073 Goettingen, Germany
| | - Elvira Hörandl
- Department of Systematics, Biodiversity and Evolution of Plants (with Herbarium), University of Goettingen, 37073 Goettingen, Germany
- Correspondence:
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Wang D, Xu X, Zhang H, Xi Z, Abbott RJ, Fu J, Liu JQ. Abiotic niche divergence of hybrid species from their progenitors. Am Nat 2022; 200:634-645. [DOI: 10.1086/721372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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Hörandl E. Novel Approaches for Species Concepts and Delimitation in Polyploids and Hybrids. PLANTS (BASEL, SWITZERLAND) 2022; 11:plants11020204. [PMID: 35050093 PMCID: PMC8781807 DOI: 10.3390/plants11020204] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Revised: 01/07/2022] [Accepted: 01/10/2022] [Indexed: 05/08/2023]
Abstract
Hybridization and polyploidization are important processes for plant evolution. However, classification of hybrid or polyploid species has been notoriously difficult because of the complexity of processes and different evolutionary scenarios that do not fit with classical species concepts. Polyploid complexes are formed via combinations of allopolyploidy, autopolyploidy and homoploid hybridization with persisting sexual reproduction, resulting in many discrete lineages that have been classified as species. Polyploid complexes with facultative apomixis result in complicated net-work like clusters, or rarely in agamospecies. Various case studies illustrate the problems that apply to traditional species concepts to hybrids and polyploids. Conceptual progress can be made if lineage formation is accepted as an inevitable consequence of meiotic sex, which is established already in the first eukaryotes as a DNA restoration tool. The turnaround of the viewpoint that sex forms species as lineages helps to overcome traditional thinking of species as "units". Lineage formation and self-sustainability is the prerequisite for speciation and can also be applied to hybrids and polyploids. Species delimitation is aided by the improved recognition of lineages via various novel -omics methods, by understanding meiosis functions, and by recognizing functional phenotypes by considering morphological-physiological-ecological adaptations.
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Affiliation(s)
- Elvira Hörandl
- Department of Systematics, Biodiversity and Evolution of Plants (with Herbarium), University of Goettingen, 37073 Göttingen, Germany
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Wong ELY, Hiscock SJ, Filatov DA. The Role of Interspecific Hybridisation in Adaptation and Speciation: Insights From Studies in Senecio. FRONTIERS IN PLANT SCIENCE 2022; 13:907363. [PMID: 35812981 PMCID: PMC9260247 DOI: 10.3389/fpls.2022.907363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Accepted: 06/03/2022] [Indexed: 05/08/2023]
Abstract
Hybridisation is well documented in many species, especially plants. Although hybrid populations might be short-lived and do not evolve into new lineages, hybridisaiton could lead to evolutionary novelty, promoting adaptation and speciation. The genus Senecio (Asteraceae) has been actively used to unravel the role of hybridisation in adaptation and speciation. In this article, we first briefly describe the process of hybridisation and the state of hybridisation research over the years. We then discuss various roles of hybridisation in plant adaptation and speciation illustrated with examples from different Senecio species, but also mention other groups of organisms whenever necessary. In particular, we focus on the genomic and transcriptomic consequences of hybridisation, as well as the ecological and physiological aspects from the hybrids' point of view. Overall, this article aims to showcase the roles of hybridisation in speciation and adaptation, and the research potential of Senecio, which is part of the ecologically and economically important family, Asteraceae.
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Affiliation(s)
- Edgar L. Y. Wong
- Department of Plant Sciences, University of Oxford, Oxford, United Kingdom
- *Correspondence: Edgar L. Y. Wong,
| | - Simon J. Hiscock
- Department of Plant Sciences, University of Oxford, Oxford, United Kingdom
- Oxford Botanic Garden and Arboretum, Oxford, United Kingdom
| | - Dmitry A. Filatov
- Department of Plant Sciences, University of Oxford, Oxford, United Kingdom
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Brennan AC, Hiscock SJ, Abbott RJ. Completing the hybridization triangle: the inheritance of genetic incompatibilities during homoploid hybrid speciation in ragworts ( Senecio). AOB PLANTS 2019; 11:ply078. [PMID: 30740200 PMCID: PMC6360072 DOI: 10.1093/aobpla/ply078] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Accepted: 01/04/2019] [Indexed: 05/24/2023]
Abstract
A new homoploid hybrid lineage needs to establish a degree of reproductive isolation from its parent species if it is to persist as an independent entity, but the role hybridization plays in this process is known in only a handful of cases. The homoploid hybrid ragwort species, Senecio squalidus (Oxford ragwort), originated following the introduction of hybrid plants to the UK approximately 320 years ago. The source of the hybrid plants was from a naturally occurring hybrid zone between S. aethnensis and S. chrysanthemifolius on Mount Etna, Sicily. Previous studies of the parent species found evidence for multiple incompatibility loci causing transmission ratio distortion of genetic markers in their hybrid progeny. This study closes the hybridization triangle by reporting a genetic mapping analysis of the remaining two paired cross combinations between S. squalidus and its parents. Genetic maps produced from F2 mapping families were generally collinear but with half of the linkage groups showing evidence of genomic reorganization between genetic maps. The new maps produced from crosses between S. squalidus and each parent showed multiple incompatibility loci distributed across the genome, some of which co-locate with previously reported incompatibility loci between the parents. These findings suggest that this young homoploid hybrid species has inherited a unique combination of genomic rearrangements and incompatibilities from its parents that contribute to its reproductive isolation.
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Affiliation(s)
- Adrian C Brennan
- Department of Biosciences, University of Durham, South Road, Durham, UK
- School of Biology, University of St Andrews, St Andrews, Fife, UK
| | - Simon J Hiscock
- Department of Plant Sciences, University of Oxford, Oxford, UK
| | - Richard J Abbott
- School of Biology, University of St Andrews, St Andrews, Fife, UK
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Caseys C, Stritt C, Glauser G, Blanchard T, Lexer C. Effects of hybridization and evolutionary constraints on secondary metabolites: the genetic architecture of phenylpropanoids in European populus species. PLoS One 2015; 10:e0128200. [PMID: 26010156 PMCID: PMC4444209 DOI: 10.1371/journal.pone.0128200] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Accepted: 04/24/2015] [Indexed: 12/18/2022] Open
Abstract
The mechanisms responsible for the origin, maintenance and evolution of plant secondary metabolite diversity remain largely unknown. Decades of phenotypic studies suggest hybridization as a key player in generating chemical diversity in plants. Knowledge of the genetic architecture and selective constraints of phytochemical traits is key to understanding the effects of hybridization on plant chemical diversity and ecological interactions. Using the European Populus species P. alba (White poplar) and P. tremula (European aspen) and their hybrids as a model, we examined levels of inter- and intraspecific variation, heritabilities, phenotypic correlations, and the genetic architecture of 38 compounds of the phenylpropanoid pathway measured by liquid chromatography and mass spectrometry (UHPLC-MS). We detected 41 quantitative trait loci (QTL) for chlorogenic acids, salicinoids and flavonoids by genetic mapping in natural hybrid crosses. We show that these three branches of the phenylpropanoid pathway exhibit different geographic patterns of variation, heritabilities, and genetic architectures, and that they are affected differently by hybridization and evolutionary constraints. Flavonoid abundances present high species specificity, clear geographic structure, and strong genetic determination, contrary to salicinoids and chlorogenic acids. Salicinoids, which represent important defence compounds in Salicaceae, exhibited pronounced genetic correlations on the QTL map. Our results suggest that interspecific phytochemical differentiation is concentrated in downstream sections of the phenylpropanoid pathway. In particular, our data point to glycosyltransferase enzymes as likely targets of rapid evolution and interspecific differentiation in the 'model forest tree' Populus.
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Affiliation(s)
- Celine Caseys
- Unit of Ecology and Evolution, Department of Biology, University of Fribourg, Fribourg, Switzerland
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, Canada
| | - Christoph Stritt
- Unit of Ecology and Evolution, Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Gaetan Glauser
- Neuchâtel Platform of Analytical Chemistry, Faculty of science, University of Neuchâtel, Neuchâtel, Switzerland
| | - Thierry Blanchard
- Unit of Ecology and Evolution, Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Christian Lexer
- Unit of Ecology and Evolution, Department of Biology, University of Fribourg, Fribourg, Switzerland
- Department of Botany and Biodiversity Research, University of Vienna, Vienna, Austria
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Moore AJ, Moore WL, Baldwin BG. Genetic and ecotypic differentiation in a Californian plant polyploid complex (Grindelia, Asteraceae). PLoS One 2014; 9:e95656. [PMID: 24755840 PMCID: PMC3995713 DOI: 10.1371/journal.pone.0095656] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2013] [Accepted: 03/31/2014] [Indexed: 01/24/2023] Open
Abstract
Studies of ecotypic differentiation in the California Floristic Province have contributed greatly to plant evolutionary biology since the pioneering work of Clausen, Keck, and Hiesey. The extent of gene flow and genetic differentiation across interfertile ecotypes that span major habitats in the California Floristic Province is understudied, however, and is important for understanding the prospects for local adaptation to evolve or persist in the face of potential gene flow across populations in different ecological settings. We used microsatellite data to examine local differentiation in one of these lineages, the Pacific Coast polyploid complex of the plant genus Grindelia (Asteraceae). We examined 439 individuals in 10 different populations. The plants grouped broadly into a coastal and an inland set of populations. The coastal group contained plants from salt marshes and coastal bluffs, as well as a population growing in a serpentine grassland close to the coast, while the inland group contained grassland plants. No evidence for hybridization was found at the single location where adjacent populations of the two groups were sampled. In addition to differentiation along ecotypic lines, there was also a strong signal of local differentiation, with the plants grouping strongly by population. The strength of local differentiation is consistent with the extensive morphological variation observed across populations and the history of taxonomic confusion in the group. The Pacific Clade of Grindelia and other young Californian plant groups warrant additional analysis of evolutionary divergence along the steep coast-to-inland climatic gradient, which has been associated with local adaptation and ecotype formation since the classic studies of Clausen, Keck, and Hiesey.
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Affiliation(s)
- Abigail J. Moore
- Institut für Spezielle Botanik und Botanischer Garten, Johannes Gutenberg-Universität Mainz, Mainz, Germany
- Department of Integrative Biology and Jepson Herbarium, University of California, Berkeley, California, United States of America
| | - William L. Moore
- David Eccles School of Business, University of Utah, Salt Lake City, Utah, United States of America
| | - Bruce G. Baldwin
- Department of Integrative Biology and Jepson Herbarium, University of California, Berkeley, California, United States of America
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Kilvitis HJ, Alvarez M, Foust CM, Schrey AW, Robertson M, Richards CL. Ecological epigenetics. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 781:191-210. [PMID: 24277301 DOI: 10.1007/978-94-007-7347-9_10] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Biologists have assumed that heritable variation due to DNA sequence differences (i.e., genetic variation) allows populations of organisms to be both robust and adaptable to extreme environmental conditions. Natural selection acts on the variation among different genotypes and ultimately changes the genetic composition of the population. While there is compelling evidence about the importance of genetic polymorphisms, evidence is accumulating that epigenetic mechanisms (e.g., chromatin modifications, DNA methylation) can affect ecologically important traits, even in the absence of genetic variation. In this chapter, we review this evidence and discuss the consequences of epigenetic variation in natural populations. We begin by defining the term epigenetics, providing a brief overview of various epigenetic mechanisms, and noting the potential importance of epigenetics in the study of ecology. We continue with a review of the ecological epigenetics literature to demonstrate what is currently known about the amount and distribution of epigenetic variation in natural populations. Then, we consider the various ecological contexts in which epigenetics has proven particularly insightful and discuss the potential evolutionary consequences of epigenetic variation. Finally, we conclude with suggestions for future directions of ecological epigenetics research.
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Affiliation(s)
- Holly J Kilvitis
- Department of Integrative Biology, University of South Florida, 4202 E Fowler Ave, Tampa, FL, 33620, USA,
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Abstract
Flowers exist in exceedingly complex fitness landscapes, in which subtle variation in each trait can affect the pollinators, herbivores and pleiotropically linked traits in other plant tissues. A whole-genome approach to flower evolution will help our understanding of plant-pollinator interactions.
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Affiliation(s)
- Elizabeth L Clare
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
| | - Florian P Schiestl
- Institute of Systematic Botany, University of Zurich, Zollikerstrasse 107, CH-8008 Zürich, Switzerland
| | - Andrew R Leitch
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
| | - Lars Chittka
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
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Rowe HC, Rieseberg LH. Genome-scale transcriptional analyses of first-generation interspecific sunflower hybrids reveals broad regulatory compatibility. BMC Genomics 2013; 14:342. [PMID: 23701699 PMCID: PMC3679827 DOI: 10.1186/1471-2164-14-342] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Accepted: 04/15/2013] [Indexed: 12/26/2022] Open
Abstract
Background Interspecific hybridization creates individuals harboring diverged genomes. The interaction of these genomes can generate successful evolutionary novelty or disadvantageous genomic conflict. Annual sunflowers Helianthus annuus and H. petiolaris have a rich history of hybridization in natural populations. Although first-generation hybrids generally have low fertility, hybrid swarms that include later generation and fully fertile backcross plants have been identified, as well as at least three independently-originated stable hybrid taxa. We examine patterns of transcript accumulation in the earliest stages of hybridization of these species via analyses of transcriptome sequences from laboratory-derived F1 offspring of an inbred H. annuus cultivar and a wild H. petiolaris accession. Results While nearly 14% of the reference transcriptome showed significant accumulation differences between parental accessions, total F1 transcript levels showed little evidence of dominance, as midparent transcript levels were highly predictive of transcript accumulation in F1 plants. Allelic bias in F1 transcript accumulation was detected in 20% of transcripts containing sufficient polymorphism to distinguish parental alleles; however the magnitude of these biases were generally smaller than differences among parental accessions. Conclusions While analyses of allelic bias suggest that cis regulatory differences between H. annuus and H. petiolaris are common, their effect on transcript levels may be more subtle than trans-acting regulatory differences. Overall, these analyses found little evidence of regulatory incompatibility or dominance interactions between parental genomes within F1 hybrid individuals, although it is unclear whether this is a legacy or an enabler of introgression between species.
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Affiliation(s)
- Heather C Rowe
- Botany Department, University of British Columbia, Vancouver, BC, Canada
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Dittrich-Reed DR, Fitzpatrick BM. Transgressive Hybrids as Hopeful Monsters. Evol Biol 2012; 40:310-315. [PMID: 23687396 PMCID: PMC3655218 DOI: 10.1007/s11692-012-9209-0] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2012] [Accepted: 11/06/2012] [Indexed: 01/27/2023]
Abstract
The origin of novelty is a critical subject for evolutionary biologists. Early geneticists speculated about the sudden appearance of new species via special macromutations, epitomized by Goldschmidt’s infamous “hopeful monster”. Although these ideas were easily dismissed by the insights of the Modern Synthesis, a lingering fascination with the possibility of sudden, dramatic change has persisted. Recent work on hybridization and gene exchange suggests an underappreciated mechanism for the sudden appearance of evolutionary novelty that is entirely consistent with the principles of modern population genetics. Genetic recombination in hybrids can produce transgressive phenotypes, “monstrous” phenotypes beyond the range of parental populations. Transgressive phenotypes can be products of epistatic interactions or additive effects of multiple recombined loci. We compare several epistatic and additive models of transgressive segregation in hybrids and find that they are special cases of a general, classic quantitative genetic model. The Dobzhansky-Muller model predicts “hopeless” monsters, sterile and inviable transgressive phenotypes. The Bateson model predicts “hopeful” monsters with fitness greater than either parental population. The complementation model predicts both. Transgressive segregation after hybridization can rapidly produce novel phenotypes by recombining multiple loci simultaneously. Admixed populations will also produce many similar recombinant phenotypes at the same time, increasing the probability that recombinant “hopeful monsters” will establish true-breeding evolutionary lineages. Recombination is not the only (or even most common) process generating evolutionary novelty, but might be the most credible mechanism for sudden appearance of new forms.
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Pritchard VL, Edmands S. THE GENOMIC TRAJECTORY OF HYBRID SWARMS: OUTCOMES OF REPEATED CROSSES BETWEEN POPULATIONS OFTIGRIOPUS CALIFORNICUS. Evolution 2012; 67:774-91. [DOI: 10.1111/j.1558-5646.2012.01814.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Taylor SJ, Rojas LD, Ho SW, Martin NH. Genomic collinearity and the genetic architecture of floral differences between the homoploid hybrid species Iris nelsonii and one of its progenitors, Iris hexagona. Heredity (Edinb) 2012; 110:63-70. [PMID: 23047202 DOI: 10.1038/hdy.2012.62] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Hybrid speciation represents a relatively rapid form of diversification. Early models of homoploid hybrid speciation suggested that reproductive isolation between the hybrid species and progenitors primarily resulted from karyotypic differences between the species. However, genic incompatibilities and ecological divergence may also be responsible for isolation. Iris nelsonii is an example of a homoploid hybrid species that is likely isolated from its progenitors primarily by strong prezygotic isolation, including habitat divergence, floral isolation and post-pollination prezygotic barriers. Here, we used linkage mapping and quantitative trait locus (QTL) mapping approaches to investigate genomic collinearity and the genetic architecture of floral differences between I. nelsonii and one of its progenitor species I. hexagona. The linkage map produced from this cross is highly collinear with another linkage map produced between I. fulva and I. brevicaulis (the two other species shown to have contributed to the genomic makeup of I. nelsonii), suggesting that karyotypic differences do not contribute substantially to isolation in this homoploid hybrid species. Similar to other studies of the genetic architecture of floral characteristics, at least one QTL was found that explained >20% variance in each color trait, while minor QTLs were detected for each morphological trait. These QTLs will serve as hypotheses for regions under selection by pollinators.
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Affiliation(s)
- S J Taylor
- Department of Biology, Texas State University-San Marcos, San Marcos, TX 78666, USA.
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14
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Kane NC, Burke JM, Marek L, Seiler G, Vear F, Baute G, Knapp SJ, Vincourt P, Rieseberg LH. Sunflower genetic, genomic and ecological resources. Mol Ecol Resour 2012; 13:10-20. [PMID: 23039950 DOI: 10.1111/1755-0998.12023] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2011] [Revised: 08/22/2012] [Accepted: 08/24/2012] [Indexed: 11/29/2022]
Abstract
Long a major focus of genetic research and breeding, sunflowers (Helianthus) are emerging as an increasingly important experimental system for ecological and evolutionary studies. Here, we review the various attributes of wild and domesticated sunflowers that make them valuable for ecological experimentation and describe the numerous publicly available resources that have enabled rapid advances in ecological and evolutionary genetics. Resources include seed collections available from germplasm centres at the USDA and INRA, genomic and EST sequences, mapping populations, genetic markers, genetic and physical maps and other forward- and reverse-genetic tools. We also discuss some of the key evolutionary, genetic and ecological questions being addressed in sunflowers, as well as gaps in our knowledge and promising areas for future research.
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Affiliation(s)
- Nolan C Kane
- Department of Ecology and Evolutionary Biology, University of Colorado at Boulder, Boulder, CO 80309, USA.
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15
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Marques I, Nieto Feliner G, Martins-Loução MA, Fuertes Aguilar J. Genome size and base composition variation in natural and experimental Narcissus (Amaryllidaceae) hybrids. ANNALS OF BOTANY 2012; 109:257-64. [PMID: 22080093 PMCID: PMC3241596 DOI: 10.1093/aob/mcr282] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
BACKGROUND AND AIMS Although there is evidence that both allopolyploid and homoploid hybridization lead to rapid genomic changes, much less is known about hybrids from parents with different basic numbers without further chromosome doubling. Two natural hybrids, Narcissus × alentejanus (2n = 19) and N. × perezlarae (2n = 29), originated by one progenitor (N. cavanillesii, 2n = 28) and two others (N. serotinus, 2n = 10 and N. miniatus, 2n = 30, respectively) allow us to study how DNA content and composition varies in such hybrids. METHODS Flow cytometry measurements with two staining techniques, PI and DAPI, were used to estimate 2C values and base composition (AT/GC ratio) in 390 samples from 54 wild populations of the two natural hybrids and their parental species. In addition, 20 synthetic F(1) hybrid individuals were also studied for comparison. KEY RESULTS Natural hybrids presented 2C values intermediate between those found in their parental species, although intra-population variance was very high in both hybrids, particularly for PI. Genome size estimated from DAPI was higher in synthetic hybrids than in hybrids from natural populations. In addition, differences for PI 2C values were detected between synthetic reciprocal crosses, attributable to maternal effects, as well as between natural hybrids and those synthetic F(1) hybrids in which N. cavanillesii acted as a mother. CONCLUSIONS Our results suggest that natural hybrid populations are composed of a mixture of markedly different hybrid genotypes produced either by structural chromosome changes, consistent with classic cytogenetic studies in Narcissus, or by transposon-mediated events.
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Affiliation(s)
- Isabel Marques
- Universidade de Lisboa, Museu Nacional de História Natural, Jardim Botânico, Lisbon, Portugal.
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Taylor SJ, Willard RW, Shaw JP, Dobson MC, Martin NH. Differential response of the homoploid hybrid species Iris nelsonii (Iridaceae) and its progenitors to abiotic habitat conditions. AMERICAN JOURNAL OF BOTANY 2011; 98:1309-1316. [PMID: 21821591 DOI: 10.3732/ajb.1100012] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
PREMISE OF THE STUDY Homoploid hybrid speciation involves the evolution of reproductive isolation between a hybrid lineage and its progenitors without a change in chromosome number. Ecological divergence presumably plays a large role in the stabilization of hybrid lineages, as all homoploid hybrid species described to date are reported to be ecologically divergent from their progenitors. However, the described ecological divergence in most systems is anecdotal and has not been empirically tested. METHODS We assessed the vegetative response of Iris nelsonii, a homoploid hybrid species, and its three progenitor species, I. brevicaulis, I. fulva, and I. hexagona, to different abiotic conditions (i.e., varied sunlight availability and flooding conditions) that largely characterize the habitats of these four species in their natural habitats in Louisiana, USA. KEY RESULTS The species differed in their responses to the water-level treatment for many of the response variables, including rhizome weight, ramet growth, plant height, and two principal components used to characterize the data. The species differed in their response to the light-level treatment for root allocation and the principal component used to characterize plant size. Iris nelsonii significantly differed from its progenitors, including its most closely related progenitor species, in response to many of the treatments. CONCLUSIONS The differential response to abiotic habitat conditions of I. nelsonii suggests that this species is ecologically divergent from its progenitor species.
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Affiliation(s)
- Sunni J Taylor
- Department of Biology, Texas State University-San Marcos, San Marcos, Texas 78666, USA.
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17
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Brouillette LC, Donovan LA. Nitrogen stress response of a hybrid species: a gene expression study. ANNALS OF BOTANY 2011; 107:101-8. [PMID: 20947669 PMCID: PMC3002466 DOI: 10.1093/aob/mcq203] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2010] [Revised: 08/13/2010] [Accepted: 09/17/2010] [Indexed: 05/24/2023]
Abstract
BACKGROUND AND AIMS Low soil fertility limits growth and productivity in many natural and agricultural systems, where the ability to sense and respond to nutrient limitation is important for success. Helianthus anomalus is an annual sunflower of hybrid origin that is adapted to desert sand-dune substrates with lower fertility than its parental species, H. annuus and H. petiolaris. Previous studies have shown that H. anomalus has traits generally associated with adaptation to low-fertility habitats, including a lower inherent relative growth rate and longer leaf lifetime. METHODS Here, a cDNA microarray is used to identify gene expression differences that potentially contribute to increased tolerance of low fertility of the hybrid species by comparing the nitrogen stress response of all three species with high- and low-nutrient treatments. KEY RESULTS Relative to the set of genes on the microarray, the genes showing differential expression in the hybrid species compared with its parents are enriched in stress-response genes, developmental genes, and genes involved in responses to biotic or abiotic stimuli. After a correction for multiple comparisons, five unique genes show a significantly different response to nitrogen limitation in H. anomalus compared with H. petiolaris and H. annuus. The Arabidopsis thaliana homologue of one of the five genes, catalase 1, has been shown to affect the timing of leaf senescence, and thus leaf lifespan. CONCLUSIONS The five genes identified in this analysis will be examined further as candidate genes for the adaptive stress response in H. anomalus. Genes that improve growth and productivity under nutrient stress could be used to improve crops for lower soil fertility which is common in marginal agricultural settings.
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RYMER PAULD, MANNING JOHNC, GOLDBLATT PETER, POWELL MARTYNP, SAVOLAINEN VINCENT. Evidence of recent and continuous speciation in a biodiversity hotspot: a population genetic approach in southern African gladioli (
Gladiolus
; Iridaceae). Mol Ecol 2010; 19:4765-82. [PMID: 20735739 DOI: 10.1111/j.1365-294x.2010.04794.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- PAUL D. RYMER
- Imperial College London, Silwood Park Campus, Ascot, Berkshire SL5 7PY, UK
- Royal Botanic Gardens, Kew, Jodrell Laboratory, Richmond, Surrey TW9 3DS, UK
| | - JOHN C. MANNING
- South African National Biodiversity Institute, Kirstenbosch Research Centre, Private Bag X7, Cape Town, South Africa
| | - PETER GOLDBLATT
- Missouri Botanical Garden, PO Box 299, St. Louis, MO 63166‐0299, USA
| | - MARTYN P. POWELL
- Imperial College London, Silwood Park Campus, Ascot, Berkshire SL5 7PY, UK
| | - VINCENT SAVOLAINEN
- Imperial College London, Silwood Park Campus, Ascot, Berkshire SL5 7PY, UK
- Royal Botanic Gardens, Kew, Jodrell Laboratory, Richmond, Surrey TW9 3DS, UK
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19
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DONOVAN LA, ROSENTHAL DR, SANCHEZ-VELENOSI M, RIESEBERG LH, LUDWIG F. Are hybrid species more fit than ancestral parent species in the current hybrid species habitats? J Evol Biol 2010; 23:805-16. [DOI: 10.1111/j.1420-9101.2010.01950.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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20
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Edelist C, Raffoux X, Falque M, Dillmann C, Sicard D, Rieseberg LH, Karrenberg S. Differential expression of candidate salt-tolerance genes in the halophyte Helianthus paradoxus and its glycophyte progenitors H. annuus and H. petiolaris (Asteraceae). AMERICAN JOURNAL OF BOTANY 2009; 96:1830-1838. [PMID: 21622304 DOI: 10.3732/ajb.0900067] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Adaptation to different habitats is considered to be a major force in the generation of organismal diversity. Understanding the genetic mechanisms that produce such adaptations will provide insights into long-standing questions in evolutionary biology and, at the same time, improve predictions of plant responses to changing environmental conditions. Here we used semiquantitative RT-PCR to study the expression of eight candidate salt-tolerance genes in leaves of the highly salt-tolerant diploid hybrid species Helianthus paradoxus and its salt-sensitive progenitor species H. annuus and H. petiolaris. Samples were collected after germination and growth under four different treatments: nonsaline (control), near-natural saline, saline with increased K(+), and saline with decreased Mg(2+) and Ca(2+). Three individuals from three populations per species were used. The hybrid species H. paradoxus constitutively under- or overexpressed genes related to potassium and calcium transport (homologues of KT1, KT2, ECA1), suggesting that these genes may contribute to the adaptation of H. paradoxus to salinity. In two other genes, variation between populations within species exceeded species level variation. Furthermore, homologues of the potassium transporter HAK8 and of a transcriptional regulator were generally overexpressed in saline treatments, suggesting that these genes are involved in sustained growth under saline conditions in Helianthus.
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Affiliation(s)
- Cécile Edelist
- University Paris-Sud, UMR 0320 / UMR 8120 Génétique Végétale, F-91190 Gif-sur-Yvette, France
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21
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Donovan LA, Ludwig F, Rosenthal DM, Rieseberg LH, Dudley SA. Phenotypic selection on leaf ecophysiological traits in Helianthus. THE NEW PHYTOLOGIST 2009; 183:868-879. [PMID: 19552693 DOI: 10.1111/j.1469-8137.2009.02916.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Habitats that differ in soil resource availability are expected to differ for selection on resource-related plant traits. Here, we examined spatial and temporal variation in phenotypic selection on leaf ecophysiological traits for 10 Helianthus populations, including two species of hybrid origin, Helianthus anomalus and Helianthus deserticola, and artificial hybrids of their ancestral parents. Leaf traits assessed were leaf size, succulence, nitrogen (N) concentration and water-use efficiency (WUE). Biomass and leaf traits of artificial hybrids indicate that the actively moving dune habitat of H. anomalus was more growth limiting, with lower N availability but higher relative water availability than the stabilized dune habitat of H. deserticola. Habitats differed for direct selection on leaf N and WUE, but not size or succulence, for the artificial hybrids. However, within the H. anomalus habitat, direct selection on WUE also differed among populations. Across years, direct selection on leaf traits did not differ. Leaf N was the only trait for which direct selection differed between habitats but not within the H. anomalus habitat, suggesting that nutrient limitation is an important selective force driving adaptation of H. anomalus to the active dune habitat.
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Affiliation(s)
- L A Donovan
- Department of Plant Biology, University of Georgia, Athens GA 30606, USA
| | - F Ludwig
- Department of Plant Biology, University of Georgia, Athens GA 30606, USA
| | - D M Rosenthal
- Department of Plant Biology, University of Georgia, Athens GA 30606, USA
| | - L H Rieseberg
- Department of Botany, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
| | - S A Dudley
- Department of Biology, McMaster University, Hamilton, Ontario, L8S 4K1, Canada
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22
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Liu SC, Lu CT, Wang JC. Reticulate hybridization of Alpinia (Zingiberaceae) in Taiwan. JOURNAL OF PLANT RESEARCH 2009; 122:305-316. [PMID: 19291357 DOI: 10.1007/s10265-009-0223-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2008] [Accepted: 01/18/2009] [Indexed: 05/27/2023]
Abstract
Reticulate hybridization is a complicated and creative mechanism in plant evolution that can cause interference in phylogenetic studies. Based on observations of intermediate morphology, low pollen fertility, and overlapping distributions of putative parent species, Yang and Wang (Proceedings of the cross-strait symposium on floristic diversity and conservation. National Museum of Natural Science, Taichung, Taiwan, pp 183-197, 1998) first proposed reticulate hybridization of Alpinia in Taiwan. In the present study, molecular tools were used to explore relationships between four parental species and their homoploidy hybrids, and the impact of hybridization on phylogeny reconstruction. Based on DNA markers, maternal heritance of the chloroplast genome, and additivity of nuclear ribosomal internal transcribed spacer, the present results provide strong support for the hybridization hypothesis. Co-existence of parental ribotypes within hybrids revealed that these hybridization events were current, while reciprocal and introgressive hybridization were inferred from chloroplast DNA data. Furthermore, iterative hybridizations involving more than two parental species may occur in notorious hybrid zones. Ecological, phenological, and physiological evidence provides insight into why such frequent hybridization occurs in Taiwanese Alpinia. In the phylogenetic tree of the Zerumbet clade reconstructed in this study, the chloroplast sequences from one hybrid species were not grouped into a subclade, implying instability caused by hybridization. Failure to find morphological apomorphies and biogeographical patterns in this clade was likely partially due to reticulate hybridization.
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Affiliation(s)
- Shu-Chuan Liu
- Department of Life Science, National Taiwan Normal University, No. 88, Ting-Chow Rd., Sect. 4, Taipei 11677, Taiwan
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23
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Abstract
Homoploid hybrid speciation has been recognized for its potential rapid completion, an idea that has received support from experimental and modeling studies. Following initial hybridization, the genomes of parental species recombine and junctions between chromosomal blocks of different parental origin leave a record of recombination and the time period before homogenization of the derived genome. We use detailed genetic maps of three hybrid species of sunflowers and models to estimate the time required for the stabilization of the new hybrid genome. In contrast to previous estimates of 60 or fewer generations, we find that the genomes of three hybrid sunflower species were not stabilized for hundreds of generations. These results are reconciled with previous research by recognizing that the stabilization of a hybrid species' genome is not synonymous with hybrid speciation. Segregating factors that contribute to initial ecological or intrinsic genetic isolation may become stabilized quickly. The remainder of the genome likely becomes stabilized over a longer time interval, with recombination and drift dictating the contributions of the parental genomes. Our modeling of genome stabilization provides an upper bound for the time interval for reproductive isolation to be established and confirms the rapid nature of homoploid hybrid speciation.
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Affiliation(s)
- C Alex Buerkle
- Department of Botany, 1000 E. University Ave., University of Wyoming, Laramie, Wyoming 82071, USA.
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24
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Baack EJ, Rieseberg LH. A genomic view of introgression and hybrid speciation. Curr Opin Genet Dev 2007; 17:513-8. [PMID: 17933508 DOI: 10.1016/j.gde.2007.09.001] [Citation(s) in RCA: 251] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2007] [Revised: 08/29/2007] [Accepted: 09/02/2007] [Indexed: 12/31/2022]
Abstract
Hybridization in plants and animals is more common and has more complex outcomes than previously realized. Genome-wide analyses of introgression in organisms ranging from oaks to sunflowers to fruit flies show that a substantial fraction of their genomes are permeable to alleles from related species. Hybridization can lead to rapid genomic changes, including chromosomal rearrangements, genome expansion, differential gene expression, and gene silencing, some of which are mediated by transposable elements. These genomic changes may lead to beneficial new phenotypes, and selection for fertility and ecological traits may in turn alter genome structure. Dramatic increases in the availability of genomic tools will produce a new understanding of the genetic nature of species and will resolve a century-old debate over the basis of hybrid vigor, while the natural recombinants found in hybrid zones will permit genetic mapping of species differences and reproductive barriers in nonmodel organisms.
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Affiliation(s)
- Eric J Baack
- Department of Botany, University of British Columbia, Vancouver, BC, Canada
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25
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Brouillette LC, Rosenthal DM, Rieseberg LH, Lexer C, Malmberg RL, Donovan LA. Genetic architecture of leaf ecophysiological traits in Helianthus. ACTA ACUST UNITED AC 2007; 98:142-6. [PMID: 17208933 PMCID: PMC2442921 DOI: 10.1093/jhered/esl063] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
We investigated quantitative trait loci (QTLs) for several leaf chemistry traits in early-generation hybrids between Helianthus annuus and Helianthus petiolaris, the parental species of the ancient diploid hybrid sunflower species Helianthus anomalus, Helianthus deserticola, and Helianthus paradoxus. We grew individuals of a second-generation backcross (BC(2)) toward H. petiolaris under optimum conditions in a glass house experiment. Trait values were measured once for each individual. In addition, genotypic data previously determined for each individual were employed for composite interval mapping of QTLs. We detected QTLs for leaf carbon concentration, leaf nitrogen concentration, leaf nitrogen per unit area, and photosynthetic nitrogen use efficiency. Leaf carbon isotope discrimination (delta(13)C) and leaf nitrogen isotopic composition (delta(15)N) were analyzed, but no significant QTLs were found for these traits. Interestingly, two neighboring loci explained a relatively large percentage of the variation in leaf nitrogen per unit area. This was notable because leaf nitrogen has been shown to strongly affect the fitness of early-generation sunflower hybrids in the H. anomalus habitat, and QTLs of large effect are expected to respond relatively quickly to selection. We speculate that the genetic architecture underlying leaf nitrogen may have facilitated the colonization of active desert sand dunes by H. anomalus.
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