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Morgan EJ, Čertner M, Lučanová M, Deniz U, Kubíková K, Venon A, Kovářík O, Lafon Placette C, Kolář F. Disentangling the components of triploid block and its fitness consequences in natural diploid-tetraploid contact zones of Arabidopsis arenosa. THE NEW PHYTOLOGIST 2021; 232:1449-1462. [PMID: 33768528 DOI: 10.1111/nph.17357] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Accepted: 03/15/2021] [Indexed: 06/12/2023]
Abstract
Hybrid seed inviability (HSI) is an important mechanism of reproductive isolation and speciation. HSI varies in strength among populations of diploid species but it remains to be tested whether similar processes affect natural variation in HSI within ploidy-variable species (triploid block). Here we used extensive endosperm, seed and F1 -hybrid phenotyping to explore HSI variation within a diploid-autotetraploid species. By leveraging 12 population pairs from three ploidy contact zones, we tested for the effect of interploidy crossing direction (parent of origin), ploidy divergence and spatial arrangement in shaping reproductive barriers in a naturally relevant context. We detected strong parent-of-origin effects on endosperm development, F1 germination and survival, which was also reflected in the rates of triploid formation in the field. Endosperm cellularization failure was least severe and F1 -hybrid performance was slightly better in the primary contact zone, with genetically closest diploid and tetraploid lineages. We demonstrated overall strong parent-of-origin effects on HSI in a ploidy variable species, which translate to fitness effects and contribute to interploidy reproductive isolation in a natural context. Subtle intraspecific variation in these traits suggests the fitness consequences of HSI are predominantly a constitutive property of the species regardless of the evolutionary background of its populations.
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Affiliation(s)
- Emma J Morgan
- Department of Botany, Faculty of Science, Charles University in Prague, Benátská 2, Prague, CZ-128 01, Czech Republic
| | - Martin Čertner
- Department of Botany, Faculty of Science, Charles University in Prague, Benátská 2, Prague, CZ-128 01, Czech Republic
- Institute of Botany of the Czech Academy of Sciences, Zámek 1, Průhonice, CZ-252 43, Czech Republic
| | - Magdalena Lučanová
- Department of Botany, Faculty of Science, Charles University in Prague, Benátská 2, Prague, CZ-128 01, Czech Republic
- Institute of Botany of the Czech Academy of Sciences, Zámek 1, Průhonice, CZ-252 43, Czech Republic
- Department of Botany, Faculty of Science, University of South Bohemia, Branišovská 31, České Budějovice, CZ-370 05, Czech Republic
| | - Utku Deniz
- Department of Botany, Faculty of Science, Charles University in Prague, Benátská 2, Prague, CZ-128 01, Czech Republic
| | - Kateřina Kubíková
- Department of Botany, Faculty of Science, Charles University in Prague, Benátská 2, Prague, CZ-128 01, Czech Republic
| | - Anthony Venon
- Department of Botany, Faculty of Science, Charles University in Prague, Benátská 2, Prague, CZ-128 01, Czech Republic
| | - Oleg Kovářík
- Datamole Inc., Vítězné Náměstí 2, Prague, CZ-160 00, Czech Republic
| | - Clément Lafon Placette
- Department of Botany, Faculty of Science, Charles University in Prague, Benátská 2, Prague, CZ-128 01, Czech Republic
| | - Filip Kolář
- Department of Botany, Faculty of Science, Charles University in Prague, Benátská 2, Prague, CZ-128 01, Czech Republic
- Institute of Botany of the Czech Academy of Sciences, Zámek 1, Průhonice, CZ-252 43, Czech Republic
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Liu Y, El-Kassaby YA. Transcriptome-wide analysis of introgression-resistant regions reveals genetic divergence genes under positive selection in Populus trichocarpa. Heredity (Edinb) 2021; 126:442-462. [PMID: 33214679 PMCID: PMC8027638 DOI: 10.1038/s41437-020-00388-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Revised: 11/04/2020] [Accepted: 11/04/2020] [Indexed: 11/09/2022] Open
Abstract
Comparing gene expression patterns and genetic polymorphisms between populations is of central importance for understanding the origin and maintenance of biodiversity. Based on population-specific gene expression levels and allele frequency differences, we sought to identify population divergence (PD) genes across the introgression-resistant genomic regions of Populus trichocarpa. Genes containing highly diverged loci [i.e., genetic divergence (GD)] or showing expression divergence (ED) between populations were widely distributed in the genome and substantially enriched in functional categories related to stress responses, disease resistance, timing of flowering, cell cycle regulation, plant growth, and development. Nine genomic regions showing evidence of strong positive selection were overlapped with GD genes, which had significant differences between Oregon (a southernmost peripheral deme) and the other demes. However, we did not find evidence that genes under positive selection show an enrichment for ED. PD genes and genes under selection pertained to the same gene classes, such as SERINE/CYSTEINE PROTEASE, ABC TRANSPORTER, GLYCOSYLTRANSFERASE and other transferases. Our analysis also revealed that GD genes were polymorphic within the species (41.9 ± 3.66 biallelic variants per gene), as previously reported in herbaceous plants. By contrast, ED genes contained less genetic variants (10.73 ± 1.14) and were likely highly expressed. In addition, we found that trans- rather than cis-acting variants considerably contribute to the evolution of >90% PD genes. Overall, this study elucidates that cohorts of PD genes agree with the general attributes of known speciation genes and GD genes will provide substrates for positive selection to operate on.
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Affiliation(s)
- Yang Liu
- Department of Forest and Conservation Sciences, The University of British Columbia, 2424 Main Mall, Vancouver, BC, V6T 1Z4, Canada.
| | - Yousry A El-Kassaby
- Department of Forest and Conservation Sciences, The University of British Columbia, 2424 Main Mall, Vancouver, BC, V6T 1Z4, Canada
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3
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The Evolution of Polymorphic Hybrid Incompatibilities in House Mice. Genetics 2018; 209:845-859. [PMID: 29692350 DOI: 10.1534/genetics.118.300840] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Accepted: 04/23/2018] [Indexed: 12/17/2022] Open
Abstract
Resolving the mechanistic and genetic bases of reproductive barriers between species is essential to understanding the evolutionary forces that shape speciation. Intrinsic hybrid incompatibilities are often treated as fixed between species, yet there can be considerable variation in the strength of reproductive isolation between populations. The extent and causes of this variation remain poorly understood in most systems. We investigated the genetic basis of variable hybrid male sterility (HMS) between two recently diverged subspecies of house mice, Mus musculus domesticus and Mus musculus musculus We found that polymorphic HMS has a surprisingly complex genetic basis, with contributions from at least five autosomal loci segregating between two closely related wild-derived strains of M. m. musculus One of the HMS-linked regions on chromosome 4 also showed extensive introgression among inbred laboratory strains and transmission ratio distortion (TRD) in hybrid crosses. Using additional crosses and whole genome sequencing of sperm pools, we showed that TRD was limited to hybrid crosses and was not due to differences in sperm motility between M. m. musculus strains. Based on these results, we argue that TRD likely reflects additional incompatibilities that reduce hybrid embryonic viability. In some common inbred strains of mice, selection against deleterious interactions appears to have unexpectedly driven introgression at loci involved in epistatic hybrid incompatibilities. The highly variable genetic basis to F1 hybrid incompatibilities between closely related mouse lineages argues that a thorough dissection of reproductive isolation will require much more extensive sampling of natural variation than has been commonly utilized in mice and other model systems.
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The role of reproductive isolation in allopolyploid speciation patterns: empirical insights from the progenitors of common wheat. Sci Rep 2017; 7:16004. [PMID: 29167543 PMCID: PMC5700127 DOI: 10.1038/s41598-017-15919-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Accepted: 11/03/2017] [Indexed: 11/15/2022] Open
Abstract
The ability to cause reproductive isolation often varies among individuals within a plant species. We addressed whether such polymorphism influenced speciation of the allopolyploid common wheat (Triticum aestivum L., AABBDD genome) by evaluating the expression of pre-pollination (outcrossing potential) and post-pollination (crossability) barriers in Aegilops tauschii Coss. (the D genome progenitor). In total, 201 Ae. tauschii accessions representing the entire natural habitat range of the species were used for anther length measurement and artificial crosses with a Triticum turgidum L. (the AB genome progenitor) tester. Intraspecific comparisons showed that both barriers were more strongly expressed in the TauL1 lineage than in the TauL2 lineage. The ability of Ae. tauschii to cause reproductive isolation in the hybridisation with T. turgidum might have markedly influenced common wheat’s speciation by inducing lineage-associated patterns of gene flow. The TauL2 accessions with high potential for natural hybridisation with T. turgidum clustered in the southern coastal Caspian region. This provided phenotypic support for the derivation of the D genome of common wheat from southern Caspian populations. The present study underscored the importance of approaches that incorporate the genealogical and geographic structure of the parental species’ reproductive isolation in understanding the mechanism of plant allopolyploid speciation.
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Kerwin RE, Sweigart AL. Mechanisms of Transmission Ratio Distortion at Hybrid Sterility Loci Within and Between Mimulus Species. G3 (BETHESDA, MD.) 2017; 7:3719-3730. [PMID: 28935753 PMCID: PMC5677164 DOI: 10.1534/g3.117.300148] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Accepted: 09/09/2017] [Indexed: 12/28/2022]
Abstract
Hybrid incompatibilities are a common correlate of genomic divergence and a potentially important contributor to reproductive isolation. However, we do not yet have a detailed understanding of how hybrid incompatibility loci function and evolve within their native species, or why they are dysfunctional in hybrids. Here, we explore these issues for a well-studied, two-locus hybrid incompatibility between hybrid male sterility 1 (hms1) and hybrid male sterility 2 (hms2) in the closely related yellow monkeyflower species Mimulus guttatus and M. nasutus By performing reciprocal backcrosses with introgression lines (ILs), we find evidence for gametic expression of the hms1-hms2 incompatibility. Surprisingly, however, hybrid transmission ratios at hms1 do not reflect this incompatibility, suggesting that additional mechanisms counteract the effects of gametic sterility. Indeed, our backcross experiment shows hybrid transmission bias toward M. guttatus through both pollen and ovules, an effect that is particularly strong when hms2 is homozygous for M. nasutus alleles. In contrast, we find little evidence for hms1 transmission bias in crosses within M. guttatus, providing no indication of selfish evolution at this locus. Although we do not yet have sufficient genetic resolution to determine if hybrid sterility and transmission ratio distortion (TRD) map to the same loci, our preliminary fine-mapping uncovers a genetically independent hybrid lethality system involving at least two loci linked to hms1 This fine-scale dissection of TRD at hms1 and hms2 provides insight into genomic differentiation between closely related Mimulus species and reveals multiple mechanisms of hybrid dysfunction.
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Affiliation(s)
- Rachel E Kerwin
- Department of Genetics, University of Georgia, Athens, Georgia 30602
| | - Andrea L Sweigart
- Department of Genetics, University of Georgia, Athens, Georgia 30602
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6
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Wade MJ, Johnson NA, Toquenaga Y. TEMPERATURE EFFECTS AND GENOTYPE‐BY‐ENVIRONMENT INTERACTIONS IN HYBRIDS: HALDANE'S RULE IN FLOUR BEETLES. Evolution 2017; 53:855-865. [DOI: 10.1111/j.1558-5646.1999.tb05379.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/1997] [Accepted: 01/08/1999] [Indexed: 11/28/2022]
Affiliation(s)
- Michael J. Wade
- Department of Biology, Jordan Hall Indiana University Bloomington Indiana 47405
| | - Norman A. Johnson
- Department of Entomology 102 Fernald, University of Massachusetts at Amherst Amherst Massachusetts 01003
| | - Yukihiko Toquenaga
- Institute of Biological Sciences, University of Tsukuba 1‐1‐1 Ten‐nou‐dai Tsukuba Japan
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Searcy KB, Macnair MR. DIFFERENTIAL SEED PRODUCTION IN
MIMULUS GUTTATUS
IN RESPONSE TO INCREASING CONCENTRATIONS OF COPPER IN THE PISTIL BY POLLEN FROM COPPER TOLERANT AND SENSITIVE SOURCES. Evolution 2017; 44:1424-1435. [DOI: 10.1111/j.1558-5646.1990.tb03836.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/1989] [Accepted: 01/09/1990] [Indexed: 11/30/2022]
Affiliation(s)
- Karen B. Searcy
- Department of Biological Sciences Mount Holyoke College South Hadley MA 01075 USA
| | - Mark R. Macnair
- Department of Biological Sciences University of Exeter Exeter EX4 4PS UK
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8
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Breeuwer JAJ, Werren JH. HYBRID BREAKDOWN BETWEEN TWO HAPLODIPLOID SPECIES: THE ROLE OF NUCLEAR AND CYTOPLASMIC GENES. Evolution 2017; 49:705-717. [PMID: 28565135 DOI: 10.1111/j.1558-5646.1995.tb02307.x] [Citation(s) in RCA: 123] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/1993] [Accepted: 08/15/1994] [Indexed: 11/30/2022]
Affiliation(s)
- Johannes A. J. Breeuwer
- Department of Biology University of Rochester Rochester New York 14627
- Institute for Systematics and Population Biology University of Amsterdam Kruislaan 320, 1098 SM Amsterdam The Netherlands
| | - John H. Werren
- Department of Biology University of Rochester Rochester New York 14627
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9
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Garner AG, Kenney AM, Fishman L, Sweigart AL. Genetic loci with parent-of-origin effects cause hybrid seed lethality in crosses between Mimulus species. THE NEW PHYTOLOGIST 2016; 211:319-31. [PMID: 26924810 DOI: 10.1111/nph.13897] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Accepted: 12/23/2015] [Indexed: 05/09/2023]
Abstract
In flowering plants, F1 hybrid seed lethality is a common outcome of crosses between closely related diploid species, but the genetic basis of this early-acting and potentially widespread form of postzygotic reproductive isolation is largely unknown. We intercrossed two closely related species of monkeyflower, Mimulus guttatus and Mimulus tilingii, to characterize the mechanisms and strength of postzygotic reproductive isolation. Then, using a reciprocal backcross design, we performed high-resolution genetic mapping to determine the genetic architecture of hybrid seed lethality and directly test for loci with parent-of-origin effects. We found that F1 hybrid seed lethality is an exceptionally strong isolating barrier between Mimulus species, with reciprocal crosses producing < 1% viable seeds. This form of postzygotic reproductive isolation appears to be highly polygenic, indicating that multiple incompatibility loci have accumulated rapidly between these closely related Mimulus species. It is also primarily caused by genetic loci with parent-of-origin effects, suggesting a possible role for imprinted genes in the evolution of Mimulus hybrid seed lethality. Our findings suggest that divergence in loci with parent-of-origin effects, which is probably driven by genomic coevolution within lineages, might be an important source of hybrid incompatibilities between flowering plant species.
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Affiliation(s)
- Austin G Garner
- Department of Genetics, University of Georgia, Athens, GA, 30602, USA
| | - Amanda M Kenney
- Department of Genetics, University of Georgia, Athens, GA, 30602, USA
- Department of Biological Sciences, St Edwards University, Austin, TX, 78704, USA
| | - Lila Fishman
- Department of Biological Sciences, University of Montana, Missoula, MT, 59812, USA
| | - Andrea L Sweigart
- Department of Genetics, University of Georgia, Athens, GA, 30602, USA
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Stanton K, Valentin CM, Wijnen ME, Stutstman S, Palacios JJ, Cooley AM. Absence of postmating barriers between a selfing vs. outcrossing Chilean Mimulus species pair. AMERICAN JOURNAL OF BOTANY 2016; 103:1030-1040. [PMID: 27283023 DOI: 10.3732/ajb.1600079] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Accepted: 05/10/2016] [Indexed: 06/06/2023]
Abstract
PREMISE OF THE STUDY Reproductive isolation between sympatric species pairs may be maintained by both pre- and postmating barriers. Here we evaluate potential barriers to mating between the outcrossing Mimulus luteus and its more highly selfing sympatric congener, M. cupreus, two members of the South American luteus complex of Mimulus. METHODS Seed set was compared following autonomous self-pollination, manual pollination, conspecific outcrossing, and sympatric and allopatric hybridization, for laboratory-maintained inbred lines and wild-collected accessions. Survival and reproductive fitness of hybrids relative to parental species were examined across environments that differed with respect to temperature and soil nutrients, two factors that vary across the ranges of M. luteus and M. cupreus. KEY RESULTS Mimulus luteus was minimally capable of autonomous self-fertilization, consistent with reliance on an animal pollinator, whereas M. cupreus was a successful selfer across all tested accessions. Postmating barriers to hybridization are negligible, in both low- and high-stress environments, across multiple sympatric and allopatric populations. CONCLUSION As in the North American M. guttatus-M. nasutus species pair, postmating barriers contribute little to isolation between M. luteus and M. cupreus. This result reinforces the importance of premating barriers, specifically species differences in reliance on, and accessibility to, animal pollinators. A unique aspect of the M. luteus-M. cupreus pair is the recent gain of red floral anthocyanin pigmentation in M. cupreus. On the basis of species differences in vegetative anthocyanin production, a facultative stress-protective response, we propose a potential stress-protective role for the constitutive floral anthocyanins of M. cupreus.
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Affiliation(s)
- Kimmy Stanton
- Whitman College Biology Department, Walla Walla, Washington 99362 USA
| | - Celine M Valentin
- Whitman College Biology Department, Walla Walla, Washington 99362 USA
| | - Marijke E Wijnen
- Whitman College Biology Department, Walla Walla, Washington 99362 USA
| | - Sage Stutstman
- Whitman College Biology Department, Walla Walla, Washington 99362 USA
| | | | - Arielle M Cooley
- Whitman College Biology Department, Walla Walla, Washington 99362 USA
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Sweigart AL, Flagel LE. Evidence of natural selection acting on a polymorphic hybrid incompatibility locus in Mimulus. Genetics 2015; 199:543-54. [PMID: 25428983 PMCID: PMC4317661 DOI: 10.1534/genetics.114.171819] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2014] [Accepted: 11/18/2014] [Indexed: 12/30/2022] Open
Abstract
As a common cause of reproductive isolation in diverse taxa, hybrid incompatibilities are fundamentally important to speciation. A key question is which evolutionary forces drive the initial substitutions within species that lead to hybrid dysfunction. Previously, we discovered a simple genetic incompatibility that causes nearly complete male sterility and partial female sterility in hybrids between the two closely related yellow monkeyflower species Mimulus guttatus and M. nasutus. In this report, we fine map the two major incompatibility loci-hybrid male sterility 1 (hms1) and hybrid male sterility 2 (hms2)-to small nuclear genomic regions (each <70 kb) that include strong candidate genes. With this improved genetic resolution, we also investigate the evolutionary dynamics of hms1 in a natural population of M. guttatus known to be polymorphic at this locus. Using classical genetic crosses and population genomics, we show that a 320-kb region containing the hms1 incompatibility allele has risen to intermediate frequency in this population by strong natural selection. This finding provides direct evidence that natural selection within plant species can lead to hybrid dysfunction between species.
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Affiliation(s)
- Andrea L Sweigart
- Department of Genetics, University of Georgia, Athens, Georgia 30602
| | - Lex E Flagel
- Department of Biology, Duke University, Durham, North Carolina 27708 Department of Plant Biology, University of Minnesota, St. Paul, Minnesota 55108
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Burge DO, Hopkins R, Tsai YHE, Manos PS. Limited hybridization across an edaphic disjunction between the gabbro-endemic shrub Ceanothus roderickii (Rhamnaceae) and the soil-generalist Ceanothus cuneatus. AMERICAN JOURNAL OF BOTANY 2013; 100:1883-1895. [PMID: 24018856 DOI: 10.3732/ajb.1200604] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
PREMISE OF THE STUDY Hybridization is thought to have played an important role in diversification of the speciose shrub genus Ceanothus; putative hybrid species have been described, and data suggest that intrinsic barriers may not exist among closely related species. However, the extent to which hybridization occurs in the wild is not known, and little is understood about how extrinsic factors such as soil chemistry may influence the process. The present research focuses on the gabbro-endemic C. roderickii and the closely related soil-generalist C. cuneatus. Though the species occur peripatrically, they remain distinct across an edaphic disjunction. • METHODS AFLP was used to quantify hybridization and introgression. Biological data and experiments were used to test for prezygotic isolation. Growth trials were used to test for local adaptation and selection against hybrids. • KEY RESULTS Ceanothus cuneatus and C. roderickii were strongly differentiated morphologically and genetically, despite a lack of evidence for prezygotic barriers. Hybrids and back-crosses were present but infrequent. Finally, there was selection against hybrids in nonnative soil. • CONCLUSIONS There is little genetic exchange between the focal species across an edaphic disjunction, despite the absence of prezygotic barriers. This result implies that soil conditions, as well as other extrinsic factors, should be considered as forces that may restrict hybridization and gene flow in Ceanothus, influencing local adaptation and speciation. Findings presented here are significant because they imply that exchange of genetic material between plants may be limited directly by the abiotic environment, rather than by the biology of the plants.
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Affiliation(s)
- Dylan O Burge
- Duke University Department of Biology, Box 90338 Durham, North Carolina 27705, USA
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13
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Investigating incipient speciation in Arabidopsis lyrata from patterns of transmission ratio distortion. Genetics 2013; 194:697-708. [PMID: 23666938 DOI: 10.1534/genetics.113.152561] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Our understanding of the development of intrinsic reproductive isolation is still largely based on theoretical models and thorough empirical studies on a small number of species. Theory suggests that reproductive isolation develops through accumulation of epistatic genic incompatibilities, also known as Bateson-Dobzhansky-Muller (BDM) incompatibilities. We can detect these from marker transmission ratio distortion (TRD) in hybrid progenies of crosses between species or populations, where TRD is expected to result from selection against heterospecific allele combinations in hybrids. TRD may also manifest itself because of intragenomic conflicts or competition between gametes or zygotes. We studied early stage speciation in Arabidopsis lyrata by investigating patterns of TRD across the genome in F2 progenies of three reciprocal crosses between four natural populations. We found that the degree of TRD increases with genetic distance between crossed populations, but also that reciprocal progenies may differ substantially in their degree of TRD. Chromosomes AL6 and especially AL1 appear to be involved in many single- and two-locus distortions, but the location and source of TRD vary between crosses and between reciprocal progenies. We also found that the majority of single- and two-locus TRD appears to have a gametic, as opposed to zygotic, origin. Thus, while theory on BDM incompatibilities is typically illustrated with derived nuclear alleles proving incompatible in hybrid zygotes, our results suggest a prominent role for distortions emerging before zygote formation.
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14
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Wright KM, Lloyd D, Lowry DB, Macnair MR, Willis JH. Indirect evolution of hybrid lethality due to linkage with selected locus in Mimulus guttatus. PLoS Biol 2013; 11:e1001497. [PMID: 23468595 PMCID: PMC3582499 DOI: 10.1371/journal.pbio.1001497] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Accepted: 01/16/2013] [Indexed: 02/01/2023] Open
Abstract
Most species are superbly and intricately adapted to the environments in which they live. Adaptive evolution by natural selection is the primary force shaping biological diversity. Differences between closely related species in ecologically selected characters such as habitat preference, reproductive timing, courtship behavior, or pollinator attraction may prevent interbreeding in nature, causing reproductive isolation. But does ecological adaptation cause reproductive incompatibilities such as hybrid sterility or lethality? Although several genes causing hybrid incompatibilities have been identified, there is intense debate over whether the genes that contribute to ecological adaptations also cause hybrid incompatibilities. Thirty years ago, a genetic study of local adaptation to copper mine soils in the wildflower Mimulus guttatus identified a locus that appeared to cause copper tolerance and hybrid lethality in crosses to other populations. But do copper tolerance and hybrid lethality have the same molecular genetic basis? Here we show, using high-resolution genome mapping, that copper tolerance and hybrid lethality are not caused by the same gene but are in fact separately controlled by two tightly linked loci. We further show that selection on the copper tolerance locus indirectly caused the hybrid incompatibility allele to go to high frequency in the copper mine population because of hitchhiking. Our results provide a new twist on Darwin's original supposition that hybrid incompatibilities evolve as an incidental by-product of ordinary adaptation to the environment.
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Affiliation(s)
- Kevin M Wright
- Department of Biology, Duke University, Durham, North Carolina, USA.
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15
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Incompatibility between X chromosome factor and pericentric heterochromatic region causes lethality in hybrids between Drosophila melanogaster and its sibling species. Genetics 2012; 191:549-59. [PMID: 22446316 DOI: 10.1534/genetics.112.139683] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The Dobzhansky-Muller model posits that postzygotic reproductive isolation results from the evolution of incompatible epistatic interactions between species: alleles that function in the genetic background of one species can cause sterility or lethality in the genetic background of another species. Progress in identifying and characterizing factors involved in postzygotic isolation in Drosophila has remained slow, mainly because Drosophila melanogaster, with all of its genetic tools, forms dead or sterile hybrids when crossed to its sister species, D. simulans, D. sechellia, and D. mauritiana. To circumvent this problem, we used chromosome deletions and duplications from D. melanogaster to map two hybrid incompatibility loci in F(1) hybrids with its sister species. We mapped a recessive factor to the pericentromeric heterochromatin of the X chromosome in D. simulans and D. mauritiana, which we call heterochromatin hybrid lethal (hhl), which causes lethality in F(1) hybrid females with D. melanogaster. As F(1) hybrid males hemizygous for a D. mauritiana (or D. simulans) X chromosome are viable, the lethality of deficiency hybrid females implies that a dominant incompatible partner locus exists on the D. melanogaster X. Using small segments of the D. melanogaster X chromosome duplicated onto the Y chromosome, we mapped a dominant factor that causes hybrid lethality to a small 24-gene region of the D. melanogaster X. We provide evidence suggesting that it interacts with hhl(mau). The location of hhl is consistent with the emerging theme that hybrid incompatibilities in Drosophila involve heterochromatic regions and factors that interact with the heterochromatin.
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Affiliation(s)
- James M Sobel
- Department of Plant Biology and Ecology, Evolutionary Biology and Behavior Program, Michigan State University, East Lansing, Michigan 48824, USA.
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Lowry DB, Modliszewski JL, Wright KM, Wu CA, Willis JH. Review. The strength and genetic basis of reproductive isolating barriers in flowering plants. Philos Trans R Soc Lond B Biol Sci 2008; 363:3009-21. [PMID: 18579478 PMCID: PMC2607309 DOI: 10.1098/rstb.2008.0064] [Citation(s) in RCA: 321] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Speciation is characterized by the evolution of reproductive isolation between two groups of organisms. Understanding the process of speciation requires the quantification of barriers to reproductive isolation, dissection of the genetic mechanisms that contribute to those barriers and determination of the forces driving the evolution of those barriers. Through a comprehensive analysis involving 19 pairs of plant taxa, we assessed the strength and patterns of asymmetry of multiple prezygotic and postzygotic reproductive isolating barriers. We then reviewed contemporary knowledge of the genetic architecture of reproductive isolation and the relative role of chromosomal and genic factors in intrinsic postzygotic isolation. On average, we found that prezygotic isolation is approximately twice as strong as postzygotic isolation, and that postmating barriers are approximately three times more asymmetrical in their action than premating barriers. Barriers involve a variable number of loci, and chromosomal rearrangements may have a limited direct role in reproductive isolation in plants. Future research should aim to understand the relationship between particular genetic loci and the magnitude of their effect on reproductive isolation in nature, the geographical scale at which plant speciation occurs, and the role of different evolutionary forces in the speciation process.
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Affiliation(s)
- David B Lowry
- University Program in Genetics and Genomics, Duke University Medical Center, Durham, NC 27710, USA.
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19
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Good JM, Handel MA, Nachman MW. Asymmetry and polymorphism of hybrid male sterility during the early stages of speciation in house mice. Evolution 2008; 62:50-65. [PMID: 18005156 PMCID: PMC2907743 DOI: 10.1111/j.1558-5646.2007.00257.x] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
House mice offer a powerful system for dissecting the genetic basis of phenotypes that isolate species in the early stages of speciation. We used a series of reciprocal crosses between wild-derived strains of Mus musculus and M. domesticus to examine F(1) hybrid male sterility, one of the primary phenotypes thought to isolate these species. We report four main results. First, we found significantly smaller testes and fewer sperm in hybrid male progeny of most crosses. Second, in some crosses hybrid male sterility was asymmetric and depended on the species origin of the X chromosome. These observations confirm and extend previous findings, underscoring the central role that the M. musculus X chromosome plays in reproductive isolation. Third, comparisons among reciprocal crosses revealed polymorphism at one or more hybrid incompatibilities within M. musculus. Fourth, the spermatogenic phenotype of this polymorphic interaction appears distinct from previously described hybrid incompatibilities between these species. These data build on previous studies of speciation in house mice and show that the genetic basis of hybrid male sterility is fairly complex, even at this early stage of divergence.
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Affiliation(s)
- Jeffrey M Good
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721, USA.
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20
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Koide Y, Onishi K, Nishimoto D, Baruah AR, Kanazawa A, Sano Y. Sex-independent transmission ratio distortion system responsible for reproductive barriers between Asian and African rice species. THE NEW PHYTOLOGIST 2008; 179:888-900. [PMID: 18507773 DOI: 10.1111/j.1469-8137.2008.02490.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
* A sex-independent transmission ratio distortion (siTRD) system detected in the interspecific cross in rice was analyzed in order to understand its significance in reproductive barriers. The S(1) gene, derived from African rice Oryza glaberrima, induced preferential abortion of both male and female gametes possessing its allelic alternative (), from Asian rice O. sativa, only in the heterozygote. * The siTRD was characterized by resolving it into mTRD and fTRD occurring through male and female gametes, respectively, cytological analysis of gametophyte development, and mapping of the S(1) locus using near-isogenic lines. The allelic distribution of the S(1) locus in Asian and African rice species complexes was also analyzed. * The siTRD system involved at least two components affecting male and female gametogeneses, respectively, including a modifier(s) that enhances fTRD. The chromosomal location of the major component causing the mTRD was delimited within an approx. 40 kb region. The S(1) locus induced hybrid sterility in any pairwise combination between Asian and African rice species complexes. * The allelic state of the S(1) locus has diverged between Asian and African rice species complexes, suggesting that the TRD system has a significant role in the reproductive barriers in rice.
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Affiliation(s)
- Yohei Koide
- Plant Breeding Laboratory, Research Faculty of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
| | - Kazumitsu Onishi
- Plant Breeding Laboratory, Research Faculty of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
| | - Daisuke Nishimoto
- Plant Breeding Laboratory, Research Faculty of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
| | - Akhil Ranjan Baruah
- Plant Breeding Laboratory, Research Faculty of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
| | - Akira Kanazawa
- Laboratory of Cell Biology and Manipulation, Research Faculty of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
| | - Yoshio Sano
- Plant Breeding Laboratory, Research Faculty of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
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21
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Abstract
Like the formation of animal species, plant speciation is characterized by the evolution of barriers to genetic exchange between previously interbreeding populations. Prezygotic barriers, which impede mating or fertilization between species, typically contribute more to total reproductive isolation in plants than do postzygotic barriers, in which hybrid offspring are selected against. Adaptive divergence in response to ecological factors such as pollinators and habitat commonly drives the evolution of prezygotic barriers, but the evolutionary forces responsible for the development of intrinsic postzygotic barriers are virtually unknown and frequently result in polymorphism of incompatibility factors within species. Polyploid speciation, in which the entire genome is duplicated, is particularly frequent in plants, perhaps because polyploid plants often exhibit ecological differentiation, local dispersal, high fecundity, perennial life history, and self-fertilization or asexual reproduction. Finally, species richness in plants is correlated with many biological and geohistorical factors, most of which increase ecological opportunities.
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Affiliation(s)
- Loren H Rieseberg
- Department of Botany, University of British Columbia, Vancouver, BC V6T 1Z4, Canada.
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22
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Wu CA, Lowry DB, Cooley AM, Wright KM, Lee YW, Willis JH. Mimulus is an emerging model system for the integration of ecological and genomic studies. Heredity (Edinb) 2007; 100:220-30. [PMID: 17551519 DOI: 10.1038/sj.hdy.6801018] [Citation(s) in RCA: 173] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The plant genus Mimulus is rapidly emerging as a model system for studies of evolutionary and ecological functional genomics. Mimulus contains a wide array of phenotypic, ecological and genomic diversity. Numerous studies have proven the experimental tractability of Mimulus in laboratory and field studies. Genomic resources currently under development are making Mimulus an excellent system for determining the genetic and genomic basis of adaptation and speciation. Here, we introduce some of the phenotypic and genetic diversity in the genus Mimulus and highlight how direct genetic studies with Mimulus can address a wide spectrum of ecological and evolutionary questions. In addition, we present the genomic resources currently available for Mimulus and discuss future directions for research. The integration of ecology and genetics with bioinformatics and genome technology offers great promise for exploring the mechanistic basis of adaptive evolution and the genetics of speciation.
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Affiliation(s)
- C A Wu
- Department of Biology, Duke University, Durham, NC 27708-0338, USA
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23
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Fishman L, Stratton DA. THE GENETICS OF FLORAL DIVERGENCE AND POSTZYGOTIC BARRIERS BETWEEN OUTCROSSING AND SELFING POPULATIONS OF ARENARIA UNIFLORA (CARYOPHYLLACEAE). Evolution 2007. [DOI: 10.1111/j.0014-3820.2004.tb01646.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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24
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Bomblies K, Weigel D. Hybrid necrosis: autoimmunity as a potential gene-flow barrier in plant species. Nat Rev Genet 2007; 8:382-93. [PMID: 17404584 DOI: 10.1038/nrg2082] [Citation(s) in RCA: 273] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Ecological factors, hybrid sterility and differences in ploidy levels are well known for contributing to gene-flow barriers in plants. Another common postzygotic incompatibility, hybrid necrosis, has received comparatively little attention in the evolutionary genetics literature. Hybrid necrosis is associated with a suite of phenotypic characteristics that are similar to those elicited in response to various environmental stresses, including pathogen attack. The genetic architecture is generally simple, and complies with the Bateson-Dobzhansky-Muller model for hybrid incompatibility between species. We survey the extensive literature on this topic and present the hypothesis that hybrid necrosis can result from autoimmunity, perhaps as a pleiotropic effect of evolution of genes that are involved in pathogen response.
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Affiliation(s)
- Kirsten Bomblies
- Department of Molecular Biology, Max Planck Institute for Developmental Biology, Spemanstrasse 37-39, 72076 Tübingen, Germany.
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25
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Abbott RJ, Comes HP. Blowin' in the wind - the transition from ecotype to species. THE NEW PHYTOLOGIST 2007; 175:197-200. [PMID: 17587369 DOI: 10.1111/j.1469-8137.2007.02127.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Affiliation(s)
- Richard J Abbott
- Mitchell Building, School of Biology, University of St Andrews, St Andrews, Fife KY16 9TH, UK
| | - Hans Peter Comes
- Department of Organismic Biology, Salzburg University, A-5020 Salzburg, Austria
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26
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Fishman L, Stratton DA. THE GENETICS OF FLORAL DIVERGENCE AND POSTZYGOTIC BARRIERS BETWEEN OUTCROSSING AND SELFING POPULATIONS OF ARENARIA UNIFLORA (CARYOPHYLLACEAE). Evolution 2004. [DOI: 10.1554/03-069] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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27
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Fishman L, Kelly AJ, Morgan E, Willis JH. A genetic map in the Mimulus guttatus species complex reveals transmission ratio distortion due to heterospecific interactions. Genetics 2001; 159:1701-16. [PMID: 11779808 PMCID: PMC1461909 DOI: 10.1093/genetics/159.4.1701] [Citation(s) in RCA: 225] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
As part of a study of the genetics of floral adaptation and speciation in the Mimulus guttatus species complex, we constructed a genetic linkage map of an interspecific cross between M. guttatus and M. nasutus. We genotyped an F(2) mapping population (N = 526) at 255 AFLP, microsatellite, and gene-based markers and derived a framework map through repeated rounds of ordering and marker elimination. The final framework map consists of 174 marker loci on 14 linkage groups with a total map length of 1780 cM Kosambi. Genome length estimates (2011-2096 cM) indicate that this map provides thorough coverage of the hybrid genome, an important consideration for QTL mapping. Nearly half of the markers in the full data set (49%) and on the framework map (48%) exhibited significant transmission ratio distortion (alpha = 0.05). We localized a minimum of 11 transmission ratio distorting loci (TRDLs) throughout the genome, 9 of which generate an excess of M. guttatus alleles and a deficit of M. nasutus alleles. This pattern indicates that the transmission ratio distortion results from particular interactions between the heterospecific genomes and suggests that substantial genetic divergence has occurred between these Mimulus species. We discuss possible causes of the unequal representation of parental genomes in the F(2) generation.
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Affiliation(s)
- L Fishman
- Department of Biology, Duke University, Durham, North Carolina 27708, USA.
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28
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Fishman L, Willis JH. EVIDENCE FOR DOBZHANSKY-MULLER INCOMPATIBILITES CONTRIBUTING TO THE STERILITY OF HYBRIDS BETWEEN MIMULUS GUTTATUS AND M. NASUTUS. Evolution 2001. [DOI: 10.1554/0014-3820(2001)055[1932:efdmic]2.0.co;2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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29
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Lopez GA, Potts BM, Tilyard PA. F1 hybrid inviability in eucalyptus: the case of E. ovata x E. globulus. Heredity (Edinb) 2000; 85 Pt 3:242-50. [PMID: 11012727 DOI: 10.1046/j.1365-2540.2000.00739.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The impact of inbreeding and hybridization on fitness was compared in the two co-occurring forest tree species, Eucalyptus ovata and E. globulus, aimed at explaining the rarity of their hybrids in nature. The success of selfing, open-pollination and outcrossing of both species and interspecific hybridization was monitored from seed-set to 10-year's growth in a field trial. There was a unilateral barrier to hybridization with seed-set obtained only with E. ovata females. The F1 hybrids exhibited reduced viability compared to intraspecific cross-types at virtually all stages of the life cycle and are clearly at a selective disadvantage compared with their open-pollinated E. ovata half-sibs with which they would directly compete in nature. Eucalyptus ovata and E. globulus overlap in their flowering time but the F1 hybrids flowered later with virtually no overlap with either species. The asynchronous flowering and reduced reproductive fitness of F1 hybrids would markedly limit the opportunity for advanced generation hybridization. Inbreeding similarly had a deleterious effect on the fitness of both species, and the F1 hybrids were most competitive with the E. ovata selfs. It is argued that changes in inbreeding levels of parental populations may be a key factor affecting the relative fitness of hybrids and their potential to impact on the pure species gene pool. Reduced fitness of the pure species through inbreeding may result in hybridization having its greatest evolutionary impact in small founder or relict populations.
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Affiliation(s)
- G A Lopez
- Cooperative Research Centre for Sustainable Production Forestry, School of Plant Science, University of Tasmania, GPO Box 252-55, Hobart, 7001, Tasmania, Australia
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30
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Consequences of cytonuclear epistasis and assortative mating for the genetic structure of hybrid populations. Heredity (Edinb) 1999. [DOI: 10.1038/sj.hdy.6884430] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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31
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Abstract
The last decade has brought renewed interest in the genetics of speciation, yielding a number of new models and empirical results. Defining speciation as 'the origin of reproductive isolation between two taxa', we review recent theoretical studies and relevant data, emphasizing the regular patterns seen among genetic analyses. Finally, we point out some important and tractable questions about speciation that have been neglected.
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Affiliation(s)
- J A Coyne
- Department of Ecology and Evolution, University of Chicago, IL 60637, USA
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32
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A polymorphism for a lethal phenotype governed by two duplicate genes in Mimulus guttatus. Heredity (Edinb) 1993. [DOI: 10.1038/hdy.1993.51] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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33
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Abstract
A previously unknown class of dominant, maternal-effect lethal M factors was found to be widespread in natural populations of the flour beetle, Tribolium castaneum, collected on several continents. Such factors are integrated into the host chromosomes at variable locations and show the remarkable property of self-selection by maternal-effect lethality to all hatchlings that do not inherit a copy of the factor itself. Offspring are rescued by either paternally or maternally inherited copies. The M-bearing chromosome is thereby perpetuated at the expense of its non-M homolog. M factors that map to different regions of the genome do not rescue one another's maternal-effect lethality. Factors expressing these properties are predicted to spread in a population, even in the absence of any additional selective advantage. Similar factors also occur in the related species T. confusum.
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Affiliation(s)
- R W Beeman
- U.S. Grain Marketing Research Laboratory, U.S. Department of Agriculture, Manhattan, KS 66502
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34
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Abstract
Many species are divided into a mosaic of genetically distinct populations, separated by narrow zones of hybridization. Studies of hybrid zones allow us to quantify the genetic differences responsible for speciation, to measure the diffusion of genes between diverging taxa, and to understand the spread of alternative adaptations.
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Affiliation(s)
- N H Barton
- Department of Genetics and Biometry, University College London, UK
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