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  • 1. Isabel, Nathalie
    et al.
    Lamothe, Manuel
    Thompson, Stacey Lee
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Laurentian Forestry Centre, Canadian Forest Service, Natural Resources Canada, Québec, Canada.
    A second-generation diagnostic single nucleotide polymorphism (SNP)-based assay, optimized to distinguish among eight poplar (Populus L.) species and their early hybrids2013In: Tree Genetics & Genomes, ISSN 1614-2942, E-ISSN 1614-2950, Vol. 9, no 2, p. 621-626Article in journal (Refereed)
    Abstract [en]

    Rapid identification of Populus L. species and hybrids can be achieved with relatively little effort through the use of primer extension-based single nucleotide polymorphism (SNP) genotyping assays. We present an optimized set of 36 SNP markers from 28 gene regions that diagnose eight poplar species (Populus angustifolia James, Populus balsamifera L., Populus deltoides Bartram, Populus fremontii Watson, Populus laurifolia Ledeb., Populus maximowiczii Henry, Populus nigra L., and Populus trichocarpa Torr. & Gray). A total of 700 DNA sequences from six Populus species (1–15 individuals per species) were used to construct the array. A set of flanking and probe oligonucleotides was developed and tested. The accuracy of the SNP assay was validated by genotyping 448 putatively "pure" individuals from 14 species of Populus. Overall, the SNP assay had a high success rate (97.6 %) and will prove useful for the identification of all Aigeiros Duby and Tacamahaca Spach. species and their early-generation hybrids within natural populations and breeding programs. Null alleles and intraspecific polymorphisms were detected for a few locus/species combinations in the Aigeiros and Tacamahaca sections. When we attempted to genotype aspens of the section Populus (Populus alba L., Populus grandidentata Michx., Populus tremula L., and Populus tremuloides Michx.), the success rate of the SNP array decreased by 13 %, demonstrating moderate cross-sectional transferability.

  • 2. Nystedt, Björn
    et al.
    Street, Nathaniel Robert
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Wetterbom, Anna
    Zuccolo, Andrea
    Lin, Yao-Cheng
    Scofield, Douglas G.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Vezzi, Francesco
    Delhomme, Nicolas
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Giacomello, Stefania
    Alexeyenko, Andrey
    Vicedomini, Riccardo
    Sahlin, Kristoffer
    Sherwood, Ellen
    Elfstrand, Malin
    Gramzow, Lydia
    Holmberg, Kristina
    Hällman, Jimmie
    Keech, Olivier
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Klasson, Lisa
    Koriabine, Maxim
    Kucukoglu, Melis
    Käller, Max
    Luthman, Johannes
    Lysholm, Fredrik
    Niittylä, Totte
    Olson, Åke
    Rilakovic, Nemanja
    Ritland, Carol
    Rosselló, Josep A.
    Sena, Juliana
    Svensson, Thomas
    Talavera-López, Carlos
    Theißen, Günter
    Tuominen, Hannele
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Vanneste, Kevin
    Wu, Zhi-Qiang
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Zhang, Bo
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Zerbe, Philipp
    Arvestad, Lars
    Bhalerao, Rishikesh
    Bohlmann, Joerg
    Bousquet, Jean
    Gil, Rosario Garcia
    Hvidsten, Torgeir R.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    de Jong, Pieter
    MacKay, John
    Morgante, Michele
    Ritland, Kermit
    Sundberg, Björn
    Thompson, Stacey Lee
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Van de Peer, Yves
    Andersson, Björn
    Nilsson, Ove
    Ingvarsson, Pär K.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Lundeberg, Joakim
    Jansson, Stefan
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    The Norway spruce genome sequence and conifer genome evolution2013In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 497, no 7451, p. 579-584Article in journal (Refereed)
    Abstract [en]

    Conifers have dominated forests for more than 200 million years and are of huge ecological and economic importance. Here we present the draft assembly of the 20-gigabase genome of Norway spruce (Picea abies), the first available for any gymnosperm. The number of well-supported genes (28,354) is similar to the >100 times smaller genome of Arabidopsis thaliana, and there is no evidence of a recent whole-genome duplication in the gymnosperm lineage. Instead, the large genome size seems to result from the slow and steady accumulation of a diverse set of long-terminal repeat transposable elements, possibly owing to the lack of an efficient elimination mechanism. Comparative sequencing of Pinus sylvestris, Abies sibirica, Juniperus communis, Taxus baccata and Gnetum gnemon reveals that the transposable element diversity is shared among extant conifers. Expression of 24-nucleotide small RNAs, previously implicated in transposable element silencing, is tissue-specific and much lower than in other plants. We further identify numerous long (>10,000 base pairs) introns, gene-like fragments, uncharacterized long non-coding RNAs and short RNAs. This opens up new genomic avenues for conifer forestry and breeding.

  • 3.
    O'Connell, Lisa M.
    et al.
    Department of Forest Sciences, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1Z4, Canada.
    Ritland, Kermit
    Department of Forest Sciences, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1Z4, Canada.
    Thompson, Stacey Lee
    bInstitut de Recherche en Biologie Végétale, Université de Montréal, 4101 Sherbrooke Est, Montréal, QC H1X 2B2, Canada.
    Patterns of post-glacial colonization by western redcedar (Thuja plicata, Cupressaceae) as revealed by microsatellite markers2008In: Botany - Botanique, Canadian Science Publishing , 2008, no 2, p. 194-203Conference paper (Refereed)
    Abstract [en]

    As knowledge of historical migration in response to climatic change allows insight into the dynamic nature of range shifts, patterns of post-glacial colonization were evaluated for the western redcedar (Thuja plicata Donn ex D. Don). We sampled and genotyped 620 trees from 23 populations across its range, including disjunct coastal and interior mesic sites. Genetic variation at eight microsatellite loci (mean alleles/locus = 10.30, mean expected heterozygosity = 0.755) was much higher than previous studies involving other markers, and inbreeding coefficients were predominantly positive (mean = 0.110). The two southernmost populations showed greatest genetic distances, while remaining populations clustered into three distinct geographic groups, comprising northern-coastal, central, and southern-interior populations, respectively. Genetic diversity decreased with latitude, while genetic and geographic distances were strongly correlated (r = 0.788). Our findings are consistent with independent routes of relatively recent colonization from one major refugium, located south of the glacial maximum, rather than ancient vicariant events. Regional bottlenecks, detected in the south of the range, may have resulted from local extinctions as the range of western redcedar advanced northward. Combined with inbreeding and the evolution of inbreeding tolerance, this may have promoted homozygosity for most classes of genetic markers as observed in other studies of this species.

  • 4. Roe, Amanda D.
    et al.
    MacQuarrie, Chris J. K.
    Gros-Louis, Marie-Claude
    Simpson, J. Dale
    Lamarche, Josyanne
    Beardmore, Tannis
    Thompson, Stacey L.
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Tanguay, Philippe
    Isabel, Nathalie
    Fitness dynamics within a poplar hybrid zone: I. Prezygotic and postzygotic barriers impacting a native poplar hybrid stand2014In: Ecology and Evolution, ISSN 2045-7758, E-ISSN 2045-7758, Vol. 4, no 9, p. 1629-1647Article in journal (Refereed)
    Abstract [en]

    Hybridization and introgression are pervasive evolutionary phenomena that provide insight into the selective forces that maintain species boundaries, permit gene flow, and control the direction of evolutionary change. Poplar trees (Populus L.) are well known for their ability to form viable hybrids and maintain their distinct species boundaries despite this interspecific gene flow. We sought to quantify the hybridization dynamics and postzygotic fitness within a hybrid stand of balsam poplar (Populus balsamifera L.), eastern cottonwood (P.deltoides Marsh.), and their natural hybrids to gain insight into the barriers maintaining this stable hybrid zone. We observed asymmetrical hybrid formation with P.deltoides acting as the seed parent, but with subsequent introgression biased toward P.balsamifera. Native hybrids expressed fitness traits intermediate to the parental species and were not universally unfit. That said, native hybrid seedlings were absent from the seedling population, which may indicate additional selective pressures controlling their recruitment. It is imperative that we understand the selective forces maintaining this native hybrid zone in order to quantify the impact of exotic poplar hybrids on this native system.

  • 5. Roe, Amanda D.
    et al.
    MacQuarrie, Chris J. K.
    Gros-Louis, Marie-Claude
    Simpson, J. Dale
    Lamarche, Josyanne
    Beardmore, Tannis
    Thompson, Stacey L.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Tanguay, Philippe
    Isabel, Nathalie
    Fitness dynamics within a poplar hybrid zone: II. Impact of exotic sex on native poplars in an urban jungle2014In: Ecology and Evolution, ISSN 2045-7758, E-ISSN 2045-7758, Vol. 4, no 10, p. 1876-1889Article in journal (Refereed)
    Abstract [en]

    Trees bearing novel or exotic gene components are poised to contribute to the bioeconomy for a variety of purposes such as bioenergy production, phytoremediation, and carbon sequestration within the forestry sector, but sustainable release of trees with novel traits in large-scale plantations requires the quantification of risks posed to native tree populations. Over the last century, exotic hybrid poplars produced through artificial crosses were planted throughout eastern Canada as ornamentals or windbreaks and these exotics provide a proxy by which to examine the fitness of exotic poplar traits within the natural environment to assess risk of exotic gene escape, establishment, and spread into native gene pools. We assessed postzygotic fitness traits of native and exotic poplars within a naturally regenerated stand in eastern Canada (Quebec City, QC). Pure natives (P.balsamifera and P.deltoides spp. deltoides), native hybrids (P.deltoidesxP.balsamifera), and exotic hybrids (trees bearing Populus nigra and P.maximowiczii genetic components) were screened for reproductive biomass, yield, seed germination, and fungal disease susceptibility. Exotic hybrids expressed fitness traits intermediate to pure species and were not significantly different from native hybrids. They formed fully viable seed and backcrossed predominantly with P.balsamifera. These data show that exotic hybrids were not unfit and were capable of establishing and competing within the native stand. Future research will seek to examine the impact of exotic gene regions on associated biotic communities to fully quantify the risk exotic poplars pose to native poplar forests.

  • 6.
    Sullivan, Alexis R.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Schiffthaler, Bastian
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Thompson, Stacey Lee
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Biology, Dalhousie University, Halifax, NS, Canada.
    Street, Nathaniel R.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Wang, Xiao-Ru
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Interspecific Plastome Recombination Reflects Ancient Reticulate Evolution in Picea (Pinaceae)2017In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 34, no 7, p. 1689-1701Article in journal (Refereed)
    Abstract [en]

    Plastid sequences are a cornerstone in plant systematic studies and key aspects of their evolution, such as uniparental inheritance and absent recombination, are often treated as axioms. While exceptions to these assumptions can profoundly influence evolutionary inference, detecting them can require extensive sampling, abundant sequence data, and detailed testing. Using advancements in high-throughput sequencing, we analyzed the whole plastomes of 65 accessions of Picea, a genus of similar to 35 coniferous forest tree species, to test for deviations from canonical plastome evolution. Using complementary hypothesis and data-driven tests, we found evidence for chimeric plastomes generated by interspecific hybridization and recombination in the clade comprising Norway spruce (P. abies) and 10 other species. Support for interspecific recombination remained after controlling for sequence saturation, positive selection, and potential alignment artifacts. These results reconcile previous conflicting plastid-based phylogenies and strengthen the mounting evidence of reticulate evolution in Picea. Given the relatively high frequency of hybridization and biparental plastid inheritance in plants, we suggest interspecific plastome recombination may be more widespread than currently appreciated and could underlie reported cases of discordant plastid phylogenies.

  • 7.
    Talbot, Patricia
    et al.
    bLaurentian Forestry Centre, Canadian Forest Service, Natural Resources Canada, 1055 rue du PEPS, Québec, QC G1V 4C7, Canada.
    Thompson, Stacey Lee
    bLaurentian Forestry Centre, Canadian Forest Service, Natural Resources Canada, 1055 rue du PEPS, Québec, QC G1V 4C7, Canada.
    Schroeder, William
    cAgroforestry Development Centre, AAFC Agri-Environment Services Branch, P.O. Box 940, No. 2 Government Road, Indian Head, SK S0G 2K0, Canada.
    Isabel, Nathalie
    bLaurentian Forestry Centre, Canadian Forest Service, Natural Resources Canada, 1055 rue du PEPS, Québec, QC G1V 4C7, Canada.
    An efficient single nucleotide polymorphism assay to diagnose the genomic identity of poplar species and hybrids on the Canadian prairies2011In: Canadian Journal of Forest Research, ISSN 0045-5067, E-ISSN 1208-6037, Vol. 41, no 5, p. 1102-1111Article in journal (Refereed)
    Abstract [en]

    Hybridization frequently occurs among poplars, both naturally and artificially, hindering identification. Over 32 million clonal poplars, predominantly hybrids, have been planted throughout the Canadian prairies over the past century, making confirmation of genomic identity important. We developed a genotyping assay that rapidly diagnoses four compatible Populus species (Populus balsamifera L. and Populus deltoides Bartr. ex Marsh.: indigenous, Populus laurifolia Ledeb. and Populus nigra L.: exotics) and their hybrids found throughout this ecozone. First, we sequenced 23 genes from representative provenances of the four Populus species to discover single nucleotide polymorphisms (SNPs). Second, we developed and validated a medium-throughput genotyping assay of 26 diagnostic SNPs within these genes. We used this assay to genotype 198 trees from natural populations as well as 30 clones (pure species and hybrids), including those broadly distributed by Agriculture and Agri-Food Canada's Agroforestry Development Centre since 1910. This suite of SNPs has the resolving power to correctly identify pure species and hybrids of Populus. We confirmed the identity of clones of well-documented origin, complex hybrids with exotic components, and paternity of open-pollinated progenies from breeding programs. This diagnostic tool should prove useful for efficient molecular fingerprinting of breeding material and for further studies of interspecific gene flow on the Canadian prairies.

  • 8.
    Thompson, Stacey Lee
    Institut de recherche en biologie végétale, Université de Montréal, 4101 Sherbrooke Est, Montréal, QC, Canada.
    A simple procedure for joint estimation of the long-term rates of sexuality and mutation in predominantly clonal populations, for use with dominant molecular markers2007In: Molecular Ecology Notes, ISSN 1471-8278, E-ISSN 1471-8286, Vol. 7, no 4, p. 567-569Article in journal (Refereed)
    Abstract [en]

    In highly clonal populations, mutation can contribute to the rate of apparent sexuality. To remove this bias, a method is presented that jointly estimates the rates of sexuality (Ns) and mutation (N mu) for populations, based upon levels of single-locus vs. multilocus clonal identity. This effectively haploid model assumes equilibrium, and can be used with dominant molecular data and in conjunction with organisms of various ploidies. Simulations indicate that while equilibrium can take thousands of generations to attain, and afterwards have a large evolutionary variance, the method gives approximate estimates of Ns.

  • 9.
    Thompson, Stacey Lee
    et al.
    Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055, rue du P.E.P.S., c.p. 10380 Succursale Sainte-Foy, Québec QC G1V 4C7 Canada.
    Bérubé, Yanik
    Department of Forest Sciences, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1Z4, Canada.
    Bruneau, Anne
    Institut de Recherche en Biologie Végétale, Université de Montréal, 4101 Sherbrooke Est, Montréal QC H1X 2B2, Canada.
    Ritland, Kermit
    Department of Forest Sciences, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1Z4, Canada.
    Three-gene identity coefficients demonstrate that clonal reproduction promotes inbreeding and spatial relatedness in yellow-cedar, Callitropsis nootkatensis2008In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 62, no 10, p. 2570-2579Article in journal (Refereed)
    Abstract [en]

    Asexual reproduction has the potential to promote population structuring through matings between clones as well as through limited dispersal of related progeny. Here we present an application of three-gene identity coefficients that tests whether clonal reproduction promotes inbreeding and spatial relatedness within populations. With this method, the first two genes are sampled to estimate pairwise relatedness or inbreeding, whereas the third gene is sampled from either a clone or a sexually derived individual. If three-gene coefficients are significantly greater for clones than nonclones, then clonality contributes excessively to genetic structure. First, we describe an estimator of three-gene identity and briefly evaluate its properties. We then use this estimator to test the effect of clonality on the genetic structure within populations of yellow-cedar (Callitropsis nootkatensis) using a molecular marker survey. Five microsatellite loci were genotyped for 485 trees sampled from nine populations. Our three-gene analyses show that clonal ramets promote inbreeding and spatial structure in most populations. Among-population correlations between clonal extent and genetic structure generally support these trends, yet with less statistical significance. Clones appear to contribute to genetic structure through the limited dispersal of offspring from replicated ramets of the same clonal genet, whereas this structure is likely maintained by mating among these relatives.

  • 10.
    Thompson, Stacey Lee
    et al.
    Institut de recherche en biologie végétale, Université de Montréal, Canada.
    Choe, Gina
    Ritland, Kermit
    Whitton, Jeannette
    Cryptic sex within male-sterile polyploid populations of the Easter daisy, Townsendia hookeri2008In: International journal of plant sciences, ISSN 1058-5893, E-ISSN 1537-5315, Vol. 169, no 1, p. 183-193Article in journal (Refereed)
    Abstract [en]

    After a transition from sexuality to asexuality, the evolutionary dynamics in apomictic lineages will largely depend on the frequency of recombination. We evaluated the presence and extent of asexuality and recombination within populations of the Easter daisy, Townsendia hookeri, from the Yukon Territory, Canada. Amplified fragment-length polymorphism (AFLP) fingerprints were used to genotype 78 individuals from four populations. Multilocus AFLP genotypes from each population were subjected to four tests for deviations from free recombination among loci, and the long-term frequency of sexuality was estimated for each population with a novel procedure. In addition, a sample of individuals was surveyed for genome size using flow cytometry, and pollen was assayed for male fertility. One male-fertile, diploid population showed evidence of rampant recombination. Two male-sterile populations (i.e., with aborted anthers) were tetraploid and asexual. The remaining population was male-sterile and included both triploids and tetraploids. Evidence of both sexuality and asexuality was uncovered in this mixed-ploidy population, at an equilibrium rate of approximately three sexual events every two generations. The presence and extent of sexuality differed with ploidy, while cryptic sex was uncovered within a morphologically asexual population, thus reinforcing the power of genome surveys to assess reproductive dynamics at the limit of a plant's geographical range.

  • 11.
    Thompson, Stacey Lee
    et al.
    Institut de Recherche en Biologie Végétale, Université de Montréal, 4101 Sherbrooke Est, Montréal QC H1X 2B2, Canada.
    Lamothe, Manuel
    Institut de Recherche en Biologie Végétale, Université de Montréal, 4101 Sherbrooke Est, Montréal QC H1X 2B2, Canada.
    Meirmans, Patrick G
    Institut de Recherche en Biologie Végétale, Université de Montréal, 4101 Sherbrooke Est, Montréal QC H1X 2B2, Canada.
    Périnet, Pierre
    Ministère des Ressources naturelles et de la Faune du Québec, 2700 Einstein, Québec, QC G1P 3W8, Canada.
    Isabel, Nathalie
    Institut de Recherche en Biologie Végétale, Université de Montréal, 4101 Sherbrooke Est, Montréal QC H1X 2B2, Canada.
    Repeated unidirectional introgression towards Populus balsamifera in contact zones of exotic and native poplars.2010In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 19, no 1, p. 132-145Article in journal (Refereed)
    Abstract [en]

    As the evolutionary significance of hybridization is largely dictated by its extent beyond the first generation, we broadly surveyed patterns of introgression across a sympatric zone of two native poplars (Populus balsamifera, Populus deltoides) in Quebec, Canada within which European exotic Populus nigra and its hybrids have been extensively planted since the 1800s. Single nucleotide polymorphisms (SNPs) that appeared fixed within each species were characterized by DNA-sequencing pools of pure individuals. Thirty-five of these diagnostic SNPs were employed in a high-throughput assay that genotyped 635 trees of different age classes, sampled from 15 sites with various degrees of anthropogenic disturbance. The degree of admixture within sampled trees was then assessed through Bayesian clustering of genotypes. Hybrids were present in seven of the populations, with 2.4% of all sampled trees showing spontaneous admixture. Sites with hybrids were significantly more disturbed than pure stands, while hybrids comprised both immature juveniles and trees of reproductive age. All three possible F1s were detected. Advanced-generation hybrids were consistently biased towards P. balsamifera regardless of whether hybridization had occurred with P. deltoides or P. nigra. Gene exchange between P. deltoides and P. nigra was not detected beyond the F1 generation; however, detection of a trihybrid demonstrates that even this apparent reproductive isolation does not necessarily result in an evolutionary dead end. Collectively, results demonstrate the natural fertility of hybrid poplars and suggest that introduced genes could potentially affect the genetic integrity of native trees, similar to that arising from introgression between natives.

  • 12.
    Thompson, Stacey Lee
    et al.
    Department of Botany and Centre for Biodiversity Research, University of British Columbia, Vancouver, British Columbia, Canada.
    Ritland, Kermit
    A novel mating system analysis for modes of self-oriented mating applied to diploid and polyploid arctic Easter daisies (Townsendia hookeri).2006In: Heredity, ISSN 0018-067X, E-ISSN 1365-2540, Vol. 97, no 2, p. 119-126Article in journal (Refereed)
    Abstract [en]

    We have developed a new model for mating system analysis, which attempts to distinguish among alternative modes of self-oriented mating within populations. This model jointly estimates the rates of outcrossing, selfing, automixis and apomixis, through the use of information in the family structure given by dominant genetic marker data. The method is presented, its statistical properties evaluated, and is applied to three arctic Easter daisy populations, one consisting of diploids, the other two of tetraploids. The tetraploids are predominantly male sterile and reported to be apomictic while the diploids are male fertile. In each Easter daisy population, 10 maternal arrays of six progeny were assayed for amplified fragment length polymorphism markers. Estimates, confirmed with likelihood ratio tests of mating hypotheses, showed apomixis to be predominant in all populations (ca. 70%), but selfing or automixis was moderate (ca. 25%) in tetraploids. It was difficult to distinguish selfing from automixis, and simulations confirm that with even very large sample sizes, the estimates have a very strong negative statistical correlation, for example, they are not independent. No selfing or automixis was apparent in the diploid population, instead, moderate levels of outcrossing were detected (23%). Low but significant levels of outcrossing (2-4%) seemed to occur in the male-sterile tetraploid populations; this may be due to genotyping error of this level. Overall, this study shows apomixis can be partial, and provides evidence for higher levels of inbreeding in polyploids compared to diploids and for significant levels of apomixis in a diploid plant population.

  • 13.
    Thompson, Stacey Lee
    et al.
    Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada.
    Whitton, Jeannette
    Patterns of recurrent evolution and geographic parthenogenesis within apomictic polyploid Easter daises (Townsendia hookeri).2006In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 15, no 11, p. 3389-3400Article in journal (Refereed)
    Abstract [en]

    Geographic patterns of parthenogenesis and the number of transitions from sexual diploidy to asexual (apomictic) autopolyploidy were examined for 40 populations of the Easter daisy, Townsendia hookeri. Analyses of pollen diameter and stainability characterized 15 sexual diploid and 25 apomictic polyploid populations from throughout the plant's western North American range. Sexual diploids were restricted to two Wisconsin refugia: Colorado/Wyoming, south of the ice sheets, and northern Yukon/Beringia. Chloroplast DNA sequencing uncovered 17 polymorphisms within the ndhF gene and trnK intron, yielding 10 haplotypes. Phylogenetic analyses indicated that five exclusively polyploid haplotypes were derived from four haplotypes that are shared among ploidies, conservatively inferring a minimum of four origins of apomictic polyploidy. Three of these apomictic polyploid origins were derived from southern sexual diploids, while the fourth origin was derived from northern sexual diploids. Analyses of regional diversity were suggestive of a formerly broad distribution for sexual diploids that has become subsequently fragmented, possibly due to the last round of glaciation. As sexual diploids were exclusively found north and south of the glacial maximum, while formerly glaciated areas were exclusively inhabited by asexual polyploids derived from both northern and southern sexual lineages, it is more likely that patterns of glaciation, as opposed to a particular latitudinal trend, played a causal role in the establishment of the observed pattern of geographic parthenogenesis in Easter daisies.

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