Sexual and asexual Taraxacum species

Mogie, Michael; Ford, Henry

doi:10.1111/j.1095-8312.1988.tb00463.x

Cited by 60 publications

(41 citation statements)

References 39 publications

(17 reference statements)

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“…Richards (1973) postulated that migration of a hybrid swarm of apomicts occurred after the last ice age and that the present polyploid apomictic genotypes are the remnants of this event. Mogie and Ford (1988) extended this hypothesis by indicating that the historical dominance of triploid apomicts in Northern Europe exists because self-incompatible diploid sexuals currently cannot or only marginally penetrate areas where triploids prevail. In large areas that are absolutely dominated by triploid apomicts, the maintenance of genotypic diversity through sexual recruitment will be limited if not absent.…”

Section: Introductionmentioning

confidence: 89%

Genetic structure of a population sample of apomictic dandelions

et al. 2003

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In Northern Europe, dandelion populations consist solely of triploid or higher polyploid apomicts. Without a regular sexual cycle or lateral gene transmission, a clonal structure is expected for Taraxacum apomicts, although this was not found by compatibility analysis. In this study, we investigate whether this observation could be suported by performing independent tests based on data from hypervariable microsatellite markers as well as more conservative data based on allozymes and matrilinear cpDNA markers. In addition, population genetic methods were used to test departure from panmictic expectations, which is expected for clonal populations. Results indicated that many data sets, again, did not agree with expectations from clonal evolution because only small groups of genotypes exhibit no marker incompatibility. Population genetic analysis revealed that virtually all genotypes, but not individuals, agreed with random segregation and genotypic equilibria. Exceptions were genotypes with rare allozyme alleles or nearly identical microsatellite genotypes. Consequently, a population sample of apomictic dandelions essentially harbours genotypes that resulted from segregation and/or recombination and only a few genotypes that may have differentiated by somatic mutations.

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Section: Introductionmentioning

confidence: 89%

Genetic structure of a population sample of apomictic dandelions

et al. 2003

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“…Low germination rates of dandelion seeds frequently are due to pathogenic infection or physical and physiological damage to seeds 8) . In addition, its seedling establishment rate is very low (1%) 9) . Thus, dandelion is often vegetatively propagated using leaf cutting methods 10) .…”

Section: Introductionmentioning

confidence: 99%

Optimization of in vitro seed germination of Taraxacum platycarpum

Lee¹,

Kim²,

Oh³

et al. 2009

Korean Journal of Environmental Agriculture

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Dandelion (Taraxacum platycarpum) has been widely utilized for medicinal purposes. However, the dandelion seeds are relatively difficult to germinate under cultivation conditions, which hampers seedling propagation of dandelion plants and reduces the opportunity of usage of such a useful medicinal plant. Thus, in this study, in vitro conditions for the dandelion seed germination were optimized to enhance the germination rate. In seed washing steps, the sequential treatments with 20% of ethanol, 20% of NaOCl, and distilled water avoided microbial contamination with the highest in vitro germination rate (67.5%) from seeds sown in germination media. The media supplemented with 1.4 g/L of MS salts and 1% of sucrose significantly enhanced the germination rate compared to the media with 4.4 g/L of MS and 3% of sucrose. Sowing the seeds vertically in the optimized media supplement conditions, 1.4 g/L of MS salts and 1% of sucrose, gave the maximum in vitro germination rate (61%), which was almost three times higher than sowing seeds on a soil pot (23%). Our results indicate that the seed washing and sowing methods including germination medium supplements can be optimized to enhance in vitro seed germination of dandelion.

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“…The high mutation load of au-todiploid parthenogenetic C. limum is also consistent with their recent origin from sexual ancestors and short persistence times as inferred from mtDNA sequence variation (Johnson and Bragg 1999). It is not entirely clear that diploids should have a higher mutation load than polyploid asexuals (Mogie and Ford 1988). For example, although polyploids should have a higher mutation load because the overall mutation rate per polyploid genome is higher, they may better mask partially recessive deleterious alleles.…”

Section: Discussionmentioning

confidence: 55%

“…Ploidy level may influence mutation load (Mogie and Ford 1988;Kondrashov 1994Kondrashov , 1997 and recent studies of the fitness of sexual and parthenogenetic snails suggest that triploid parthenogens do not suffer reductions in fitness components compared to sexuals. In the New Zealand snail Potamopyrgus antipodarum, there is a twofold fitness advantage to autotriploid parthenogens relative to sexuals under stressful and nonstressful conditions (Jokela et al 1997;Lively et al 1998).…”

Section: Discussionmentioning

confidence: 99%

“…Hybrid parthenogens may have more than a twofold advantage if they exhibit heterosis for fitness (Vrijenhoek 1990). Likewise, polyploids may be better buffered against deleterious recessive mutations even though they should have a higher mutation rate than diploid sexuals and parthenogens (Mogie and Ford 1988;Kondrashov 1994Kondrashov , 1997. Ideally, an examination of these hypotheses would involve sexuals and nonhybrid asexuals with similar ploidy levels.…”

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confidence: 99%

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POPULATION STRUCTURE, PARASITISM, AND SURVIVORSHIP OF SEXUAL AND AUTODIPLOID PARTHENOGENETICCAMPELOMA LIMUM

Johnson¹

2000

Evolution

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Abstract. Two theories for the maintenance of sexual reproduction, the Red Queen hypothesis and mutation accumulation, suggest that the dispersal rates of sexuals and asexuals may determine the elimination or persistence of asexuals. Under higher dispersal rates of asexuals, asexuals may temporarily escape virulent parasites and reduce the effects of deleterious mutations. In the present study, I examine the population structure, parasite loads, and juvenile survivorship of Campeloma limum sexuals and autodiploid parthenogens from the southeastern U.S. Atlantic coastal plain. Using mtDNA sequence variation, it is shown that parthenogenetic haplotypes with limited sequence divergence are geographically widespread throughout this region and there is no significant population differentiation over a broad geographical scale. Sexual C. limum populations show significant mtDNA differentiation among and within river drainages and there is significant isolation by distance. These patterns are consistent with a recent origin and range expansion of parthenogens. Prevalence of infection by digenetic trematodes is significantly higher in autodiploid parthenogens, and the variance of prevalence is also higher in autodiploid parthenogens. I argue that the latter pattern indicates that unparasitized parthenogens have temporarily escaped these virulent parasites, but recolonization of these populations by trematodes results in high infection levels (Ͼ 40%), possibly due to reduced variation in resistance genes. I also examined whether the survivorship of juvenile sexuals and parthenogens varied under different stress levels. Sexual juveniles had twofold higher survivorship in all environments. Compared to polyploid parthenogens, autodiploid parthenogens may be less buffered against the effects of deleterious recessive alleles. I propose that the combined effects of higher parasitism and reduced juvenile survivorship of these autodiploid parthenogens accounts for the spatial distribution of sexual and parthenogenetic C. limum in the Atlantic coastal plain. Parthenogens may persist by higher dispersal rates into marginal habitats where there is a temporary escape from digenetic trematodes and competition with sexuals.

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Sexual and asexual Taraxacum species

Cited by 60 publications

References 39 publications

Genetic structure of a population sample of apomictic dandelions

Genetic structure of a population sample of apomictic dandelions

Optimization of in vitro seed germination of Taraxacum platycarpum

POPULATION STRUCTURE, PARASITISM, AND SURVIVORSHIP OF SEXUAL AND AUTODIPLOID PARTHENOGENETICCAMPELOMA LIMUM

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