The role of tetraploids in the sexual–asexual cycle in dandelions (Taraxacum)

Verduijn, M. H.; Dijk, Peter J. van; Damme, Jos M. M. Van

doi:10.1038/sj.hdy.6800515

Cited by 59 publications

(54 citation statements)

References 41 publications

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“…Detailed information about the information sources for the individual populations can be found in electronic supplementary material, table S1. The populations in Germany were shown earlier to consist mainly of triploids, while plants in the Swiss Alps are mostly diploid [29,35], allowing us to study the impact of M. melolontha on the evolution of secondary metabolites in both triploid apomictic and diploid obligate outcrossing plants. In both Germany and the Swiss Alps, we analysed three to four local herbivory, local control and regional control populations in spring 2013.…”

Section: Materials and Methods (A) Identification And Characterizationmentioning

confidence: 99%

A below-ground herbivore shapes root defensive chemistry in natural plant populations

et al. 2016

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Plants display extensive intraspecific variation in secondary metabolites. However, the selective forces shaping this diversity remain often unknown, especially below ground. Using Taraxacum officinale and its major native insect root herbivore Melolontha melolontha, we tested whether below-ground herbivores drive intraspecific variation in root secondary metabolites. We found that high M. melolontha infestation levels over recent decades are associated with high concentrations of major root latex secondary metabolites across 21 central European T. officinale field populations. By cultivating offspring of these populations, we show that both heritable variation and phenotypic plasticity contribute to the observed differences. Furthermore, we demonstrate that the production of the sesquiterpene lactone taraxinic acid b-D-glucopyranosyl ester (TA-G) is costly in the absence, but beneficial in the presence of M. melolontha, resulting in divergent selection of TA-G. Our results highlight the role of soil-dwelling insects for the evolution of plant defences in nature. BackgroundHeritable intraspecific variation is a common feature of many biological traits. Genetic variation results from heterogeneous selection pressures in relation to genetic architecture, population substructures and gene flow [1 -4]. In plants, local differences in both abiotic and biotic factors may drive trait evolution [5]. Insect herbivores, the most abundant and diverse plant consumers, have long been suspected to play an important role in this context [6]. Recent studies demonstrate that herbivore abundance can covary with the expression of plant defence metabolites [7], that the exclusion of phytophagous insects can lead to a relaxation of defences within a few generations [8] and that defence genes are under differential selection across environments [9,10]. Together, these studies show that the temporal and spatial variation in above-ground herbivore communities can shape plant defensive chemistry.In contrast with the ecological and evolutionary dynamics of above-ground plant-herbivore interactions, below-ground interactions have received little attention, despite the importance of roots for plant fitness and the high concentrations of secondary metabolites in below-ground organs [11][12][13][14]. The rhizosphere differs from the phyllosphere in both biotic and abiotic conditions [15], and the selective forces shaping variation in secondary metabolites may therefore differ between the two environments. The evolution of root secondary metabolites may for instance be driven by herbivores [11,12,16], pathogens [17] and symbionts [18], as well as nutrient availability [19], salt, drought and cold stress [20]. By comparing one mainland and two island populations, Watts et al. [21] showed that geographical isolation, including the escape from pocket gophers (Geomyidae), resulted in the evolutionary decline of root alkaloid concentrations of the host plant Eschscholzia californica (Papaveraceae). The specific potential of root herbivores to shap...

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Section: Materials and Methods (A) Identification And Characterizationmentioning

confidence: 99%

A below-ground herbivore shapes root defensive chemistry in natural plant populations

et al. 2016

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“…In contrast, the transition from triploidy to high ploidy levels has been reported in plants, e.g. in dandelions (Menken et al 1995;Verduijn et al 2004).…”

Section: Introductionmentioning

confidence: 90%

Production of diploid and triploid offspring by inbreeding of the triploid planarian Dugesia ryukyuensis

et al. 2008

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Triploidy has generally been considered to be an evolutionary dead end due to problems of chromosomal pairing and segregation during meiosis. Thus, the formation of tetraploids and diploids from triploid types is a rare phenomenon. In the present study, we demonstrated that inbreeding of the triploid planarian Dugesia ryukyuensis resulted in both diploid and triploid offspring in nature. In the triploids of D. ryukyuensis, chiasmata between homologous chromosomes were observed in both female and male germ lines. This result suggests that both diploid and triploid offspring of this species are produced bisexually by zygotic fusion between sperm and eggs. Hence, this phenomenon may be a novel mechanism in planarian for escaping the triploid state.

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“…The second explanation is that balancing selection maintains clonal diversity, which includes diversity in pollen production. It is known that the pollen produced by asexuals, even though it is largely inviable, can occasionally pollinate sexual diploid dandelions, resulting in gene flow between the sexuals and asexuals (Verduijn et al, 2004). The occurrence of gene flow between sexuals and Number of seed heads and percentage of inviable seeds were log-transformed; the percentage of seeds that germinated was arcsinetransformed prior to analysis.…”

Section: Fitness Benefit Of Male Sterilitymentioning

confidence: 99%

“…To reach this balance, the effective rate of production of new clonal lineages through pollen produced by asexuals has to be equal to the same 38% per generation. In a study of a dandelion population containing both sexuals and asexuals, Verduijn et al (2004) found that less than 2% of the offspring produced by sexuals was polyploid. Even if newly produced clonal lineages have a fitness benefit compared to the existing lineages (eg due to purging of deleterious mutations or escape from specialised parasites), the rate of gene flow required to balance the fitness benefit of male sterility would have to be unrealistically high, especially when considering the finding that newly created clones had a much lower seed set than established clones (De Kovel and De Jong, 2000).…”

Section: Pg Meirmans Et Almentioning

confidence: 99%

“…Crosses between sexuals and asexuals generally result in diploid, triploid and tetraploid offspring, though the latter are very rare in natural populations (Verduijn et al, 2004). Hybridisations between sexuals and asexuals are believed to be relatively common in natural populations as most variation at allozyme and microsatellite loci is shared between the sexuals and the asexuals (Menken et al, 1995;Meirmans et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

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Male sterility in triploid dandelions: asexual females vs asexual hermaphrodites

Meirmans

Nijs²,

Tienderen³

2005

Heredity

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Male reproductive output, pollen in plants and sperm in animals has been shown to constitute a substantial cost for many organisms. In parthenogenetic hermaphrodites, selection is therefore expected to reduce the allocation of resources to male reproductive output. However, sustained production of pollen or sperm has been observed in numerous asexual hermaphrodites. We studied the widespread production of pollen by triploid asexual dandelions, Taraxacum sect. Ruderalia, comparing rare male sterile individuals with pollen producing asexuals. We found that individuals can show plasticity in the production of pollen, but that it is nevertheless possible to distinguish between (facultatively) male sterile asexuals and male fertile asexuals. Based on evidence from genetic markers and crosses, we conclude that the male sterility in asexual dandelions is caused by nuclear genes, in contrast to the cytoplasmically inherited male sterility previously found in sexual dandelions. Male sterile lineages did not produce more seeds per flower head, heavier seeds or seeds that were more viable. However, male sterile plants did produce more seed heads and hence more seeds than pollen producing ones, indicating that they were able to reallocate resources toward seed production. Considering the difference in seed production, it remains puzzling that not more asexual dandelions are male sterile.

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The role of tetraploids in the sexual–asexual cycle in dandelions (Taraxacum)

Cited by 59 publications

References 41 publications

A below-ground herbivore shapes root defensive chemistry in natural plant populations

A below-ground herbivore shapes root defensive chemistry in natural plant populations

Production of diploid and triploid offspring by inbreeding of the triploid planarian Dugesia ryukyuensis

Male sterility in triploid dandelions: asexual females vs asexual hermaphrodites

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