Population differentiation in grassland vegetation

Ernst, W. H. O.

doi:10.1007/978-94-009-4055-0_14

Cited by 15 publications

(8 citation statements)

References 65 publications

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“…Field comparisons between metalliferous and non-metalliferous sites (Ernst, Schat & Verkleij, 1990), or between hyperaccumulating and nonhyperaccumulating species (Baker & Proctor, 1988), ignore a plethora of factors other than metal accumulation, that could explain herbivore abundance in nature. Studies demonstrating that hyperaccumulators are toxic to animals feeding upon them (Ernst, 1987;Boyd & Martens, 1994), although of considerable importance to environmental toxicology, do not demonstrate that hyperaccumulation benefits the plant or would evolve under selection pressures of herbivory.…”

Section: Discussionmentioning

confidence: 99%

Deterrence of herbivory by zinc hyperaccumulation in Thlaspi caerulescens (Brassicaceae)

1997

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SUMMARYPlants known as byperaccumulators take up and sequester bigb concentrations of potentially toxic elements from metalliferous soils. We tested tbe hypothesis tbat zinc hyperaccumulation benefits plants by deterring berbivory. In laboratory feeding trials, tbree species of herbivores were allowed to choose between Thlaspi caerulescens (Brassicaceae) plants grown in low-Zn and Zn-amended culture solution. Locusts (Schistocerca gregaria), slugs (Deroceras caruanae), and caterpillars (Pieris brassicae) all showed significant preferences for plants witb lower foliar Zn concentrations. Such differential feeding could result in selection pressures favouring tbe evolution of byperaccumulation. Tbe findings are also relevant to current proposals to exploit byperaccumulation as a means of remediating metal-contaminated soils.

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Section: Discussionmentioning

confidence: 99%

Deterrence of herbivory by zinc hyperaccumulation in Thlaspi caerulescens (Brassicaceae)

1997

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“…Snaydon & Davies (1982) showed that genetic differentiation may occur over periods as short as six years and can be caused by increased fertilization. Because population differentiation is known to be due to a combination of various ecologically important factors (Ernst 1987), and fertilization regimes were comparable at both sites, unidentified factors, such as the degree of initial genetic variability, microhabitat variation and competition, were probably partially involved in differentiation. Differences in gene flow can also be excluded to a great extent because the size of the experiment, the spacing between treatments, the surrounding vegetation and the mating possibilities were comparable at both sites.…”

Section: Discussionmentioning

confidence: 99%

Fertilization and defoliation frequency affect genetic diversity of Festuca pratensis Huds. in permanent grasslands

et al. 1998

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Permanent pastures and meadows are species‐rich vegetation systems that play an important role in the ecology and agriculture of temperate climates. Intensive management reduces species diversity and may also influence the genetic diversity within individual species and populations. The objective of this study was to assess genetic variability of meadow fescue, an important component of species‐rich grasslands, and to determine whether fertilization and defoliation frequency influence genetic variability within natural populations. Genetic diversity of six natural populations and three cultivars of Festuca pratensis was investigated using randomly amplified polymorphic DNA (RAPD) markers and agronomic traits. Samples of natural populations were taken from two unrelated long‐term experiments, where treatments had been applied for 11–38 years. RAPD analysis detected a clear genetic distinction of the cultivars from the natural populations. Genetic variability within cultivars was lower than within natural populations. Analysis of molecular variance (AMOVA) showed a significant effect of management on genetic variability. Fertilization and frequent defoliation led to a reduction in genetic variability within natural populations. Analysis of agronomic traits was only partially congruent with the results of RAPD analysis. This study shows that significant genetic variability exists within cultivars and natural populations of Festuca pratensis and can be reduced by intensive management.

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“…In this paper, we identify those biotic interactions that are likely to be affected by the high metal contents of hyperaccumulating plant species, summarize current knowledge about each in relation to metal hyperaccumulation, and outline important questions that are worthy of future investigation. 1971Baker 1981Kruckeberg et al 1993 Disposal from plant body Wild 1978Baker 1981 Farago & Cole 1988 Drought resistance Severne 1974Baker & Walker 1990Robertson 1992Mesjasz-Przybylowicz et al 1996Interference Baker & Brooks 1989Gabrielli et al 1991Wilson & Agnew 1992Gabrielli et al 1997Inadvertent uptake Severne & Brooks 1972 Baker & Walker 1989 Pathogen/herbivore defence Reeves et al 1981Ernst 1987Ernst et al 1990 Second, elemental defences cannot be degraded as can occur with secondary compounds, due to the elemental nature of the metal ions.…”

Section: Introductionmentioning

confidence: 99%

“…Most studies of the defensive function of hyperaccumulated metals have dealt with folivorous insects (e.g., Ernst 1987;Pollard & Baker 1997). There are two different pathways by which defence is achieved.…”

Section: Introductionmentioning

confidence: 99%

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The significance of metal hyperaccumulation for biotic interactions

1998

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Metal hyperaccumulating plants contain very high metal contents. Because of the general toxicity of metals, chemically-mediated biotic interactions involving hyperaccumulating plants may differ greatly from those of non-hyperaccumulators. Recent research has demonstrated a defensive function for hyperaccumulated metals against herbivores and pathogens. We predict that some herbivore/pathogen species have evolved metal tolerance, and suggest that resulting high metal levels in herbivores/pathogens may defend them against their own predators. Little is known regarding interference and commensal interactions involving hyperaccumulating plants. Decreased competition may occur through an interference interaction similar to allelopathy, in which enrichment of metal in the soil under a hyperaccumulator plant's canopy may inhibit another plant species, thus resulting in ''elemental allelopathy''. Metal enrichment of soil under hyperaccumulators also may result in commensalism if another plant species (possibly another hyperaccumulator) derives a benefit from growing in the metal-enriched soil under the canopy of a hyperaccumulating overstory plant. It seems likely that high-metal plant litter will host a specialized microflora of decomposers and may affect nutrient cycling rates. Mutualist biotic interactions also may be affected by the elevated metal contents of hyperaccumulating species. Mycorrhizal fungi may form mutualisms with hyperaccumulators, but the phenomenon is poorly-explored. The few cases investigated to date have not detected mycorrhizae. Pollination and seed dispersal mechanisms may require biotic vectors that might be affected by plant metal content. Hyperaccumulating plants may have solved this dilemma in three ways. First, some may rely on abiotic vectors for pollen or seed dispersal. Second, biotic vectors used by these species may have varied diets and thus dilute metal intake to non-toxic levels. Finally, biotic vectors may have evolved tolerance of elevated dietary levels of metals, and perhaps have become specialists on hyperaccumulator species.

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Population differentiation in grassland vegetation

Cited by 15 publications

References 65 publications

Deterrence of herbivory by zinc hyperaccumulation in Thlaspi caerulescens (Brassicaceae)

Deterrence of herbivory by zinc hyperaccumulation in Thlaspi caerulescens (Brassicaceae)

Fertilization and defoliation frequency affect genetic diversity of Festuca pratensis Huds. in permanent grasslands

The significance of metal hyperaccumulation for biotic interactions

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