<i>Briza media</i> L.

Dixon, Jean M.

doi:10.1046/j.1365-2745.2002.00684.x

Cited by 25 publications

(17 citation statements)

References 54 publications

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“…To evaluate the genetic diversity in this community, we sampled, as a proxy, populations of the grass Briza media L. Briza media is a diploid (2n = 14), perennial, hemicryptophyte species characteristic of calcareous grassland habitats (Dixon 2002; Prentice et al. 2006).…”

Section: Methodsmentioning

confidence: 99%

Human influence lowers plant genetic diversity in communities with extinction debt

Helm¹,

Oja

Saar

et al. 2009

Journal of Ecology

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Summary1. Loss of plant species induced by adverse human influence and habitat fragmentation might be delayed due to a slow response to changed environmental conditions. This phenomenon is known as extinction debt, which can lead to the underestimation of actual threats to biodiversity. To adequately estimate the condition of recently fragmented plant communities and avoid future loss of species, good indicators of forthcoming extinctions are needed. 2. We studied the behaviour of genetic diversity of a relatively common habitat specialist grass Briza media in fragmented calcareous grasslands in which the extinction debt has been previously documented. Species richness in this system is shown to be determined by historical landscape patterns and human population densities prevailing centuries ago. We hypothesize that genetic diversity in this grassland system is related to current landscape patterns and contemporary human impact since genetic diversity might react more quickly to environmental changes than species diversity. 3. In contrast to species diversity, genetic diversity was indeed best described by current connectivity of grasslands. Additionally, genetic diversity was negatively related to current human population density, indicating an adverse effect of contemporary human settlements on studied species. The faster response of genetic diversity to changed environmental conditions compared to species richness was further supported by the absence of an expected correlation between species richness and genetic diversity. 4. Human population density a century ago had a positive effect on genetic diversity. A similar effect has been demonstrated for species richness in these grasslands, indicating that traditional land use in the past has supported the development of both genetic and species diversity. 5. Synthesis. Genetic diversity of Briza media in fragmented communities is reacting quickly to changes in landscape structure and anthropogenic pressure. Our results confirm that plant species can be prone to genetic deterioration due to habitat fragmentation and negative anthropogenic impact even if the decline in species richness has been delayed by extinction debt. Thus, a decrease of population genetic diversity in fragmented communities can be taken as the first indication of future species losses.

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Section: Methodsmentioning

confidence: 99%

Human influence lowers plant genetic diversity in communities with extinction debt

Helm¹,

Oja

Saar

et al. 2009

Journal of Ecology

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“…0.7 mg) and are dispersed from July on, but dispersal distance is very limited because they are primarily dispersed by gravity (Schleuning et al, 2009). The grass B. media usually produces one flower stalk per ramet from June to July (Dixon, 2002) and is the only one of the three study species that can also propagate by clonal growth (McLellan et al, 1997).…”

Section: Study Species and Seed Collectionmentioning

confidence: 99%

Plant population differentiation and climate change: responses of grassland species along an elevational gradient

Frei

Ghazoul

Matter

et al. 2013

Global Change Biology

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Mountain ecosystems are particularly susceptible to climate change. Characterizing intraspecific variation of alpine plants along elevational gradients is crucial for estimating their vulnerability to predicted changes. Environmental conditions vary with elevation, which might influence plastic responses and affect selection pressures that lead to local adaptation. Thus, local adaptation and phenotypic plasticity among low and high elevation plant populations in response to climate, soil and other factors associated with elevational gradients might underlie different responses of these populations to climate warming. Using a transplant experiment along an elevational gradient, we investigated reproductive phenology, growth and reproduction of the nutrient-poor grassland species Ranunculus bulbosus, Trifolium montanum and Briza media. Seeds were collected from low and high elevation source populations across the Swiss Alps and grown in nine common gardens at three different elevations with two different soil depths. Despite genetic differentiation in some traits, the results revealed no indication of local adaptation to the elevation of population origin. Reproductive phenology was advanced at lower elevation in low and high elevation populations of all three species. Growth and reproduction of T. montanum and B. media were hardly affected by garden elevation and soil depth. In R. bulbosus, however, growth decreased and reproductive investment increased at higher elevation. Furthermore, soil depth influenced growth and reproduction of low elevation R. bulbosus populations. We found no evidence for local adaptation to elevation of origin and hardly any differences in the responses of low and high elevation populations. However, the consistent advanced reproductive phenology observed in all three species shows that they have the potential to plastically respond to environmental variation. We conclude that populations might not be forced to migrate to higher elevations as a consequence of climate warming, as plasticity will buffer the detrimental effects of climate change in the three investigated nutrient-poor grassland species.

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“…In order to better understand the four-dimensional non-supersymmetric models emerging from string theory, we take as our starting point the ten-dimensional non-supersymmetric heterotic SO(16)×SO(16) theory [26,11,27]. Its low energy spectrum is given in Table 1.…”

Section: Non-supersymmetric So(16)×so(16) Heterotic Stringmentioning

confidence: 99%

“…Indeed, the standard lore wants that supersymmetry is predicted by string theory. However, this is simply not true: String theory only requires worldsheet supersymmetry, but not necessarily in target space [26,11,27].…”

Section: Introductionmentioning

confidence: 99%

Model building with the non-supersymmetric heterotic SO(16)×SO(16) string

Nibbelink

2015

J. Phys.: Conf. Ser.

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In this talk we review recent investigations [1] of the non-supersymmetric heterotic SO(16)×SO(16) string on orbifolds and smooth Calabi-Yaus. Using such supersymmetry preserving backgrounds allows one to re-employ commonly known model building techniques. We will argue that tachyons do not appear on smooth Calabi-Yaus to leading order in α and gs. Twisted tachyons may arise on singular orbifolds, where some of these approximations break down. However, they get lifted in full blow-up. Finally, we show that model searches is viable by identifying over 12,000 of SM-like models on various orbifold geometries.

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Briza media L.

Cited by 25 publications

References 54 publications

Human influence lowers plant genetic diversity in communities with extinction debt

Human influence lowers plant genetic diversity in communities with extinction debt

Plant population differentiation and climate change: responses of grassland species along an elevational gradient

Model building with the non-supersymmetric heterotic SO(16)×SO(16) string

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