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20 results for “white clover”
Dataset accompanying Nölke et al. 2022. The choice of the white clover population alters overyielding of mixtures with perennial ryegrass and chicory and underlying processes. Scientific Reports
<p>This repository contains biomass and nitrogen yield data as well as data on diversity effects used by Nölke et al. in an article published in Scientific Reports (2022).</p> <p>Metadata are provided in the first excel worksheet ('explanation_overview'). For further details please see the original research article.</p>
Red and white clover provide food resources for honeybees and wild bees in urban environments
<p>Pollination is a key ecological process both in wild plant species and in economically important crops. Global land use change and urbanization are known to alter plant-pollinator interactions, but our understanding of how the local (i.e. size of green area, food resource availability) and landscape (surrounding green area) context affect pollinators in urban landscapes remains understudied. We selected two co-occurring clover species, Trifolium pratense and T. repens. to assess whether mixed stands of common wildflowers provide resources for a diverse pollinator assemblage by supporting differently adapted/specialized pollinator species. We further wanted to test how environmental factors (flower diversity, resource availability, size and percentage of green area) alter plant-pollinator interactions in urban environments. We studied the pollinator assemblage and visitation rate of pollinators in 1 m² plots in 21 green areas of different sizes in the city of Vienna (Austria). In addition, we assessed the surrounding landscape context by estimating the percentage of green area in perimeters of 100 m, 500 m and 1000 m around each study plot and measured local flower resource availability. We found that proportions of pollinator taxa differed significantly between white and red clover, with T. repens mainly pollinated by Apis mellifera, and T. pratense primarily pollinated by different bumblebee species. Visitation frequency was positively correlated to local resource availability (number of anthetic Trifolium inflorescences in each plot), but independent of the surrounding landscape context (i.e. percentage of green area). We conclude that the establishment and maintenance even of small patches of different common wildflowers help maintain a diverse bee community in urban environments. Particularly large-flowered species may be important for supporting long-tongued, late emerging pollinators such as certain bumblebee species.</p>
Phenotype and QTL mapping data from: Genetic trade-offs underlie divergent life history strategies for local adaptation in white clover
<p>Local adaptation is common in plants, yet characterization of its underlying genetic basis is rare in herbaceous perennials. Moreover, while many plant species exhibit intraspecific chemical defense polymorphisms, their importance for local adaptation remains poorly understood. We examined the genetic architecture of local adaptation in a perennial, obligately-outcrossing herbaceous legume, white clover (<i>Trifolium repens</i>). This widespread species displays a well-studied chemical defense polymorphism for cyanogenesis (HCN release following tissue damage) and has evolved climate-associated cyanogenesis clines throughout its range. Two biparental F<sub>2</sub> mapping populations, derived from three parents collected in environments spanning the U.S. latitudinal species range (Duluth, MN, St. Louis, MO and Gainesville, FL), were grown in triplicate for two years in reciprocal common garden experiments in the parental environments (6,012 total plants). Vegetative growth and reproductive fitness traits displayed trade-offs across reciprocal environments, indicating local adaptation. Genetic mapping of fitness traits revealed a genetic architecture characterized by allelic trade-offs between environments, with 100% and 80% of fitness QTL in the two mapping populations showing significant QTL X E interactions, consistent with antagonistic pleiotropy. Across the genome there were three hotspots of QTL co-localization. Unexpectedly, we found little evidence that the cyanogenesis polymorphism contributes to local adaptation. Instead, divergent life history strategies in reciprocal environments were major fitness determinants: selection favored early investment in flowering at the cost of multi-year survival in the southernmost site vs. delayed flowering and multi-year persistence in the northern environments. Our findings demonstrate that multi-locus genetic tradeoffs contribute to contrasting life history characteristics that allow for local adaptation in this outcrossing herbaceous perennial.</p>
Beyond cyanogenesis: Temperature gradients drive environmental adaptation in North American white clover (Trifolium repens L.)
<p>Species that repeatedly evolve phenotypic clines across environmental gradients have been highlighted as ideal systems for characterizing the genomic basis of local environmental adaptation. However, few studies have assessed the importance of observed phenotypic clines for local adaptation: conspicuous traits that vary clinally may not necessarily be the most critical in determining local fitness. The present study was designed to fill this gap, using a plant species characterized by repeatedly-evolved adaptive phenotypic clines. White clover is naturally polymorphic for its chemical defense cyanogenesis (HCN release with tissue damage); climate-associated cyanogenesis clines have evolved throughout its native and introduced range worldwide. We performed landscape genomic analyses on 415 wild genotypes from 43 locations spanning much of the North American species range to assess the relative importance of cyanogenesis loci vs. other genomic factors in local climatic adaptation. We find clear evidence of local adaptation, with temperature-related climatic variables best describing genome-wide differentiation between sampling locations. The same climatic variables are also strongly correlated with cyanogenesis frequencies and gene copy number variations (CNVs) at cyanogenesis loci. However, landscape genomic analyses indicate no significant contribution of cyanogenesis loci to local adaptation. Instead, several genomic regions containing promising candidate genes for plant response to seasonal cues are identified — some of which are shared with previously-identified QTLs for locally-adaptive fitness traits in North American white clover. Our findings suggest that local adaptation in white clover is likely determined primarily by genes controlling the timing of growth and flowering in response to local seasonal cues. More generally, this work suggests that caution is warranted when considering the importance of conspicuous phenotypic clines as primary determinants of local adaptation.</p>
Variable expression of cyanide detoxification and tolerance genes in cyanogenic and acyanogenic white clover (Trifolium repens L.)
<p><strong>Premise of the study:</strong> β-cyanoalanine synthase (β-CAS) and alternative oxidase (AOX) play important roles in the ability of plants to detoxify and tolerate hydrogen cyanide (HCN) stress. These functions are critical for all plants, as HCN is produced at low levels during basic metabolic processes, but are likely to be especially important in cyanogenic species, which release high levels of HCN following tissue damage. However, their expression has not been examined in cyanogenic species, nor has it been compared between cyanogenic and acyanogenic genotypes within a species.</p> <p><strong>Methods:</strong> We used a natural polymorphism for cyanogenesis in white clover to examine β-CAS and Aox gene expression in relation to cyanogenesis-associated HCN exposure. We identified all β-CAS and Aox gene copies present in the genome, including members of the <em>Aox1, Aox2a</em> and <em>Aox2d </em>subfamilies previously reported in legumes. Expression levels were compared between cyanogenic and acyanogenic genotypes, and under conditions of leaf tissue damage compared to undamaged tissue. </p> <p><strong>Key results:</strong> Results indicate that β-CAS and Aox2a expression are differentially elevated in cyanogenic genotypes, and that tissue damage is not required to induce this increased expression. <em>Aox2d</em>, in contrast, appears to be upregulated as a generalized wounding response.</p> <p><strong>Conclusions:</strong> These findings suggest a heightened constitutive role for both HCN detoxification (via elevated β-CAS expression) and HCN-toxicity mitigation (via elevated <em>Aox2a </em>expression) in plants that are capable of cyanogenesis. As such, freezing-induced cyanide autotoxicity is unlikely to be the primary selective factor in the evolution of climate-associated cyanogenesis clines. </p>
Variable expression of cyanide detoxification and tolerance genes in cyanogenic and acyanogenic white clover (Trifolium repens L.)
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Phenotype and QTL mapping data from: Genetic trade-offs underlie divergent life history strategies for local adaptation in white clover
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Data from: Continent-wide climatic variation drives local adaptation in North American white clover
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Beyond cyanogenesis: Temperature gradients drive environmental adaptation in North American white clover (Trifolium repens L.)
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Red and white clover provide food resources for honeybees and wild bees in urban environments
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Data from: Contrasting the effects of natural selection, genetic drift and gene flow on urban evolution in white clover (Trifolium repens)
Urbanization is a global phenomenon with profound effects on the ecology and evolution of organisms. We examined the relative roles of natural selection, genetic drift and gene flow in influencing the evolution of white clover (Trifolium repens), which thrives in urban and rural areas. Trifolium repens exhibits a Mendelian polymorphism for the production of hydrogen cyanide (HCN), a potent antiherbivore defence. We quantified the relative frequency of HCN in 490 populations sampled along urban-rural transects in 20 cities. We also characterized genetic variation within 120 populations in eight cities using 16 microsatellite loci. HCN frequency increased by 0.6% for every km from an urban centre, and the strength of this relationship did not significantly vary between cities. Populations did not exhibit changes in genetic diversity with increasing urbanization, indicating that genetic drift is unlikely to explain urban-rural clines in HCN frequency. Populations frequently exhibited isolation-by-distance and extensive gene flow along most urban-rural transects, with the exception of a single city that exhibited genetic differentiation between urban and rural populations. Our results show that urbanization repeatedly drives parallel evolution of an ecologically important trait across many cities that vary in size, and this evolution is best explained by urban-rural gradients in natural selection.
Data from: Contrasting the effects of natural selection, genetic drift and gene flow on urban evolution in white clover (Trifolium repens)
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Data from: Searching for the bull's-eye: agents and targets of selection vary among geographically disparate cyanogenesis clines in white clover (Trifolium repens L.)
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Data from: Evolution of drought resistance strategies following the introduction of white clover (Trifolium repens L.)
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Data from: Aridity shapes cyanogenesis cline evolution in white clover (Trifolium repens L.)
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Data from: Recurrent gene deletions and the evolution of adaptive cyanogenesis polymorphisms in white clover (Trifolium repens L.)
Understanding the molecular evolution of genes that underlie intraspecific polymorphisms can provide insights into the process of adaptive evolution. For adaptive polymorphisms characterized by gene presence/absence (P/A) variation, underlying loci commonly show signatures of long-term balancing selection, with gene-presence and gene-absence alleles maintained as two divergent lineages. We examined the molecular evolution of two unlinked P/A polymorphisms that underlie a well-documented adaptive polymorphism for cyanogenesis (hydrogen cyanide release with tissue damage) in white clover. Both cyanogenic and acyanogenic plants occur in this species, and the ecological forces that maintain this chemical defense polymorphism have been studied for several decades. Using a sample of 65 plants, we investigated the molecular evolution of sequences flanking the two underlying cyanogenesis genes: Ac/ac (controlling the presence/absence of cyanogenic glucosides), and Li/li (controlling the presence/absence of their hydrolyzing enzyme, linamarase). A combination of genome-walking, PCR assays, DNA sequence analysis, and Southern blotting was used to test whether these adaptive P/A polymorphisms show evidence of long-term balancing selection, or whether gene-absence alleles have evolved repeatedly through independent deletion events. For both loci, we detect no signatures of balancing selection in closest flanking genomic sequences. Instead, we find evidence for variation in the size of the deletions characterizing gene-absence alleles. These observations strongly suggest that both of these polymorphisms have been evolving through recurrent gene deletions over time. We discuss the genetic mechanisms that could account for this surprising pattern and the implications of these findings for mechanisms of rapid adaptive evolution in white clover.
Data from: Rapid evolution of an adaptive cyanogenesis cline in introduced North American white clover (Trifolium repens L.)
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Data from: Network size‐dependent impact on vegetative growth and sexual reproduction in clonal patches of white clover Trifolium repens
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Data from: Recurrent gene deletions and the evolution of adaptive cyanogenesis polymorphisms in white clover (Trifolium repens L.)
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Transcriptome analysis of a red-flowered white clover mutant
GEO Series GSE101059. Trifolium repens. 6 samples. Type: Expression profiling by high throughput sequencing.
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