Bet-hedging via between-year seed dormancy is a costly strategy for plants in unpredictable environments. Theoretically, fitness costs can be reduced through a parental environmental effect when the ...environment is partly predictable. We tested whether populations from environments that differ in predictability diverged in parental effects on seed dormancy.
Common garden-produced seeds of the two annual plant species Biscutella didyma and Bromus fasciculatus collected along an aridity gradient were grown under 12 irrigation treatments. Offspring germination was evaluated and related to environmental correlations between generations and their fitness consequences at the four study sites.
One species exhibited strong seed dormancy that increased with unpredictability in seasonal precipitation. The parental effect on seed dormancy also increased proportionally with the environmental correlation between precipitation in the parental season and seedling density in the following season; this correlation increased from mesic to arid environments.
Because fitness was negatively related to density, this parental effect may be adaptive. However, the lack of dormancy in the second species indicates that bet-hedging is not the only strategy for annual plants in arid environments.
Our results provide the first evidence for clinal variation in the relative strength of parental effects along environmental gradients.
Growing evidence shows that epigenetic mechanisms contribute to complex traits, with implications across many fields of biology. In plant ecology, recent studies have attempted to merge ecological ...experiments with epigenetic analyses to elucidate the contribution of epigenetics to plant phenotypes, stress responses, adaptation to habitat, and range distributions. While there has been some progress in revealing the role of epigenetics in ecological processes, studies with non‐model species have so far been limited to describing broad patterns based on anonymous markers of DNA methylation. In contrast, studies with model species have benefited from powerful genomic resources, which contribute to a more mechanistic understanding but have limited ecological realism. Understanding the significance of epigenetics for plant ecology requires increased transfer of knowledge and methods from model species research to genomes of evolutionarily divergent species, and examination of responses to complex natural environments at a more mechanistic level. This requires transforming genomics tools specifically for studying non‐model species, which is challenging given the large and often polyploid genomes of plants. Collaboration among molecular geneticists, ecologists and bioinformaticians promises to enhance our understanding of the mutual links between genome function and ecological processes.
In general, studies on plant phenotypic plasticity concentrate on plant responses to different levels of a single environmental factor. Under natural conditions, however, multiple environmental ...factors often vary simultaneously. I studied the consequences for lifetime fitness caused by single treatments or treatment combinations by investigating patterns of phenotypic plasticity within and between generations. The parental plants (three genotypes of the annual plant Arabidopsis thaliana) received zero, one or two stress treatments at an early life‐stage. The treatments included wounding, shading, chilling, and their pairwise combinations. In the second generation, offspring of treated plants received either the parental or no treatment. Offspring of non‐treated plants were reared under all treatment conditions. Plants responded strongly to the treatments, especially through delayed reproduction, which positively affected lifetime fitness. Notably, treatment combinations triggered stronger plastic responses on average. Because the delay in reproduction was offset by a delay in senescence, the treatments resulted in a fitness gain instead of a loss. However, under adverse environmental conditions, this delay represents a potential fitness cost, especially when the time for reproduction is limited. The treatments ‘wounding’ and ‘shading’ triggered parental effects that increased fitness only in plants that themselves received the treatment. Untreated offspring of wounded or shaded parents performed like control plants. Also, these parental effects were not accompanied by potential fitness costs, such as delayed reproduction. Chilling triggered genotype‐specific parental effects that increased or reduced fitness. Of the treatment combinations only ‘wounding’ and ‘shading’ resulted in genotype‐specific parental effects that increased or reduced fitness independently of offspring treatment. These results suggest that the response of annual plants to treatment combinations triggers predominantly within‐generation plastic responses that include potential fitness costs, which cannot be inferred from studies that manipulate environmental factors individually. Therefore, single treatment studies likely underestimate the costs of plasticity in natural environments.
Transgenerational environmental effects can trigger strong phenotypic variation. However, it is unclear how cues from different preceding generations interact. Also, little is known about the genetic ...variation for these life history traits.
Here, we present the effects of grandparental and parental mild heat, and their combination, on four traits of the third-generation phenotype of 14 Arabidopsis thaliana genotypes. We tested for correlations of these effects with climate and constructed a conceptual model to identify the environmental conditions that favour the parental effect on flowering time.
We observed strong evidence for genotype-specific transgenerational effects. On average, A. thaliana accustomed to mild heat produced more seeds after two generations. Parental effects overruled grandparental effects in all traits except reproductive biomass. Flowering was generally accelerated by all transgenerational effects. Notably, the parental effect triggered earliest flowering in genotypes adapted to dry summers. Accordingly, this parental effect was favoured in the model when early summer heat terminated the growing season and environments were correlated across generations.
Our results suggest that A. thaliana can partly accustom to mild heat over two generations and genotype-specific parental effects show non-random evolutionary divergence across populations that may support climate change adaptation in the Mediterranean.
Altitudinal gradients in mountain regions are short‐range clines of different environmental parameters such as temperature or radiation. We investigated genomic and phenotypic signatures of ...adaptation to such gradients in five Arabidopsis thaliana populations from the North Italian Alps that originated from 580 to 2350 m altitude by resequencing pools of 19–29 individuals from each population. The sample includes two pairs of low‐ and high‐altitude populations from two different valleys. High‐altitude populations showed a lower nucleotide diversity and negative Tajima's D values and were more closely related to each other than to low‐altitude populations from the same valley. Despite their close geographic proximity, demographic analysis revealed that low‐ and high‐altitude populations split between 260 000 and 15 000 years before present. Single nucleotide polymorphisms whose allele frequencies were highly differentiated between low‐ and high‐altitude populations identified genomic regions of up to 50 kb length where patterns of genetic diversity are consistent with signatures of local selective sweeps. These regions harbour multiple genes involved in stress response. Variation among populations in two putative adaptive phenotypic traits, frost tolerance and response to light/UV stress was not correlated with altitude. Taken together, the spatial distribution of genetic diversity reflects a potentially adaptive differentiation between low‐ and high‐altitude populations, whereas the phenotypic differentiation in the two traits investigated does not. It may resemble an interaction between adaptation to the local microhabitat and demographic history influenced by historical glaciation cycles, recent seed dispersal and genetic drift in local populations.
Semi‐natural mountain grasslands are increasingly exposed to environmental stress under climate change. However, which are the environmental factors that limit plants in these grasslands? Also, is ...the present management effective against these changes? Fitness‐related functional traits may offer a way to detect changes in performance and provide new insights into their vulnerability to climate change. We investigated changes in performance and variability of functional traits of the mountain grassland target species Arnica montana along a climate gradient in Central German low mountain ranges. This gradient represents at its lower end climate conditions that are expected at its upper end under future climate change. We measured vegetative, generative, and physiological traits to account for multiple ways of plant responses to the environment. Using mixed effects and multivariate models, we evaluated changes in trait values among individuals as well as the variability of their populations in order to assess performance under changing summer aridity and different management regimes. Fitness‐related performance of most traits showed strongly positive associations with reduced summer aridity at higher elevations, while only specific leaf area and leaf dry matter content showed no association. This suggests a higher performance level at less arid montane sites and that the physiological traits are less sensitive to this climate change factor. The coefficient of variation of almost all traits declined steadily with decreasing site aridity. We suggest that this reduced variability indicates a lower environmental stress level for A. montana toward its environmental optimum at montane elevations, especially because the trait performance increased simultaneously. Surprisingly, management factors and habitat characteristics had only low influence on both trait performance and variability. In summary, summer aridity had a stronger effect to shape the trait performance and variability of A. montana under increased environmental stress than management and other habitat characteristics.
We illustrate that summer aridity predicts the performance and variability of fitness‐related functional traits of the threatened mountain grassland species Arnica montana under climate change conditions and highlight that increased environmental stress will considerably affect the fitness of Arnica montana, while management has only limited influence to mediate impacts.
In mountain regions, topological differences on the microscale can strongly affect microclimate and may counteract the average effects of elevation, such as decreasing temperatures. While these ...interactions are well understood, their effect on plant adaptation is understudied.
We investigated winter frost hardiness of Arabidopsis thaliana accessions originating from 13 sites along altitudinal gradients in the Southern Alps during three winters on an experimental field station on the Swabian Jura and compared levels of frost damage with the observed number of frost days and the lowest temperature in eight collection sites.
We found that frost hardiness increased with elevation in a log‐linear fashion. This is consistent with adaptation to a higher frequency of frost conditions, but also indicates a decreasing rate of change in frost hardiness with increasing elevation. Moreover, the number of frost days measured with temperature loggers at the collection sites correlated much better with frost hardiness than the elevation of collection sites, suggesting that populations were adapted to their local microclimate. Notably, the variance in frost days across sites increased exponentially with elevation. Together, our results suggest that strong microclimate heterogeneity of high alpine environments can preserve functional genetic diversity among small populations.
Synthesis: Here, we tested how plant populations differed in their adaptation to frost exposure along an elevation gradient and whether microsite temperatures improve the prediction of frost hardiness. We found that local temperatures, particularly the number of frost days, are a better predictor of the frost hardiness of plants than elevation. This reflects a substantial variance in frost frequency between sites at similar high elevations. We conclude that high mountain regions harbor microsites that differ in their local microclimate and thereby can preserve a high functional genetic diversity among them. Therefore, high mountain regions have the potential to function as a refugium in times of global change.
Natural populations of Arabidopsis thaliana collected along an altitudinal gradient in the Southern Alps were studied regarding their adaptation to frost exposure. We tested the hypothesis that microsite temperatures are a better predictor for frost hardiness than elevation. We found that small scale local temperatures, particularly the derived number of frost days, predict frost hardiness better in the high mountains. This is due to the fact that high elevation sites differed strongly in frost frequency. These results indicate that high mountains offer heterogeneous microsites which can preserve a high functional genetic diversity between small populations which, in turn, have the potential to function as refuges in times of global climate change.
A growing number of restoration projects require large amounts of seeds. As harvesting natural populations cannot cover the demand, wild plants are often propagated in large‐scale monocultures. There ...are concerns that this cultivation process may cause genetic drift and unintended selection, altering the genetic properties of the cultivated populations and reducing their genetic diversity. Such changes could reduce the pre‐existing adaptation of restored populations and limit their adaptability to environmental change.
We used single nucleotide polymorphism (SNP) markers and a pool‐sequencing approach to test for genetic differentiation and changes in gene diversity during cultivation in 19 wild grassland species, comparing source populations and up to four consecutive cultivation generations. We linked the magnitudes of genetic changes to the species' breeding systems and seed dormancy to understand the roles of these traits in genetic change.
Cultivation changed the genetic composition across cultivated generations only moderately. The genetic differentiation resulting from cultivation was much lower than the natural genetic differentiation between different source regions. The propagated generations harboured even higher gene diversity than wild‐collected seeds. Genetic change was stronger in self‐compatible than self‐incompatible species, probably due to increased outcrossing in monocultures.
Synthesis and applications. Our study suggests that large‐scale seed production maintains the genetic integrity of natural populations. Increased genetic diversity may even indicate increased adaptive potential of propagated seeds, which would make them especially suitable for ecological restoration. Yet, it remains to be tested whether these molecular patterns will be mirrored also by plant phenotypes. Further, we used seeds from Germany and Austria, where the seed production is regulated and certified, and we do not know yet whether other seed production systems perform equally well.
Zusammenfassung
Die wachsende Zahl von Renaturierungsprojekten erfordert große Mengen an Saatgut. Die Ernte von Saatgut aus natürlichen Populationen kann den Bedarf nicht decken, daher werden Wildpflanzen oft in großflächigen Monokulturen vermehrt. Es gibt Bedenken, dass dieser Kultivierungsprozess zu genetischer Drift und unbeabsichtigter Selektion führt, wodurch sich die genetischen Eigenschaften der kultivierten Populationen verändern und ihre genetische Vielfalt verringert werden. Solche genetischen Veränderungen könnten die bereits bestehende lokale Angepasstheit verringern und die Fähigkeit sich an neue Umweltveränderungen anzupassen einschränken.
Wir verwenden “single nucleotide polymorphism“ (SNP)‐Marker und einen Pool‐Sequenzierungsansatz, um die genetische Differenzierung und Veränderungen der genetischen Diversität während der Kultivierung in 19 wilden Graslandarten zu testen, wobei wir Quellpopulationen und bis zu vier aufeinanderfolgende Kultivierungsgenerationen verglichen. Danach haben wir berechnet ob der Grad der genetischen Veränderung von dem Bestäubungssystem und der Samendormanz der Arten abhängt.
Die Kultivierung veränderte die genetische Zusammensetzung über die kultivierten Generationen hinweg nur mäßig. Die genetische Differenzierung, die durch den wiederholten Anbau resultierte, war viel geringer als die natürliche genetische Differenzierung zwischen verschiedenen Herkunftsregionen. Die vermehrten Generationen enthielten eine noch höhere Genvielfalt als Pflanzen von wild gesammeltem Saatgut. Die genetische Veränderung war bei selbstkompatiblen Arten stärker als bei selbstinkompatiblen Arten, wahrscheinlich aufgrund einer erhöhten Auskreuzung in Monokulturen.
Synthese und Anwendungen. Unsere Studie legt nahe, dass die groß angelegte Saatgutproduktion in Monokultur die genetische Integrität natürlicher Populationen erhält. Eine erhöhte genetische Diversität kann sogar auf ein erhöhtes Anpassungspotential von vermehrtem Saatgut hindeuten, was es besonders geeignet für eine Wiederherstellung von Ökosystemen mit unterschiedlichen Startbedingungen machen würde. Ob sich die vorgefundenen molekularen Muster auch in den Phänotypen widerspiegeln, muss noch getestet werden. Das von uns untersuchte Saatgutproduktionssystem aus Deutschland und Österreich ist stark reguliert und zertifiziert, so dass unsere Ergebnisse evtl. nicht weltweit übertragbar sind.
Our study suggests that large‐scale seed production maintains the genetic integrity of natural populations. Increased genetic diversity may even indicate increased adaptive potential of propagated seeds, which would make them especially suitable for ecological restoration. Yet, it remains to be tested whether these molecular patterns will be mirrored also by plant phenotypes. Further, we used seeds from Germany and Austria, where the seed production is regulated and certified, and we do not know yet whether other seed production systems perform equally well.
The selection of plant provenance for ecological restoration is an intensively debated topic. Throughout this debate, arguments mostly focus on plant performance, but little attention is paid to the ...effects of provenance on other members of the restored ecosystem. On the other hand, in restoration projects that focus specifically on supporting interacting biota, for example, wildflower strips among fields to support pollinators, the provenance choice is often not considered, partly because the effect of provenance on pollinators is unknown. In this pioneering case study, we tested whether pollinators differentiate between experimental plant communities of different provenances.
We established experimental plant communities with the same species composition but with plants originating from three different provenances. We then recorded plant phenology and observed pollinators and flower visitors interacting with these experimental communities and related the pollinator visitation to the provenance identity.
The provenances of the experimental plant communities had a strong and significant effect on the diversity and abundance of flower–pollinator interactions, with one provenance interacting two times as often as the other two provenances. The effect was driven by the differences in flowering phenology among provenances.
Synthesis and applications. Plant provenances substantially differ in their interactions with local pollinators. Therefore, the selection of plant provenance should be considered when planning restoration projects for the support of pollinators.
Die richtige Auswahl der Herkunft von Pflanzen für die ökologische Renaturierung ist ein intensiv diskutiertes Thema. In dieser Debatte liegt der Fokus in erster Linie auf der Performance der Pflanzen. Weit weniger Aufmerksamkeit erhält die Auswirkung der Herkunft auf andere Mitglieder des wiederhergestellten Ökosystems. In Renaturierungsprojekten, wiederum, die sich speziell auf die Unterstützung interagierender Biota konzentrieren, z.B. Blühstreifen zwischen Feldern zur Unterstützung von Bestäubern, wird die Wahl der Herkunft der Pflanzen häufig nicht berücksichtigt. Dies ist teilweise darauf zurückzuführen, dass die Wirkung der Herkunft auf Bestäuber unbekannt ist. In dieser wegbereitenden Fallstudie testeten wir, ob Bestäuber zwischen experimentellen Pflanzengemeinschaften verschiedener Provenienzen unterscheiden.
Wir etablierten experimentelle Pflanzengemeinschaften mit der gleichen Artenzusammensetzung, aber mit Pflanzen aus drei verschiedenen Herkünften. Anschließend erfassten wir die Phänologie der Pflanzen, beobachteten Bestäuber und Blütenbesucher, die mit diesen experimentellen Gemeinschaften interagierten, und setzten den Besuch der Bestäuber mit der Herkunft der Pflanzen in Beziehung.
Die Herkünfte der experimentellen Pflanzengemeinschaften hatten einen starken und signifikanten Einfluss auf die Vielfalt und Häufigkeit von Blüten‐Bestäuber‐Interaktionen, wobei eine Herkunft doppelt so häufig besucht wurde wie die anderen beiden. Dieser Effekt wurde durch die Unterschiede in der Blühphänologie zwischen den Herkünften hervorgerufen.
Synthese und Anwendungen. Pflanzenherkünfte unterscheiden sich erheblich in ihren Interaktionen mit lokalen Bestäubern. Daher sollte bei der Planung von Renaturierungsprojekten zur Unterstützung von Bestäubern die Auswahl des Herkunftsortes der Pflanzen berücksichtigt werden.
Plant provenances substantially differ in their interactions with local pollinators. Therefore, the selection of plant provenance should be considered when planning restoration projects for the support of pollinators.
The UN Decade on Ecosystem Restoration calls for upscaling restoration efforts, but many terrestrial restoration projects are constrained by seed availability. To overcome these constraints, wild ...plants are increasingly propagated on farms to produce seeds for restoration projects. During on-farm propagation, the plants face non-natural conditions with different selection pressures, and they might evolve adaptations to cultivation that parallel those of agricultural crops, which could be detrimental to restoration success. To test this, we compared traits of 19 species grown from wild-collected seeds to those from their farm-propagated offspring of up to four cultivation generations, produced by two European seed growers, in a common garden experiment. We found that some plants rapidly evolved across cultivated generations towards increased size and reproduction, lower within-species variability, and more synchronized flowering. In one species, we found evolution towards less seed shattering. These trait changes are typical signs of the crop domestication syndrome, and our study demonstrates that it can also occur during cultivation of wild plants, within only few cultivated generations. However, there was large variability between cultivation lineages, and the observed effect sizes were generally rather moderate, which suggests that the detected evolutionary changes are unlikely to compromise farm-propagated seeds for ecosystem restoration. To mitigate the potential negative effects of unintended selection, we recommend to limit the maximum number of generations the plants can be cultivated without replenishing the seed stock from new wild collections.
PDF
