Genetic differentiation within multiple common grassland plants supports seed transfer zones for ecological restoration

How to successfully improve the biodiversity of city grasslands?

Urban grasslands (UG) are among the most common types of urban green areas. They are usually species poor, and spontaneous plant migration, which can increase biodiversity, is limited. To improve the range of ecosystem services provided by UG, various seed mixtures are applied during the establishment and restoration of UG. These mixtures vary in content, quality, and cost. High-quality seed mixtures are expensive and are usually only available in small amounts. Meanwhile, alternative methods of seed introduction (e.g., fresh hay application, seeds harvested by brush) have not been well studied in UG restoration, and inexpensive commercial mixtures could have low quality and lead to poor restoration outcomes. Here, we tested the effectiveness of different seed sources to create high-quality UG at two study sites. Based on the results, all seed addition methods increased the species richness of restored grasslands. The outcome of seed addition was satisfactory regardless of differences in residual vegetation species composition and soil properties between the sites. The species richness on plots that received a commercial mixture of flower meadow plants dedicated to pollinators decreased after overwintering. The alternative seed sources (fresh hay and seed incidentally collected during mowing) yielded grassland quality that was comparable to that on plots that received high-quality mixtures with known seed origin (a seminatural meadow mixture and a mixture with the addition of grasses).

Is there a massive glacial-Holocene flora continuity in Central Europe?

The prevailing paradigm about the Quaternary ecological and evolutionary history of Central European ecosystems is that they were repeatedly impoverished by regional extinctions of most species during the glacial periods, followed by massive recolonizations from southern and eastern refugia during interglacial periods. Recent literature partially contradicts this view and provides evidence to re-evaluate this Postglacial Recolonization Hypothesis and develop an alternative one. We examined the long-term history of the flora of the Carpathian (Pannonian) Basin by synthesising recent advances in ecological, phylogeographical, palaeoecological and palaeoclimatological research, and analysing the cold tolerance of the native flora of a test area (Hungary, the central part of the Carpathian Basin). We found that (1) many species have likely occurred there continuously since before the Last Glacial Maximum (LGM); (2) most of the present-day native flora (1404 species, about 80%) can occur in climates as cold as or colder than the LGM (mean annual temperature ≤+3.5°C); and (3) grasslands and forests can be species-rich under an LGM-like cold climate. These arguments support an alternative hypothesis, which we call the Flora Continuity Hypothesis. It states that long-term continuity of much of the flora in the Carpathian Basin is more plausible than regional extinctions during the LGM followed by massive postglacial recolonizations. The long-term continuity of the region's flora may have fundamental implications not only for understanding local biogeography and ecology (e.g. the temporal scale of processes), but also for conservation strategies focusing on protecting ancient species-rich ecosystems and local gene pools.

Seed sourcing for climate-resilient grasslands: The role of seed source diversity during early restoration establishment

Restoration advocates for the use of local seed in restoration, but theory suggests that diverse seed sources may enhance genetic diversity and longer term evolutionary potential within restored communities. However, few empirical studies have evaluated whether species and genetic diversity within species impacts plant community composition following restoration. The goal of this research is to compare the effects of single and multi-sourced seed mix treatments on plant community diversity following restoration. Species establishment, abundance, and diversity were compared following two restoration seed mix treatments created to include 14 species commonly used in grassland restoration. We compared the application of seed mixes designed using a single population per species with those containing five populations per species across sites in Minnesota and South Dakota, United States. Early plant establishment and richness mostly reflected non-seeded species across both sites, although seeded species established at a slightly higher rate in year two following restoration. At the South Dakota site, community composition largely reflected changes associated with establishment across the growing season as opposed to seed mix treatment. This contrasted with the Minnesota site, where community composition appeared to be strongly influenced by seed mix treatment. While there is some evidence seed mix treatment may be influencing the emergent community across sites, spatial heterogeneity across the Minnesota restoration site likely influenced diversity in early emergence over that of seed mix treatment. Indeed, varying land-use history across both sites likely contributed to differences in species composition observed at this early stage of the restoration. This suggests that seed mix treatment may have limited impact on early post-restoration emergence diversity relative to the importance of land-use history. However, future monitoring will be needed to evaluate whether the impact of seed mix treatment on community composition changes over time.

Genetic diversity and population structure of Vernonia amygdalina Del. in Uganda based on genome wide markers

Determining the extent and distribution of genetic diversity is an essential component of plant breeding. In the present study, we explored the genetic diversity and population structure of Vernonia amygdalina, a fodder, vegetable and medicinal species of Africa and some parts of Yemen. Most empirical studies demonstrate that populations that are separated by geographic or ecological factors may experience genetic differentiation resulting from restricted gene flow between populations. A total of 238 individuals were sampled from two populations: i) Lake Victoria crescent (LVC) and ii) Southern and Eastern Lake Kyoga basin (SEK) agroecological zones of Uganda and genotyped using DArT platform. Of the two populations, the overall mean observed heterozygosity (Ho) was low to medium (Ho = 0.07[silicoDArTs] and 0.2[SNPs]). Inbreeding levels were also very low (-0.04 to -0.08) suggesting the presence of random mating. Partitioning of genetic structure in the two populations indicated that SEK exhibited a higher genetic diversity than LVC. The principal coordinates analysis (PCA) showed no geographical structuring, consistent with the low genetic differentiation (Fst = 0.00) and the low Euclidean genetic distance (1.38-1.39) between the LVC and SEK populations. However, STRUCTURE analysis with admixture models revealed weak possible genetic clusters with very small genetic distance among them. Overall, the results suggest low genetic diversity and weak genetic differentiation between the two populations. One possible explanation of the results could be the presence of human assisted gene flow over long distances.

The General Trends of Genetic Diversity Change in Alien Plants' Invasion

Genetic diversity is associated with invasion dynamics during establishment and expansion stages by affecting the viability and adaptive potential of exotics. There have been many reports on the comparison between the genetic diversity of invasive alien species (IAS) in and out of their native habitats, but the conclusions were usually inconsistent. In this work, a standard meta-analysis of the genetic diversity of 19 invasive plants based on 26 previous studies was carried out to investigate the general trend for the change of IASs' genetic diversity during their invasion process and its real correlation with the invasion fate. Those 26 studies were screened from a total of 3557 peer-reviewed publications from the ISI Web of Science database during the period of January 2000 to May 2022. Based on the selected studies in this work, a general reduction of IASs' genetic diversity was found in non-native populations compared to that in native ones, while the difference was not significant. This finding suggested that regardless of the change in genetic diversity, it had no substantial effect on the outcome of the invasion process. Therefore, genetic diversity might not serve as a reliable indicator for risk assessment and prediction of invasion dynamic prediction in the case of IASs.

Trends in grassland science: Based on the shift analysis of research themes since the early 1900s

Grasslands, one of the major terrestrial ecosystems, are essential for the maintenance of ecological and production functions; however, they are undergoing extensive degradation. The development and cutting-edge explorations in grassland science are critical to addressing challenges such as climate change and the increasing influence of human activities. To identify research trends in grassland science, latent Dirichlet allocation (LDA) topic modelling was used to conduct an automated content analysis on 123,829 papers available on Web of Science Core Collection from 1900 to 2020. Results from this analysis showed that grassland research has become increasing multidisciplinary, accompanied by a pronounced reduction in the relative frequency of traditional production-oriented research and an increase in the themes focusing on ecological functions and modern technologies. Changes in research activities have been uneven globally, with a significant increase in the number of publications in China and Brazil, which probably reflects an increased support from various governmental agencies in these countries. Additionally, in 2019, China surpassed the United States in terms of the total number of publications. Further, this study identified important topics and emerging challenges in grassland research, such as biodiversity conservation, climate changes, and genetic considerations. Comprehensive improvement of education, research, global cooperation, and funding strategies will be necessary to promote grassland science research on frontier themes and to effectively address the social and environmental challenges in the new era.

Seeds harvested during mowing from semi-natural grasslands as an ad hoc but effective solution for grassland restoration

Species-rich grasslands formed by local ecotypes of native species provide numerous ecosystem services both in rural areas as well as urban grasslands. Nonetheless, their area is still too small, making grasslands one of the most frequently restored habitats. Successful restoration requires high-quality seed material, which is expensive and often not easy to acquire. In this study, we tested the potential of seeds accidentally collected during the mowing of a semi-natural grassland for grassland restoration. We tested seed purity, species composition, and germination capability in both laboratory and field conditions. Ninety percent of the collected material consisted of pure seeds of numerous species. Their germination capability was relatively low but still sufficient for successful grassland restoration under a typical seed density/mass per unit area seeding ratio. The germination capacity was the highest in the first two weeks after sowing and increased with overwintering seed storage. The results suggested that the seeds could be successfully used for species-rich grassland restoration. In terms of advantages, the seed mixture had a low cost and contained native species seeds representing local ecotypes. In terms of disadvantages, there was a relatively low amount of seed material and an inability to plan the time of seed harvesting. Thus, the use of the accidentally collected seeds can be considered an effective but rather ad hoc solution.

Evolution of plant drought strategies and herbivore tolerance after two decades of climate change

Ongoing global warming, coupled with increased drought frequencies, together with other biotic drivers may have resulted in complex evolutionary adaptation. The resurrection approach, comparing ancestors raised from stored seeds with their contemporary descendants under common conditions, is a powerful method to test for recent evolution in plant populations. We used 21-26-yr-old seeds of four European plant species - Matthiola tricuspidata, Plantago crassifolia, Clinopodium vulgare and Leontodon hispidus - stored in seed banks together with re-collected seeds from their wild populations. To test for evolutionary changes, we conducted a glasshouse experiment that quantified heritable changes in plant responses to drought and simulated insect herbivory. In three out of the four studied species, we found evidence that descendants had evolved shorter life cycles through faster growth and flowering. Shifts in the osmotic potential and leaf dry matter content indicated that descendants also evolved increased drought tolerance. A comparison of quantitative genetic differentiation (Q_ST ) vs neutral molecular differentiation (F_ST ) values, using double digest restriction-site associated DNA (ddRAD) genotyping data, suggested that directional selection, and therefore adaptive evolution, was underlying some of the observed phenotypic changes. In summary, our study revealed evolutionary changes in plant populations over the last decades that are consistent with adaptation of drought escape and tolerance as well as herbivory avoidance.

Using crushed waste bricks for urban greening with contrasting grassland mixtures: no negative effects of brick-augmented substrates varying in soil type, moisture and acid pre-treatment

Ecological restoration aims at supporting biodiversity and ecosystem services, and urban greening is a great opportunity to achieve this goal. This is facilitated by species-rich seed mixtures based on local provenances, which are designed for certain nutrient and moisture regimes based on functional plant traits. Such grassland mixtures might be cultivated on crushed waste bricks, which would be a new component of water-holding urban substrates. Thus, we studied the effects of brick quantity and quality, acid pre-treatment of bricks, soil type and moisture on biomass of designed seed mixtures. Three greenhouse experiments were conducted, with substrates consisting of different brick ratios (5% vs. 30%), brick types (clean production waste vs. demolition material), and brick treatments (acid vs. control) tested on three trait-based mixtures and a non-regional commercial standard mixture. The trait-based mixtures included information on specific leaf area, seed mass and grass-to-legume ratio. There were no negative effects of demolition bricks, soil texture and moisture on grassland biomass. Acid-treated clean porous bricks improved biomass production of the standard and intermediate mixtures, while the effect was minimal with demolition bricks. Designed seed mixtures had a biomass similar to the standard mixture under dry conditions but did not benefit from high moisture like the standard mixture. In conclusion, waste bricks are a useful additive for urban restoration substrates to save raw material, and specifically designed regional mixtures can replace commercial grassland types on these substrates.

Pollen transfer and patterns of reproductive success in pure and mixed populations of nectariferous Platanthera bifolia and P. chlorantha (Orchidaceae)

Plant species evolution is driven by many factors that have different roles in space and time. Using different field and laboratory methods, we studied reproductive patterns and their determinants in pure and mixed P. bifolia and P. chlorantha populations in different habitats. We also considered the probability of hybridisation between these two species and the role of intra-population processes in maintaining species integrity. Generally, we found a high level of reproductive success in both Platantherans. In both species, male (MRS) and female (FRS) reproductive success depended on floral display, and male reproductive success additionally on population structure. The flower traits were only weakly related to reproductive success. Moths' assemblages varied spatially and temporally, and their diversity and numbers were correlated with MRS in the year, when their abundance was markedly lower. Analysis of patterns of pollen transfer showed that pollen was transported up to 25 m (average 8.2 ± 4.83 m) and showed gene exchange between these two Platanthera species. The germination level of both species was significantly lower than seed viability, although P. bifolia seed germinated with higher frequency than P. chlorantha seeds. We noted differences in viability and germination of seeds developed as an effect of experimental interspecies crossings and those developed from natural pollination. The presence of intermediate ecotypes together with observations of spontaneous interspecies crosses in the field and viability of seeds produced in interspecies crossing suggest that both pre- and postzygotic reproductive barriers are not complete and do not prevent hybrid production.

Strategies to work towards long-term sustainability and resiliency of nature-based solutions in coastal environments: A review and case studies

The need for sustainable and resilient long-term strategies for coastal restoration and development projects is largely the result of pressures brought by changing climate conditions and growing human populations along coastal boundaries. As anthropogenic impacts along our coasts increase, the demand for sustainable, nature-based solutions (NbS) will grow commensurately. Trusted approaches are needed for successful implementation of NbS, especially in regions hardest hit by environmental changes. Nearshore strategies for new construction and protection of existing coastal infrastructure are shifting rapidly from hardened approaches to more ecologically aligned techniques that work with natural forces and enhance natural habitat. This paper highlights the benefits of living shorelines composed of ecotypic native plants, wave attenuation structures for coastal protection, and managed retreat to restore coastal environments while supporting and maintaining natural habitats. We review several NbS and present two case studies to illustrate the value of incorporating nature-based approaches to vulnerable coastal environments and highlight the importance of maximizing synergies and understanding trade-offs in their long-term use. Integr Environ Assess Manag 2022;18:123-134. © 2021 SETAC.

Local adaptation to precipitation in the perennial grass Elymus elymoides: Trade-offs between growth and drought resistance traits

Understanding local adaptation to climate is critical for managing ecosystems in the face of climate change. While there have been many provenance studies in trees, less is known about local adaptation in herbaceous species, including the perennial grasses that dominate arid and semiarid rangeland ecosystems. We used a common garden study to quantify variation in growth and drought resistance traits in 99 populations of Elymus elymoides from a broad geographic and climatic range in the western United States. Ecotypes from drier sites produced less biomass and smaller seeds, and had traits associated with greater drought resistance: small leaves with low osmotic potential and high integrated water use efficiency (δ13C). Seasonality also influenced plant traits. Plants from regions with relatively warm, wet summers had large seeds, large leaves, and low δ13C. Irrespective of climate, we also observed trade-offs between biomass production and drought resistance traits. Together, these results suggest that much of the phenotypic variation among E. elymoides ecotypes represents local adaptation to differences in the amount and timing of water availability. In addition, ecotypes that grow rapidly may be less able to persist under dry conditions. Land managers may be able to use this variation to improve restoration success by seeding ecotypes with multiple drought resistance traits in areas with lower precipitation. The future success of this common rangeland species will likely depend on the use of tools such as seed transfer zones to match local variation in growth and drought resistance to predicted climatic conditions.

Genetic Variation of Typical Plant Species in Hay Meadows: The Effect of Land Use History, Landscape Structure, and Habitat Quality

Global changes in land use are threatening the diversity of many ecosystems on both the intra- and interspecific levels. Among these ecosystems are the species-rich hay meadows, which have drastically declined in quality and quantity, due to land use intensification or abandonment in recent decades. The remaining genetic resources of their plant species must therefore be protected. To determine the driving forces impacting genetic variation in common hay meadow species (Dactylis glomerata, Heracleum sphondylium, andTrifolium pratense), we used data on the land use history, historic and present landscape structure and habitat quality. Our results showed average genetic diversity within the study sites, with low differentiation levels and a high gene flow among grasslands. Land use history, landscape structure and habitat quality were found to be related to the distribution of genetic diversity in the studied species, highlighting the complex forces acting in these ecosystems and showing the specific impact of litter accumulation on genetic diversity. Both historic and current environmental variables influence genetic diversity, demonstrating the importance of the land use history of a habitat. The most important group of variables impacting genetic variation in all three species was the landscape structure (e.g., distance to the nearest-located urban area or grassland). Also important was the influence of litter cover on genetic diversity inD. glomerata, which provides an interesting starting point for further research.

Diversity Patterns of Bermuda Grass along Latitudinal Gradients at Different Temperatures in Southeastern China

Cynodon dactylon (L.) Pers. (common Bermuda grass) has a limited capacity to grow at low temperatures, which limits its geographical range. Exploring its evolutionary relationship across different environmental gradients is necessary to understand the effects of temperature change on the genetics of common Bermuda grass. In this study, high-throughput transcriptome sequencing was performed on 137 samples of C. dactylon from 16 latitudinal gradients to explore the differential molecular markers and analyze genetic diversity and structure along latitudinal gradients at different temperatures. We primarily sampled more high-quality single nucleotide polymorphisms (SNPs) from populations at lower and middle latitudes. Greater intraspecific genetic variation at each level of temperature treatment could be due to factors such as wind pollination and asexual breeding. Populations of C. dactylon at high latitudes differed from populations at middle and low latitudes, which was supported by a principal component analysis (PCA) and genetic structure analysis, performed at different temperatures. We observed more genetic variation for low-latitude populations at 5 °C, according to an analysis of three phylogenetic trees at different temperature levels, suggesting that low temperatures affected samples with low cold resistance. Based on the results of phylogenetic analysis, we found that samples from high latitudes evolved earlier than most samples at low latitudes. The results provide a comprehensive understanding of the evolutionary phenomenon of landscape genetics, laying the groundwork for future structural and comparative genomic studies of C. dactylon.

Evolutionary legacy of a forest plantation tree species (Pinus armandii): Implications for widespread afforestation

Many natural systems are subject to profound and persistent anthropogenic influence. Human-induced gene movement through afforestation and the selective transportation of genotypes might enhance the potential for intraspecific hybridization, which could lead to outbreeding depression. However, the evolutionary legacy of afforestation on the spatial genetic structure of forest tree species has barely been investigated. To do this properly, the effects of anthropogenic and natural processes must be examined simultaneously. A multidisciplinary approach, integrating phylogeography, population genetics, species distribution modeling, and niche divergence would permit evaluation of potential anthropogenic impacts, such as mass planting near-native material. Here, these approaches were applied to Pinus armandii, a Chinese endemic coniferous tree species, that has been mass planted across its native range. Population genetic analyses showed that natural populations of P. armandii comprised three lineages that diverged around the late Miocene, during a period of massive uplifts of the Hengduan Mountains, and intensification of Asian Summer Monsoon. Only limited gene flow was detected between lineages, indicating that each largely maintained is genetic integrity. Moreover, most or all planted populations were found to have been sourced within the same region, minimizing disruption of large-scale spatial genetic structure within P. armandii. This might be because each of the three lineages had a distinct climatic niche, according to ecological niche modeling and niche divergence tests. The current study provides empirical genetic and ecological evidence for the site-species matching principle in forestry and will be useful to manage restoration efforts by identifying suitable areas and climates for introducing and planting new forests. Our results also highlight the urgent need to evaluate the genetic impacts of large-scale afforestation in other native tree species.

Genotypic and phenotypic distinctness of restored and indigenous populations of Pimpinella saxifraga L. 8 or more years after restoration

The recovery of altered or damaged ecosystems demands large-scale reintroductions of seeds. In the past, ecological restoration in Germany was carried out with non-local seeds of naturally occurring species. We here analysed whether the genetic pattern of the introduced non-local seeds (R = restored) of Pimpinella saxifraga are still detectable several years after application and whether the phenotype differs from that of the regional gene pool (I = indigenous) of the species. We collected material from individuals of R and I sites, conducted a common garden experiment and tested for genetic, morphological and phenotypic differences. In a cutting experiment we investigate treatment effects on indigenous and restored populations. At all investigated sites we only found P. saxifraga individuals with comparatively similar genome sizes. The population genetic analysis revealed two large and quite distinct molecular clusters, separating indigenous and restored individuals along the first axis. None of the vegetative, but two of the reproductive fitness parameters differed between individuals of the R and I sites. Cutting always had a significant influence on all analysed vegetative and reproductive fitness parameters, regardless of the individuals' origin. The effects of mowing always mask origin-specific characteristics, which then disappear. Genotypic coexistence reduces the availability of niches for the local genotype and may eventually lead to genotypic competition or introgression. We therefore recommend not to use non-local genotypes of this species in the region. Instead, we recommend using the genetically diverse local genotypes of P. saxifraga for restoration purposes.

Alpine Pioneer Plants in Soil Bioengineering for Slope Stabilization and Restoration: Results of a Preliminary Analysis of Seed Germination and Future Perspectives

Stabilization of slopes subject to landslide by measures with low impact, such as those of bioengineering, is a topic of interest. The use of scarcely studied alpine pioneer plants could contribute to innovation in soil bioengineering and restoration ecology but to use them, knowledge of the ex situ germinability of their seeds is fundamental. This research analysed the germinability of seeds of nine alpine pioneer species (Papaver aurantiacum, Rumex scutatus, Tofieldia calyculata, Pulsatilla alpina, Silene glareosa, Adenostyles alpina, Dryas octopetala, Laserpitium peucedanoides and Laserpitium krapfii) treated with water, gibberellic acid (GA3) and/or calcium carbonate at room temperature. The seeds had different responses to the treatments: Laserpitium peucedanoides, L. krapfii and Silene glareosa showed difficulty in germinating (germination < 2.5%), while Dryas octopetala had good germination (39–61%) regardless of treatment. GA3 significantly increased the seed germination rate of Papaver aurantiacum, Pulsatilla alpina, Rumex scutatus and Tofieldia calyculata, while the addition of calcium carbonate made the seeds of Rumex scutatus and Tofieldia calyculata germinate more quickly. Results are discussed focusing on the perspectives of using alpine pioneer species in future soil bioengineering work for slopes stabilization and restoration, and on the actions that stakeholders should take to make this happen.

Habitat matters - Strong genetic and epigenetic differentiation in Linum catharticum from dry and wet grasslands

Plant species differ in their ecological amplitude, with some species occurring in very different habitats under strongly differentiated environmental conditions. We were interested in to what extent the occurrence of Linum catharticum in dry calcareous grasslands (Bromion) and wet litter meadows (Molinion), two habitats on opposing ends concerning, for example, moisture level, is reflected on the genetic and epigenetic level. Using AFLP (amplified fragment length polymorphisms) and MSAP (methylation sensitive amplification polymorphisms) analyses, we studied the genetic and epigenetic variation of L. catharticum from calcareous grasslands and litter meadows. From each habitat, we included five study sites with 16 individuals per sampling location. We observed lower genetic than epigenetic diversity, but considerable differentiation among habitats, which was stronger on the genetic than the epigenetic level. Additionally, we observed a strong correlation of genetic and epigenetic distance, irrespective of geographic distance. The dataset included a large portion of fragments exclusively found in individuals from one or the other habitat. Some epigenetic fragments even occurred in different methylation states depending on the habitat. We conclude that environmental effects act on both the genetic and epigenetic level, producing the clear differentiation among plant individuals from calcareous grasslands and litter meadows. These results may also point into the direction of ecotype formation in this species.

Spatial grain of adaptation is much finer than ecoregional-scale common gardens reveal

Adaptive variation among plant populations must be known for effective conservation and restoration of imperiled species and predicting their responses to a changing climate. Common-garden experiments, in which plants sourced from geographically distant populations are grown together such that genetic differences may be expressed, have provided much insight on adaptive variation. Common-garden experiments also form the foundation for climate-based seed-transfer guidelines. However, the spatial scale at which population differentiation occurs is rarely addressed, leaving a critical information gap for parameterizing seed-transfer guidelines and assessing species' climate vulnerability. We asked whether adaptation was evident among populations of a foundational perennial within a single "empirical" seed-transfer zone (based on previous common-garden findings evaluating very distant populations) but different "provisional" seed zones (groupings of areas of similar climate and are not parameterized from common-garden data). Seedlings from three populations originating from similar conditions within an intermediate elevation were planted into gardens nearby at the same elevation, or 250-450 m higher or lower in elevation and 0.4-25 km away. Substantial variation was observed between gardens in survival (ranging 2%-99%), foliar crown volume (7.8-22.6 dm3), and reproductive effort (0%-65%), but not among the three transplanted populations. The between garden variation was inversely related to climatic differences between the gardens and seed-source populations, specifically the site differences in maximum-minimum annual temperatures. Results suggest that substantial site-specificity in adaptation can occur at finer scales than is accounted for in empirical seed-transfer guidance when the guidance is derived from broadscale common-garden studies. Being within the same empirical seed zone, geographic unit, and even within 10 km distance may not qualify as "local" in the context of seed transfer. Moving forward, designing common-garden experiments so that they allow for testing the scale of adaptation will help in translating the resulting seed-transfer guidance to restoration projects.

Combining genotype, phenotype, and environmental data to delineate site-adjusted provenance strategies for ecological restoration

Despite the importance of climate-adjusted provenancing to mitigate the effects of environmental change, climatic considerations alone are insufficient when restoring highly degraded sites. Here we propose a comprehensive landscape genomic approach to assist the restoration of moderately disturbed and highly degraded sites. To illustrate it we employ genomic data sets comprising thousands of single nucleotide polymorphisms from two plant species suitable for the restoration of iron-rich Amazonian Savannas. We first use a subset of neutral loci to assess genetic structure and determine the genetic neighbourhood size. We then identify genotype-phenotype-environment associations, map adaptive genetic variation, and predict adaptive genotypes for restoration sites. Whereas local provenances were found optimal to restore a moderately disturbed site, a mixture of genotypes seemed the most promising strategy to recover a highly degraded mining site. We discuss how our results can help define site-adjusted provenancing strategies, and argue that our methods can be more broadly applied to assist other restoration initiatives.

The importance of quantitative trait differentiation in restoration: landscape heterogeneity and functional traits inform seed transfer guidelines

For widely distributed species, understanding the scale over which genetic variation correlates to landscape structure and composition is critical. Particularly within the context of restoration, the evolution of genetic differences may impact success if seeds are maladapted to the restoration environment. In this study, we used Geum triflorum to quantify the scale over which genetic differences for quantitative traits important to adaptation have evolved, comparing the proportion of variance attributed to broad regional- and local population-level effects. Geum triflorum is a widely distributed species spanning a range of environments, including alvar and prairie habitats, which have extreme regional differences in soil-moisture availability. Alvar habitats are regions of thin soil over limestone that experience substantial seasonal variation in water availability, from flooding to desiccation annually. This contrasts with prairie habitats, whose deeper soils mitigate irregular flood-desiccation cycles. Using a common garden experiment, we evaluated 15 traits broadly grouped into three trait classes: resource allocation, stomatal characteristics, and leaf morphological traits for individuals sourced from prairie and alvar environments. We quantified the proportion of trait variance explained by regional- and population-scale effects and compared the proportion of regional- and population-trait variances explained across trait classes. Significant regional differentiation was observed for the majority of quantitative traits; however, population-scale effects were equal or greater than regional effects, suggesting that important genetic differences may have evolved across the finer population scale. Stomatal and resource allocation trait classes exhibited substantial regional differentiation relative to morphological traits, which may indicate increased strength of selection for stomatal and resource allocation traits relative to morphological traits. These patterns point towards the value in considering the scale over which genetic differences may have evolved for widely distributed species and identify different functional trait classes that may be valuable in establishing seed transfer guidelines.

STRUCTURE is more robust than other clustering methods in simulated mixed-ploidy populations

Analysis of population genetic structure has become a standard approach in population genetics. In polyploid complexes, clustering analyses can elucidate the origin of polyploid populations and patterns of admixture between different cytotypes. However, combining diploid and polyploid data can theoretically lead to biased inference with (artefactual) clustering by ploidy. We used simulated mixed-ploidy (diploid-autotetraploid) data to systematically compare the performance of k-means clustering and the model-based clustering methods implemented in STRUCTURE, ADMIXTURE, FASTSTRUCTURE and INSTRUCT under different scenarios of differentiation and with different marker types. Under scenarios of strong population differentiation, the tested applications performed equally well. However, when population differentiation was weak, STRUCTURE was the only method that allowed unbiased inference with markers with limited genotypic information (co-dominant markers with unknown dosage or dominant markers). Still, since STRUCTURE was comparatively slow, the much faster but less powerful FASTSTRUCTURE provides a reasonable alternative for large datasets. Finally, although bias makes k-means clustering unsuitable for markers with incomplete genotype information, for large numbers of loci (>1000) with known dosage k-means clustering was superior to FASTSTRUCTURE in terms of power and speed. We conclude that STRUCTURE is the most robust method for the analysis of genetic structure in mixed-ploidy populations, although alternative methods should be considered under some specific conditions.

Rapid evolution in native plants cultivated for ecological restoration: not a general pattern

The growing number of restoration projects worldwide increases the demand for seed material of native species. To meet this demand, seeds are often produced through large-scale cultivation on specialised farms, using wild-collected seeds as the original sources. However, during cultivation, plants experience novel environmental conditions compared to those in natural populations, and there is a danger that the plants in cultivation are subject to unintended selection and lose their adaptation to natural habitats. Although the propagation methods are usually designed to maintain as much natural genetic diversity as possible, the effectiveness of these measures have never been tested. We obtained seed of five common grassland species from one of the largest native seed producers in Germany. For each species, the seeds were from multiple generations of seed production. We used AFLP markers and a common garden experiment to test for genetic and phenotypic changes during cultivation of these plants. The molecular markers detected significant evolutionary changes in three out of the five species and we found significant phenotypic changes in two species. The only species that showed substantial genetic and phenotypic changes was the short-lived and predominantly selfing Medicago lupulina, while in the other, mostly perennial and outcrossing species, the observed changes were mostly minor. Agricultural propagation of native seed material for restoration can cause evolutionary changes, at least in some species. We recommend caution, particularly in selfing and short-lived species, where evolution may be more rapid and effects may thus be more severe.

Adaptive differentiation among populations of the Mediterranean dry grassland species Brachypodium retusum: The role of soil conditions, grazing, and humidity

PREMISE OF THE STUDY

Genetic differentiation in plant species may result from adaptation to environmental conditions, but also from stochastic processes. The drivers selecting for local adaptation and the contribution of adaptation to genetic differentiation are often unknown. Restoration and succession studies have revealed different colonization patterns for Brachypodium retusum, a common Mediterranean grass. In order to understand these patterns, we tested population differentiation and adaptation to different environmental factors.

METHODS

Structured sampling of 12 populations from six sites and two soil types within site was used to analyze the spatial and environmental structure of population differentiation. Sampling sites differ in grazing intensity and climate. We tested germination and growth in a common garden. In subsets, we analyzed the differential response to stone cover, grazing and soil moisture.

KEY RESULTS

We found significant differences among populations. The site explained population differentiation better than soil, suggesting a dominant influence of climate and/or genetic drift. Stone cover had a positive influence on seedling establishment, and populations showed a differential response. However, this response was not related to environmental differences between collection sites. Regrowth after clipping was higher in populations from the more intensively grazed Red Mediterranean soils suggesting an adaptation to grazing. Final germination was generally high even under drought, but germination response to differences in soil moisture was similar across populations.

CONCLUSIONS

Adaptive population differentiation in germination and early growth may have contributed to different colonization patterns. Thus, the provenance of B. retusum needs to be carefully considered in ecological restoration.

Are local plants the best for ecosystem restoration? It depends on how you analyze the data

One of the key questions in ecosystem restoration is the choice of the seed material for restoring plant communities. The most common strategy is to use local seed sources, based on the argument that many plants are locally adapted and thus local seed sources should provide the best restoration success. However, the evidence for local adaptation is inconsistent, and some of these inconsistencies may be due to different experimental approaches that have been used to test for local adaptation. We illustrate how conclusions about local adaptation depend on the experimental design and in particular on the method of data analysis. We used data from a multispecies reciprocal transplant experiment and analyzed them in three different ways: (1) comparing local vs. foreign plants within species and sites, corresponding to tests of the “local is best” paradigm in ecological restoration, (2) comparing sympatric vs. allopatric populations across sites but within species, and (3) comparing sympatric and allopatric populations across multiple species. These approaches reflect different experimental designs: While a local vs. foreign comparison can be done even in small experiments with a single species and site, the other two approaches require a reciprocal transplant experiment with one or multiple species, respectively. The three different analyses led to contrasting results. While the local/foreign approach indicated lack of local adaptation or even maladaptation, the more general sympatric/allopatric approach rather suggested local adaptation, and the most general cross‐species sympatric/allopatric test provided significant evidence for local adaptation. The analyses demonstrate how the design of experiments and methods of data analysis impact conclusions on the presence or absence of local adaptation. While small‐scale, single‐species experiments may be useful for identifying the appropriate seed material for a specific restoration project, general patterns can only be detected in reciprocal transplant experiments with multiple species and sites.