Annual Plant Species Research Articles

Temporal host–symbiont dynamics in community contexts: Impacts of host fitness and vertical transmission efficiency on symbiosis prevalence

Abstract Symbiotic associations play a role in plant ecology and evolution, but the outcome of the interaction depends on the life‐history traits of the partners and the environmental context. Although symbiosis with vertically transmitted microorganisms should result in mutualism, it is not clear how the transmission process aligns with the outcome of the context‐dependent symbiosis. For 3 years, we sampled individuals of an annual plant species that forms symbiosis with a vertically transmitted fungal endophyte, in paired stands of two contrasting vegetation communities (humid mesophytic meadows [HMM]: productive/low stress, and humid prairies [HP]: less productive/high stress). We estimated the prevalence of symbiosis at the population level, and the fitness of the plant, the symbiotic status and vertical transmission efficiency at the individual level. Over 3 years, the prevalence of symbiosis was ≈100% in HMM and ≈75% in HP. Plant fitness was very low and high in years with precipitation below and above the yearly mean, respectively. The higher fitness of endophyte‐symbiotic plants was evident in the HMM and high precipitation years. Vertical transmission of endophytes was higher in HMM (≈96%) compared to HP (≈93%) and was not related to plant fitness. Despite transmission inefficiencies in HP, changes in prevalence within the growing season (from seeds to the final plant stand) suggest a fitness advantage for symbiotic plants. Vertical transmission is expected to promote mutualism as it aligns partners' fitness. Although symbiotic plants showed higher fitness and the probability of transmission failures was higher among low‐fitness plants, the variation in transmission efficiency between plants and vegetation communities was not related to the fitness of the individual host. Our study provides evidence that context‐dependent vertical transmission efficiency and endophyte‐mediated fitness advantages interact complexly to determine the prevalence of symbiosis in populations that occur in contrasting vegetation communities. Read the free Plain Language Summary for this article on the Journal blog.

Evaluating trait variation and covariation in perennial, herbaceous crop candidate species using herbarium specimens

AbstractContemporary agriculture in many parts of the world consists of annual plant species grown in monoculture, but recently interest has focused on developing perennial, herbaceous species for use in perennial polycultures that offer greater ecosystem services relative to annual monocultures. Because few perennial, herbaceous species were domesticated by early farmers, one of the initial steps in identifying wild, perennial, herbaceous species for potential crop development is understanding patterns of variation and covariation among reproductive traits that underpin yield and vegetative traits. Herbaria can serve as a valuable resource for taxonomically broad surveys of phenotypic variation and covariation for pre-breeding. In this study, we used herbarium specimens to investigate trait variation and covariation in five genera of the legume family (Fabaceae). We addressed two questions: (1) do vegetative and reproductive traits vary as a function of life span (annual vs. perennial species), and are these differences consistent across genera?; and (2) how do vegetative and reproductive traits correlate with one another across lifespan and/or within genera? Reproductive traits and vegetative traits were measured on 535 herbarium specimens representing annual and perennial species of Astragalus, Lupinus, Phaseolus, Strophostyles, and Vigna. While species exhibited intra- and interspecific variation, few morphological differences were observed among annual and perennial species. Correlations among vegetative traits and among reproductive traits were mostly positive when significant, and perennial species generally exhibited more positive correlations between vegetative and reproductive traits than annual species. These data have potential relevance for perennial crop development, and provide further support that herbaria represent a rich, relatively untapped resource of information about plant trait variation and covariation.

Germination phenology alters species coexistence outcomes

Abstract Species‐specific phenological responses to changing climate are reshuffling the timing of species interactions, however we do not fully understand the consequences of these changes for species' population dynamics and community composition. In this study, we experimentally manipulated the timing of germination for five annual plant species from southern California and used pairwise competition experiments and coexistence theory to quantify how phenological shifts may impact species interactions and coexistence. We found that phenological shifts may help promote coexistence when they confer an advantage for competitively inferior species, but in other cases promote dominance by competitively superior species. Earlier germination generally increased species' performance relative to competitors, but the relative changes in intra‐and inter‐specific interactions caused more complex effects on niche and fitness differences. Phenological differences tended to reduce stabilising niche differences for many species pairs and reduced overall coexistence probabilities. Synthesis. While phenological differences among species have typically been considered a form of niche partitioning, it seems increasingly likely that phenological offsets could destabilise species coexistence. The net effects of changing phenology on species coexistence will depend on the complex combinations of effects on intra‐ and inter‐specific interactions, which remain challenging to predict.

Poaceae Pollen as the Leading Aeroallergen

The relevance of aerobiological topics is evidenced by the fact that from July 1 to July 5, 2024, an unusual event was held in Vilnius (Lithuania), including the 8th European Symposium on Aerobiology (8th ESA), the 12th International Congress on Aerobiology (12th ICA) and the 5th International Ragweed Conference (5th IRC). World Aerobiology 2024 is an event of unprecedented scale. It discussed the use of artificial intelligence (AI) for calculating and interpreting aerobiological monitoring data. But so far, AI cannot identify all taxa, so careful counting and identification of plant pollen and fungal spores is only possible for a human researcher. Aerobiological monitoring using volumetric traps remains the gold standard of research. In the world community, there are networks of biological monitoring of air quality with the study of the concentration of plant pollen and fungal spores in the air. Through an application on a mobile phone, you can find out the forecast of periods of maximum risk, during which patients with hay fever are exposed to the main aeroallergens. Popular queries from Internet users relate to the complex problem of climate change, environmental pollution and aeroallergens. There is no National Aerobiological Monitoring system in Kyrgyzstan, but the Meteonova service has launched a pollen forecast application for mobile phones, which is still in the testing stage and does not reflect the real features of the aerobiological spectrum. It is known that in the world there are more than 12,000 species in the Poaceae family, classified into 771 genera belonging to 12 subfamilies. In Kyrgyzstan, 300 anemophilous species of annual perennial plants grow, releasing a huge amount of pollen into the atmosphere in the spring and summer. Poaceae pollen is still one of the top ten global aeroallergens, being the leading cause of hay fever, by predominant size, classified as biological pollutants (PM10). The concentration of cereal pollen was consistently observed in the air of Karakol during all seasons of the study and ranged from 167 to 174 days. Its daily maximum concentrations were detected in June-July; the distribution of pollen in the air is unimodal. The influence of the anthropogenic triad on fluctuations in the concentration of cereal pollen was established: climate change (temperature) and land use systems, as well as environmental pollution, which manifested itself in the degradation of pollen grains and the appearance of damaged and unidentified biological particles. The purpose of this article is to study the concentration of cereal pollen in the air, their integrative contribution to the aerobiological spectrum in the city of Karakol as dominant pollen allergens.

Exploring Valeriana species: Unraveling anticonvulsant potential through phytochemistry and pharmacology

Background and aims: The Valerianaceae comprises about 300 species of annual and perennial plants found worldwide. Several species are utilized for biological purposes, while others are consumed. The various Valeriana species have different therapeutic effects, including sleep aid, sedative and anxiolytic, and anticonvulsant effects. The study intends to review the phytochemistry, pharmacological activities, and molecular pathways of these plants to explore their potential as therapeutic options for seizures and epilepsy. Methods: Until 2023, all relevant information about Valeriana species was gathered from PubMed, Scopus, Web of Science, and Embase. Valerianaceae, Valeriana, valeric acid, and Valeriana officinalis, phytochemical composition, in vivo investigations, epilepsy, neuroprotective, anticonvulsant, GABA, seizure, and preclinical and clinical research were among the search terms utilized for this review. Results: Based on the results obtained from the studies conducted in this field, significant anticonvulsant effects of various compounds extracted from the Valeriana species have been observed in multiple animal models, including pentylenetetrazole (PTZ)- and maximal electroshock (MES)-induced seizures in mice, rats, and zebrafish. It has also been determined that the molecular and pharmacological mechanisms involved in these anti-epileptic effects are increasing the GABA pathway, inhibiting the NMDA receptor and adenosine pathways, and nitric oxide (NO) modulation. Moreover, these compounds synergize with clonazepam, diazepam, phenobarbital, and phenytoin. Conclusion: It is recommended to prepare proper drug forms and study its anticonvulsant effects in clinical studies.

The heritability of fitness in a wild annual plant population with hierarchical size structure.

The relative magnitude of additive genetic vs. residual variation for fitness traits is important in models for predicting the rate of evolution and population persistence in response to changes in the environment. In many annual plants, lifetime reproductive fitness is correlated with end-of-season plant biomass, which can vary significantly from plant to plant in the same population. We measured end-of-season plant biomasses and obtained single nucleotide polymorphism (SNP) genotypes of plants in a dense, natural population of the annual plant species Impatiens capensis with hierarchical size structure. These data were used to estimate the amount of heritable variation for position in the size hierarchy and for plant biomass. Additive genetic variance for a position in the size hierarchy and plant biomass were both significantly different from zero. These results are discussed in relationship to the theory for the heritability of fitness in natural populations and ecological factors that potentially influence heritable variation for fitness in this species.

The outbreak of teak leaf blight disease caused by Alternaria alternata in the semi‐arid Bundelkhand region of India

AbstractTectona grandis is a vital hardwood tree species with substantial industrial and economic importance. From 2020 to 2021, an unusual leaf blight disease was observed in T. grandis saplings planted in the Nursery of the Central Agroforestry Research Institute (CAFRI), Jhansi, India. Disease incidence was recorded as 50%–70% with 40%–82% severity over two consecutive years on over 1000 saplings. The leaf blight disease was extensive, leading to defoliation of young leaves and mortality of teak saplings in the nursery. The pathogen was identified as Alternaria alternata following standard laboratory procedures and sequence analysis of the internal transcribed spacer (ITS) region of the ribosomal RNA (rRNA). The pathogenicity of two isolates, A. alternata TgAa1 and TgAa2, was proven under greenhouse conditions. Phylogenetic analysis revealed the close association of TgAa1 and TgAa2 with other pathogenic A. alternata strains in the NCBI database. A. alternata is considered a severe foliar pathogen, known to cause leaf spot and leaf blight diseases in many annual and perennial plant species. Correct diagnosis and prevention are emphasized to contain the spread of teak leaf blight to other regions in India. This is the first report of A. alternata causing Tectona grandis leaf blight in the Bundelkhand region of India.

Phytochemical Profile of Eruca sativa and Its Therapeutic Potential in Disease Prevention and Treatment

Eruca sativa (E. sativa), commonly known as arugula, salad arugula, or simply arugula, is an annual plant species belonging to the Brassicaceae family. This leafy vegetable is widely cultivated for its edible leaves, characterized by a distinctive peppery flavor. The seeds are used for their rich fatty acid oils. This botanical specimen has been incorporated into various forms of traditional medicinal practices such as anti-inflammatory, depurative, diuretic, digestive, aphrodisiac, and rubefacient effects. The plant contains various bioactive compounds, including antioxidants, vitamins, minerals, carotenoids, glucosinolates, and flavonoids. This vegetable's broad therapeutic potential and diverse components are under ongoing research, enhancing our understanding of its medicinal properties. This review explores the phytochemical components of E. sativa and its efficacy in treating various diseases, offering a summary of its medicinal properties. Furthermore, it emphasizes the plant's importance in human health and suggests potential directions for future research in natural medicine.

Post-heading accumulation of nonstructural carbohydrates and nitrogen in rice (Oryza sativa L.) roots

ContextRoots are plant organs that absorb nutrients and water. While roots serve as sink organs for nutrients in perennial and woody plant species, the dynamics of nutrient accumulation in roots for annual plant species, particularly in crop species like Oryza sativa L. (rice), are not well understood. Japanese rice cultivars bred for whole-crop silage exhibit large aboveground biomass and a notably small number of spikelets. This sink-source imbalance leads to the accumulation of non-structural carbohydrates (NSC) in stems after heading. Research questionIt is hypothesized that rice cultivars with substantial aboveground biomass might also develop significant belowground biomass. Consequently, the sink-source imbalance may result in NSC accumulation in roots. This study aims to test two hypotheses: firstly, that newly developed small-panicle rice cultivars accumulate NSC in roots post-heading, and secondly, that this post-heading NSC accumulation in roots can be influenced by cultural practices affecting spikelet number per panicle. MethodsTwo small-panicle cultivars, Tachisuzuka and Tachiayaka, and two large-panicle cultivars, Kusanohoshi and Hoshiaoba, were grown using different methods of three cultural practices: nitrogen application, transplanting season, and planting density. Measurements of dry matter, NSC (starch and sugars), and nitrogen in each plant part (panicle, leaf, stem, and roots) were taken over time after heading. The spikelet number per panicle was also counted. ResultsPost-heading, the small-panicle cultivars exhibited NSC accumulation in roots, a phenomenon not observed in the large-panicle cultivars. Although the three cultural practices altered the spikelet number per panicle and thus the sink capacity of the small-panicle cultivars, root NSC accumulation remained unaffected. Additionally, nitrogen weight per unit field area increased with increases in root weight in the small-panicle cultivars. ConclusionsThe imbalance in the sink-source relationship is likely responsible for the post-heading NSC accumulation in roots observed in small-panicle cultivars. However, the lack of root response in NSC accumulation to changes in panicle sink capacity suggests other mechanisms might be involved in root NSC accumulation. Notably, significant amounts of NSC and nitrogen remain in the roots of small-panicle cultivars after harvest. ImplicationsThe accumulation of NSC and nitrogen in roots post-heading could potentially enhance crop growth in subsequent years.

Urban meadow—a recipe for long-lasting anti-smog land cover

This study evaluates for the first time whether 33 species of annual and perennial herbaceous plants originating from a moderate climate continue to be capable of air filtration of particulate matter (PM) at the end of the growing season. Research was undertaken in November in two urban meadows located in trafficked areas of Białystok (Poland). The study reveals that despite the lateness in the season, tested species remained capable of PM accumulation. Deposition of total PM exceeding 100 μg·cm−2 was found on S. vulgaris, S. latifolia, T. pratense, E. vulgare, and A. officinalis. The finest and most toxic fraction was accumulated most effectively by S. latifolia, E. vulgare, and L. vulgare (>12 μg·cm−2). Taraxacum officinale and M. sylvestris retained c. 60% of PM in their epicuticular wax. A slight significant correlation was found between rosette growth pattern and deposition of total PM on foliage, while the accumulation of the finest fraction was correlated with a simple leaf shape. These results support the usefulness of urban meadows as long-lasting air bio-filters provided that their composition includes species that have a confirmed, prolonged PM accumulation capacity and that the meadow is not mown in autumn.

Chemical composition and antimicrobial activity of an apolar extract from Lactuca serriola L. leaves

Lactuca serriola L. is an annual herbaceous plant species belonging to the Asteraceae family, called Prickly lettuce, Wild lettuce, and Jagged lettuce. L. serriola grows on grassy and rocky slopes in many regions in Europe, Asia, Australia, Africa, and North, Central and South America. The plant is used as a natural pharmaceutical agent in primary health care due to its analgesic, anti-inflammatory, antibacterial, and antioxidant properties, which are attributed to the compounds it contains. However, this is the first study demonstrating the antimicrobial activity of L. serriola essential oil. In this study, L. serriola essential oil was obtained by hydrodistillation of plant leaves and analyzed by Gas Chromatography-Mass Spectrometry (GS-MS); subsequently, antimicrobial properties of the essential oil were evaluated using agar dilution and broth microdilution methods. As a result of the GS-MS analysis, hexadecanoic acid, oleic acid, myristic acid, hexahydrofarnesyl acetone, β-ionone, and n-tetradecyl butanoate were found as dominant components in the plant essential oil with the rate of 6.61%, 4.84%, 2.05, 1.55%, 1.3%, and 1.09% (v/v), respectively. The MIC value of L. serriola essential oil against Enterobacter aerogenes,Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans, and Candida tropicalis was found to be 0.94 μLmL−1, and MIC values were determined as 1.87 μLmL−1 and 0.47 μLmL−1 against Klebsiella pneumonia and Candidaparapsilosis, respectively. These results have opened a new horizon regarding the usability of L. serriola essential oil as a pharmacological therapeutic antibacterial and antifungal agent.

Individual vital rates respond differently to local‐scale environmental variation and neighbour removal

Abstract Understanding how plant fitness varies along natural gradients is critical for predicting responses to environmental change. However, individual vital rates are often used as fitness proxies without knowing how other vital rates vary along the same gradients. We investigated how canopy cover, plant–plant interactions, water availability and soil properties influenced the emergence, survival, seed production and population growth rates of eight annual plant species in semi‐arid Western Australia. We sowed seeds into sun‐exposed and shaded blocks across a reserve, removed all neighbouring plants from half of the interaction neighbourhoods, and used rainout shelters to reduce and increase precipitation relative to ambient plots. Canopy cover had strong negative effects on emergence, but few direct impacts on other vital rates and population growth rates. Direct competitive effects on survival and seed production were rare, although evident for population growth rate for 3/8 species. Competition was stronger in open than shaded plots for half of the species. Canopy cover also interacted with the watering treatment to influence survival of half of the species, but watering alone had few direct impacts on species' vital and population growth rates. We found only positive significant correlations between pairs of rates, and survival and seed production were far more frequently correlated with population growth rate than emergence. Synthesis. Our study illustrates that vital rates can respond to the same local‐scale environmental variation in different ways that are likely not driven by life history trade‐offs. We caution against using emergence as a proxy for population growth rate and emphasise that no single vital rate was a reliable fitness proxy overall. Interactions among abiotic and biotic factors were important drivers of vital and population growth rates for some species, highlighting the need to account for plant–plant interactions when predicting population responses to environmental change.

Studies of the molecular mechanisms of grape (<i>Vitis vinifera</i> L.) resistance to low-temperature stress

Abiotic stressors are the main factors limiting the expansion of territories occupied by grape plantations. Industrial viticulture is concentrated in the south of Russia and is limited by climatic factors that do not allow large-scale production in other regions of the country.The present review considers the molecular mechanisms of resistance to low-temperature stress and discusses the role of the main genes determining the ability of plants to survive and acclimatize during a critical temperature drop.One of the most studied ways of responding to cold stress is the interaction of genes in the ICE-CBF-COR cascade, however, a more accurate understanding of the genes responsible for resistance to abiotic environments specifically in grapes requires additional studies. A series of studies of functions of transcription factors and related genes of response to low-temperature stress in various species (Arabidopsis, tea, orange, blueberry, and grape) have identified four main regulons: 1) CBF/DREB, 2) NAC/ZF-HD, 3) AREB/ABF, and 4) MYC/MYB. Studies have demonstrated the function of the HOS1 gene, which negatively regulates the work of ICE1 (a key resistance factor). The review considers candidate genes in various species of annual plants: ICE1, HOS1, SIZ1, MPK3, MPK6, in families of genes: CBF, COR, RD 29A, LTI78, ERD, LEA; DREB1, ADREB1B; WRKY10, and in perennial crops: ICE1, CBF1, HSP70, SUS1, GST, DHN1, BMY5, BHLH102, GR-RBP3, ICE1, GOLS1, GOLS3; CBF; COR27, RD29B, NCED1, ERF105, ZAT10, SAP15, WRKY3, and LEA.Until recently, interspecific hybridization was the leading method for obtaining cold-resistant grape varieties. The main donor of resistance is V. аmurensis Rupr. Recently, the research focused on the genetic basis of grape resistance to low temperatures is actively developing. For instance, a comparative analysis of the transcriptomes of two species contrasting in this trait, i.e. V. amurensis, resistant to low temperatures, and V. vinifera L. with low cold resistance, made it possible to identify three additional candidate genes with an increased expression in response to exposure to low temperatures, namely CBF3, ERF105 and ZAT10. At the same time, the practical application of modern accelerated breeding methods requires the identification of all additional key genes responsible for resistance to low-temperature stress. The components from the cascade of sequentially expressing ICE–CBF–COR genes (ICE1, ICE2, CBF1, CBF2, CBF3, and HOS1) have been selected as candidate genes.

Dispersing across habitat boundaries: Uncovering the demographic fates of populations in unsuitable habitat

AbstractPatchy landscapes are characterized by abrupt transitions between habitats, forcing species to cross habitat boundaries in order to spread. Although individuals that disperse into unsuitable habitat are often presumed dead in population models, reality may be more nuanced. If survival within an unsuitable habitat is possible (however transiently), then through time, individuals may be able to reach distant, suitable habitat. In this study, conducted with annual plant species in a fragmented Californian grassland, we examined the fate of habitat specialists moving between serpentine patches and an invaded nonserpentine matrix. First, we tested whether habitat specialists use seed dormancy to transiently survive beyond the habitat boundary. We found that dormancy maintained populations of patch specialists deep into the matrix—these patterns were not observed for matrix specialists in serpentine patches. Seeds of patch specialists that lacked morphologies for assisted dispersal accumulated downslope of patches, suggesting that even the most dispersal‐limited species could eventually reach suitable patches even if they first land in the matrix. Second, because an invasive matrix specialist (Avena fatua) is highly abundant, we were interested in determining whether seeds spilled into serpentine patches were strong enough to maintain sink populations. We found that A. fatua was largely absent deep in patches, where the components of fitness plummeted and there was no evidence of a dormant seedbank (in contrast to a sizable seedbank of patch specialists in the matrix). Our results suggest that the demographic fates of individuals that land in unsuitable habitat depend on the direction by which the boundary is crossed (patch ➝ matrix ≠ matrix ➝ patch), with different ecological consequences for species in each habitat type. Dormancy is often understood as a mechanism for persisting in the face of temporal variability but may serve as a means of traversing unsuitable habitat in patchy systems, warranting its consideration in estimates of habitat connectivity.

Facilitation against herbivory more important than resource‐based niche differences for plant coexistence in a field experiment

Abstract Theory suggests that eutrophication impacts plant community biodiversity by constraining niche differences and increasing competitive inequalities among species, leading to the exclusion of weaker competitors. However, explicit tests of nutrient effects on the strength and direction of inter‐ and intraspecific plant–plant interactions that dictate coexistence are lacking, especially in complex field settings where multiple processes can simultaneously affect plant growth and reproduction. We conducted a field experiment in southeastern Vancouver Island, Canada, using four annual grassland plant species to test how species interactions responded to eutrophication and the covariation of herbivore pressure and neighbour species light‐ and moisture‐use. We found that focal species reproduction was limited by nutrient availability and herbivory, such that the nature of species interactions was context‐dependent. Competitive interactions failed to predict species persistence under these conditions. Instead, facilitation was critical—phytometers grown without neighbours consistently failed to produce seed under herbivore pressure meaning that fecundity significantly increased with neighbour density. Synthesis. Our work demonstrates the importance of species interactions in plant community responses to eutrophication but emphasizes that ‘indirect’ drivers of plant performance may influence or overwhelm nutrient effects on plant–plant competition. The widespread occurrence of mortality overcome primarily by facilitation highlights the importance of positive density dependence. Overall, our results suggest that knowledge of resource niche overlap may be insufficient to explain plant community responses to eutrophication. This highlights the necessity of considering the broader environmental context when leveraging ecological theory to understand global change effects in empirical settings.

Effects of intraspecific variation in a native species' phenology on its coexistence with non‐native plants

Intraspecific trait variation is ubiquitous and is likely to influence species coexistence. Despite theoretical progress, empirical work on the effects of intraspecific variation on the dynamics of competing species is rare. This is because of the formidable empirical requirements necessary to link intraspecific variation in species' functional traits with intraspecific variation in the demographic and competitive rates that mediate coexistence. Here we partially overcome these challenges to determine how intraspecific variation in reproductive phenology in a native Californian annual plant species Lasthenia californica affects its ability to coexist with two non‐native species Bromus madritensis and Lactuca serriola that display contrasting phenological patterns. Using data from a field experiment, we empirically parameterize a model of competitive population dynamics, accounting for the effects of intraspecific phenological trait variation on the native species' response to both intra‐ and interspecific competition. We find that intraspecific variation in phenology drives differences in the native species' response to competition. Moreover, simulations of the parameterized model show that this variation improves the competitive performance of the native species. This occurs because of the effects of nonlinear averaging mediated by a nonlinear, concave‐up competition function that is a general feature of competition across a wide range of taxa. While intraspecific variation improves competitive performance, we also find that the magnitude of the benefit is predicted to be insufficient to prevent competitive exclusion against the non‐native species with early phenogy Bromus. Against the second non‐native species with later phenology Lactuca, intraspecific variation is predicted to result in coexistence where competitive exclusion would otherwise occur, but we could not rule out alternative qualitative outcomes for this interaction.

Precipitation timing and soil substrate drive phenology and fitness of Arabidopsis thaliana in a Mediterranean environment

Abstract In Mediterranean climates, the timing of seasonal rains determines germination, flowering phenology and fitness. As climate change alters seasonal precipitation patterns, it is important to ask how these changes will affect the phenology and fitness of plant populations. We addressed this question experimentally with the annual plant species Arabidopsis thaliana. In a first experiment, we manipulated the date of rainfall onset and recorded germination phenology on sand and soil substrates. In a second experiment, we manipulated germination date, growing season length and mid‐season drought to measure their effects on flowering time and fitness. Within each experiment, we manipulated seed dormancy and flowering time using multilocus near‐isogenic lines segregating strong and weak alleles of the seed dormancy gene DOG1 and the flowering time gene FRI. We synthesized germination phenology data from the first experiment with fitness functions from the second experiment to project population fitness under different seasonal rainfall scenarios. Germination phenology tracked rainfall onset but was slower and more variable on sand than on soil. Many seeds dispersed on sand in spring and summer delayed germination until the cooler temperatures of autumn. The high‐dormancy DOG1 allele also prevented immediate germination in spring and summer. Germination timing strongly affected plant fitness. Fecundity was highest in the October germination cohort and declined in spring germinants. The late flowering FRI allele had lower fecundity, especially in early fall and spring cohorts. Projections of population fitness revealed that: (1) Later onset of autumn rains will negatively affect population fitness. (2) Slow, variable germination on sand buffers populations against fitness impacts of variable spring and summer rainfall. (3) Seasonal selection favours high dormancy and early flowering genotypes in a Mediterranean climate with hot dry summers. The high‐dormancy DOG1 allele delayed germination of spring‐dispersed fresh seeds until more favourable early fall conditions, resulting in higher projected population fitness. These findings suggest that Mediterranean annual plant populations are vulnerable to changes in seasonal precipitation, especially in California where rainfall onset is already occurring later. The fitness advantage of highly dormant, early flowering genotypes helps explain the prevalence of this strategy in Mediterranean populations. Read the free Plain Language Summary for this article on the Journal blog.

Weak evidence of trade-offs modulated by seed mass among a guild of closely related winter annuals

Plant-plant interactions are integral to the establishment and persistence of diversity in plant communities. For annual plant species that depend on seeds to regenerate, seed characteristics that confer fitness advantages may mediate processes such as plant-plant interactions. Seed mass is known to vary widely and has been shown to associate with species’ differences in stress tolerance and competitive effects. However, understanding of how seed mass influences species’ responses to competition is less well understood. Using natural assemblages of six closely related annual plant species in Western Australia, we implemented a thinning study to assess how seed mass influences the outcomes of plant-plant interactions. We found relatively weak evidence for competition or facilitation among species. Our strongest results indicated that heavy-seeded species had lower survivorship than light-seeded species when interacting with heterospecifics. Seed mass was also negatively related to overall survival, counter to expectations. These findings indicate some evidence for trade-offs mediated by seed mass in this system. However, we acknowledge that other factors may have influenced our results, such as the use of natural assemblages (rather than using sowing experiments) and the presence of important small-scale environmental variation not captured with our choice of abiotic variables. Further research is required to clarify the role of seed mass in this diverse annual system, ideally including many focal species, and using sowing experiments.

Assessment of multiple herbicide protection seed treatments for seed-based restoration of native perennial bunchgrasses and sagebrush across multiple sites and years.

The invasion of exotic, annual plant species is a leading contributor to ecological degradation in drylands globally, and the use of pre-emergent herbicide to control these species is common. Pre-emergent herbicides pose challenges for seed-based restoration due to toxicity to the seeds of desired species. Herbicide protection (HP) technologies pose a potential solution by using activated carbon seed treatments to protect desirable seeds from herbicide exposure. In the sagebrush steppe ecosystem of North America, we used an adaptive small plot design over three planting years to test for effects on seeding outcomes (seedling density and size) of large and small multi-seed HP pellets, several single-seed HP coatings, and carbon banding treatments at geographically dispersed sites for several perennial bunchgrasses and the keystone perennial shrub, Wyoming big sagebrush. We also compared different methods of seed delivery and litter pre-seeding management. Seeding success was low overall, especially for sagebrush, and it was clear that other, often less predictable barriers to establishment than herbicide exposure, such as inadequate spring moisture, were strong drivers of seeding outcomes. Despite this, HP treatments were associated with higher seedling density than bare seed in multiple instances, most notably for grasses. The large HP pellet occasionally outperformed the small HP pellet, and several HP coatings performed similarly to the small pellet. Surprisingly, we did not see consistent negative effects of pre-emergent herbicide on unprotected bare seed. We conclude that HP seed treatments show some promise to improve seeding success in the presence of herbicide, but that consistent success will require further improvements to HP treatments as well as integration with other innovations and approaches.

A Field Survey of Syrphid Species and Adult Densities on Annual Flowering Plants in the Northeastern United States.

With the long-term goal of exploring the viability of conservation biological control of cabbage aphid Brevicoryne brassicae (L.) (Hemiptera: Aphididae) in the northeastern United States, adult syrphid flies (Diptera: Syrphidae) were observed on several species of annual insectary plants at farm sites in Connecticut, Massachusetts, and New Hampshire. Insectary plant species included alyssum, Lobularia maritima (L.) (Brassicales: Brassicaceae), buckwheat, Fagopyrum esculentum (Moench) (Caryophyllales: Polygonaceae), phacelia, Phacelia tanacetifolia (Bentham) (Boraginales: Hydrophyllaceae), calendula, Calendula officinalis (L.) (Asterales: Asteraceae) and ammi, Ammi majus (L.) (Apiales: Apiaceae). Among these insectary plants, alyssum had the longest bloom period and attracted the most syrphids. We identified 21 species of syrphid flies from insectary plants. The three most prevalent species collected were the aphidophagous Toxomerus marginatus (Say) (Diptera: Syrphidae) (70.1% of samples) and T. geminatus (Say) (Diptera: Syrphidae) (8.8% of samples), as well as the non-aphidophagous Syritta pipiens (L.) (Diptera: Syrphidae) (13.1% of samples). The benefits of including these insectary plant species as a companion to Brassica (L.) (Brassicales: Brassicaceae) cropping systems are discussed.