Abstract Plant species face myriad threats to their survival, including climate change and habitat destruction. On Oʻahu in Hawaiʻi, Scaevola taccada L., a coastal dune shrub, is highly impacted by human activities and environmental threats. Despite its ubiquity across Pacific islands, the extent and distribution of genetic diversity within individual islands is unclear. We surveyed genomic diversity using double digest restriction associated DNA sequencing (ddRAD-seq) in eight populations of S. taccada on Oʻahu. Using principal components (PCA) and STRUCTURE analyses, we assessed whether genetic diversity was structured geographically and the extent to which selection and migration structured genetic diversity. We analyzed climate and leaf thickness data to understand how patterns of genetic diversity were correlated with environmental and trait variation. Our analyses pointed to a trend in which populations in protected areas were genetically differentiated from, and harbored less genetic diversity than, human dominated areas. Analyses of genetic structure indicated that western beach populations were differentiated from eastern beach populations. FST outlier analyses suggest that selection is not primarily responsible for the differentiation seen between the protected populations and the human dominated areas. Our results demonstrate that S. taccada populations in protected natural areas harbored unique genetic variation compared to human dominated beach parks, but that protected populations also had significantly reduced genetic variation compared to most other populations. Relatively few FST outliers, paired with evidence of continued gene flow, suggests that current levels of genetic diversity are more a function of isolation and drift as opposed to selection.
Abstract Functional traits express the ecological and evolutionary attributes of individuals that compose taxa, providing robust criteria to detect speciation when integrated with phylogenies. We tested this approach in Sonchus asper (L.) Hill, a putatively self-fertilising annual weed that has recently been reported to exhibit extensive floral and life-form variation across the northern Mediterranean. This variability was already documented in the nineteenth century, but it is incongruent with current subspecific classifications based on leaf arrangement. We sampled 40 populations encompassing this variation, assigning each to (a) one of the four morphotypes defined by floral traits and life forms, and (b) a leaf arrangement group. To assess their taxonomic relevance, we tested grouping characters as functional traits and analysed the consistency of these assignments with the phylogeny (ITS/ETS and chloroplast DNA markers), and genetic structure (AFLP markers). Phylogenetic analysis using floral traits and life forms identified three well-supported clades that contradict leaf-arrangement taxonomy. The earliest-diverging clade comprises the common, annual, self-fertilising S. asper. The remaining two clades consist of self-incompatible plants: one contains the rhizomatous morphotype, whereas the other groups annual and biennial plants. These life-history strategies exhibited distinct AFLP-based genetic profiles, alongside complex cpDNA phylogeographical patterns. The congruence between DNA analyses and functional value of floral and life-form traits corroborates the proposed morphotypes as distinct evolutionary lineages. This reveals unaccounted-for biodiversity and supports reinstating historical taxa. Our study shows that combining functional traits with genealogical relationships provides a powerful operational taxonomic criterion that integrates ecological and evolutionary species concepts.
Seed banking supports conservation, but freshly collected and stored seed may differ in important characteristics. Our resurrection study assessed differences in seedling traits from stored and fresh populations of six native plant species in the Great Basin, where invasive annual grasses increase fire frequency to the detriment of native plants. We evaluated stored seed collected through the Seeds of Success programme and contemporary re-collections from the same population 3-11 years later, including sites that burned between collection dates and paired, unburned sites. We sowed seeds in a common garden and measured differences in seed mass, emergence (timing and total), survival, and multiple size traits. We observed temporal changes in trait means for at least one trait in every species irrespective of burn history. The direction of change varied among species, and very few traits changed in variance. Seed mass and emergence traits changed most frequently (12 of 17 measures changed over time), with fewer changes in mortality and size traits (6 of 24). Changes may reflect sampling, ageing, or maternal effects, or changes in gene frequency from drift or natural selection. Evidence consistent with adaptive evolutionary response to disturbance was observed in Elymus elymoides, with burned sources shifting towards smaller plant size and earlier emergence, with lower variance. Regardless of cause, widespread differences in seed and seedling traits between wild populations and seed banked seeds provide support for continued seed banking efforts, as intra-population phenotypes often differ between ex situ seed collections and in situ wild populations.
Abstract Understanding and managing invasive taxa requires accurate identification, which can be challenging when the invader is an interspecific hybrid. An example of this is the hybrid cattail Typha x glauca, which is found in a widespread and expanding hybrid zone in North America along with its parent species T. latifolia and T. angustifolia. In some regions this hybrid is considered invasive because it dominates wetlands, reduces biodiversity, and alters ecosystem functioning. It is also a complex hybrid zone that includes advanced-generation hybrids and hybrid backcrosses to both parent species (hereafter collectively referred to as non-F1 hybrids). Previous studies have shown that gross morphological characters of non-F1 hybrids overlap with those of their parent species, and this can hinder identification and hence monitoring and management programs in areas of high non-F1 abundance. Here we show that microscopic pollen and bracteole characteristics are overall highly reliable for taxonomic identification, as they agreed with the genotype-based taxonomic assignments for 409/426 (96%) and 232/244 (95%) of plants, respectively, with non-F1 hybrids the most common source of error. Although these characteristics are limited to flowering plants, and in the case of pollen to a relatively short period of time, they are relatively easy to apply; however, the abundance of T. latifolia may be underestimated if plants are identified from inflorescence traits. Nevertheless, this low-cost method for distinguishing cattail taxa could facilitate research into this expanding hybrid zone, plus targeted management of hybrid cattails in areas where they dominate wetlands and disrupt ecosystems.
Sri Lankan wild rice, Oryza nivara and Oryza rhizomatis, are two threatened species occurring in habitats with contrasting dry and wet seasonal patterns. Both species produce dormant seeds at dispersal, yet their germination phenology remains poorly understood. This study aimed to elucidate their germination strategies and dormancy mechanisms to support conservation efforts. We hypothesized that dormancy alleviation in these species is niche-specific; specifically, that O. rhizomatis requires longer periods of dry storage (after-ripening) and shorter period of flooding than O. nivara. (i) Freshly harvested seeds of both species were subjected to nine dry-storage periods (0, 2, 4, 6, 8, 10, 12, 18, and 20 months) at 25°C and 60% relative humidity (RH). Following storage, seeds were incubated on moist tissue paper for 30 days at 25°C under a 12 h light/dark regime. Additionally, a second set of seeds stored for 6, 8, 18, and 20 months was exposed to flooding treatments (FTs) (1, 2, or 4 weeks) prior to incubation. (ii) In both species, germination percentage increased up to ∼80% with increasing dry-storage periods up to 12 months. Under prolonged dry storage, germination percentage declined in O. rhizomatis and none of the seeds germinated in O. nivara. In O. rhizomatis, a short FT (1 week) increased the germination percentage compared with dry storage alone, whereas longer flooding periods (2-4 weeks) reduced it. In contrast, flooding had no significant effect on seed germination in O. nivara. (iii) Overall, prolonged drying effectively breaks dormancy in both species, preventing germination immediately after dispersal when drought risk is high and seedling survival is low. The species exhibit distinct physiological dormancy breaking responses that likely contribute to their differing ecological and geographical distributions. Predicted increases in precipitation under climate change may constrain recruitment by limiting dry after-ripening or increasing flooding duration, posing a particularly high risk for the endemic O. rhizomatis.
Plant species interactions in woodlands help maintain the coexistence of trees and groundcover, contributing to high plant diversity. Interactions can be either positive or negative and take place both above and below ground. Both competitive and facilitative interactions have been documented in longleaf pine woodlands, but the dynamics of these interactions and their effects on plant physiology are poorly understood. Our objective was to quantify the impact of tree root exclusion on physiology and growth of understory plant functional types (PFTs) that represent the diversity of longleaf pine woodlands. We used trenching to isolate understory plants from tree roots and compared soil moisture, leaf water potential (Ψ), leaf-level gas exchange, and plant growth for four understory species representing different PFTs in trenched root exclusion plots and untrenched control plots. We hypothesized that root exclusion would reduce understory plant performance compared to untrenched control plots by isolating plants from facilitative effects of canopy trees, but our hypothesis was not supported. We observed better plant performance in trenched plots for some PFTs, and no differences in plant growth for any PFT. These data suggest competitive effects of tree root presence, but results varied among PFT. The study period was unusually wet, with rainfall 53% above normal. In the context of previous studies, these results suggest that belowground competition is more important than facilitation during a wet year, and the relationship between longleaf pines and understory plants shifts from facilitation to competition depending on rainfall.
Although floral colour polymorphism is common in angiosperms, the functional nature of polymorphic traits within a species remains poorly understood. Colour morphs may differ in traits other than colour, including nectar reward, pollinator visitation, and reproductive compatibility. We studied bract colour polymorphism in a nocturnal ginger, Curcuma caulina, to ask: (i) Do the nectar rewards, hawkmoth visitations, and reproductive compatibility differ among morphs? (ii) Do the morphs differ in their female reproductive success, and does this correlate with their observed abundance? We measured floral and vegetative traits in three dominant morphs and compared nectar rewards, nocturnal pollinator visitation rates, intra- and inter-morph compatibility, and natural fruit and seed production. The morphs did not differ in morphology but differed in their bract colour and within-population abundance. The common green-red morph has low-energy nectar, low pollinator visitation rates, and is self-incompatible, but has the highest reproductive success. The rare red-white morph, despite high-energy nectar, higher pollinator visitation rates, and a leaky self-compatibility, shows lower female reproductive success. Thus, the morphs have contrasting nectar traits, reproductive compatibility, and reproductive success. Path analyses indicated that nectar reward, pollinator visitation, reproductive compatibility, and abundance jointly explained variation in female reproductive outcomes, although their effects differed among morphs. These results show that bract colour morphs of C. caulina differ in multiple ecological and reproductive traits and provide a foundation for future studies testing male fitness, seedling survival, clonal structure, and abiotic selection.
The southern Atlantic coastal dunes of South America formed ca. 6000-4000 years ago. Within this dynamic landscape, three dioecious species of Poa occur: Poa lanuginosa, a widely distributed species, and two dune endemics, Poa bergii and Poa schizantha, occupying contrasting microhabitats from foredunes to interdunal slacks and inland grasslands. We investigated the evolutionary relationships, population structure, and extent of introgression among these dune-adapted grasses, conducting a population-level phylogenomic analysis using genotyping-by-sequencing. Genome-wide data provided robust phylogenetic resolution, whereas Neighbor-Net analyses revealed reticulate relationships and admixture among taxa. We tested introgression, and significant signals of gene flow were detected across major groups. Bayesian and discriminant analysis of principal components analyses identified distinct genetic lineages within both dune endemics. Poa bergii comprised three geographically structured genetic groups, and P. schizantha showed clear internal differentiation despite its restricted distribution. Instead, P. lanuginosa has a broad distribution across both dune and continental habitats and was inferred to be a paraphyletic lineage that may represent the ancestral lineage of both dune endemic species. These distinct patterns of divergence and population structure indicate species-specific evolutionary responses to a recent and dynamic dune landscape, in which habitat heterogeneity and differential environmental tolerance have driven lineage diversification. Together, our findings highlight the role of coastal dune dynamics in recent adaptation and speciation. Ongoing gene flow alongside clear lineage structure is consistent with recent and still incomplete speciation among these dune species. Poa schizantha emerged as the most differentiated lineage, combining morphological distinctiveness, ecological specialization, and strong genomic structure. Our results emphasize the importance of integrating population genetics into conservation strategies to preserve both endemic taxa and ongoing evolutionary processes in threatened coastal environments.
Forest persistence amid shifting climate conditions requires sufficient tree recruitment for sustaining populations. In dryland ecosystems where precipitation can be episodic and variable, changes in precipitation pulse regimes may be critically important for seedling establishment, as some populations may be locally adapted to variable resource availability. We conducted a greenhouse common garden experiment to evaluate Pinus monophylla seedling responses to varying watering pulse regimes. We used seeds from four sites representing endpoints of range-wide gradients of climatic water deficit and summer precipitation. Seedlings received the same amount of total water, but the water was applied in three different pulse patterns. We compared morphological and physiological traits in response to the three watering regimes, exploring whether responses were consistent with possible local adaptations. Seedlings demonstrated substantial trait differences among seed sources but few differences among water pulse treatments. Multivariate analysis of seedling traits suggested that seed source climate was related to two trade-offs in resource-use strategies: (i) acquisitive leaf traits versus seedling biomass and (ii) water use efficiency versus nitrogen use efficiency. A better understanding of intraspecific trait variation (ITV) can facilitate predictions of drought and temperature responses and help to identify suitable seed sources for P. monophylla restoration. While observed levels of ITV provide indirect evidence of local adaptation, this variation was not related to different precipitation pulse responses. However, the observed relationship between seed source climate and patterns of ITV suggests that local resource-use strategies underlying successful tree regeneration may constrain responses to a changing climate.
While mobile apps are becoming more accurate at identifying vascular plants, it is unclear whether accuracy is maintained when doing plot-based surveys, where image acquisition is limited to a small pool of individuals that often lack ideal identification features. We evaluated two free plant identification apps, Flora Incognita and iNaturalist, using 5291 field images of 119 species from 54 plots of 0.8 m2, from graminoid-dominated grassland and forested sites. We examined the top-1 identification (ID) accuracy as a function of botanical (growth form and reproductive state) and photographic (image quality and background) parameters. We used score fusion to test whether combining multiple images of the same individual (perspective combination) improved ID accuracy. Top-1 ID accuracy was consistently higher in Flora Incognita (79.2% overall) as compared to 66.5% in iNaturalist. No groups reached the reference expert accuracy of plot-based surveys (90%-95%). Images featuring reproductive structures significantly improved ID accuracy, particularly for graminoids (overall +8.9% in Flora Incognita, +17.1% in iNaturalist), and high-quality images increased accuracy significantly for graminoids and herbs in iNaturalist. Combining multiple images improved the overall ID accuracy of vascular plants in iNaturalist by 6% and 1.7% in Flora Incognita, with significant improvement for herbs and shrubs in iNaturalist. We provide recommendations for ID success in the field for app users as well as app developers to optimize image acquisition for species identification in surveying and monitoring efforts.
Islands sustain an outstanding proportion of Earth's biodiversity. However, modern molecular studies on oceanic island floras have typically focused on endemics, which leaves many research questions involving other types of taxa unaddressed. In this study, we analyse the patterns of genetic variation in two co-occurring native nonendemics (NNE) that are common components of lowland habitats across the Canarian archipelago: Launaea arborescens (Asteraceae), a wind-dispersed species, and Lycium intricatum (Solanaceae), an endozoochorus species. We predicted that, given their presumably recent colonization of the archipelago, both lineages should show a genetic pattern compatible with a stepping-stone model, i.e. from the easternmost islands (closest to mainland Africa) to the western islands. We carried out exhaustive sampling in all the islands of distribution and in neighbouring mainland areas (SW Morocco). Using three plastid DNA regions, we calculated levels of haplotype diversity, conducted analyses of spatial distribution of molecular variance, and tested various models of colonization and gene flow with complementary coalescent-based approaches. For comparison, we additionally performed a literature review to assess general patterns of haplotype diversity on plant species with similarly widespread distributions across the archipelago. A stepping-stone model of island colonization was only partly supported by our results, since back-colonization of mainland areas was a scenario equally supported by coalescent analyses and estimates of historical gene flow. Both species showed that the easternmost islands represented de facto a genetic continuum of the neighbouring mainland area. However, Lycium generally displayed much higher rates of gene flow than Launaea, which may be due to secondary dispersal mediated by predatory birds. Lastly, our literature survey revealed that both NNE harbour unprecedented high levels of genetic diversity on the easternmost Canary islands. This study illustrates that the phylogeographical analysis of NNE provides novel insights into island biogeography, since these taxa can deviate from common patterns observed in endemic lineages.
As a core region for global high-altitude carbon cycling, the Qinghai-Tibet Plateau is a key region influencing the regulation of the global terrestrial carbon balance. However, the mechanisms controlling the accumulation of soil organic carbon (SOC) in this fragile ecosystem remain unclear. We surveyed 98 sample sites in the northeastern Qinghai-Tibet Plateau and analysed the data using Bayesian statistical methods. The 0-20 cm SOC storage in the Qinghai region is ∼0.37 Pg. Horizontally, SOC exhibited a decreasing trend from east to west, while vertically, it decreased with increasing soil depth, with a reduction of 24.28%. The result showed that plant cover and mean annual precipitation (MAP) were the dominant positive drivers of SOC accumulation in both soil layers (the 95% credible interval did not overlap with zero). Notably, plant cover and mean annual temperature had stronger effects on SOC in the surface layer. The Bayesian structural equation model indicated that plant cover, MAP, Shannon diversity index, and the litter C/N ratio collectively explained 68% of the variation in SOC across both layers. The path coefficient (standardized effect size) of MAP on SOC increased with soil depth, whereas that of plant cover decreased, indicating that the influence of environmental factors on SOC accumulation is dependent on depth. These results demonstrate that accurately predicting the Qinghai-Tibet Plateau's SOC accumulation necessitates the explicit consideration of local plant cover conditions and concurrent precipitation shifts regarding existing SOC accumulation.
Plant-induced defences against herbivores have the potential to modify plant growth, fitness, and the outcome of plant-herbivore interactions. Plants use a variety of cues to initiate the induction of defences, including physical tissue damage, cues released by damaged plant tissues of neighbouring plants (e.g. methyl jasmonate, MeJA), and cues that indicate herbivore presence but are not associated with herbivore damage (e.g. locomotion mucus of herbivorous molluscs). Evidence shows that both herbivore-damage and herbivore-presence cues can generate induced defences in herbaceous plants over relatively short time periods. However, the immediate and long-term effects of these cues on seedlings of deciduous broad-leaved woody plants remain poorly understood. Here, we compare the effects of two cues, MeJA and locomotion mucus of the dusky slug Arion subfuscus, on the growth and defence traits of sugar maple, Acer saccharum, seedlings at multiple timepoints. Specifically, we exposed 4-week-old seedlings to these cues in a greenhouse experiment and quantified their effects on seedling growth, total phenolics, and growth of spongy moth Lymantria dispar across the seedlings' growing season. As expected, MeJA had a negative effect on seedling growth, a positive effect on total phenolics, and no effect on the growth of L. dispar. In contrast, the slug locomotion mucus did not negatively affect growth or change total phenolic levels. Our results highlight that herbivore cues can induce responses in seedling growth and defence in deciduous broad-leaved woody plant seedlings; however, these responses vary with cue type and the induced responses decay for some seedling traits but not others.
Most species of orchids become autotrophic after the formation of the first leaf develops; however, some mycoheterotrophic species remain achlorophyllous at maturity and non-photosynthetic throughout their entire life cycles, depending on fungal associations for survival. However, the mechanisms governing carbon and nitrogen exchange between mycoheterotrophic plants and their associated fungi remain largely unexplored in neotropical regions. Studies with mycoheterotrophic orchids from tropical regions and different subfamilies contribute to a better understanding of the nutrition mode of these plants, and allow evaluation of the role that morphological and anatomical characteristics play in the mycoheterotrophic way of life. Samples of different individuals of Pogoniopsis schenckii were fixed and subjected to standard anatomical techniques for light microscopy, histochemical tests, transmission and scanning electron microscopy and stable isotope analysis. Pogoniopsis schenckii exhibits two distinct root types: one with acute apex and another with a rounded apex. Fungal hyphae were found in all roots but were not organized into typical pelotons; instead, they were distributed throughout the epidermis and cortex, including within cells associated with starch storage. Our isotopic results suggest that P. schenckii acquires carbon and nitrogen through its symbiotic fungi from the soil. The root system of P. schenckii exhibits two root morphotypes that differ in size, apex shape, and anatomy. The observed patterns of 13C and 15N abundances in P. schenckii suggest that this mycoheterotrophic orchid is associated with ectomycorrhizal fungi. Additionally, we described two trends in the degradation of the semi-coiled hyphae found within the epidermal and cortical cells of the two root morphotypes of this mycoheterotrophic species.
Plant organs are shed through a tightly regulated process called abscission, which involves coordinated changes that enable cell separation and formation of a new protective barrier. However, the cellular processes within the abscission zone, where plant organs detach, are largely understudied. This gap is mainly due to difficulties in visualizing this region, due to its small size and location often being obscured by other plant tissues. Here, we present a simple and accessible method to visualize changes in cell shape and lignification in the abscission zone of Arabidopsis thaliana floral organs. Cell walls are stained with calcofluor white and lignin is simultaneously detected using its intrinsic autofluorescence. This inexpensive approach allows clear imaging of cellular changes during abscission zone development and can be applied to mutants with abscission-related defects.
As a key species in China's ecologically fragile Sanjiangyuan region, Juniperus tibetica faces severe threats from Arceuthobium oxycedri. This study preliminarily identified the mistletoe species parasitizing J. tibetica as A. oxycedri. The results of physiological parameter measurements indicate that infection with A. oxycedri significantly increased the activity of peroxidase (POD), catalase (CAT), polyphenol oxidase (PPO), phenylalanine ammonia-lyase (PAL), cinnamaldehyde dehydrogenase (CAD), glutathione peroxidase (GSH-Px), as well as the malondialdehyde (MDA) and proline (PRO) content in J. tibetica. This suggests that, under A. oxycedri infection, J. tibetica resists the infection by scavenging reactive oxygen species, increasing lignin content and enhancing drought-related physiological indicators. Multi-omics analysis indicates that following infection by A. oxycedri, the major enriched pathways in J. tibetica associated with the A. oxycedri invasion are all linked to drought stress defence. It is hypothesized that the growth and reproduction of A. oxycedri require the uptake of large amounts of water from the host, its parasitism leads to an imbalance in the host's water transport, thereby triggering drought-stress-related response mechanisms. These findings are consistent with the results of physiological parameter measurements. This study provides preliminary insights into the physiological and molecular mechanisms by which J. tibetica responds to A. oxycedri stress, offering a theoretical basis for the effective control of the occurrence and damage caused by A. oxycedri.
Higher ambient temperatures during rice cropping season reduce grain yield and quality, yet maturity group-specific responses to heat stress are largely unknown. A field trials of 36 rice varieties were conducted in Arkansas, United States, using two planting dates in a randomized complete block design with four replications under season-long conventional flood irrigation. Varieties were classified into early (n = 8), medium (n = 13), and late maturing (n = 15) based on heading dates. Cumulative heat exposure was quantified by using heat degree days (HDD) within key developmental stages. Heat stress effects were most pronounced during nighttime, suggesting that the observed yield and quality alterations were largely attributable to high nighttime temperatures (HNT). Early-maturing varieties showed greater tolerance to HNT, as evidenced by a non-significant decline in grain yield as the HDD increased. In contrast, medium- and late-maturing varieties exhibited significant yield losses per unit HDD (medium: -0.368 g plant-1 per °C·day; ∼0.9% per HDD; late: -1.024 g plant-1 per °C·day; ∼1.4% per HDD). Grain traits varied among maturity groups, with medium- and late-maturing varieties producing thinner and chalkier grains, while early-maturing varieties largely maintained grain weight. Across traits, variety and maturity group explained most variation, and significant variety × planting date interactions highlighted exploitable genotype-by-environment (G × E) effects on nighttime heat tolerance. Early-maturing varieties, including Norin 20, ZAO 402, and Geumobyeo, demonstrated strong resilience to HNT stress. Planting dates adjustments may, therefore, offer a practical adaptation strategy to mitigate heat stress under warming cropping seasons, although further investigation is needed.
Feralization is an evolutionary process that can reverse domestication traits, giving rise to invasive or weedy plants. Brassica rapa is an example of extensive diversification, producing multiple domesticated crops, while its non-crop forms persist as weeds in disturbed habitats worldwide. In Argentina, the spread of this weed has increased since 2012, when populations resistant to glyphosate (transgenic) and to acetohydroxyacid synthase (AHAS)-inhibiting herbicides (non-transgenic) were first reported. Despite their spread across more than one million hectares with economic consequences, their origin and genetic diversity remain unknown. This study aims to evaluate the genetic diversity and population structure of Argentinian B. rapa accessions and try to infer the origin of herbicide-resistant populations. We analysed 56 Argentinian accessions and compared them with 568 accessions worldwide using genotyping-by-sequencing. A total of 15 790 SNPs were used to analyse genetic diversity, population structure, and phylogeny. Resistant and susceptible Argentinian accessions formed a genetically homogeneous group distinct from global populations. An exception was a population from southwestern Argentina, which clustered separately. The lowest genetic differentiation was observed with weedy strains from South and North America and with European turnips, suggesting a shared origin and local differentiation. The genetic similarity between resistant and susceptible accessions suggests that herbicide resistance may have emerged via local gene flow from transgenic Brassica napus cultivated informally in Argentina. Overall, our findings improve understanding of the genetic diversity and evolutionary history of this weed and provide a genomic baseline for future management strategies, as well as insights into transgene escape.
The study of seed trait variation is essential for developing effective conservation strategies, understanding plant recruitment, and predicting the long-term persistence of endemic/rare plant species under environmental change. This study examines the seed ecology of Iberodes littoralis subsp. gallaecica, a narrow endemic to coastal dune systems in north-western Spain. Seeds collected from five populations over 7 years were grown in a glasshouse to investigate variation in seed mass, germination rate, time to germination, and seedling relative growth rate (RGR). To evaluate the role of resource availability, seeds were sown in two substrate types: dune sand alone and mixed with compost. Seed traits varied significantly among years and populations. Overall, older seeds germinated less and took longer to germinate than younger seeds. Heavier seeds had greater germination percentages, but the effect of seed mass on time to germination differed among years. Seeds produced under higher maternal rainfall were lighter, which in turn influenced germination timing and seedling RGR, indicating an indirect effect of maternal environment on seed performance. Germination rates were lower in the substrate amended with compost, but those seedlings had a higher RGR. These results suggest that using fresh seeds maximizes restoration success, and when fresh material is unavailable, the largest seeds should be selected. While fertilisation can enhance early seedling growth, it may not improve germination success. Our findings highlight the complex interplay among seed age, seed mass, population differences and substrate conditions in shaping germination and early growth of this narrow endemic.
Pollen availability and self-compatibility studies in grasses inform restoration by identifying limitations to germinable seed production. Seed set alone indicates pollen limitation and self-fertilization ability but not self-compatibility, as seeds may not germinate. We tested whether wiregrass (Aristida beyrichiana) is pollen-limited and self-compatible in two southeastern U.S. pine savannas differing in ecology and fire frequency. Pollen limitation and self-compatibility were assessed by comparing seed set and germination from naturally pollinated inflorescences, those supplemented with outcross pollen, and those restricted to self-pollen. All treatments produced seeds, but filled and germinable seed numbers varied by site. The wetter, triennially burned site produced significantly more germinable seeds than the drier, annually burned site. Pollen was not limiting: open and outcross-supplemented inflorescences produced similar seed numbers within each site. Based on seed production, wiregrass appeared capable of self-fertilization, but germination data revealed near -zero viability of selfed seeds, indicating severe inbreeding depression rather than true self-incompatibility. Thus, wiregrass is not pollen-limited but exhibits strong embryonic inbreeding depression, implying an obligate outcrossing mating system. This helps explain why wiregrass often produces few viable seeds despite high seed production. Our findings highlight the importance of including germination data in reproductive studies, as seed production alone can mask other biological constraints. For wiregrass, frequent fires likely promote pollen movement and successful outcrossing. These insights inform restoration efforts by clarifying reproductive limitations in a foundational pine savanna species. This has important implications for restoration efforts, particularly in sourcing and evaluating seed material for ecological resilience and long-term establishment.
