Intraspecific trait variation in plants: a renewed focus on its role in ecological processes

Spatiotemporal variation of chasmogamy and cleistogamy in a native perennial grass: fecundity, reproductive allocation and allometry

It is difficult to assess the relative variability or stability of chasmogamous (CH) and cleistogamous (CL) reproduction in perennial herbs with mixed mating because long-term data in natural populations are unavailable. Here, the aim was to quantify and compare spatial (between-habitat) and temporal (among-year) variation in CH and CL reproduction over 5 years in two subpopulations of the native perennial grass Danthonia compressa. This species produces CH spikelets on terminal panicles in early summer, while axillary CL spikelets, including a basal cleistogene, mature into the autumn. Flowering tillers were collected from a sunny woodland edge and an adjacent shady interior habitat for 5 consecutive years (2017-21). Seed set, fecundity, seed mass and biomass allocation were recorded for the two floral types along with tiller vegetative mass. Bivariate line fitting was used for allometric analysis of CH and CL fecundity. Seed set, fecundity, mass per seed and allocation to seeds differed between floral types and showed significant variation between habitats and among years. Seed set and fecundity in CH panicles were greater than that of axillary CL panicles in most years. Tiller mass positively affected axillary CL seed production and mass of the basal cleistogene. Fecundity and allocation among years were more variable for CH compared to CL reproduction. High seed set and fecundity of CH spikelets suggest that pollination does not limit reproduction via chasmogamy. Late maturation of axillary CL spikelets provides additional fecundity, especially in larger plants along sunny woodland edges. The heavy cleistogene at the tiller base could be important to population persistence, analogous to the axillary bud bank of other perennial grasses that are not cleistogamous. The spatiotemporal stability of CL reproduction underscores the ecological significance of cleistogamy to reproductive fitness.

AraDiv: a dataset of functional traits and leaf hyperspectral reflectance of Arabidopsis thaliana

Data from functional trait databases have been increasingly used to address questions related to plant diversity and trait-environment relationships. However, such databases provide intraspecific data that combine individual records obtained from distinct populations at different sites and, hence, environmental conditions. This prevents distinguishing sources of variation (e.g., genetic-based variation vs. phenotypic plasticity), a necessary condition to test for adaptive processes and other determinants of plant phenotypic diversity. Consequently, individual traits measured under common growing conditions and encompassing within-species variation across the occupied geographic range have the potential to leverage trait databases with valuable data for functional and evolutionary ecology. Here, we recorded 16 functional traits and leaf hyperspectral reflectance (NIRS) data for 721 widely distributed Arabidopsis thaliana natural accessions grown in a common garden experiment. These data records, together with meteorological variables obtained during the experiment, were assembled to create the AraDiv dataset. AraDiv is a comprehensive dataset of A. thaliana's intraspecific variability that can be explored to address questions at the interface of genetics and ecology.

Higher local intra- than interspecific variability in water- and carbon-related leaf traits among Neotropical tree species

BACKGROUND AND AIMS

Intraspecific variability in leaf water-related traits remains little explored despite its potential importance in the context of increasing drought frequency and severity. Studies comparing intra- and interspecific variability of leaf traits often rely on inappropriate sampling designs that result in non-robust estimates, mainly owing to an excess of the species/individual ratio in community ecology or, on the contrary, to an excess of the individual/species ratio in population ecology.

METHODS

We carried out virtual testing of three strategies to compare intra- and interspecific trait variability. Guided by the results of our simulations, we carried out field sampling. We measured nine traits related to leaf water and carbon acquisition in 100 individuals from ten Neotropical tree species. We also assessed trait variation among leaves within individuals and among measurements within leaves to control for sources of intraspecific trait variability.

KEY RESULTS

The most robust sampling, based on the same number of species and individuals per species, revealed higher intraspecific variability than previously recognized, higher for carbon-related traits (47-92 and 4-33 % of relative and absolute variation, respectively) than for water-related traits (47-60 and 14-44 % of relative and absolute variation, respectively), which remained non-negligible. Nevertheless, part of the intraspecific trait variability was explained by variation of leaves within individuals (12-100 % of relative variation) or measurement variations within leaf (0-19 % of relative variation) and not only by individual ontogenetic stages and environmental conditions.

CONCLUSIONS

We conclude that robust sampling, based on the same number of species and individuals per species, is needed to explore global or local variation in leaf water- and carbon-related traits within and among tree species, because our study revealed higher intraspecific variation than previously recognized.

The potential of trait data to increase the availability of bioindicators: A case study using plant conservatism values

Biological indicators are commonly used to evaluate ecosystem condition. However, their use is often constrained by the availability of information with which to assign species-specific indicator values, which reflect species' responses to the environmental conditions being evaluated by the indicator. As these responses are driven by underlying traits, and trait data for numerous species are available in publicly accessible databases, one possible approach to approximating missing bioindicator values is through traits. We used the Floristic Quality Assessment (FQA) framework and its component indicator of disturbance sensitivity, species-specific ecological conservatism scores (C-scores), as a study system to test the potential of this approach. We tested the consistency of relationships between trait values and expert-assigned C-scores and the trait-based predictability of C-scores across five regions. Furthermore, as a proof-of-concept exercise, we used a multi-trait model to try to reconstruct C-scores, and compared the model predictions to expert-assigned scores. Out of 20 traits tested, there was evidence of regional consistency for germination rate, growth rate, propagation type, dispersal unit, and leaf nitrogen. However, the individual traits showed low predictability (R²  = 0.1-0.2) for C-scores, and a multi-trait model produced substantial classification errors; in many cases, >50% of species were misclassified. The mismatches may largely be explained by the inability to generalize regionally varying C-scores from geographically neutral/naive trait data stored in databases, and the synthetic nature of C-scores. Based on these results, we recommend possible next steps for expanding the availability of species-based bioindication frameworks such as the FQA. These steps include increasing the availability of geographic and environmental data in trait databases, incorporating data about intraspecific trait variability into these databases, conducting hypothesis-driven investigations into trait-indicator relationships, and having regional experts review our results to determine if there are patterns in the species that were correctly or incorrectly classified.

Phenotypic Plasticity Strategy of Aeluropus lagopoides Grass in Response to Heterogenous Saline Habitats

Understanding the response variation of morphological parameters and biomass allocation of plants in heterogeneous saline environments is helpful in evaluating the internal correlation between plant phenotypic plasticity mechanism and biomass allocation. The plasticity of plants alters the interaction among individuals and their environment and consequently affects the population dynamics and aspects of community and ecosystem functioning. The current study aimed to assess the plasticity of Aeluropus lagopoides traits with variation in saline habitats. Understanding the habitat stress tolerance strategy of A. lagopoides is of great significance since it is one of the highly palatable forage grass in the summer period. Five different saline flat regions (coastal and inland) within Saudi Arabia were targeted, and the soil, as well as the morphological and physiological traits of A. lagopoides, were assessed. Comprehensive correlation analyses were performed to correlate the traits with soil, region, or among each other. The soil analysis revealed significant variation among the five studied regions for all measured parameters, as well as among the soil layers showing the highest values in the upper layer and decreased with the depth. Significant differences were determined for all tested parameters of the morphological and reproductive traits as well as for the biomass allocation of A. lagopoides, except for the leaf thickness. In the highly saline region, Qaseem, A. lagopoides showed stunted aerial growth, high root/shoot ratio, improved root development, and high biomass allocation. In contrast, the populations growing in the low saline region (Jizan) showed the opposite trend. Under the more stressful condition, like in Qaseem and Salwa, A. lagopoides produce low spikes in biomass and seeds per plant, compared to the lowest saline habitats, such as Jouf. There was no significant difference in physiological parameters except stomatal conductance (g_s), which is highest in the Jizan region. In conclusion, the population of A. lagopoides is tolerant of harsh environments through phenotypic plasticity. This could be a candidate species to rehabilitate the saline habitats, considering saline agriculture and saline soil remediation.

A Theoretical Framework for Trait-Based Eco-Evolutionary Dynamics: Population Structure, Intraspecific Variation, and Community Assembly

AbstractHow is trait diversity in a community apportioned between and within coevolving species? Disruptive selection may result in either a few species with large intraspecific trait variation (ITV) or many species with different mean traits but little ITV. Similar questions arise in spatially structured communities: heterogeneous environments could result in either a few species that exhibit local adaptation or many species with different mean traits but little local adaptation. To date, theory has been well-equipped to either include ITV or to dynamically determine the number of coexisting species, but not both. Here, we devise a theoretical framework that combines these facets and apply it to the above questions of how trait variation is apportioned within and between species in unstructured and structured populations, using two simple models of Lotka-Volterra competition. For unstructured communities, we find that as the breadth of the resource spectrum increases, ITV goes from being unimportant to crucial for characterizing the community. For spatially structured communities on two patches, we find no local adaptation, symmetric local adaptation, or asymmetric local adaptation, depending on how much the patches differ. Our framework provides a general approach to incorporate ITV in models of eco-evolutionary community assembly.

Intraspecific trait variation and changing life-history strategies explain host community disease risk along a temperature gradient

Predicting how climate change will affect disease risk is complicated by the fact that changing environmental conditions can affect disease through direct and indirect effects. Species with fast-paced life-history strategies often amplify disease, and changing climate can modify life-history composition of communities thereby altering disease risk. However, individuals within a species can also respond to changing conditions with intraspecific trait variation. To test the effect of temperature, as well as inter- and intraspecifc trait variation on community disease risk, we measured foliar disease and specific leaf area (SLA; a proxy for life-history strategy) on more than 2500 host (plant) individuals in 199 communities across a 1101 m elevational gradient in southeastern Switzerland. There was no direct effect of increasing temperature on disease. Instead, increasing temperature favoured species with higher SLA, fast-paced life-history strategies. This effect was balanced by intraspecific variation in SLA: on average, host individuals expressed lower SLA with increasing temperature, and this effect was stronger among species adapted to warmer temperatures and lower latitudes. These results demonstrate how impacts of changing temperature on disease may depend on how temperature combines and interacts with host community structure while indicating that evolutionary constraints can determine how these effects are manifested under global change. This article is part of the theme issue 'Infectious disease ecology and evolution in a changing world'.

Characteristics of plant trait network and its influencing factors in impounded lakes and channel rivers of South-to-North Water Transfer Project, China

Trait-based approaches have been widely used to evaluate the effects of variable environments on submerged macrophytes communities. However, little research focused on the response of submerged macrophytes to variable environmental factors in impounded lakes and channel rivers of water transfer project, especially from a whole plant trait network (PTN) perspective. Here, we conducted a field survey designed to clarify the characteristic of PTN topology among impounded lakes and channel rivers of the East Route of South-to-North Water Transfer Project (ERSNWTP) and to unravel the effects of determining factors on the PTN topology structure. Overall, our results showed that leaf-related traits and organ mass allocation traits were the hub traits of PTNs in impounded lakes and channel rivers of the ERSNWTP, which traits with high variability were more likely to be the hub traits. Moreover, PTNs showed different structures among impounded lakes and channel rivers, and PTNs topologies were related to the mean functional variation coefficients of lakes and channel rivers. Specially, higher mean functional variation coefficients represented tight PTN, and lower mean functional variation coefficients indicated loose PTN. The PTN structure was significantly affected by water total phosphorus and dissolved oxygen. Edge density increased, while average path length decreased with increasing total phosphorus. Edge density and average clustering coefficient showed significant decreases with increasing dissolved oxygen, while average path length and modularity exhibited significant increases with increasing dissolved oxygen. This study explores the changing patterns and determinants of trait networks along environmental gradients to improve our understanding of ecological rules regulating trait correlations.

Rethinking the nature of intraspecific variability and its consequences on species coexistence

Intraspecific variability (IV) has been proposed to explain species coexistence in diverse communities. Assuming, sometimes implicitly, that conspecific individuals can perform differently in the same environment and that IV increases niche overlap, previous studies have found contrasting results regarding the effect of IV on species coexistence. We aim at showing that the large IV observed in data does not mean that conspecific individuals are necessarily different in their response to the environment and that the role of high-dimensional environmental variation in determining IV has largely remained unexplored in forest plant communities. We first used a simulation experiment where an individual attribute is derived from a high-dimensional model, representing "perfect knowledge" of individual response to the environment, to illustrate how large observed IV can result from "imperfect knowledge" of the environment. Second, using growth data from clonal Eucalyptus plantations in Brazil, we estimated a major contribution of the environment in determining individual growth. Third, using tree growth data from long-term tropical forest inventories in French Guiana, Panama and India, we showed that tree growth in tropical forests is structured spatially and that despite a large observed IV at the population level, conspecific individuals perform more similarly locally than compared with heterospecific individuals. As the number of environmental dimensions that are well quantified at fine scale is generally lower than the actual number of dimensions influencing individual attributes, a great part of observed IV might be represented as random variation across individuals when in fact it is environmentally driven. This mis-representation has important consequences for inference about community dynamics. We emphasize that observed IV does not necessarily impact species coexistence per se but can reveal species response to high-dimensional environment, which is consistent with niche theory and the observation of the many differences between species in nature.

Long-term, large-scale experiment reveals the effects of seed limitation, climate, and anthropogenic disturbance on restoration of plant communities in a biodiversity hotspot

Ecological restoration is essential for maintaining biodiversity in the face of dynamic, global changes in climate, human land use, and disturbance regimes. Effective restoration requires understanding bottlenecks in plant community recovery that exist today, while recognizing that these bottlenecks may relate to complex histories of environmental change. Such understanding has been a challenge because few long-term, well-replicated experiments exist to decipher the demographic processes influencing recovery for numerous species against the backdrop of multiyear variation in climate and management. We address this challenge through a long-term and geographically expansive experiment in longleaf pine savannas, an imperiled ecosystem and biodiversity hotspot in the southeastern United States. Using 48 sites at three locations spanning 480 km, the 8-y experiment manipulated initial seed arrival for 24 herbaceous plant species and presence of competitors to evaluate the impacts of climate variability and management actions (e.g., prescribed burning) on plant establishment and persistence. Adding seeds increased plant establishment of many species. Cool and wet climatic conditions, low tree density, and reduced litter depth also promoted establishment. Once established, most species persisted for the duration of the 8-y experiment. Plant traits were most predictive when tightly coupled to the process of establishment. Our results illustrate how seed additions can restore plant diversity and how interannual climatic variation affects the dynamics of plant communities across a large region. The significant effects of temperature and precipitation inform how future climate may affect restoration and conservation via large-scale changes in the fundamental processes of establishment and persistence.

Genotypic variation rather than ploidy level determines functional trait expression in a foundation tree species in the presence and absence of environmental stress

BACKGROUND AND AIMS

At the population level, genetic diversity is a key determinant of a tree species' capacity to cope with stress. However, little is known about the relative importance of the different components of genetic diversity for tree stress responses. We compared how two sources of genetic diversity, genotype and cytotype (i.e. differences in ploidy levels), influence growth, phytochemical and physiological traits of Populus tremuloides in the presence and absence of environmental stress.

METHODS

In a series of field studies, we first assessed variation in traits across diploid and triploid aspen genotypes from Utah and Wisconsin under non-stressed conditions. In two follow-up experiments, we exposed diploid and triploid aspen genotypes from Wisconsin to individual and interactive drought stress and defoliation treatments and quantified trait variations under stress.

KEY RESULTS

We found that (1) tree growth and associated traits did not differ significantly between ploidy levels under non-stressed conditions. Instead, variation in tree growth and most other traits was driven by genotypic and population differences. (2) Genotypic differences were critical for explaining variation of most functional traits and their responses to stress. (3) Ploidy level played a subtle role in shaping traits and trait stress responses, as its influence was typically obscured by genotypic differences. (4) As an exception to the third conclusion, we showed that triploid trees expressed 17 % higher foliar defence (tremulacin) levels, 11 % higher photosynthesis levels and 23 % higher rubisco activity under well-watered conditions. Moreover, triploid trees displayed greater drought resilience than diploids as they produced 35 % more new tissue than diploids when recovering from drought stress.

CONCLUSION

Although ploidy level can strongly influence the ecology of tree species, those effects may be relatively small in contrast to the effects of genotypic variation in highly diverse species.

Provenance, genotype, and flooding influence growth and resource acquisition characteristics in a clonal, riparian shrub

PREMISE

Riparian plants can exhibit intraspecific phenotypic variability across the landscape related to temperature and flooding gradients. Phenotypes that vary across a climate gradient are often partly genetically determined and may differ in their response to inundation. Changes to inundation patterns across a climate gradient could thus result in site-specific inundation responses. Phenotypic variability is more often studied in riparian trees, yet riparian shrubs are key elements of riparian systems and may differ from trees in phenotypic variability and environmental responses.

METHODS

We tested whether individuals of a clonal, riparian shrub, Pluchea sericea, collected from provenances spanning a temperature gradient differed in their phenotypes and responses to inundation and to what degree any differences were related to genotype. Plants were subjected to different inundation depths and a subset genotyped. Variables related to growth and resource acquisition were measured and analyzed using hierarchical, multivariate Bayesian linear regressions.

RESULTS

Individuals from different provenances differed in their phenotypes, but not in their response to inundation. Phenotypes were not related to provenance temperature but were partially governed by genotype. Growth was more strongly influenced by inundation, while resource acquisition was more strongly controlled by genotype.

CONCLUSIONS

Growth and resource acquisition responses in a clonal, riparian shrub are affected by changes to inundation and plant demographics in unique ways. Shrubs appear to differ from trees in their responses to environmental change. Understanding environmental effects on shrubs separately from those of trees will be a key part of evaluating impacts of environmental change on riparian ecosystems.

Jack pine of all trades: Deciphering intraspecific variability of a key adaptive trait at the rear edge of a widespread fire-embracing North American conifer

PREMISE

Understanding mechanisms fostering long-term persistence of marginal populations should provide key insights about species resilience facing climate change. Cone serotiny is a key adaptive trait in Pinus banksiana (jack pine), which shows phenotypic variation according to the fire regime. Compared to range-core populations within the fire-prone boreal forest, low and variable serotiny in rear-edge populations suggest local adaptation to uncommon and unpredictable wildfire regime. We assessed environmental/physiological factors that might modulate intraspecific variation in cone serotiny.

METHODS

We experimentally subjected closed cones to incrementing temperatures, then tested seed germination to determine whether and how various ecological factors (cone age, branch height, tree size, tree age) are related to cone dehiscence and seed viability in jack pines from rear-edge and range-core populations in eastern Canada.

RESULTS

Cones from rear-edge populations dehisce at a lower opening temperature, which increases with cone age. Cones from range-core stands open at a more constant, yet higher temperature. Cones from rear-edge stands take between 13 and 27 years to reach the level of serotiny achieved at the range core. At the rear edge, seed viability is steady (51%), whereas it decreases from 70% to 30% in 20 years at the range core.

CONCLUSIONS

We inferred the mechanisms of a bet-hedging strategy in rear-edge populations, which ensures steady recruitment during fire-free intervals and successful postfire regeneration. This capacity to cope with infrequent and unpredictable fire regime should increase the resilience of jack pine populations as global changes alter fire dynamics of the boreal forest.

Intraspecific variation in genome size in Artemisia argyi determined using flow cytometry and a genome survey

Different collections and accessions of Artemisia argyi (Chinese mugwort) harbour considerable diversity in morphology and bioactive compounds, but no mechanisms have been reported that explain these variations. We studied genome size in A. argyi accessions from different regions of China by flow cytometry. Genome size was significantly distinct among origins of these 42 Chinese mugwort accessions, ranging from 8.428 to 11.717 pg. There were no significant intraspecific differences among the 42 accessions from the five regions of China. The clustering analysis showed that these 42 A. argyi accessions could be divided into three groups, which had no significant relationship with geographical location. In a genome survey, the total genome size of A. argyi (A15) was estimated to be 7.852 Gb (or 8.029 pg) by K-mer analysis. This indicated that the results from the two independent methods are consistent, and that the genome survey can be used as an adjunct to flow cytometry to compensate for its deficiencies. In addition, genome survey can provide the information about heterozygosity, repeat sequences, GC content and ploidy of A. argyi genome. The nuclear DNA contents determined here provide a new reference for intraspecific variation in genome size in A. argyi, and may also be a potential resource for the study of genetic diversity and for breeding new cultivar.

Consequences of interplant trait variation for canopy light absorption and photosynthesis

Plant-to-plant variation (interplant variation) may play an important role in determining individual plant and whole canopy performance, where interplant variation in architecture and photosynthesis traits has direct effects on light absorption and photosynthesis. We aimed to quantify the importance of observed interplant variation on both whole-plant and canopy light absorption and photosynthesis. Plant architecture was measured in two experiments with fruiting tomato crops (Solanum lycopersicum) grown in glasshouses in the Netherlands, in week 16 (Exp. 1) or week 19 (Exp. 2) after transplanting. Experiment 1 included four cultivars grown under three supplementary lighting treatments, and Experiment 2 included two different row orientations. Measured interplant variations of the architectural traits, namely, internode length, leaf area, petiole angle, and leaflet angle, as well as literature data on the interplant variation of the photosynthesis traits alpha, J max28, and V cmax28, were incorporated in a static functional-structural plant model (FSPM). The FSPM was used to analyze light absorption and net photosynthesis of whole plants in response to interplant variation in architectural and photosynthesis traits. Depending on the trait, introducing interplant variation in architecture and photosynthesis traits in a functional-structural plant model did not affect or negatively affected canopy light absorption and net photosynthesis compared with the reference model without interplant variation. Introducing interplant variation of architectural and photosynthesis traits in FSPM results in a more realistic simulation of variation of plants within a canopy. Furthermore, it can improve the accuracy of simulation of canopy light interception and photosynthesis although these effects at the canopy level are relatively small (<4% for light absorption and<7% for net photosynthesis).

Phenotypic variation of a new synthetic allotetraploid Arabidopsis kamchatica enhanced in natural environment

The phenotypic variation of vegetative organs and reproductive organs of newly synthesized and natural Arabidopsis kamchatica genotypes was investigated in both a controlled environment and a natural environment in an experimental garden. When we compared the variation of their leaf shape as a vegetative organ, the synthetic A. kamchatica individuals grown in the garden showed larger variation compared with the individuals incubated in a growth chamber, suggesting enhanced phenotypic variation in a natural fluctuating environment. In contrast, the natural A. kamchatica genotypes did not show significant change in variation by growth condition. The phenotypic variation of floral organs by growth condition was much smaller in both synthetic and natural A. kamchatica genotypes, and the difference in variation width between the growth chamber and the garden was not significant in each genotype as well as among genotypes. The higher phenotypic variation in synthetic leaf may imply flexible transcriptomic regulation of a newly synthesized polyploid compared with a natural polyploid.

Climate and the biotic community structure plant resistance across biogeographic groups of yellow monkeyflower

Characterizing correlates of phytochemical resistance trait variation across a landscape can provide insight into the ecological factors that have shaped the evolution of resistance arsenals. Using field-collected data and a greenhouse common garden experiment, we assessed the relative influences of abiotic and biotic drivers of genetic-based defense trait variation across 41 yellow monkeyflower populations from western and eastern North America and the United Kingdom. Populations experience different climates, herbivore communities, and neighboring vegetative communities, and have distinct phytochemical resistance arsenals. Similarities in climate as well as herbivore and vegetative communities decline with increasing physical distance separating populations, and phytochemical resistance arsenal composition shows a similarly decreasing trend. Of the abiotic and biotic factors examined, temperature and the neighboring vegetation community had the strongest relative effects on resistance arsenal differentiation, whereas herbivore community composition and precipitation have relatively small effects. Rather than simply controlling for geographic proximity, we jointly assessed the relative strengths of both geographic and ecological variables on phytochemical arsenal compositional dissimilarity. Overall, our results illustrate how abiotic conditions and biotic interactions shape plant defense traits in natural populations.

Intraspecific and sex-dependent variation of leaf traits along altitude gradient in the endangered dioecious tree Taxus fuana Nan Li & R.R. Mill

Plant intraspecific trait variation (ITV) including sex-dependent differences are matters of many ecological consequences, from individual to ecosystem, especially in endangered and rare species. Taxus fuana is an endangered dioecious species with small and isolated populations endemic to the Himalayas region. Little is known about its trait variation between sexes, and among populations. In this study, 18 leaf traits from 179 reproductive trees (males and females) along the altitude (2600-3200m a.s.l.) of the T. fuana populations distributed in Gyirong County, Tibet, China, were measured. ITV and sources of variation in leaf traits were assessed. The relationship between leaf traits of males and females and altitude was analyzed separately. Variations in leaf traits of T. fuana ranged from 3.1% to 24.2%, with the smallest in leaf carbon content and the largest in leaf thickness to area ratio. On average 78.13% of the variation in leaf traits was from within populations and 21.87% among populations. The trends in leaf width, leaf nitrogen to phosphorus ratio, leaf carbon to nitrogen ratio, leaf carbon isotope ratio, and leaf nitrogen isotope ratio in relation to altitude were the same for males and females. Leaf length to width ratio varied significantly with altitude only in males, while leaf phosphorus content, leaf nitrogen content, and leaf carbon to phosphorus ratio varied significantly with altitude only in females. The correlation coefficients of most leaf traits of females with altitude were larger than that of males. In the relationship between leaf traits, there was a high similarity among males and females, but the altitude accounted for more explanation in females than in males. Our results suggested that the variation in leaf traits of T. fuana was small and did not dominate the interspecific competition in the local communities. Adaptation to the altitude gradient of T. fuana might be through altering nutrient storage processes and water use efficiency. Adaptation of male and female T. fuana to environmental changes showed differences, where the males were more tolerant and the females responded greatly to altitude. The differences in adaptation strategies between male and female T. fuana may be detrimental to the maintenance of their populations.

Local adaptation of seed and seedling traits along a natural aridity gradient may both predict and constrain adaptive responses to climate change

PREMISE

Variation in seed and seedling traits underlies how plants interact with their environment during establishment, a crucial life history stage. We quantified genetic-based variation in seed and seedling traits in populations of the annual plant Plantago patagonica across a natural aridity gradient, leveraging natural intraspecific variation to predict how populations might evolve in response to increasing aridity associated with climate change in the Southwestern U.S.

METHODS

We quantified seed size, seed size variation, germination timing, and specific leaf area in a greenhouse common garden, and related these traits to the climates of source populations. We then conducted a terminal drought experiment to determine which traits were most predictive of survival under early-season drought.

RESULTS

All traits showed evidence of clinal variation-seed size decreased, germination timing accelerated, and specific leaf area increased with increasing aridity. Populations with more variable historical precipitation regimes showed greater variation in seed size, suggestive of past selection shaping a diversified bet-hedging strategy mediated by seed size. Seedling height, achieved via larger seeds or earlier germination, was a significant predictor of survival under drought.

CONCLUSIONS

We documented substantial interspecific trait variation as well as clinal variation in several important seed and seedling traits, yet these slopes were often opposite to predictions for how individual traits might confer drought tolerance. This work shows that plant populations may adapt to increasing aridity via correlated trait responses associated with alternative life history strategies, but that trade-offs might constrain adaptive responses in individual traits.

Environmental variation drives the decoupling of leaf and root traits within species along an elevation gradient

BACKGROUND AND AIMS

Plant performance is enhanced by balancing above- and below-ground resource uptake through the intraspecific adjustment of leaf and root traits. It is assumed that these organ adjustments are at least partly coordinated, so that analogous leaf and root traits broadly covary. Understanding the extent of such intraspecific leaf-root trait covariation would strongly contribute to our understanding of how plants match above- and below-ground resource use strategies as their environment changes, but comprehensive studies are lacking.

METHODS

We measured analogous leaf and root traits from 11 species, as well as climate, soil and vegetation properties along a 1000-m elevation gradient in the French Alps. We determined how traits varied along the gradient, to what extent this variation was determined by the way different traits respond to environmental cues acting at different spatial scales (i.e. within and between elevations), and whether trait pairs covaried within species.

KEY RESULTS

Leaf and root trait patterns strongly diverged: across the 11 species along the gradient, intraspecific leaf trait patterns were largely consistent, whereas root trait patterns were highly idiosyncratic. We also observed that, when compared with leaves, intraspecific variation was greater in root traits, due to the strong effects of the local environment (i.e. at the same elevation), while landscape-level effects (i.e. at different elevations) were minor. Overall, intraspecific trait correlations between analogous leaf and root traits were nearly absent.

CONCLUSIONS

Our study suggests that environmental gradients at the landscape level, as well as local heterogeneity in soil properties, are the drivers of a strong decoupling between analogous leaf and root traits within species. This decoupling of plant resource acquisition strategies highlights how plants can exhibit diverse whole-plant acclimation strategies to modify above- and below-ground resource uptake, improving their resilience to environmental change.

Characterization, costs, cues and future perspectives of phenotypic plasticity

BACKGROUND

Plastic responses of plants to the environment are ubiquitous. Phenotypic plasticity occurs in many forms and at many biological scales, and its adaptive value depends on the specific environment and interactions with other plant traits and organisms. Even though plasticity is the norm rather than the exception, its complex nature has been a challenge in characterizing the expression of plasticity, its adaptive value for fitness and the environmental cues that regulate its expression.

SCOPE

This review discusses the characterization and costs of plasticity and approaches, considerations, and promising research directions in studying plasticity. Phenotypic plasticity is genetically controlled and heritable; however, little is known about how organisms perceive, interpret and respond to environmental cues, and the genes and pathways associated with plasticity. Not every genotype is plastic for every trait, and plasticity is not infinite, suggesting trade-offs, costs and limits to expression of plasticity. The timing, specificity and duration of plasticity are critical to their adaptive value for plant fitness.

CONCLUSIONS

There are many research opportunities to advance our understanding of plant phenotypic plasticity. New methodology and technological breakthroughs enable the study of phenotypic responses across biological scales and in multiple environments. Understanding the mechanisms of plasticity and how the expression of specific phenotypes influences fitness in many environmental ranges would benefit many areas of plant science ranging from basic research to applied breeding for crop improvement.

"Realistic strategies" and neutral processes drive the community assembly based on leaf functional traits in a subtropical evergreen broad-leaved forest

Neutral-theory-based stochastic and niche-theory-based determinative processes are commonly used to explain the mechanisms of natural community assembly. However, considerable uncertainty remains regarding the relative importance of different ecological processes in shaping forest communities. Functional traits and phylogeny provide important information about plant environmental adaptation strategies and evolutionary history and promise a better mechanistic and predictive understanding of community assembly. Based on nine leaf functional traits and phylogenetic data of 18 dominant species in a Lithocarpus glaber-Cyclobalanopsis glauca evergreen broad-leaved forest, we analyzed the variation in traits, explored the influence of phylogeny and environment on leaf traits, and distinguished the relative effects of spatial and environmental variables on functional traits and phylogenetic compositions. The results showed the following: (i) Leaf traits had moderate intraspecific variation, and significant interspecific variation existed especially among life forms. (ii) Significant phylogenetic signals were detected only in leaf thickness and leaf area. The correlations among traits both supported "the leaf economics spectrum" at the species and community levels, and the relationships significantly increased or only a little change after removing the phylogenetic influence, which showed a lack of consistency between the leaf functional trait patterns and phylogenetic patterns. We infer the coexistent species tended to adopt "realism" to adapt to their habitats. (iii) Soil total potassium and phosphorus content, altitude, aspect, and convexity were the most critical environmental factors affecting functional traits and phylogenetic composition. Total environmental and spatial variables explained 63.38% of the variation in functional trait composition and 47.96% of the variation in phylogenetic structures. Meanwhile, the contribution of pure spatial factors was significantly higher than that of the pure environment. Stochastic processes played dominant roles in driving community functional trait assembly, but determinative processes such as environmental filtering had a stronger effect on shaping community phylogenetic structure at a fine scale.

Exploring the impact of trait number and type on functional diversity metrics in real-world ecosystems

The use of trait-based approaches to understand ecological communities has increased in the past two decades because of their promise to preserve more information about community structure than taxonomic methods and their potential to connect community responses to subsequent effects of ecosystem functioning. Though trait-based approaches are a powerful tool for describing ecological communities, many important properties of commonly-used trait metrics remain unexamined. Previous work in studies that simulate communities and trait distributions show consistent sensitivity of functional richness and evenness measures to the number of traits used to calculate them, but these relationships have yet to be studied in actual plant communities with a realistic distribution of trait values, ecologically meaningful covariation of traits, and a realistic number of traits available for analysis. Therefore, we propose to test how the number of traits used and the correlation between traits used in the calculation of functional diversity indices impacts the magnitude of eight functional diversity metrics in real plant communities. We will use trait data from three grassland plant communities in the US to assess the generality of our findings across ecosystems and experiments. We will determine how eight functional diversity metrics (functional richness, functional evenness, functional divergence, functional dispersion, kernel density estimation (KDE) richness, KDE evenness, KDE dispersion, Rao's Q) differ based on the number of traits used in the metric calculation and on the correlation of traits when holding the number of traits constant. Without a firm understanding of how a scientist's choices impact these metric, it will be difficult to compare results among studies with different metric parametrization and thus, limit robust conclusions about functional composition of communities across systems.

Within-species variation of seed traits of dune engineering species across a European climatic gradient

Within-species variation is a key component of biodiversity and linking it to climatic gradients may significantly improve our understanding of ecological processes. High variability can be expected in plant traits, but it is unclear to which extent it varies across populations under different climatic conditions. Here, we investigated seed trait variability and its environmental dependency across a latitudinal gradient of two widely distributed dune-engineering species (Thinopyrum junceum and Calamagrostis arenaria). Seed germination responses against temperature and seed mass were compared within and among six populations exposed to a gradient of temperature and precipitation regimes (Spiekeroog, DE; Bordeaux, FR; Valencia, ES; Cagliari, IT, Rome, IT; Venice, IT). Seed germination showed opposite trends in response to temperature experienced during emergence in both species: with some expectation, in populations exposed to severe winters, seed germination was warm-cued, whereas in populations from warm sites with dry summer, seed germination was cold-cued. In C. arenaria, variability in seed germination responses disappeared once the seed coat was incised. Seed mass from sites with low precipitation was smaller than that from sites with higher precipitation and was better explained by rainfall continentality than by aridity in summer. Within-population variability in seed germination accounted for 5 to 54%, while for seed mass it was lower than 40%. Seed trait variability can be considerable both within- and among-populations even at broad spatial scale. The variability may be hardly predictable since it only partially correlated with the analyzed climatic variables, and with expectation based on the climatic features of the seed site of origin. Considering seed traits variability in the analysis of ecological processes at both within- and among-population levels may help elucidate unclear patterns of species dynamics, thereby contributing to plan adequate measures to counteract biodiversity loss.

Genetic divergence along a climate gradient shapes chemical plasticity of a foundation tree species to both changing climate and herbivore damage

Climate change is threatening the persistence of many tree species via independent and interactive effects on abiotic and biotic conditions. In addition, changes in temperature, precipitation, and insect attacks can alter the traits of these trees, disrupting communities and ecosystems. For foundation species such as Populus, phytochemical traits are key mechanisms linking trees with their environment and are likely jointly determined by interactive effects of genetic divergence and variable environments throughout their geographic range. Using reciprocal Fremont cottonwood (Populus fremontii) common gardens along a steep climatic gradient, we explored how environment (garden climate and simulated herbivore damage) and genetics (tree provenance and genotype) affect both foliar chemical traits and the plasticity of these traits. We found that (1) Constitutive and plastic chemical responses to changes in garden climate and damage varied among defense compounds, structural compounds, and leaf nitrogen. (2) For both defense and structural compounds, plastic responses to different garden climates depended on the climate in which a population or genotype originated. Specifically, trees originating from cool provenances showed higher defense plasticity in response to climate changes than trees from warmer provenances. (3) Trees from cool provenances growing in cool garden conditions expressed the lowest constitutive defense levels but the strongest induced (plastic) defenses in response to damage. (4) The combination of hot garden conditions and simulated herbivory switched the strategy used by these genotypes, increasing constitutive defenses but erasing the capacity for induction after damage. Because Fremont cottonwood chemistry plays a major role in shaping riparian communities and ecosystems, the effects of changes in phytochemical traits can be wide reaching. As the southwestern US is confronted with warming temperatures and insect outbreaks, these results improve our capacity to predict ecosystem consequences of climate change and inform selection of tree genotypes for conservation and restoration purposes.

A trait-environment relationship approach to participatory plant breeding for organic agriculture

The extent of intraspecific variation in trait-environment relationships is an open question with limited empirical support in crops. In organic agriculture, with high environmental heterogeneity, this knowledge could guide breeding programs to optimize crop attributes. We propose a three-dimensional framework involving crop performance, crop traits, and environmental axes to uncover the multidimensionality of trait-environment relationships within a crop. We modeled instantaneous photosynthesis (A_sat ) and water-use efficiency (WUE) as functions of four phenotypic traits, three soil variables, five carrot (Daucus carota) varieties, and their interactions in a national participatory plant breeding program involving a suite of farms across Canada. We used these interactions to describe the resulting 12 trait-environment relationships across varieties. We found one significant trait-environment relationship for A_sat (taproot tissue density-soil phosphorus), which was consistent across varieties. For WUE, we found that three relationships (petiole diameter-soil nitrogen, petiole diameter-soil phosphorus, and leaf area-soil phosphorus) varied significantly across varieties. As a result, WUE was maximized by different combinations of trait values and soil conditions depending on the variety. Our three-dimensional framework supports the identification of functional traits behind the differential responses of crop varieties to environmental variation and thus guides breeding programs to optimize crop attributes from an eco-evolutionary perspective.

Can evolutionary history predict plant plastic responses to climate change?

Plant plastic responses are critical to the adaptation and survival of species under climate change, but whether they are constrained by evolutionary history (phylogeny) is largely unclear. Plant leaf traits are key in determining plants' performance in different environments, and if these traits and their variation are phylogenetically dependent, predictions could be made to identify species vulnerable to climate change. We compiled data on three leaf traits (photosynthetic rate, specific leaf area, and leaf nitrogen content) and their variation under four environmental change scenarios (warming, drought, elevated CO₂ , or nitrogen addition) for 434 species, from 210 manipulation experiments. We found phylogenetic signal in the three traits but not in their variation under the four scenarios. This indicates that closely related species show similar traits but that their plastic responses could not be predicted from species relatedness under environmental change. Meanwhile, phylogeny weakened the slopes but did not change the directions of conventional pairwise trait relationships, suggesting that co-evolved leaf trait pairs have consistent responses under contrasting environmental conditions. Phylogeny can identify lineages rich in species showing similar traits and predict their relationships under climate change, but the degree of plant phenotypic variation does not vary consistently across evolutionary clades.

Sources and consequences of mismatch between leaf disc and whole-leaf leaf mass per area (LMA)

PREMISE

Leaf mass per area (LMA), which is an important functional trait in leaf economic spectrum and plant growth analysis, is measured from leaf discs or whole leaves. Differences between the measurement methods may lead to large differences in the estimates of LMA values.

METHODS

We examined to what extent estimates of LMA based on whole leaves match those based on discs using 334 woody species from a wide range of biomes (tropics, subtropics, savanna, and temperate), whether the relationship varied by leaf morphology (tissue density, leaf area, leaf thickness), punch size (0.6- and 1.0-cm diameter), and whether the extent of intraspecifc variation for each species matches.

RESULTS

Disc-based estimates of species mean LMA matched the whole-leaf estimates well, and whole-leaf LMA tended to be 9.69% higher than leaf-disc LMA. The ratio of whole-leaf LMA to leaf-disc LMA was higher for species with higher leaf tissue density and larger leaves, and variance in the ratio was greater for species with lower leaf tissue density and thinner leaves. Estimates based on small leaf discs also inflated the ratio. The extent of the intraspecific variation only weakly matched between whole-leaf and disc-based estimates (R²  = 0.08).

CONCLUSIONS

Our results suggest that simple conversion between whole-leaf and leaf-disc LMA is difficult for species obtained with a small leaf punch, but it should be possible for species obtained with a large+ leaf punch. Accurately representing leaf traits will likely require careful selection between leaf-disc and whole-leaf traits depending on the objectives. Quantifying intraspecific variation using leaf discs should be also considered with caution.

Trait ecology of startup plants

Startup plants include seedlings and basal and epicormic resprouts. It has long been held that startups have different strategies from adult plants, but theory for what trait differences to expect is limited and not yet quantitatively tested. Three applicable concepts are analogous to human startup firms, R-shift, and trait-growth theory. All three suggest startups should be built with lower construction costs than established plants. This appears to be almost always true in terms of leaf mass per area (LMA), though many comparisons are complicated by the startups growing in lower light. Trait-growth theory predicts LMA should increase progressively with height or total leaf area, driven by higher conductive-pathway costs associated with each unit leaf area, and by greater reward from slowing leaf turnover. Basal resprouts often have somewhat higher LMA than seedlings, but possibly this is simply because they are larger. A number of eminently testable questions are identified. Prospects are good for a theoretically cogent and field-tested body of knowledge about plant startups.

Organization and epigenomic control of RNA polymerase III-transcribed genes in plants

The genetic information linearly scripted in chromosomes is wrapped in a ribonucleoprotein complex called chromatin. The adaptation of its compaction level and spatiotemporal organization refines gene expression in response to developmental and environmental cues. RNA polymerase III (RNAPIII) is responsible for the biogenesis of elementary non-coding RNAs. Their genes are subjected to high duplication and mutational rates, and invade nuclear genomes. Their insertion into different epigenomic environments raises the question of how chromatin packing affects their individual transcription. In this review, we provide a unique perspective to this issue in plants. In addition, we discuss how the genomic organization of RNAPIII-transcribed loci, combined with epigenetic differences, might participate to plant trait variations.

Unravelling Trait-Environment Relationships at Local and Regional Scales in Temperate Forests

Understanding the trait-environment relationships has been a core ecological research topic in the face of global climate change. However, the strength of trait-environment relationships at the local and regional scales in temperate forests remains poorly known. In this study, we investigated the local and regional scale forest plots of the natural broad-leaved temperate forest in northeastern China, to assess what extent community-level trait composition depends on environmental drivers across spatial scales. We measured five key functional traits (leaf area, specific leaf area, leaf carbon content, leaf nitrogen content, and wood density) of woody plant, and quantified functional compositions of communities by calculating the "specific" community-weighted mean (CWM) traits. The sum of squares decomposition method was used to quantify the relative contribution of intraspecific trait variation to total trait variation among communities. Multiple linear regression model was then used to explore the community-level trait-environment relationships. We found that (i) intraspecific trait variation contributed considerably to total trait variation and decreased with the spatial scale from local to regional; (ii) functional composition was mainly affected by soil and topography factors at the local scale and climate factor at the regional scale, while explaining that variance of environment factors were decreased with increasing spatial scale; and (iii) the main environment driver of functional composition was varied depending on the traits and spatial scale. This work is one of the few multi-scale analyses to investigate the environmental drivers of community functional compositions. The extent of intraspecific trait variation and the strength of trait-environment relationship showed consistent trends with increasing spatial scale. Our findings demonstrate the influence of environmental filtering on both local- and regional-scale temperate forest communities, and contribute to a comprehensive understanding of trait-environment relationships across spatial scales.

Intraspecific variation in plant economic traits predicts trembling aspen resistance to a generalist insect herbivore

Patterns of trait expression within some plant species have recently been shown to align with the leaf economics spectrum paradigm. Resistance to herbivores is also expected to covary with leaf economics traits. We selected 36 mature Populus tremuloides genotypes in a common garden to assess whether aspen leaf economics patterns follow those observed among species globally. We also evaluated leaf economics strategies in the context of insect resistance by conducting bioassays to determine the effects of plant traits on preference and performance of Lymantria dispar. We found that: (1) intraspecific trait patterns of P. tremuloides parallel those exhibited by the interspecific leaf economics spectrum, (2) herbivores preferred leaves from genotypes with resource-acquisitive strategies, and (3) herbivores also performed best on genotypes with resource-acquisitive strategies. We conclude that a leaf economics spectrum that incorporates defense traits is a useful tool for explaining intraspecific patterns of variation in plant strategies, including resistance to herbivores.

Shifting Importance of Abiotic versus Biotic Filtering from Intact Mature Forests to Post-Clearcut Secondary Forests

Although ecologists often emphasize the roles of environmental- versus biotic-filtering in structuring forest communities, the relative importance of these processes could vary among undisturbed versus disturbed forests. To test this assumption, we gathered leaf traits and site conditions data from intact mature forests (control), moderately disturbed shrublands, and severely disturbed plantations from subtropical China. We found that plantations had higher leaf area, specific leaf area, leaf nitrogen and phosphorus concentrations but lower leaf thickness, dry matter content, and C:N than the shrubland or mature forest, suggesting the dominance of resource acquisition strategy in plantations versus conservation strategy in the mature forests. Plantations also had significantly lower trait ranges than mature forest or shrubland, suggesting the play of stringent environmental filtering in the plantation. However, intraspecific trait variations in leaf dry matter content and C:N were substantial in plantation, while interspecific variation in leaf thickness was high in mature forests, suggesting the importance of intra- versus inter-specific competition in plantation versus mature forests. Results from our species-level analysis were consistent with the community-level results mentioned above. Overall, our study demonstrates the shifting importance of environmental and biotic filtering from disturbed to undisturbed forests.

Distinct Cold Acclimation of Productivity Traits in Arabidopsis thaliana Ecotypes

Improvement of crop climate resilience will require an understanding of whole-plant adaptation to specific local environments. This review places features of plant form and function related to photosynthetic productivity, as well as associated gene-expression patterns, into the context of the adaptation of Arabidopsis thaliana ecotypes to local environments with different climates in Sweden and Italy. The growth of plants under common cool conditions resulted in a proportionally greater emphasis on the maintenance of photosynthetic activity in the Swedish ecotype. This is compared to a greater emphasis on downregulation of light-harvesting antenna size and upregulation of a host of antioxidant enzymes in the Italian ecotype under these conditions. This differential response is discussed in the context of the climatic patterns of the ecotypes’ native habitats with substantial opportunity for photosynthetic productivity under mild temperatures in Italy but not in Sweden. The Swedish ecotype’s response is likened to pushing forward at full speed with productivity under low temperature versus the Italian ecotype’s response of staying safe from harm (maintaining redox homeostasis) while letting productivity decline when temperatures are transiently cold. It is concluded that either strategy can offer directions for the development of climate-resilient crops for specific locations of cultivation.

Above- and below-ground functional trait coordination in the Neotropical understory genus Costus

The study of plant functional traits and variation among and within species can help illuminate functional coordination and trade-offs in key processes that allow plants to grow, reproduce and survive. We studied 20 leaf, above-ground stem, below-ground stem and fine-root traits of 17 Costus species from forests in Costa Rica and Panama to answer the following questions: (i) Do congeneric species show above-ground and below-ground trait coordination and trade-offs consistent with theory of resource acquisition and conservation? (ii) Is there correlated evolution among traits? (iii) Given the diversity of habitats over which Costus occurs, what is the relative contribution of site and species to trait variation? We performed a principal components analysis (PCA) to assess for the existence of a spectrum of trait variation and found that the first two PCs accounted for 21.4 % and 17.8 % of the total trait variation, respectively, with the first axis of variation being consistent with a continuum of resource-acquisitive and resource-conservative traits in water acquisition and use, and the second axis of variation being related to the leaf economics spectrum. Stomatal conductance was negatively related to both above-ground stem and rhizome specific density, and these relationships became stronger after accounting for evolutionary relatedness, indicating correlated evolution. Despite elevation and climatic differences among sites, high trait variation was ascribed to individuals rather than to sites. We conclude that Costus species present trait coordination and trade-offs that allow species to be categorized as having a resource-acquisitive or resource-conservative functional strategy, consistent with a whole-plant functional strategy with evident coordination and trade-offs between above-ground and below-ground function. Our results also show that herbaceous species and species with rhizomes tend to agree with trade-offs found in more species-rich comparisons.

Local hydrological gradients structure high intraspecific variability in plant hydraulic traits in two dominant central Amazonian tree species

Addressing the intraspecific variability of functional traits helps understand how climate change might influence the distribution of organismal traits across environments, but this is notably understudied in the Amazon, especially for plant hydraulic traits commonly used to project drought responses. We quantified the intraspecific trait variability of leaf mass per area, wood density, and xylem embolism resistance for two dominant central Amazonian tree species, along gradients of water and light availability, while accounting for tree age and height. Intraspecific variability in hydraulic traits was high, with within-species variability comparable to the whole-community variation. Hydraulic trait variation was modulated mostly by the hydrological environment, with higher embolism resistance of trees growing on deep-water-table plateaus compared with shallow-water-table valleys. Intraspecific variability of leaf mass per area and wood density was mostly modulated by intrinsic factors and light. The different environmental and intrinsic drivers of variation among and within individuals lead to an uncoupled coordination among carbon acquisition/conservation and water-use traits. Our findings suggest multivariate ecological strategies driving tropical tree distributions even within species, and reflect differential within-population sensitivities along environmental gradients. Therefore, intraspecific trait variability must be considered for accurate predictions of the responses of tropical forests to climate change.

Small herbivores and abiotic heterogeneity promote trait variation of a saltmarsh plant in local communities

Intraspecific trait variation (ITV) enables plants to respond to global changes. However, causes for ITV, especially from biotic components such as herbivory, are not well understood. We explored whether small vertebrate herbivores (hares and geese) impact ITV of a dominant clonal plant (Elytrigia atherica) in local communities. Moreover, we looked at the relative importance of their direct (e.g., selective grazing) and indirect effects (altering genotypic richness/diversity and abiotic environment) on ITV. We used exclosures at two successional stages in a Dutch saltmarsh, where grazing pressure at the early successional stage was ca. 1.5 times higher than that of the intermediate successional stage. We measured key functional traits of E. atherica including height, aboveground biomass, flowering (flower or not), specific leaf area, and leaf dry matter content in local communities (1 m × 1 m plots) inside and outside the exclosures. We determined genotypic richness and diversity of each plant using molecular markers. We further measured abiotic variations in topography and clay thickness (a proxy for soil total nitrogen). Structural equation models revealed that small herbivores significantly promoted ITV in height and flowering at the early successional stage, while they marginally promoted ITV in height at the intermediate successional stage. Moreover, the direct effects of herbivores played a major role in promoting ITV. Small herbivores decreased genotypic diversity at the intermediate successional stage, but genotypic richness and diversity did not impact ITV. Small herbivores did not alter topographic variation and variation in clay thickness, but these variations increased ITV in all traits at the early successional stage. Small herbivores may not only impact trait means in plants as studies have shown but also their ITV.

Climate variability supersedes grazing to determine the anatomy and physiology of a dominant grassland species

Grassland ecosystems are historically shaped by climate, fire, and grazing which are essential ecological drivers. These grassland drivers influence morphology and productivity of grasses via physiological processes, resulting in unique water and carbon-use strategies among species and populations. Leaf-level physiological responses in plants are constrained by the underlying anatomy, previously shown to reflect patterns of carbon assimilation and water-use in leaf tissues. However, the magnitude to which anatomy and physiology are impacted by grassland drivers remains unstudied. To address this knowledge gap, we sampled from three locations along a latitudinal gradient in the mesic grassland region of the central Great Plains, USA during the 2018 (drier) and 2019 (wetter) growing seasons. We measured annual biomass and forage quality at the plot level, while collecting physiological and anatomical traits at the leaf-level in cattle grazed and ungrazed locations at each site. Effects of ambient drought conditions superseded local grazing treatments and reduced carbon assimilation and total productivity in A. gerardii. Leaf-level anatomical traits, particularly those associated with water-use, varied within and across locations and between years. Specifically, xylem area increased when water was more available (2019), while xylem resistance to cavitation was observed to increase in the drier growing season (2018). Our results highlight the importance of multi-year studies in natural systems and how trait plasticity can serve as vital tool and offer insight to understanding future grassland responses from climate change as climate played a stronger role than grazing in shaping leaf physiology and anatomy.

Importance of Plants with Extremely Small Populations (PSESPs) in Endemic-Rich Areas, Elements Often Forgotten in Conservation Strategies

The distribution of the threatened fern Ophioglossum vulgatum L., a plant with extremely small populations (PSESPs) in Sardinia, is characterized by small disjunct populations with only a few individuals, and little is known about its status in the wild. To provide information for the conservation of O. vulgatum and with the aim to develop an in situ conservation strategy, we investigated its distribution, population size, and habitat. Field surveys confirmed that the species grows in only five localities. Two representative populations were selected for this study (Funtanamela and Gedili), and in each population, all plants were mapped and monitored monthly from April to August over an 8-year period. During the study, the populations had a very low number of reproductive plants and the populations appeared to be in decline, with the total number of plants per population slightly decreased in Gedili while a sharp reduction was recorded in Funtanamela due to wild boar threat. A fence was built in order to protect the site from further damage, but no noticeable signals of recovery were observed. The most urgent conservation requirement for this species is to preserve the threatened habitat of the remnant populations. Further field surveys and research are also required for an improved understanding of the species’ status.

Leaf trait variation in species-rich tropical Andean forests

Screening species-rich communities for the variation in functional traits along environmental gradients may help understanding the abiotic drivers of plant performance in a mechanistic way. We investigated tree leaf trait variation along an elevation gradient (1000-3000 m) in highly diverse neotropical montane forests to test the hypothesis that elevational trait change reflects a trend toward more conservative resource use strategies at higher elevations, with interspecific trait variation decreasing and trait integration increasing due to environmental filtering. Analysis of trait variance partitioning across the 52 tree species revealed for most traits a dominant influence of phylogeny, except for SLA, leaf thickness and foliar Ca, where elevation was most influential. The community-level means of SLA, foliar N and Ca, and foliar N/P ratio decreased with elevation, while leaf thickness and toughness increased. The contribution of intraspecific variation was substantial at the community level in most traits, yet smaller than the interspecific component. Both within-species and between-species trait variation did not change systematically with elevation. High phylogenetic diversity, together with small-scale edaphic heterogeneity, cause large interspecific leaf trait variation in these hyper-diverse Andean forests. Trait network analysis revealed increasing leaf trait integration with elevation, suggesting stronger environmental filtering at colder and nutrient-poorer sites.