Intraspecific Trait Variation Research Articles

Intraspecific variation in crayfish behavioral traits affects leaf litter breakdown in streams.

Although intraspecific trait variation is increasingly recognized as affecting ecosystem processes, few studies have examined the ecological significance of among-population variation in behavioral traits in natural ecosystems. In freshwater habitats, crayfish are consumers that can influence ecosystem structure (e.g., macroinvertebrate communities) and function (e.g., leaf litter breakdown). To test whether crayfish behavioral traits (activity, boldness, and foraging voracity) are major contributors of leaf litter breakdown rates in the field, we collected rusty crayfish (Faxonius rusticus) from eight streams across the midwestern USA and measured behaviors using laboratory assays. At the same streams, we measured breakdown rates of leaf packs that were accessible or inaccessible to crayfish. Our results provide evidence that among-population variation in crayfish boldness and foraging voracity was a strong predictor of leaf litter breakdown rates, even after accounting for commonly appreciated environmental drivers (water temperature and human land use). Our results suggest that less bold rusty populations (i.e., emerged from shelter more slowly) had greater direct impacts on leaf litter breakdown than bold populations (P = 0.001, r2 = 0.85), potentially because leaf packs can be both a shelter and food resource to crayfish. Additionally, we found that foraging voracity was negatively related to breakdown rates in leaf packs that were inaccessible to crayfish (P = 0.025, r2 = 0.60), potentially due to a trophic cascade from crayfish preying on other invertebrates that consume leaf litter. Overall, our results add to the growing evidence that trait variation in animals may be important for understanding freshwater ecosystem functioning.

Environmental and genetic drivers of physiological and functional traits in a key canopy species

The resilience of forests worldwide is challenged by climate change. Large-scale tree mortality and dieback events have been documented across continents in recent decades. The adaptive capacity of forests is important for predicting forest resistance and resilience to future climates yet remains largely unknown. We grew 12 populations of a widespread foundation tree species (Corymbia calophylla), originating from different temperature and rainfall regimes, in two common garden trials in Western Australia that had similar temperature but contrasting rainfall conditions. We quantified intraspecific trait variation at these two sites to estimate genetically determined trait variation with climate origin (genetic adaptation) and trait variation associated with environment (phenotypic plasticity). We aimed to determine the 1) contribution of genetic and environmental factors on growth, functional, and physiological trait variation; 2) coordination of leaf traits within the context of the leaf economic spectrum (LES) in variable rainfall conditions; and 3) role of local or regional climate adaptation influencing tree growth and water use efficiency. Growth and physiological traits were differentially expressed across populations and sites, highlighting the importance of genetic adaptation and phenotypic plasticity. Leaf traits reflected a more water conservative strategy with higher water use efficiency, high foliar nitrogen content, and low specific leaf area, as predicted by the LES, in trees at the dry site measured in autumn after the warm summer. Local adaptation was detected in growth and leaf water use efficiency traits at the regional climate, not the local population, scale. Plants from the cool region had greater performance than those from the warm region in most plant traits. Home-site rainfall was not a good predictor of trait expression. The capacity of C. calophylla to respond to low water availability through genetic adaptation and phenotypic plasticity may enable it to maintain optimal performance in drier conditions associated with climate change.

Computed tomography reconstructions of burrow networks for the Opheliid polychaete, Armandia cirrhosa

The morphology and architecture of structures formed by sediment-dwelling invertebrates, such as excavations or burrows, are often assumed to be characteristic of a given species, consistent across a range of environmental conditions, and used to categorise species contributions to ecosystem functioning. However, very few investigations use non-invasive high-resolution techniques capable of determining fine scale variations in burrow form and complexity, or consider whether or not the form of the burrow is context dependent. Here, we provide replicate high-resolution micro-focus computed tomography data for the complete burrow systems of the Opheliid polychaete, Armandia cirrhosa, across a range of salinity and habitat conditions. These data provide reference models which can be used by ecologists investigating intraspecific variation in species traits and organism-sediment interactions and, more generally, by those tasked with pattern and shape recognition of objects that are morphologically highly variable and which adjust their architecture with changing circumstance or context.

Intraspecific leaf trait variation of the heterophyllous amphibious plant Luronium natans: a trait-based study

AbstractHeterophylly, a type of intraspecific trait variation (ITV), is commonly observed in aquatic and amphibious plants. In this study, we focused on Luronium natans (L.) Raf., as a model species to investigate ITV, specifically looking at variations within different leaf types. The objective was to test general hypotheses regarding ITV across various leaf traits. We collected 210 leaves from the homogeneous environments of softwater lakes in northwestern Poland to measure six leaf traits: leaf area (LA), leaf dry weight (LDW), specific leaf area (SLA), leaf dry mass content (LDMC), circularity, and leaf width/length ratio (shape traits). These leaves were categorized into three types based on the shoot: heterophyllous shoots with floating leaves (HF), heterophyllous shoots with submerged leaves (HS), and submerged rosettes with linear leaves (S). Significant differences were observed in LA and LDMC within these leaf types and in SLA between HF and S types. ITV within each shoot type exhibited a wide range of variation, particularly in LA, LDW, SLA, and LDMC, with shape traits displaying stronger variability than functional traits. Our results indicate lower ITV of functional leaf traits within the same heterophyllous shoots compared to fully submerged leaves in a rosette form. We also noted negative correlations between SLA-LDMC and LA-circularity trait pairs, suggesting a variation–covariation pattern in leaf traits with minimal influence from water environmental factors.

Intraspecific variation in leaf traits and evolutionary plant strategies of three macrophytes across an environmental gradient in Eastern Amazon

Intraspecific variation in leaf traits and evolutionary plant strategies of three macrophytes across an environmental gradient in Eastern Amazon

Integrating spatial analyses of genomic and physiological data to understand avian responses to environmental change.

Projected rates of climate change over the next century are expected to force species to shift ranges, adapt or acclimate to evade extinction. Predicting which of these scenarios may be most likely is a central challenge for conserving biodiversity in the immediate future. Modeling frameworks that take advantage of intraspecific variation across environmental gradients can be particularly important for meeting this challenge. While these space-for-time approaches are essential for climatic and genomic modeling approaches, mechanistic models that incorporate ecological physiology data into assessing species vulnerabilities rarely include intraspecific variation. A major reason for this gap is the general lack of empirical data on intraspecific geographic variation in avian physiological traits. In this review, we outline the evidence for and processes shaping geographic variation in avian traits. We use the example of evaporative water loss to underscore the lack of research on geographic variation even in traits central to cooling costs in birds. We next demonstrate how shifting the focus of avian physiological research to intraspecific variation can facilitate greater integration with emerging genomics approaches. Finally, we outline important next steps for an integrative approach to advance understanding of avian physiological adaptation within species. Addressing the knowledge gaps outlined in this review will contribute to an improved predictive framework that synthesizes environmental, morphological, physiological, and genomic data to assess species specific vulnerabilities to a warming planet.

Species-specific and environment-sensitive functional traits in six steppe plant species with different roles in community

Plant functional traits are often considered as indicators of plant-environment relationship; however, some plant features can be highly taxonomic-specific. The study of intraspecific trait variation is essential to understand what functional traits are influenced by the phylogeny and what traits are more dependent on environment. We studied six common steppe plant species in two natural vegetation plots near lake Baikal in Southern Siberia different in climate aridity and grazing degree: site 1 - native true grass steppe under lower climate aridity, site 2 - high disturbed sagebrush steppe under higher aridity. Plant functional traits showed different relevance to species and environment. Plant height, leaf thickness (LT), mesophyll cell volume (Vcell), and the chloroplast number per cell had the greatest contribution to differences between species and varied slightly within a species. Photosynthesis (Amax) and transpiration (E) rates, chlorophyll content, mesophyll surface area per leaf area unit (Ames/A) were more dependent on environment than on species. Amax and E decreased in all studied species in more adverse conditions of site 2, however plants differed in mechanisms of these changes. In Stipa krylovii, Artemisia frigida and Potentilla acaulis, most abundant in true steppe (site 1) mesophyll cell sizes, cell and chloroplast number per leaf area decreased in site 2. Other species, Artemisia scoparia, Potentilla bifurca and Allium anisopodium which were more abundant in disturbed steppe (site 2), had larger cells and showed an increase in cell and chloroplast number per leaf area in site 2 and decrease in the photosynthetic capacity of a chloroplast. We concluded that the leaf thickness and cell size belong to species-specific features, whereas Amax, pigment content and integral mesophyll traits as Ames/A are more indicative for plant-environment relationships and their response to growth conditions depend on the ecological strategy of a species.

Climate change may shift metapopulations towards unstable source-sink dynamics in a fire-killed, serotinous shrub.

Climate change, with warming and drying weather conditions, is reducing the growth, seed production, and survival of fire-adapted plants in fire-prone regions such as Mediterranean-type ecosystems. These effects of climate change on local plant demographics have recently been shown to reduce the persistence time of local populations of the fire-killed shrub Banksia hookeriana dramatically. In principle, extinctions of local populations may be partly compensated by recolonization events through long-distance dispersal mechanisms of seeds, such as post-fire wind and bird-mediated dispersal, facilitating persistence in spatially structured metapopulations. However, to what degree and under which assumptions metapopulation dynamics might compensate for the drastically increased local extinction risk remains to be explored. Given the long timespans involved and the complexity of interwoven local and regional processes, mechanistic, process-based models are one of the most suitable approaches to systematically explore the potential role of metapopulation dynamics and its underlying ecological assumptions for fire-prone ecosystems. Here we extend a recent mechanistic, process-based, spatially implicit population model for the well-studied fire-killed and serotinous shrub species B. hookeriana to a spatially explicit metapopulation model. We systematically tested the effects of different ecological processes and assumptions on metapopulation dynamics under past (1988-2002) and current (2003-2017) climatic conditions, including (i) effects of different spatio-temporal fires, (ii) effects of (likely) reduced intraspecific plant competition under current conditions and (iii) effects of variation in plant performance among and within patches. In general, metapopulation dynamics had the potential to increase the overall regional persistence of B. hookeriana. However, increased population persistence only occurred under specific optimistic assumptions. In both climate scenarios, the highest persistence occurred with larger fires and intermediate to long inter-fire intervals. The assumption of lower intraspecific plant competition caused by lower densities under current conditions alone was not sufficient to increase persistence significantly. To achieve long-term persistence (defined as >400 years) it was necessary to additionally consider empirically observed variation in plant performance among and within patches, that is, improved habitat quality in some large habitat patches (≥7) that could function as source patches and a higher survival rate and seed production for a subset of plants, specifically the top 25% of flower producers based on current climate conditions monitoring data. Our model results demonstrate that the impacts of ongoing climate change on plant demographics are so severe that even under optimistic assumptions, the existing metapopulation dynamics shift to an unstable source-sink dynamic state. Based on our findings, we recommend increased research efforts to understand the consequences of intraspecific trait variation on plant demographics, emphasizing the variation of individual traits both among and within populations. From a conservation perspective, we encourage fire and land managers to revise their prescribed fire plans, which are typically short interval, small fires, as they conflict with the ecologically appropriate spatio-temporal fire regime for B. hookeriana, and likely as well for many other fire-killed species.

Multidimensional trait space outlines the effects of changes in abiotic filtering on aquatic plant community from sub-Antarctic ponds

In the current context of climate changes, which causes strong habitat variation, an understanding of the mechanisms underlying plant community dynamics is crucial to predict species fates. The taking of inter- and intraspecific trait variability into account would aid the identification of these mechanisms. Recently, a method involving the calculation of hypervolumes (n-dimensional spaces of trait values) was developed for the study of plant responses to their environments. Through hypervolume comparison, we examined the effects of interannual variations in abiotic conditions on aquatic plant communities in ponds of the sub-Antarctic Iles Kerguelen. This model system is particularly relevant for the examination of the consequences of climate changes–related habitat variation, as aquatic plant communities are adapted to cold and overall stable habitat conditions and the sub-Antarctic climate is changing rapidly. We conducted field sampling over four years at three sites. For all aquatic species, we measured five foliar, shoot, and clonal traits characterizing individual growth strategies that are likely to respond to variations in abiotic conditions on 1565 ramets over the four years. We measured 10 abiotic variables to characterize the plants’ habitats every three months during the survey period. Hypervolumes were calculated for each site and year to assess variation in aquatic plant strategies at the community level. We demonstrated (i) the importance of spatiotemporal gradients of trophic status, temperature, and pH and dissolved oxygen concentration for the functional structure of aquatic plant communities; (ii) that the shape of the mean response was trait dependent, with traits related to plant metabolism (specific leaf area and specific internode mass) and three-dimensional space exploration (height and internode length) responding to the three spatiotemporal abiotic gradients; (iii) that selection pressures were especially high on aerial traits relative to clonal traits; and (iv) that given the community response to interannual variations of abiotic conditions, environmental changes should impact macrophyte community productivity. Synthesis. We conclude that the examination of interannual abiotic variation over four years is sufficient to detect rapid responses of macrophyte communities, with likely reliance on phenotypic plasticity. Our findings may inform the characterization of future functional changes in aquatic plant communities of the sub-Antarctic region, where similar species are found.

Genetic and phenotypic differentiation in functional traits of Iris pseudacorus L. in native and introduced Mediterranean climate ranges

Intraspecific variation in functional traits between native and introduced plant species may underlie resilience and invasiveness of introduced species. We explored if observed phenotypic variation of Iris pseudacorus L. between populations in the native vs. introduced ranges results from genetic differentiation and/or phenotypic plasticity. Seeds were collected from populations along estuarine stress gradients within populations in both Guadalquivir Estuary (Andalusia, Spain) and San Francisco Bay-Delta Estuary (California, USA). Genetic analysis was performed on leaf tissue from plants in each seed donor population. Germinants (n = 48: 6 plants × 4 populations × 2 ranges) were grown for 12 months in a common garden experiment (CGE). We then evaluated 25 traits including growth, biomass allocation, morphological and biochemical responses. Geographic range explained relative intraspecific trait variation segregating native from introduced phenotypes. Native plants had lower specific leaf area (− 34%) and carbohydrate concentrations in rhizomes (− 63%) than introduced plants, providing evidence of genetic differentiation. Higher genetic diversity and 27% higher phenotypic variation (CGE) of native vs. introduced plants indicated longer-term adaptive processes in the native range. Genetic distance of introduced populations (field) increased along with their phenotypic distance (CGE), suggesting rapid genetic differentiation. Phenotypic plasticity also explained some observed inter-range differences under field conditions not expressed by plants in the CGE. Management of the introduced I. pseudacorus populations should be established urgently since they represent novel genotypes with key functional traits that can support invasiveness through increased competitive ability and physiological stress tolerances to sea level rise.

Extending the CWM approach to intraspecific trait variation: how to deal with overly optimistic standard tests?

Community weighted means (CWMs) are widely used to study the relationship between community-level functional traits and environment. For certain null hypotheses, CWM-environment relationships assessed by linear regression or ANOVA and tested by standard parametric tests are prone to inflated Type I error rates. Previous research has found that this problem can be solved by permutation tests (i.e., the max test). A recent extension of the CWM approach allows the inclusion of intraspecific trait variation (ITV) by the separate calculation of fixed, site-specific, and intraspecific CWMs. The question is whether the same Type I error rate inflation exists for the relationship between environment and site-specific or intraspecific CWM. Using simulated and real-world community datasets, we show that site-specific CWM-environment relationships have also inflated Type I error rate, and this rate is negatively related to the relative ITV magnitude. In contrast, for intraspecific CWM-environment relationships, standard parametric tests have the correct Type I error rate, although somewhat reduced statistical power. We introduce an ITV-extended version of the max test, which can solve the inflation problem for site-specific CWM-environment relationships and, without considering ITV, becomes equivalent to the "original" max test used for the CWM approach. We show that this new ITV-extended max test works well across the full possible magnitude of ITV on both simulated and real-world data. Most real datasets probably do not have intraspecific trait variation large enough to alleviate the problem of inflated Type I error rate, and published studies possibly report overly optimistic significance results.

Intraspecific Trait Variation Regulates Biodiversity and Community Productivity of Shrublands in Drylands

Intraspecific variation (Intra-V) has played an important role in determining the responses of ecosystem functions to climate change. However, its specific role in the regulation of ecosystem functions during community assembly is less investigated. In this study, we conducted a transect survey in northwest China and determined different plant functional types, namely resource-conservative, medium, and resource-acquisitive strategies, which describe resource-use strategies of plants in multi-functional dimensions. Plant functional traits including canopy, wood density (WD), height, specific leaf area (SLA), and leaf nitrogen (N) and phosphorus (P) concentrations were determined. Ecological filters, including external filtering (assembly processes at the regional scale), internal filtering (assembly processes within a certain community), and functional redundancy, were employed to examine plant environment interactions. We found that with the decrease in environmental pressure, dominant shrub plants changed from conservative to acquisition species in drylands. Specifically, a benign environment (such as stable and adequate precipitation, loose soil, and increased acid deposition) significantly increased plant mean traits, such as SLA and WD of shrubs, especially for conservative strategy plants. In addition, a benign environment mainly reduced the functional redundancy of SLA (FRedSLA) by strengthening internal filtering and, ultimately, increased aboveground biomass but decreased species richness. Our results suggest that conservative strategy plants with stronger adaptability to the external environment may exhibit more competitive advantages and play a more important role in community construction under future climate scenarios of gradual warming and wetting in northwest China. Our results also revealed that trait-based Intra-V may be a more reasonable ecological filter than plant mean traits for predicting the structure and function of dryland ecosystems.

Patterns and driving factors of functional traits of desert species with different elevational distributions in the Tibetan Plateau and adjacent areas

Variations in functional traits serve as measures of plants’ ability to adapt to environment. Exploring the patterns of functional traits of desert plants along elevational gradients is helpful to understand the responses and adaptation strategies of species to changing environments. However, it is unknown whether the relationship between functional traits and elevation is affected by differences in the species’ elevational distributions (elevation preference and species’ range). Importantly, most researches have concerned with differences in mean trait values and ignored intraspecific trait variation. Here, we measured functional traits of desert plants along a wide elevational gradient in the Tibetan Plateau and adjacent areas and explored functional trait patterns over elevation in species with different elevational distributions. We decomposed trait variation and further investigated characterizations of intraspecific variation. Ultimately, the main drivers of trait variation were identified using redundancy analysis. We found that species’ elevational distributions significantly influenced the relationship of functional traits such as plant height, leaf dry matter content, leaf thickness, leaf nitrogen and carbon content with elevation. Species with a lower elevational preference showed greater trait variation than species with a higher elevational preference, suggesting that species that prefer high elevation are more conservative facing environmental changes. We provide evidence that interspecific trait variation in leaf thickness and leaf carbon content decreased with increasing species’ range, indicating that increased variations in resistance traits within species make greater responsiveness to environmental changes, enabling species a wider range. Elevation, temperature and precipitation were the main drivers of trait variation in species with a low elevational preference, while the effect of precipitation on trait variation in species with a high elevational preference was not significant. This study sheds new insights on how plants with different elevational distributions regulate their ecological strategies to cope with changing environments.

Temperature influences desiccation resistance of bumble bees

Ongoing climate change has increased temperatures and the frequency of droughts in many parts of the world, potentially intensifying the desiccation risk for insects. Because resisting desiccation becomes more difficult at higher temperatures and lower humidity, avoiding water loss is a key challenge facing terrestrial insects. However, few studies have examined the interactive effects of temperature and environmental humidity on desiccation resistance in insects. Such studies on bees (Hymenoptera: Apoidea: Anthophila) are especially rare, despite their ecological and economic importance. Here, we crossed temperature (20, 25, and 30 °C) with humidity (<5, 50, >95 % RH) manipulations and measured time to mortality, water loss rates, and the water content at mortality of bumble bees (Bombus impatiens). We found that both higher temperature and lower humidity increased water loss rates, while warmer temperatures reduced survival time and lower humidity decreased water content at mortality. Additionally, we observed large intraspecific variation in water balance traits between colonies, and larger individuals survived longer and could tolerate more water loss before mortality. This study raises important questions about the mechanisms underpinning water loss in bumble bees and suggests that frequent access to nectar may be especially important for bumble bees’ water balance and survival in a warming and drying climate.

Trait-dependent importance of intraspecific variation relative to species turnover in determining community functional composition following nutrient enrichment.

Community weighted mean trait, i.e., functional composition, has been extensively used for upscaling of individual traits to the community functional attributes and ecosystem functioning in recent years. Yet, the importance of intraspecific trait variation relative to species turnover in determining changes in CWM still remains unclear, especially under nutrient enrichment scenarios. In this study, we conducted a global data synthesis analysis and three nutrient addition experiments in two sites of alpine grassland to reveal the extent to which species turnover and ITV contribute to shift in CWM in response to nutrient enrichment. The results consistently show that the importance of ITV relative to species turnover in regulating CWM in response to nutrient enrichment strongly depends on trait attributes rather than on environmental factors (fertilization type, climatic factors, soil properties, and light transmittance). For whole plant traits (height) and leaf morphological traits, species turnover is generally more important than ITV in determining CWM following most treatments of nutrient addition. However, for leaf nutrient traits, ITV outweighed species turnover in determining shifts in CWM in response to almost all treatments of nutrient addition, regardless of types and gradients of the nutrient addition. Thus, our study not only provides robust evidence for trait-dependent importance of ITV in mediating community functional composition, but also highlights the need to consider the nature of functional traits in linking ITV to community assembly and ecosystem functioning under global nutrient enrichment scenarios.

Biological invasions are a population-level rather than a species-level phenomenon.

Biological invasions pose a rapidly expanding threat to the persistence, functioning and service provisioning of ecosystems globally, and to socio-economic interests. The stages of successful invasions are driven by the same mechanism that underlies adaptive changes across species in general-via natural selection on intraspecific variation in traits that influence survival and reproductive performance (i.e., fitness). Surprisingly, however, the rapid progress in the field of invasion science has resulted in a predominance of species-level approaches (such as deny lists), often irrespective of natural selection theory, local adaptation and other population-level processes that govern successful invasions. To address these issues, we analyse non-native species dynamics at the population level by employing a database of European freshwater macroinvertebrate time series, to investigate spreading speed, abundance dynamics and impact assessments among populations. Our findings reveal substantial variability in spreading speed and abundance trends within and between macroinvertebrate species across biogeographic regions, indicating that levels of invasiveness and impact differ markedly. Discrepancies and inconsistencies among species-level risk screenings and real population-level data were also identified, highlighting the inherent challenges in accurately assessing population-level effects through species-level assessments. In recognition of the importance of population-level assessments, we urge a shift in invasive species management frameworks, which should account for the dynamics of different populations and their environmental context. Adopting an adaptive, region-specific and population-focused approach is imperative, considering the diverse ecological contexts and varying degrees of susceptibility. Such an approach could improve and refine risk assessments while promoting mechanistic understandings of risks and impacts, thereby enabling the development of more effective conservation and management strategies.

Elevation differentially shapes functional diversity patterns in understorey forest communities when considering intraspecific and interspecific trait variability

AbstractQuestionsWhat is the relative importance of interspecific and intraspecific trait variation and their covariation in the herb layer of European temperate beech forests, and how do they vary with elevation? Is there evidence of interspecific trait convergence at higher elevations, as postulated by the habitat‐filtering hypothesis, and is this convergence enhanced or counteracted by intraspecific variation?LocationNational Park “Foreste Casentinesi, Monte Falterona and Campigna”, Italy.MethodsWe measured four functional traits – plant height, specific leaf area (SLA), leaf dry matter content (LDMC) and leaf area – across 775 individuals from 60 herb‐layer species in 28 forest plots (10 m × 10 m) spanning an 800 m elevation gradient. For each trait in each plot, we computed community‐weighted means (CWMs) and the standardized effect size of functional diversity (SES‐FD). We decomposed total trait variation into its interspecific and intraspecific components, and their covariation. We run linear regression models to assess the impact of elevation on these three components of functional variation. Lastly, we investigated whether higher elevation communities exhibited lower SES‐FD, indicating functional convergence that could hint to a stronger habitat filtering.ResultsInterspecific trait variation was more important than the intraspecific counterpart both for CWMs and SES‐FD. Only CWMs calculated for plant height and LDMC showed a significant relationship with elevation. Low‐elevation communities featured taller, more‐conservative species, whereas shorter, faster‐growing species were more common at higher elevations. SES‐FD remained consistently negative for species turnover and total variation, suggesting stable functional convergence across the gradient.ConclusionsOur findings suggest that interspecific and intraspecific trait variability can be decoupled along an elevation gradient, stressing the importance of individually considering each component of trait variation when studying community composition. Elevation significantly influenced various components of plant community trait variation, with habitat filtering playing a substantial role in selecting plants with specific traits across elevations.

Inter‐ and intraspecific stomatal morphological traits vary in response to topographic habitat changes

AbstractQuestionsStomata can reflect the plant's adaptation to environmental changes. However, the variation patterns of stomatal traits across different habitats and their relationships with environmental drivers are still poorly understood. Here, we assessed the extent of interspecific and intraspecific variation in stomatal traits in two typical riparian forests, and investigated how stomatal traits adapt to habitat change as well as trait–environment relationships.LocationThe Irtysh River Basin in China.MethodsWe measured the stomatal density (SD), stomatal size (SS), and stomatal relative area (SRA) of dominant plant species from two riparian forests: (1) a riparian forest in the valley and (2) a riparian forest in the pediment plain. We analyzed the stomatal trait variation patterns of dominant plant species in different habitats. We then quantified the magnitude of intraspecific and interspecific stomatal trait variability and evaluated the relationships between stomatal traits and environmental factors.ResultsWe found that SD and SRA were significantly higher in pediment plain forests than in valley forests, whereas SS was not significantly different between these habitats. The SD and SRA of trees in pediment plain forests were significantly higher than those in valley forests, whereas there were no significant differences in understory plants between habitats. The interspecific variation in each stomatal trait was significantly higher than the intraspecific variation. Stomatal traits were more related to the soil environment than to climatic factors.ConclusionsResponse strategies of stomatal traits to habitat changes differed between species and functional groups, and trait–environment relationships depended on the habitat type of the riparian forest. Our analysis of stomata trait variation implies adaptive strategies in species of natural riparian forest. Insights into trait–environment relationships could be used to predict carbon and water cycling, and vegetation changes in riparian forests of arid regions, especially in the context of climate change.

Intraspecific transitioning of ecological strategies in Pinus massoniana trees across restoration stages.

Intraspecific variation in plant functional traits and ecological strategies is typically overlooked in most studies despite its pivotal role at the local scales and along short environmental gradients. While CSR theory has been used to classify ecological strategies (competitive C; stress-tolerant, S; ruderal, R) in different plant species, its ability to explain intraspecific variation in ecological strategies remains uncertain. Here, we sought to investigate intraspecific variation in ecological strategies for Pinus massoniana, a pioneer conifer tree for ecological restoration in Changting County, southeast China. By measuring key leaf traits and canopy height of 252 individuals at different ontogenetic stages from three plots spanning distinctive stages along early ecological restoration and calculating their C, S, and R scores, we constructed an intraspecific CSR system. All individual strategies shifted across three restoration stages, with adults from higher S component to higher C component while juveniles from higher S component to higher R component. Our results suggest that while strategies of all P. massoniana individuals start with tolerance to environmental stress, as restoration proceeds, adult transition towards completion for light, whereas juveniles shift to an acquisitive resource use. The study reveals an intraspecific pattern of strategy variation during forest restoration, contributing to our understanding of how plants adapt to diverse environments.

Does intraspecific variation in Trissolcus japonicus affect its response to non-target hosts?

Host specificity is a key criterion for the implementation of any biological control program. In parasitoid wasps, host specificity is mediated by their response to chemical cues directly and indirectly associated with their hosts during foraging. Although intraspecific variation in foraging behaviour is documented, it is rarely integrated into risk assessment studies of potential biological control agents, as is the case for Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae), an Asian egg parasitoid and biological control agent of the invasive Halyomorpha halys (Stål) (Hemiptera: Pentatomidae). In the present study, we compared the behavioural response of T. japonicus females of an adventive line present in Switzerland and an Asian line (Beijing USDA), recently mass released in Italy, to cues of its target host H. halys and non-target host Pentatoma rufipes (L.) (Hemiptera: Pentatomidae). We observed minimal differences in host acceptance, exploitation and suitability in no-choice tests. In contrast, the behavioural response to host contact kairomones left on leaf substrates significantly differed between the two lines. While both lines preferred chemical footprints of H. halys in comparison to P. rufipes, females of the Beijing USDA line responded more strongly to host kairomones. The observed intraspecific variation in behavioural traits highlights the relevance of considering genetically distinct parasitoid lines and their host foraging behaviour in biological risk assessment studies. However, the implications of intraspecific variation in parasitoid foraging behaviour for biological control of a pest and non-target effects in the field remain challenging to predict.