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Data from: Trait plasticity and tradeoffs shape intraspecific variation in competitive response in a foundation tree species

<ul> <li>The ability to tolerate neighboring plants (i.e., degree of competitive response) is a key determinant of plant success in high-competition environments. Plant genotypes adjust their functional trait expression under high levels of competition, which may help explain intraspecific variation in competitive response. However, the relationships between traits and competitive response are not well understood, especially in trees. In this study, we investigated among-genotype associations between tree trait plasticity and competitive response. </li> <li>We manipulated competition intensity in experimental stands of trembling aspen (Populus tremuloides) to address the covariance between competition-induced changes in functional trait expression and aspects of competitive ability at the genotype level. </li> <li>Genotypic variation in the direction and magnitude of functional trait responses, especially those of crown foliar mass, phytochemistry, and leaf physiology, was associated with genotypic variation in competitive response. Traits exhibited distinct plastic responses to competition, with varying degrees of genotypic variation and covariance with other trait responses. </li> <li>The combination of genotypic diversity and covariance among functional traits led to tree responses to competition that were coordinated among traits yet variable among genotypes. Such relationships between tree traits and competitive success have the potential to shape stand-level trait distributions over space and time. </li> </ul>

Data from: Trait-environment interactions affect plant establishment success during restoration

Establishment and persistence are central to community assembly and are determined by how traits interact with the environment to determine performance ('trait-environment interactions'). Community assembly studies have rarely considered such trait-environment interactions, however, which can lead to incorrect inferences about how traits affect assembly. We evaluated how functional traits, environmental conditions, and trait-environment interactions structure plant establishment, as a measure of performance. Within 12 prairie restorations created by sowing 70 species, we quantified environmental conditions and counted individuals of each seeded species to quantify first year establishment. Three trait-environment interactions structured establishment. Leaf nitrogen interacted with herbivore pressure, as low leaf nitrogen species established relatively better under higher herbivory than species with high leaf nitrogen. Soil moisture interacted with root mass fraction (RMF), with low RMF species establishing better with low soil moisture and higher RMF species better on wetter soils. Specific leaf area (SLA) interacted with light availability, as low SLA species established better under high light conditions and high SLA species under low light conditions. Our work illustrates how community assembly can be better described by trait-environment interactions than correlating traits or environment with performance. This knowledge can assist species selection to maximize restoration success.Establishment and persistence are central to community assembly and are determined by how traits interact with the environment to determine performance ('trait-environment interactions'). Community assembly studies have rarely considered such trait-environment interactions, however, which can lead to incorrect inferences about how traits affect assembly. We evaluated how functional traits, environmental conditions, and trait-environment interactions structure plant establishment, as a measure of performance. Within 12 prairie restorations created by sowing 70 species, we quantified environmental conditions and counted individuals of each seeded species to quantify first year establishment. Three trait-environment interactions structured establishment. Leaf nitrogen interacted with herbivore pressure, as low leaf nitrogen species established relatively better under higher herbivory than species with high leaf nitrogen. Soil moisture interacted with root mass fraction (RMF), with low RMF species establishing better with low soil moisture and higher RMF species better on wetter soils. Specific leaf area (SLA) interacted with light availability, as low SLA species established better under high light conditions and high SLA species under low light conditions. Our work illustrates how community assembly can be better described by trait-environment interactions than correlating traits or environment with performance. This knowledge can assist species selection to maximize restoration success.

Contrasting patterns of sexually selected traits in Mediterranean and continental populations of European mouflon

The expression of sexually selected traits in highly dimorphic ungulates may be influenced by environmental quality. Variations in habitat conditions can impose different constraints on the allocation of energy resources to male life-history traits, and possibly alter the female preferences for specific features. Here, we compared the horn growth patterns in male European mouflon Ovis aries musimon living in different habitats (Mediterranean vs. continental) but sharing a common genetic origin. We hypothesized that the expression of sexually selected traits such as horn development should be promoted in more favourable habitat conditions (i.e., Mediterranean). Using linear mixed models on data retrieved from individuals harvested under the same hunting regime, we found longer horns and greater individual variance in horn segment length in the Mediterranean population than in the continental one. Furthermore, Mediterranean rams showed no evidence of compensatory horn growth, as opposed to the continental rams. Unexpectedly, horn base circumference was greater in the continental habitat than in the Mediterranean one. The overall results suggest different patterns of investment in horns in the two populations, with seemingly stronger pressure and consequences of sexual selection on mouflon rams living in more favourable environments. Although the role of hunters' selectivity cannot be excluded a priori, our data suggest that the differences in the expression of sexually selected traits in our study populations may be influenced by environmental conditions. Because sexual selection can impose substantial fitness costs on individuals, further investigations on the trade-offs between reproduction and survival would improve our understanding of the dynamics of mouflon populations living in different environmental conditions.

Data from: Are belowground clonal traits good predictors of ecosystem functioning in temperate grasslands?

Dataset contains data on biomass distribution, soil characteristics and trait data for 52 temperate grasslands. Data are presented at community level. Biomass distribution (aboveground biomass, rhizome biomass, and root biomass) and soil chemistry data are original. The trait data are from existing databases and are presented as averages for a community (not weighted by species abundance).

Traits and depth: what do hydroids tell us about morphology and life-history strategies in the deep sea?

Aim: Traits affect the survival and reproduction of individuals in different habitat conditions, ultimately altering their distributions. In the oceans, changes in environmental conditions with bathymetry may influence the occurrence of specific traits. Therefore, characterizing trait variation with depth can illuminate drivers related to the distribution of diversity of forms, functions, and life histories. We aimed to investigate patterns of variation in the diversified life histories and morphologies of hydroids with depth, integrating these patterns with the natural history of the group and ecological principles of the deep sea. Location: Atlantic Ocean and adjacent polar seas, from 50 m to 5,330 m deep. Time period: Present day. Major taxa studied: Hydrozoa. Methods: Analyses were based on 14 traits collected for a total of 4,668 specimens of hydroids, belonging to 438 species. Records were divided into 12 depth strata for comparisons. We evaluated: how each trait varies with depth; whether variation in some traits is affected by the presence of other traits; how traits covary; and similarities in trait compositions among depth strata. Results: Traits of hydroids vary with depth, with more pronounced differences for regions deeper than 1,000 m. Hydroids are generally smaller, infertile, solitary, meroplanktonic, and devoid of protective structures with increasing depth. The relationship, however, is not always linear. Also, some covariation and correlation between traits was evident. For example, depth may affect size differently according to the presence of specific traits such as structures protecting against predation. The lower proportion of fertile specimens recorded in the deep sea suggests that chances for genetic recombination are reduced in deep-sea populations, ultimately leading to a slower rate of evolution. Main conclusions: We identified novel trends in hydroid trait variation with depth by combining observations on morphology, ecology, and life history, clarifying selection pressures on hydroids in the deep sea.

Data from: Demographic traits improve predictions of spatiotemporal changes in community resilience to drought

<ol> <li>Communities are increasingly threatened by extreme weather events. The cumulative effects of such events are typically investigated by assessing community resilience, i.e., the extent to which affected communities can achieve pre-event states. However, a mechanistic understanding of the processes underlying resilience is frequently lacking and requires linking various measures of resilience to demographic responses within natural communities.</li> <li>Using 13 years of data from a shrub community that experienced a severe drought in 2005, we use generalized additive models to investigate temporal changes in three measures of resilience. We assess whether community-weighted, species-specific demographic traits such as longevity and reproductive output can predict changes in resilience and how the performance of these traits compares to more commonly used plant functional traits such as leaf area or root dry-matter content.</li> <li>We find significant spatiotemporal variation in community dynamics after the drought. Overall, demographic traits are better at predicting absolute and relative resilience in total plant cover, but functional traits outperform demographic traits when resilience in community composition is assessed. All resilience measures show non-linear and context-specific responses to demographic and functional traits; and these responses depend strongly on the severity of initial drought impact.</li> <li> Synthesis: Our work demonstrates that a full picture of the mechanisms underlying community responses to drought requires the assessment of numerous species-specific characteristics (including demographic and functional traits) and how these characteristics differentially affect complementary measures of community changes through time. </li> </ol>

Dynamic feedbacks among tree functional traits, termite populations and deadwood turnover

1. Changes in the composition of plant functional traits may affect ecosystem processes through influencing trophic interactions. Bottom-up control by plant species through food availability to animals may vary with time. However, such dynamics and their consequences for deadwood turnover are poorly known for detrital food webs. 2. We introduce a dynamic conceptual model of the feedback of (deadwood-feeding) termite populations, tree functional traits and deadwood decomposition. We hypothesized that tree functional diversity (in terms of a wood resource economic spectrum, WES) supports the sustenance of termite populations via complementary food supplied through time, as deadwood varies in traits both initially between species and because of different decomposition rates. Simultaneously, the consumption of deadwood by termites was hypothesized to sustain deadwood turnover in a functionally diverse forest by the same temporal mechanism of changing wood quality of multiple species over time. 3. We tested our hypothesis through an 18-month termite-exclusion decomposition experiment by incubating coarse (i.e., 5 cm diameter) deadwood of 34 woody species in two subtropical forests in East China. One site still sustained a healthy population of pangolins as the keystone termite predator, while another had lost its pangolins due to hunting and illegal wildlife trade. 4. The results supported our hypothesis: in the first 12 months, termites amplified the positive linear relationship between % wood mass loss and initial wood quality (WES). In contrast, between 12 and 18 months, termite-mediated consumption, and associated wood mass loss, showed a humpback relation with the initial WES. This shift in termite preference of deadwood species along the WES indicated complementary food availability to termites through time. 5. Synthesis. Our findings imply that tree functional composition, through variation in deadwood quality through decomposition time, can help to sustain termite populations and thereby forest carbon turnover. Future studies need to test whether and how our conceptual model may apply to other detrital systems and food webs. In general, food web research would benefit from a stronger focus on temporal patterns for better understanding the interactions of basal resource functional traits and consumers on ecosystem functions.

Data from: The soil microbial community alters patterns of selection on flowering time and fitness related traits in Ipomoea purpurea

Premise of the study Plant flowering time plays an important role in plant fitness and thus evolutionary processes. Soil microbial communities are diverse and have a large impact, both positive and negative, on the host plant. However, owing to few available studies, how the soil microbial community may influence the evolutionary response of plant populations is not well understood. Here we sought to uncover if below-ground microbial communities act as an agent of selection on flowering and growth traits in the common morning glory, Ipomoea purpurea. Methods We performed a controlled greenhouse experiment in which genetic lines of I. purpurea were planted into either sterilized soils, or soils that were sterilized and re-inoculated with the microbial community from original field soil. This allowed us to directly test the influence of alterations to the microbial community on plant growth, flowering, and fitness, as well as assess patterns of selection in both soil microbial environments. Results We found that a more complex soil microbial community resulted in larger plants that produced more flowers. Selection strongly favored earlier flowering when plants were grown in the complex microbial environment than compared to sterilized soil. Additionally, we uncovered a pattern of negative correlational selection on growth rate and flowering time, indicating that selection favored different combinations of growth and flowering traits in the simplified versus complex soil community. Conclusions Together these results suggest the soil microbial community is a selective agent on flowering time and ultimately that soil microbial community influences important plant evolutionary processes.

Data from: On the inconsistency of pollinator species traits for predicting either response to land-use change or functional contribution

The response and effect trait framework, if supported empirically, would provide for powerful and general predictions about how biodiversity loss leads to loss in ecosystem function. This framework proposes that species traits will explain how different species respond to disturbance (i.e. response traits) as well as their contribution to ecosystem function (i.e. effect traits). However, predictive response and effect traits remain elusive for most systems. Here, we use data on crop pollination services provided by native, wild bees to explore the role of six commonly used species traits in determining both species' response to land-use change and the subsequent effect on crop pollination. Analyses were conducted in parallel for three crop systems (watermelon, cranberry, and blueberry) located within the same geographical region (mid-Atlantic USA). Bee species traits did not strongly predict species' response to land-use change, and the few traits that were weakly predictive were not consistent across crops. Similarly, no trait predicted species' overall functional contribution in any of the three crop systems, although body size was a good predictor of per capita efficiency in two systems. Overall we were unable to make generalizable predictions regarding species responses to land-use change and its effect on the delivery of crop pollination services. Pollinator traits may be useful for understanding ecological processes in some systems, but thus far the promise of traits-based ecology has yet to be fulfilled for pollination ecology.

Data from: Predicting peatland carbon fluxes from non-destructive plant traits

1. Determining the plant traits that best predict carbon (C) storage is increasingly important as global change drivers will affect plant species composition and ecosystem C cycling. Despite the critical role of peatlands in the global C cycle, trait-flux relationships in peatlands are relatively unknown. 2. We assessed the ability of four non-destructive plant traits to predict carbon dioxide (CO2) and methane (CH4) fluxes over two growing seasons in a temperate peatland in Ontario, Canada. We examined relationships between C-fluxes and leaf area, leaf persistence (deciduous, evergreen), growth form (woody, herbaceous), and aerenchyma tissue. To explore potential inconsistencies between different scales of data aggregation, traits were analysed at the level of plots, species and microsites. 3. CO2 fluxes showed a positive relationship with leaf area and leaf persistence, and a negative relationship with proportion of woody species. CH4 fluxes showed a positive relationship with aerenchyma and leaf area. The significance of trait-flux relationships differed based on whether data were averaged at the level of plot, species or microsite. 4. We recommend applying leaf area as a non-destructive trait to other systems where it is not ideal to measure traits destructively. A better understanding of the relationships between above and belowground traits is likely needed to further explain variation in ecosystem respiration and CH4 fluxes from plant traits.

opencc-zeroDec 2019View details →

Variations in leaf economics spectrum traits for an evergreen coniferous species: Tree size dominates over environment factors

<ol> <li>Many leaf traits strongly vary with tree size and environmental factors, but the importance of these factors to intraspecific variations of leaf traits in forest trees have rarely been <a>simultaneously</a> evaluated.</li> <li>We measured needle longevity and specific leaf area (SLA) and nitrogen (N) content of every needle age (0 to 4 year old) for 65 individuals with 0.3-100 cm diameter at breast height (DBH) for an evergreen coniferous species, Pinus koraiensis Sieb. et Zucc., in Northeast China. We <a>simultaneously</a> evaluated effects of tree size (DBH or tree height) and environment factors (light intensity, soil N content and water availability) on the needle longevity, SLA, foliage N content as well as the slopes of regressions of SLA and foliage N content against needle age.</li> <li>All of the studied leaf traits and slopes of regressions of SLA and foliage N content against needle age were significantly related to tree size. Tree height had a greater impact on SLA and area-based leaf N content (Narea), whereas DBH was more important for needle longevity and mass-based leaf N content (Nmass). The environment variables, light intensity, soil N content and water availability, were rather minor factors for trait variations compared with tree size. Significant influences of light intensity were found only on needle longevity, and soil N and water availability had no effects on the leaf traits.</li> <li>Our study clearly showed that tree size is an important driver of intraspecific variations in the key leaf traits of Pinus koraiensis in a natural forest. We also emphasize the importance of DBH or tree height varies depending on leaf traits, suggesting various mechanisms of size effects on the intraspecific variations in leaf traits. We suggest that ecological significance of leaf trait variations needs reconsideration incorporating tree size effect.</li> </ol>

opencc-zeroDec 2010View details →

Data from: What makes a leaf tough? Patterns of correlated evolution between leaf toughness traits and demographic rates among 197 shade-tolerant woody species in a neotropical forest

Slow-growing juveniles of shade-tolerant plant species are predicted to have tough leaves because of the high cost of leaf replacement in shade relative to potential carbon gain. We assessed the degree of correlated evolution among eight traits associated with leaf toughness and their relationships with growth and mortality rates of 197 tree and shrub species from the understory of the 50-hectare forest dynamics plot on Barro Colorado Island, Panama. Path analysis with phylogenetically independent contrasts revealed that leaves attained material toughness (resistance to fracture per unit fracture area) through increases in tissue density, percent cellulose per unit dry mass, and vein fracture toughness. Lamina density and cellulose content evolved independently, and thus represent different paths to material toughness. Structural toughness (resistance to fracture per unit fracture length) depended on material toughness and lamina thickness. Mortality rates of individuals 1-10 cm in stem diameter were negatively correlated with material toughness and lamina density, but were independent of structural toughness and cell wall fiber contents. Leaf toughness traits were uncorrelated with relative growth rates. These results imply that material toughness enhances resistance to natural enemies, which increases survival and offsets the biomass allocation cost of producing tough leaves in the shaded understory.

Data from: Juvenile divergence in adaptive traits among seven sympatric fish eco-morphs arises before moving to different lacustrine habitats

Identifying the mechanisms initiating sympatric diversification in vertebrates has remained a conceptual challenge. Here we analyze an assemblage of sympatric charr (Salvelinus malma) morphs from landlocked Lake Kronotskoe basin as a model to uncover the divergence pathways in freshwater fishes during the early life history stages. All morphs have distinct developmental biology, but a similar developmental rate retardation compared to the ancestor. Our study reveals that adult morphological differences, which acquire functionality at maturation, originate in the early juvenile stages due to heterochrony in skeletogenesis and allometric changes triggered by variation in metabolic activity. The craniofacial differences among the morphs result from asynchronous development of several skeletal modules. The accelerated ossification of teeth-armed bones occurs in predatory feeding morphs, while cranial cover ossification is promoted in benthivorous morphs. These contrasting growth patterns have led to seven phenotypes that span a range far beyond the ancestral variability. The most distinct morphs are a riverine-spawning, epilimnetic predator and a lacustrine-spawning, profundal benthic feeder. Taken together, we argue that the adaptive morphological differentiation in these sympatric freshwater fishes is driven by diverging patterns in ossification rate and metabolic activity against a background of uneven somatic growth. This divergence is primarily associated with basic environmental differences on the nursery grounds that might be unrelated to resource use. This non-heritable phenotype divergence is then exposed to natural selection that could result in further adaptive genetic changes.

opencc-zeroDec 2015View details →

Data from: Bat trait, genetic and pathogen data from large-scale investigations of African fruit bats (Eidolon helvum)

Bats, including African straw-coloured fruit bats (Eidolon helvum), have been highlighted as reservoirs of many recently emerged zoonotic viruses. This common, widespread and ecologically important species was the focus of longitudinal and continent-wide studies of the epidemiological and ecology of Lagos bat virus, henipaviruses and Achimota viruses. Here we present a spatial, morphological, demographic, genetic and serological dataset encompassing 2827 bats from nine countries over an 8-year period. Genetic data comprises cytochrome b mitochondrial sequences (n=608) and microsatellite genotypes from 18 loci (n=544). Tooth-cementum analyses (n=316) provide rare age-specific serologic data for a lyssavirus, a henipavirus and two rubulaviruses. This dataset contributes a substantial volume of data on the ecology of E. helvum and its viruses and will be valuable for a wide range of studies, including viral transmission dynamic modelling in age-structured populations, investigation of seasonal reproductive asynchrony in wide-ranging species, ecological niche modelling, inference of island colonisation history, exploration of relationships between island and body size, and various spatial analyses of demographic, morphometric or serological data.

Data from: Male-limited secondary sexual trait interacts with environment in determining female fitness

Selection for secondary sexual traits (SSTs) elaboration may increase intralocus sexual conflict over the optimal values of traits expressed from shared genomes. This conflict can reduce female fitness, and the resulting gender load can be exacerbated by environmental stress, with consequences for a population's ability to adapt to novel environments. However, how the evolution of SSTs interacts with environment in determining female fitness is not well understood. Here, we investigated this question using replicate lines of bulb mites selected for increased or decreased prevalence of a male SST—thickened legs used as weapons. The fitness of females from these lines was measured at a temperature to which the mites were adapted (24°C), as well as at two novel temperatures: 18°C and 28°C. We found the prevalence of the SST interacted with temperature in determining female fecundity. At 28°C, females from populations with high SST prevalence were less fecund than females from populations in which the SST was rare, but the reverse was true at 18°C. Thus, a novel environment does not universally depress female fitness more in populations with a high degree of sexually selected dimorphism. We discuss possible consequences of the interaction we detected for adaptation to novel environments.

Data from: Acclimation of leaf traits in seasonal light environments: are non-native species more plastic?

1. In temperate deciduous forests, understory light environments vary dramatically throughout spring, summer, and autumn due to tree canopy leaf display. This variability in light level is a physiological challenge for understory species that produce sun-adapted leaves in the spring before being shaded by the tree canopy. Similarly, some understory species display leaves late into autumn after the tree canopy senesces. 2. Many species in North American deciduous forests with extended leaf display are not native to North America. Since many non-native species have been shown to have greater plasticity than natives, we hypothesized that leaves of non-native species may be more plastic with respect to seasonal light changes than natives, and that this plasticity may allow them to assimilate more carbon in the same environment. 3. We measured leaf traits and photosynthetic capacity of 17 native and 13 non-native understory shrub species in a common garden in Syracuse, New York, during spring, summer, and autumn. We tested for the contribution of seasonal mean and variance (plasticity) of leaf traits to a species' average photosynthetic rate and total leaf production. We also analyzed the extent to which leaf adjustments depended on whether plants continued to produce new leaves over the growing season. 4. Leaf traits of both native and non-native species varied seasonally, but plasticity varied in extent and contribution to overall carbon gain. Non-native species had the highest seasonal plasticity, but, contrary to our hypothesis, such plasticity did not contribute to their overall carbon gain. However, leaf trait plasticity was adaptive for native species that continued to produce leaves throughout the year, primarily due to increases in quantum efficiency and electron transport rate in leaves produced mid-year compared to leaves produced early in the year. 5. Synthesis. Despite large adjustments in leaf traits across seasonal light environments for both native species and non-native species, we found little evidence that leaf-level plasticity drives non-native invasion or contributes strongly to annual carbon gain or productivity in understory species. Instead, differences in mean leaf traits across seasons are sufficient to explain carbon gain advantages of non-native woody species in deciduous forests.

Data from: Adding landscape genetics and individual traits to the ecosystem function paradigm reveals the importance of species functional breadth

Animal pollination mediates both reproduction and gene flow for the majority of plant species across the globe. However, past functional studies have focused largely on seed production; although useful, this focus on seed set does not provide information regarding species-specific contributions to pollen-mediated gene flow. Here we quantify pollen dispersal for individual pollinator species across more than 690 ha of tropical forest. Specifically, we examine visitation, seed production, and pollen-dispersal ability for the entire pollinator community of a common tropical tree using a series of individual-based pollinator-exclusion experiments followed by molecular-based fractional paternity analyses. We investigate the effects of pollinator body size, plant size (as a proxy of floral display), local plant density, and local plant kinship on seed production and pollen-dispersal distance. Our results show that while large-bodied pollinators set more seeds per visit, small-bodied bees visited flowers more frequently and were responsible for more than 49% of all long distance (beyond 1 km) pollen-dispersal events. Thus, despite their size, small-bodied bees play a critical role in facilitating long-distance pollen-mediated gene flow. We also found that both plant size and local plant kinship negatively impact pollen dispersal and seed production. By incorporating genetic and trait-based data into the quantification of pollination services, we highlight the diversity in ecological function mediated by pollinators, the influential role that plant and population attributes play in driving service provision, and the unexpected importance of small-bodied pollinators in the recruitment of plant genetic diversity.

Data from: Intraspecific trait variation and trade-offs within and across populations of a toxic dinoflagellate

Intraspecific trait diversity can promote the success of a species, as complementarity of functional traits within populations may enhance its competitive success and facilitates resilience to changing environmental conditions. Here, we experimentally determined the variation and relationships between traits in 15 strains of the toxic dinoflagellate Alexandrium ostenfeldii derived from two populations. Measured traits included growth rate, cell size, elemental composition, nitrogen uptake kinetics, toxin production and allelochemical potency. Our results demonstrate substantial variation in all analyzed traits both within and across populations, particularly in nitrogen affinity, which was even comparable to interspecific variation across phytoplankton species. We found distinct trade-offs between maximum nitrogen uptake rate and affinity, and between defensive and competitive traits. Furthermore, we identified differences in trait variation between the genetically similar populations. The observed high trait variation may facilitate development and resilience of harmful algal blooms under dynamic environmental conditions.

Data from: Quantifying the effects of ecological constraints on trait expression using novel trait-gradient analysis parameters

1. Complex processes related to biotic and abiotic forces can impose limitations to assembly and composition of plant communities. Quantifying the effects of these constraints on plant functional traits across environmental gradients, and among communities, remains challenging. We define ecological constraint (Ci) as the combined, limiting effect of biotic interactions and environmental filtering on trait expression (i.e., the mean value and range of functional traits). 2. Here we propose a set of novel parameters to quantify this constraint by extending the trait-gradient analysis (TGA) methodology. The key parameter is ecological constraint, which is dimensionless and can be measured at various scales, e.g., on population and community levels. It facilitates comparing the effects of ecological constraints on trait expressions across environmental gradients, as well as within and among communities. 3. We illustrate the implementation of the proposed parameters using the bark thickness of 14 woody species along an aridity gradient on granite outcrops in southwestern Australia. We found a positive correlation between increasing environmental stress and strength of ecological constraint on bark thickness expression. Also, plants from more stressful habitats (shrublands on shallow soils and in sun-exposed locations) displayed higher ecological constraint for bark thickness than plants in more benign habitats (woodlands on deep soils and in sheltered locations). 4. The relative ease of calculation and dimensionless nature of Ci allow it to be readily implemented at various scales and make it widely applicable. It therefore has the potential to advance the mechanistic understanding of the ecological processes shaping trait expression. Some future applications of the new parameters could be investigating the patterns of ecological constraints i) among communities from different regions, ii) on different traits across similar environmental gradients, and iii) for the same trait across different gradient-types.

Data from: Biophysical dependences among functional wood traits

1. Wood properties and especially wood density have been used as functional traits organized along major axes of species life history and strategy. Beyond statistical analyses, a better mechanistic understanding of relationships among wood traits is essential for ecologically relevant interpretation of wood trait variations. 2. A set of theoretical relationships mechanistically linking wood basic density with some other wood traits is derived from cellular material physics. These theoretical models picture basic physical constraints and thus provide null-hypotheses for further ecological studies. Analysis is applied to data from two original datasets and several datasets extracted from literature. 3. Results emphasize the strong physical constraint behind the link between basic density and maximal storable water on the one hand, and elastic modulus on the other hand. Beyond these basic physical constraints, the developed framework reveals physically less expected trends: the amount of free water available for physiological needs increases in less dense wood of fast growing species, the cell wall stiffness decreases with density in temperate species and is higher in sapling stages in the rainforest understorey where competition for light is associated to high mechanical risk. 4. We emphasize the use of theoretically independent traits derived from models of cellular material physics to investigate the functional variation of wood traits together with their environmental and phylogenetic variations. Although the current study is limited to basic density, green wood lumen saturation and wood specific modulus, we further emphasize the identification of complementary independent wood traits representing other biomechanical functions, nutrient storage, hydraulic conductance and resistance to drought.