Showing papers in "Functional Ecology in 2018"

Fungal inoculants in the field: Is the reward greater than the risk?

Abstract: Biofertilizers are a large part of the global agricultural economy. Recently, there has been an increase in the number of companies producing fungal inoculants. Whether these inoculants are useful is not clear; they are difficult to monitor in the field. The unintended consequences of inoculants in natural systems is not known, but if invasive, they may pose a threat to soil and plant biodiversity and ecosystem functioning. A plain language summary is available for this article.

C:N:P stoichiometry in China's forests: From organs to ecosystems

Abstract: Summary Ecological stoichiometry connects different levels of biology, from the gene to the globe, by scaling up elemental ratios (e.g., carbon [C], nitrogen [N], and phosphorus [P]). Thus, ecological stoichiometry could be a powerful tool for revealing certain physiological processes of plants. However, C:N:P stoichiometry remains unclear at the community and ecosystem level, despite it being potentially important for primary productivity. In this study, we measured the C, N, and P content of different plant organs, litter, and soil in 9 natural forest ecosystems (cold-temperate to tropical forests along a 3700-km transect in China) to explore C:N:P stoichiometry and the main influencing factors. C:N:P stoichiometry was evaluated for different components in the forest ecosystems (plant community, soil, litter, and ecosystem) and, at the community level, for different organs (leaves, branches, trunks, and roots) from 803 plant species. The ratios of C:P and N:P decreased with increasing latitude, with spatial patterns being primarily regulated by climate. Interestingly, the homeostasis of N, P, and N:P was highest in leaves, followed by branches, roots, and trunk, supporting the hypothesis that more active organs have a higher capacity to maintain relatively stable element content and ratios. At the community level, the leaf N:P ratio indicated increasing P limitation in forests of lower latitude (i.e., more southerly) in China's forests. Our findings demonstrate the spatial patterns of C:N:P stoichiometry and the strategies of element distribution among different organs in a plant community, providing important data on C:N:P to improve the parameterization of future ecological models. This article is protected by copyright. All rights reserved.

Deciphering the associations between soil microbial diversity and ecosystem multifunctionality driven by long‐term fertilization management

Abstract: An increasing number of studies indicate that microbial diversity plays a crucial role in the mediation of ecosystem multifunctionality (EMF) in natural ecosystems. However, this point remains mostly overlooked in managed ecosystems, especially in agriculture. Here, we compiled promising strategies for the targeted exploitation of the associations between microbial diversity and EMF of agricultural soils using samples from two long-term (more than 30 years) experimental field sites in southern China. The two sites experienced a similar monsoon climate and fertilization management practices. We used high-throughput amplicon sequencing, structural equation modelling and random forest analysis, to analyse our data and validate our hypotheses. We found that soil physiochemical properties and the C-, N-, P- and S-cycle enzyme activities were increased with the increase in microbial diversity. Specifically, a positive linear relationship was observed between microbial diversity and EMF, which was mediated by long-term fertilization management via changes in soil microbial communities and physiochemical properties. Random forest analysis and SEM showed that the important role of microbial diversity on EMF was maintained even when simultaneously taking multiple multifunctionality drivers (soil physiochemical properties, soil aggregation and enzymatic patterns) into account. In addition, microbial diversity, C-cycle enzyme activity and pH value are feasible predictors of EMF; these factors were shown to be the main drivers of EMF of arable soils. Our findings suggest that there may be a limited degree of multifunctional redundancy in arable soils. The relationship we observed between microbial diversity and EMF suggests that management practices that foster more diverse soil microbial communities may have the potential to improve the functioning of agroecosystems. plain language summary

Atmospheric nitrogen deposition in terrestrial ecosystems: Its impact on plant communities and consequences across trophic levels

Abstract: The global nitrogen cycle has been greatly perturbed by human activities resulting in elevated nitrogen deposition in many parts of the world. The threat nitrogen deposition poses to ecosystem function and biodiversity is increasingly recognised. In terrestrial systems, impacts on the plant community are mainly through eutrophication and soil acidification. Interactions with secondary environmental drivers such as extreme weather and disease are also key mechanisms. Impacts on consumers can be caused by changes in the quality or quantity of food as a result of changes in food plant chemistry or species composition, changes in vegetation structure leading to a change in the availability of prey species, nesting sites or cooled microclimates or changes in the phenology of plants leading to causing phenological asynchrony. Primary consumers have received considerably less research attention than plants but negative impacts have been observed for both folivorous insects and pollinators. Mammal herbivores have received little research attention. New analysis of changes in plant traits along a gradient of nitrogen deposition in the UK shows that plants pollinated by large bees were negatively associated with N deposition whilst low pH was associated with lower nectar production, reduced occurrence of plants pollinated by long‐tongued insects and a reduction in plants with larger floral units. Very few studies have investigated the effects on secondary consumers, but those that have suggest that there are likely to be negative impacts. This review identifies considerable knowledge gaps in the impacts of N deposition on higher tropic levels and highlights that for many groups, knowledge of N deposition impacts is patchy at best. Evidence that has been collected suggests that there are likely to be impacts on primary and secondary consumers making this a priority area for investigation.

Soil organic matter availability and climate drive latitudinal patterns in bacterial diversity from tropical to cold temperate forests

Abstract: Bacteria are one of the most abundant and diverse groups of micro-organisms and mediate many critical terrestrial ecosystem processes. Despite the crucial ecological role of bacteria, our understanding of their large-scale biogeography patterns across forests, and the processes that determine these patterns lags significantly behind that of macroorganisms. Here, we evaluated the geographic distributions of bacterial diversity and their driving factors across nine latitudinal forests along a 3,700-km north-south transect in eastern China, using high-throughput 16S rRNA gene sequencing. Four of 32 phyla detected were dominant: Acidobacteria, Actinobacteria, Alphaproteobacteria and Chloroflexi (relative abundance>5%). Significant increases in bacterial richness and phylogenetic diversity were observed for temperate forests compared with subtropical or tropical forests. The soil organic matter (SOM) mineralisation rate (SOMmin, an index of SOM availability) explained the largest significant variations in bacterial richness. Variation partition analysis revealed that the bacterial community structure was closely correlated with environmental variables and geographic distance, which together explained 80.5% of community variation. Among all environmental factors, climatic features (MAT and MAP) were the best predictors of the bacterial community structure, whereas soil pH and SOMmin emerged as the most important edaphic drivers of the bacterial community structure. Plant functional traits (community weighted means of litter N content) and diversity resulted in weak but significant correlations with the bacterial community structure. Our findings provide new evidence of bacterial biogeography patterns from tropical to cold temperate forests. Additionally, the results indicated a close linkage among soil bacterial diversity, climate and SOM decomposition, which is critical for predicting continental-scale responses under future climate change scenarios and promoting sustainable forest ecosystem services. A is available for this article.

Variation of stomatal traits from cold-temperate to tropical forests and association with water use efficiency

Abstract: 1.Stomata control carbon and water vapor exchange between leaves and the atmosphere, thus it can influence water use efficiency and reflect plant adaptation to climate. However, the spatial patterns of leaf stomatal traits and relationships between stomatal trait and water use efficiency across natural communities remain unclear. 2.We measured stomatal density, stomatal size, and stomatal area fraction for 737 plant species from nine forests ranging from tropical to cold-temperate forests. 3.Stomatal density, stomatal size, and stomatal area fraction were all log-normally distributed, and different across species, plant functional groups (trees, shrubs, and herbs), and communities. At the regional scale, variation in stomatal traits was primarily related to species, followed by climate and soil types. 4.The community-weighted mean of stomatal size increased linearly with latitude, whereas those of stomatal density and stomatal area fraction showed humpbacked relationship. The community-weighted mean of stomatal area fraction was correlated with climatic aridity, consistent with the adaptation strategies of plant species to achieve high maximum rates of gas exchange in arid regions when water is available. Further, community-weighted mean of stomatal area fraction was positively correlated with water use efficiency in natural forest communities, indicating that plants have lower stomatal conductance in order to adapt greater aridity conditions. 5.These findings highlight the strong associations of stomatal traits with plant functional group and climate at a regional scale, representing the adaptation strategies of stomatal traits across natural forest communities to climate. This article is protected by copyright. All rights reserved.

Soil fertility and species traits, but not diversity, drive productivity and biomass stocks in a Guyanese tropical rainforest

Abstract: Tropical forests store and sequester large amounts of carbon in above- and below-ground plant biomass and soil organic matter (SOM), but how these are driven by abiotic and biotic factors remains poorly understood. Here, we test the effects of abiotic factors (light variation, caused by logging disturbance, and soil fertility) and biotic factors (species richness and functional trait composition) on biomass stocks (above-ground biomass, fine root biomass), SOM and productivity in a relatively monodominant Guyanese tropical rainforest. This forest grows on nutrient-poor soils and has few species that contribute most to total abundance. We, therefore, expected strong effects of soil fertility and species’ traits that determine resource acquisition and conservation, but not of diversity. We evaluated 6 years of data for 30 0.4-ha plots and tested hypotheses using structural equation models. Disturbance increased productivity but decreased above-ground biomass stocks. Soil phosphorus (P) enhanced above-ground biomass and productivity, whereas soil nitrogen reduced fine root biomass. In contrast to expectations, trait values representing acquisitive strategies (e.g. high leaf nutrient concentration) increased biomass stocks, possibly because they indicate higher nutrient absorption and thus higher biomass build-up. However, under harsh conditions where biomass increase is slow, acquisitive trait values may increase respiration and vulnerability to hazards and therefore increase biomass loss. As expected, species richness did not affect productivity. We conclude that light availability (through disturbance) and soil fertility—especially P—strongly limit forest biomass productivity and stocks in this Guyanese forest. Low P availability may cause strong environmental filtering, which in turn results in a small set of dominant species. As a result, community trait composition but not species richness determines productivity and stocks of biomass and SOM in tropical forest on poor soils. A plain language summary is available for this article.

Trait selection and community weighting are key to understanding ecosystem responses to changing precipitation regimes

Abstract: 1Department of Biology, Colorado State University, Fort Collins, Colorado; 2Graduate Degree Program in Ecology, Colorado State University, Fort Collins, Colorado; 3Department of Forest and Rangeland Stewardship, Colorado State University, Fort Collins, Colorado; 4Hawkesbury Institute for the Environment, Western Sydney University, Richmond, NSW, Australia; 5Department of Bio-agricultural Sciences and Pest Management, Colorado State University, Fort Collins, Colorado and 6Università degli studi di Trieste, TS, Trieste, Italy

Variation in leaf anatomical traits from tropical to cold‐temperate forests and linkage to ecosystem functions

Abstract: Leaf anatomical traits may reflect plants adaption to environmental changes and influence ecosystem functions, as they regulate light absorption and gas exchange to some extent. Here, we hypothesized that leaf anatomical traits were closely related to gross primary productivity (GPP) because photosynthesis commonly occurs in the chloroplasts of palisade and spongy tissues in leaf. Eight leaf anatomical traits were measured in 916 plant species inhabiting from tropical to cold-temperate forests in eastern China: adaxial epidermis thickness (AD), abaxial epidermis thickness (AB), leaf thickness (LT), palisade tissue thickness (PT), and spongy tissue thickness (ST), palisade–spongy tissue ratio (PT/ST), palisade tissue–leaf thickness ratio (PT/LT), and spongy tissue–leaf thickness ratio (ST/LT). Leaf anatomical traits showed significant latitudinal patterns at species, plant functional group (PFG), and community levels (p < .05), and they differed between PFG and community. Temperature and precipitation were the main factors influencing AD, AB, PT/ST, and PT/LT, explaining 33–72% of the total variation at large scale. Furthermore, AB, LT, PT/ST, and PT/LT were significantly correlated with the aridity index. Our findings filled the data gap of plant anatomical traits at regional scales, and broadened current knowledge on the adaptation strategies of plant anatomical traits, which also provided new evidence for linkages of plant traits and functioning across natural communities. A plain language summary is available for this article.

Comparing traits of native and alien plants: can we do better?

Abstract: A frequent question in invasion ecology is whether the traits of alien plant species differ from natives. This question is increasingly addressed at the plant community scale to assess the role trait differences play in community assembly. Nevertheless, there remains considerable debate as to the value of native vs. alien trait comparisons. Recommendations are made to address seven conceptual and methodological limitations in current approaches used to assess trait differences between native and alien plants: account for spatial scale dependence, make an informed choice of traits, evaluate multiple trait dimensions, incorporate intraspecific trait variation, use appropriate null models, examine environmental gradients, and assess temporal variation in trait spectra. Tackling these limitations will dramatically improve the value of native vs. alien trait comparisons. Traits should be selected based on expectations of abiotic and/or biotic constraints. Phylogenetic distances can provide valuable insights but are no substitute for the measurement of individual traits when contrasting alien and native species. An ideal set of traits would include one or more leaf, stem, seed and root traits as well as flowering phenology and plant height at maturity. Comparisons of intraspecific trait variation among native and alien species within the same plant community are rare but could improve predictions of interspecific competition and the response of communities to plant invasions. The full plant community should be examined rather than selected species subsets and comparisons between native and alien species traits are better undertaken at a neighbourhood scale. The frequency distribution of alien and native species traits may change over time through competitive exclusion as well as contemporary evolution. Repeated surveys of species abundances and traits are required to understand the consequences of trait differences between aliens and natives for plant community assembly. Analyses of the role of species traits in plant invasions need to quantify differences in a priori identified traits within communities along suitable environmental gradients and test hypothetical trait patterns against appropriate null expectations. The infrequent application of such approaches may explain the limited generalisations regarding the role of trait differences between native and alien species in the invasion of plant communities. A plain language summary is available for this article.

Soil and vegetation carbon turnover times from tropical to boreal forests

Abstract: Terrestrial ecosystems currently function as a net carbon (C) sink for atmospheric C dioxide (CO2), but whether this C sink can persist with global climate change is still uncertain. Such uncertainty largely comes from C turnover time in an ecosystem, which is a critical parameter for modelling C cycle and evaluating C sink potential. Our current understanding of how long C can be stored in soils and vegetation and what controls spatial variations in C turnover time on a large scale is still very limited. We used data on C stocks and C influx from 2,753 plots in vegetation and 1,087 plots in soils and investigated the spatial patterns as well controlling factors of C turnover times across forest ecosystems in eastern China. Our results showed a clear latitudinal pattern of C turnover times, with the shortest turnover times in the low-latitude zones and the longest turnover times in the high-latitude zones. Mean annual temperature and mean annual precipitation were the most important controlling factors on soil C turnover times, while forest age accounted for the majority of variations in the vegetation C turnover times. Forest origin (planted or natural forest) was also responsible for the variations in vegetation C turnover times, while forest type and soil properties were not the dominant controlling factors. Our study highlights the different dominant controlling factors in soil and vegetation C turnover times and different mechanisms underlying above- and below-ground C turnover. These findings are essential to better understand (and reduce uncertainty) in predictive models of coupled C–climate system. A plain language summary is available for this article.

Effects of disturbance frequency and severity on plant traits: An assessment across a temperate flora

Abstract: Summary 1.Recent analyses of plant traits across large sets of species have revolutionized our understanding of plant functional differentiation. However, understanding of ecological relevance of this differentiation is contingent upon knowledge of environmental preferences of species, namely along gradients of disturbance and productivity for which no quantitative data were available until recently. 2.We examined the relationships of key functional traits (life-history categories, leaf-height-seed traits, clonal growth and bud bank traits) in the herb-dominated flora of Central Europe to species niche positions along the gradients of disturbance frequency, disturbance severity and productivity. 3.Life-history categories and bud bank size showed the strongest response to disturbance and productivity, whereas relationship of leaf-height-seed traits were much weaker. A number of traits, including clonal growth form and bud bank size, showed significantly unimodal response to disturbance frequency. Responses of many traits to disturbance frequency were different from their responses to disturbance severity. 4.Our findings support the notions that disturbance and productivity are key gradients of species functional differentiation and that disturbance severity and frequency select for different trait suites. Further the data indicate that in a predominantly herbaceous flora the traits of lifespan, clonal growth and resprouting show stronger relationship to the environment than the leaf-height-seed traits, which are more important in floras with high proportions of woody species. Since most previous trait analyses are based on woody-plant-dominated floras, patterns revealed in a herb-dominated flora deepen our understanding of the full range of variation within the plant kingdom. This article is protected by copyright. All rights reserved.

Delivering the promises of trait-based approaches to the needs of demographic approaches, and vice versa

Abstract: Few facets of biology vary more than functional traits and life-history traits. To explore this vast variation, functional ecologists and population ecologists have developed independent approaches that identify the mechanisms behind and consequences of trait variation.Collaborative research between researchers using trait-based and demographic approaches remains scarce. We argue that this is a missed opportunity, as the strengths of both approaches could help boost the research agendas of functional ecology and population ecology.This special feature, which spans three journals of the British Ecological Society due to its interdisciplinary nature, showcases state-of-the-art research applying trait-based and demographic approaches to examine relationships between organismal function, life history strategies and population performance across multiple kingdoms. Examples include the exploration of how functional trait × environment interactions affect vital rates and thus explain population trends and species occurrence; the coordination of seed traits and dispersal ability with the pace of life in plants; the incorporation of functional traits in dynamic energy budget models; or the discovery of linkages between microbial functional traits and the fast-slow continuum.Despite their historical isolation, collaborative work between functional ecologists and population ecologists could unlock novel research pathways. We call for an integrative research agenda to evaluate which and when traits are functional, as well as their ability to describe and predict life history strategies and population dynamics. We highlight promising, complementary research avenues to overcome current limitations. These include a more explicit linkage of selection gradients in the context of functional trait-vital rate relationships, and the implementation of standardised protocols to track changes in traits and vital rates over time at the same location and individuals, thus allowing for the explicit incorporation of trade-offs in analyses of covariation of functional traits and life-history traits.

Different phylogenetic and environmental controls of first‐order root morphological and nutrient traits: Evidence of multidimensional root traits

Abstract: Summary 1.Although fine roots are essential for the water and nutrient uptake of plants, there is limited understanding of root trait variation and the underlying mechanism. 2.Here, six first-order root morphological and chemical traits were measured for 181 species from eight subtropical and boreal forests to test the hypothesis of different phylogenetic and environmental regulations of root morphological and nutrient traits result in the multidimensions of root traits. 3.Two independent root trait dimensions between root thickness and nutrient traits were detected at both species and community levels. At the species level, diameter-related traits were mainly restricted by phylogenetic structure and showed little plasticity to the changing environments, whereas the variation in woody root nutrient was influenced significantly by soil variables. For community-level traits, the diameter-related axis scores of principal component analysis (PCA) were mainly driven by mean annual temperature (MAT) through shifting species composition, whereas the root nutrient-related axis scores were strongly influenced by soil P availability. 4.From both species and community levels, our study confirms, that the root-thickness-related dimension and root nutrient dimension represent new support for the multidimensionality of root traits which are driven by different selection pressure. This study also underlines that the community-aggregated traits might serve as a promising avenue to improve our understanding of community assemblage processes, allowing us to predict changes of vegetation distributions in a changing climate. This article is protected by copyright. All rights reserved.

Linking diversity, synchrony and stability in soil microbial communities

Abstract: 1. It is becoming well established that plant diversity is instrumental in stabilizing the temporal functioning of ecosystems through population dynamics and the so-called insurance or portfolio effect. However, it is unclear whether diversity-stability relationships and the role of population dynamics in soil microbial communities parallel those in plant communities. 2. Our study took place in a long-term land management experiment with and without perturbation to the soil ecosystem by tilling. We assessed the impacts of the soil perturbation on the diversity, synchrony and stability relationships in soil fungal and bacterial communities. 3. We found that the perturbation to the soil ecosystem not only reduced the abundance and richness of the fungal community, but it also reduced the temporal stability in both bacterial and fungal abundance. The fungal community abundance was destabilized by soil tilling due to reduced richness and increased temporal variation of individual taxa. In contrast, soil tilling destabilized the bacterial community abundance by reducing the temporal variation of individual taxa. Both bacterial and fungal community abundances were more temporally variable when taxa fluctuated more synchronously through time. 4. Our results show that land management practices, such as tilling, can destabilize soil microbial abundance by reducing the richness and disrupting the temporal dynamics belowground. However, the differences in the mechanisms that underlie the temporal variations in fungal and bacterial net abundances suggests that the mechanisms that drive the stability can differ among guilds of organisms within the same system. The different temporal responses between the fungal and bacterial communities are likely linked to changes in edaphic properties resulting from the physical alteration of the soil structure.

Decreased mitochondrial metabolic requirements in fasting animals carry an oxidative cost.

Abstract: Many animals experience periods of food shortage in their natural environment. It has been hypothesised that the metabolic responses of animals to naturally-occurring periods of food deprivation may have long-term negative impacts on their subsequent life-history.In particular, reductions in energy requirements in response to fasting may help preserve limited resources but potentially come at a cost of increased oxidative stress. However, little is known about this trade-off since studies of energy metabolism are generally conducted separately from those of oxidative stress.Using a novel approach that combines measurements of mitochondrial function with in vivo levels of hydrogen peroxide (H2O2) in brown trout (Salmo trutta), we show here that fasting induces energy savings in a highly metabolically active organ (the liver) but at the cost of a significant increase in H2O2, an important form of reactive oxygen species (ROS).After a 2-week period of fasting, brown trout reduced their whole-liver mitochondrial respiratory capacities (state 3, state 4 and cytochrome c oxidase activity), mainly due to reductions in liver size (and hence the total mitochondrial content). This was compensated for at the level of the mitochondrion, with an increase in state 3 respiration combined with a decrease in state 4 respiration, suggesting a selective increase in the capacity to produce ATP without a concomitant increase in energy dissipated through proton leakage. However, the reduction in total hepatic metabolic capacity in fasted fish was associated with an almost two-fold increase in in vivo mitochondrial H2O2 levels (as measured by the MitoB probe).The resulting increase in mitochondrial ROS, and hence potential risk of oxidative damage, provides mechanistic insight into the trade-off between the short-term energetic benefits of reducing metabolism in response to fasting and the potential long-term costs to subsequent life-history traits.

Trait matching and phylogeny as predictors of predator–prey interactions involving ground beetles

Abstract: Summary With global change modifying species assemblages, our success in predicting ecosystem level consequences of these new communities will depend, in part, on our ability to understand biotic interactions. Current food web theory considers interactions between numerous species simultaneously, but descriptive models are unable to predict interactions between newly co-occurring species. Incorporating proxies such as functional traits and phylogeny into models could help infer predator/ prey interactions. Here we used trait-matching between predator feeding traits and prey vulnerability traits, along with phylogeny (used as a proxy for chemical defence and other traits difficult to document), to infer predatory interactions using ground beetles as model organisms. A feeding experiment was conducted involving 20 ground beetle and 115 prey species to determine which pair of species did or did not interact. Eight predator and four prey functional traits were measured directly on specimens. Then, using a modeling approach based on the matching-centrality formalism, we evaluated 511 predictive ecological models that tested different combinations of all predator and prey functional traits, and phylogenetic information. The most parsimonious model accurately predicted 81 % of the observed realized and unrealized interactions, using phylogenetic information and the trait-matches predator biting force/ prey cuticular toughness and predator/ prey body size ratio. The best trait-based models predicted correctly >80 % which species interact (realized interactions), but predict 75 %. The matching of predator biting force and prey cuticular toughness demonstrated a better predictive power than the commonly used predator/ prey body size ratio. Our novel model combining both functional traits and phylogeny extends beyond existing descriptive approaches and could represent a valuable tool to predict consumer/ resource interactions of newly introduced species and to resolve cryptic food webs. This article is protected by copyright. All rights reserved.

Life in the intertidal: Cellular responses, methylation and epigenetics

Abstract: 1. Phenotypic plasticity is essential for the persistence of organisms under changing environmental conditions but the control of the relevant cellular mechanisms including which genes are involved and the regulation of those genes remains unclear. One way to address this issue is to evaluate links between gene expression, methylation and phenotype using transplantation and common garden experiments within genetically homogeneous populations. 2. This approach was taken using the Antarctic limpet Nacella concinna. In this species, two distinct phenotypes are associated with the intertidal and subtidal zones. The in situ gene expression and methylation profiles of intertidal and subtidal cohorts were directly compared before and after reciprocal transplantation as well as after a common garden acclimation to aquarium conditions for 9 months. 3. Expression profiles showed significant modulation of cellular metabolism to habitat zone with the intertidal profile characterised by transcription modules for antioxidant production, DNA repair and the cytoskeleton reflecting the need to cope with continually fluctuating and stressful conditions including wave action, UV irradiation and desiccation. 4. Transplantation had an effect on gene expression. The subtidal animals transplanted to the intertidal zone modified their gene expression patterns towards that of an intertidal profile. In contrast, many of the antioxidant genes were still differentially expressed in the intertidal animals several weeks after transplantation into the relatively benign subtidal zone. 5. Furthermore, a core of genes involved in antioxidation was still preferentially expressed in intertidal animals at the end of the common garden experiment. Thus, acclimation in an aquarium tank for 9 months did not completely erase the intertidal gene expression profile. 6. Significant methylation differences were measured between intertidal and subtidal animals from the wild and after transplantation, which were reduced on common garden acclimation. This suggests that epigenetic factors play an important role in physiological flexibility associated with environmental niche.

Testing the stability of behavioural coping style across stress contexts in the Trinidadian guppy

Abstract: Within populations, individuals can vary in stress response, a multivariate phenomenon comprising neuroendocrine, physiological and behavioural traits.Verbal models of individual stress "coping style" have proposed that the behavioural component of this variation can be described as a single axis, with each individual's coping style being consistent across time and stress contexts.Focusing on this behavioural component of stress response and combining repeated measures of multiple traits with a novel multivariate modelling framework, we test for the existence of coping style variation and assess its stability across contexts in the Trinidadian guppy (Poecilia reticulata).Specifically, we test the following hypotheses: (1) there exists repeatable among-individual behavioural (co)variation ("personality") within a mild stress context consistent with a risk-averse-risk-prone continuum of behavioural coping style, (2) there is population-level plasticity in behaviour as a function of stressor severity, (3) there is among-individual variation in plasticity (i.e. IxE), and (4) the presence of IxE reduces cross-context stability of behavioural coping style.We found significant repeatable among-individual behavioural (co)variation in the mild stress context (open field trial), represented as an I matrix. However, I was not readily described by a simple risk-averse-risk-prone continuum as posited by the original coping style model. We also found strong evidence for population-level changes in mean behaviour with increasing stressor severity (simulated avian and piscine predation risks).Single-trait analyses did show the presence of individual-by-environment interactions (IxE), as among-individual cross-context correlations were significantly less than +1. However, multitrait analysis revealed the consequences of this plasticity variation were minimal. Specifically, we found little evidence for changes in the structure of I between mild and moderate stress contexts overall, and only minor changes between the two moderate contexts (avian vs. piscine predator).We show that a multivariate approach to assessing changes in among-individual (co)variance across contexts can prevent the over-interpretation of statistically significant, but small, individual-by-environment effects. While behavioural flexibility enables populations (and individuals) to respond rapidly to changes in the environment, multivariate personality structure can be conserved strongly across such contexts. A plain language summary is available for this article.

Do carotenoid‐based ornaments entail resource trade-offs? An evaluation of theory and data

Abstract: Carotenoidbased displays have become textbook examples of honest signals of individual quality (Dugatkin, 2013). Although some studies have failed to find consistent evidence that carotenoidbased traits are related to physiological performance (Dale, 2000; Dowling & Mulder, 2006; Smith, Raberg, Ohlsson, Granbom, & Hasselquist, 2007), behavioural ecologists have generally embraced the idea that carotenoidbased coloration can serve as a conditiondependent signal of quality (AlonsoAlvarez et al., 2004; Hill, 1991; Kemp, Herberstein, & Grether, 2012; McGraw & Ardia, 2003; Peters, Denk, Delhey, & Kempenaers, 2004; Velando, BeamonteBarrientos, & Torres, 2006). Accordingly, recent research on carotenoidbased ornamentation has focused on the mechanisms by which coloration can be a reliable signal of fundamental aspects of performance, such as immune system function or avoidance of oxidative stress. Current discussions of the mechanisms that might create a link between carotenoid coloration and performance have been dominated by the resource tradeoff hypothesis, which proposes that carotenoid coloration is an honest signal of individual quality because only highquality individuals can allocate sufficient carotenoid resources away from critical physiological processes to achieve fullcolour ornamentation (Figure 1). The resource tradeoff hypothesis is founded on three key assumptions: (1) carotenoid pigments are limited resources such that most individuals do not possess sufficient carotenoids to maximize performance in all avenues simultaneously; (2) carotenoid pigments play important roles in physiological processes, particularly in immune response and/or antioxidant defence; and hence, (3) carotenoidbased ornaments reflect quality because only highquality individuals can allocate to both sides of the tradeoff associated with carotenoid pigments. The main purpose of this synthesis was to provide a critical assessment of these three major assumptions of the resource tradeoff hypothesis for explaining honesty in carotenoidbased coloration. We limit the scope of our discussion to studies of birds, which are the group of animals that have been most extensively studied with regard to carotenoid signalling. Received: 6 October 2017 | Accepted: 17 April 2018 DOI: 10.1111/1365-2435.13122

Contemporary climate-driven range shifts: Putting evolution back on the table

Abstract: As the climate continues to change, species are moving to track their climatic niches. Although we are gaining a clearer picture of where and how quickly species ranges are moving, a mechanistic understanding of these changes is still nascent. Evolutionary changes in ranges and range‐limiting traits over contemporary time‐scales have received relatively little attention, possibly due to the mismatch in scale between rapid contemporary range shifts and the historical evolution of species ranges over millions of years. But recent experimental work has shown that range‐limiting traits can evolve rapidly over decadal time‐scales, effectively putting evolution back on the table towards the goal of a mechanistic understanding of contemporary range shifts. Here, I review the role of evolution in shaping range shift responses to recent climate change from the perspective of the past (shared evolutionary history, or phylogenetic signal in range shifts and range‐limiting traits), present (variation in range‐limiting traits) and future (incorporating evolution of range‐limiting traits into range forecasts from species distribution models). In each of these areas, I found a critical role for evolution in understanding historical constraints and future changes in species ranges over contemporary time‐scales: shared evolutionary history may constrain range shift responses for some taxa; compensatory mechanisms of phenotypic plasticity and adaptive evolution can modulate the range shift response; and incorporating evolution into species distribution models can qualitatively alter forecasts of future range shifts. Yet, more can be done in this context, and so I conclude by outlining near‐ and long‐term goals for improving our understanding of the role of evolution in shaping species ranges in a rapidly changing world. A plain language summary is available for this article.

Global drivers of tree seedling establishment at alpine treelines in a changing climate

Abstract: 1. Alpine and Arctic treeline expansion depends on establishment of tree seedlings beyond the current treeline, which is expected to occur with climate warming. However, treelines often fail to res ...