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Evidence for phenotypic plasticity in brain size and the size of different brain parts is widespread, but experimental investigations into this effect remain scarce and are usually conducted using individuals from a single population. As the costs and benefits of plasticity may differ among populations, the extent of brain plasticity may also differ from one population to another. In a common garden experiment conducted with three-spined sticklebacks (Gasterosteus aculeatus) originating from four different populations, we investigated whether environmental enrichment (aquaria provided with structural complexity) caused an increase in the brain size or size of different brain parts compared to controls (bare aquaria). We found no evidence for a positive effect of environmental enrichment on brain size or size of different brain parts in either of the sexes in any of the populations. However, in all populations, males had larger brains than females, and the degree of sexual size dimorphism (SSD) in relative brain size ranged from 5.1 to 11.6% across the populations. Evidence was also found for genetically based differences in relative brain size among populations, as well as for plasticity in the size of different brain parts, as evidenced by consistent size differences among replicate blocks that differed in their temperature.

Climatic warming is a primary driver of change in ecosystems worldwide. Here, we synthesize responses of species richness and evenness from 187 experimental warming studies in a quantitative meta-analysis. We asked 1) whether effects of warming on diversity were detectable and consistent across terrestrial, freshwater and marine ecosystems, 2) if effects on diversity correlated with intensity, duration, and experimental unit size of temperature change manipulations, and 3) whether these experimental effects on diversity interacted with ecosystem types. Using multilevel mixed linear models and model averaging, we also tested the relative importance of variables that described uncontrolled environmental variation and attributes of experimental units. Overall, experimental warming reduced richness across ecosystems (mean log-response ratio = -0.091, 95% bootstrapped CI: -0.13, -0.05) representing an 8.9% decline relative to ambient temperature treatments. Richness did not change in response to warming in freshwater systems, but was more strongly negative in terrestrial (-11.8%) and marine (-10.5%) experiments. In contrast, warming impacts on evenness were neutral overall and in aquatic systems, but weakly negative on land (7.6%). Intensity and duration of experimental warming did not explain variation in diversity responses, but negative effects on richness were stronger in smaller experimental units, particularly in marine systems. Model-averaged parameter estimation confirmed these main effects while accounting for variation in latitude, ambient temperature at the sites of manipulations, venue (field versus lab), community trophic type, and whether experiments were open or closed to colonization. These analyses synthesize extensive experimental evidence showing declines in local richness with increased temperature, particularly in terrestrial and marine communities. However, the more variable effects of warming on evenness were better explained by the random effect of site identity, suggesting that effects on species' relative abundances were contingent on local species composition.

Eretmocerus warrae (Hymenoptera: Aphelinidae) is a specialist parasitoid that is used for the control of the greenhouse whitefly, Trialeurodes vaporariorum (Hemiptera: Aleyrodidae). We investigated how temperature affects the body-size, life-time oviposition, and longevity of E. warrae at different stages of life. The body-sizes of both this parasitoid and its host are influenced by temperature. Body-volume indices that reflect body-sizes fell by 47.7 % in T. vaporariorum compared with 57.6% in E. warrae when temperature increased from 20 to 32 °C. The life-time oviposition of female adults of E. warrae that grew at the immature developmental temperature of 20 °C was 86 ± 22 eggs, more than 66 ± 11 eggs at 26 °C, and 65 ± 23 eggs at 32 °C. Besides the influence on fecundity, temperature also influences the oviposition behaviour at the adult stage. More eggs were oviposited at 20 and 26 °C than at 32 °C. Higher temperatures reduced survival in the immature developmental stages and longevity in adults. Adult females lived for a maximum of 8.9 ± 1.8 days at 20 °C and laid a maximum of 97.4 ± 23.2 eggs when reared at 20 °C and maintained at 26 °C as adults. Adult body-size is positively correlated with life-time oviposition but not adult longevity. The results imply that temperature influences the nature of interactions between a parasitoid and its host. Larger wasps can live longer and parasitise more hosts, which should improve their performance as biological control agents.

In an increasingly anthropic world, humans have profound impacts on the distribution and behaviour of marine fishes. The increased human presence has modified fishesf antipredator behavioural responses, and consequently flight decisions, as a function of their changed perceptions of risk. Understanding how fish react to human presence can help identify the most vulnerable functional groups/species and estimate impacts caused by human disturbance. Shoal and body size are known to influence fish flight initiation distance (FID; the distance between the predator and prey when the prey begins to escape); however, few studies attempt to test the moderators of these relationships. Here, we present a comprehensive meta]analysis evaluating FID of fish in response to human presence. Specifically, we investigated six candidate moderators that could influence the relationship between FID with shoal and body size. Our results showed that individual fish size was strongly and positively correlated with FID and the most important moderator that explained the variance in individual body size]FID relationship was shoaling behaviour. However, and somehow surprisingly, we detected no significant relationship between shoal size and FID. We discuss how these results can inform the development of fish conservation strategies and ultimately assist in the management of marine protected areas.

Conodonts are among the first vertebrates to have evolved mineralized tooth-like structures. Among these, the so-called P1 elements are known to have been used to break down food and display a wide variety of morphologies. In particular, the repeated independent evolution of platform-like P1 elements have been suggested to correspond to similar functional constraints linked to diet. To test this hypothesis of convergence, we measured size (as element length) for various conodont taxa and used it as a proxy for trophic level. We then tested the correlation between size and platform presence/absence, both on raw data and in a phylogenetic context. Retaining or excluding the platform traits from the character matrix has limited impact on the resulting phylogeny. Contrary to platform presence/absence, size shows no phylogenetic signal. Using the raw data, size and platform presence appear positively correlated. That correlation, however, is no longer significant if one corrects for the phylogeny. We conclude that platform presence cannot be explained by an enlargement of the conodont element, be it via a trophic-level change or developmental constraints. This suggests that conodonts as a whole, and in particular platform-bearing conodonts, were an ecologically diverse group and that the various known platform types are likely to reflect different, rather than convergent, ecological niches.

Currently organisms are experiencing changes in their environment at an unprecedented rate. Therefore, the study of the contributions to and responses in traits linked to fitness is crucial, as they have direct consequences on a population's success in persisting under such a change. Daphnia is used as a model organism as the genus contains keystone primary consumers in aquatic food webs. A life-history table experiment (LHTE) using four species of Daphnia was conducted to compare variation in life-history traits among species across two different environmental conditions (high and low phosphorus availability). Results indicate that the food quality environment had the most impact on life-history traits, while genetic contributions to traits were higher at the species-level than clonal-level. Higher trait variation and species-level responses to P-limitation were more evident in reproductive traits, while growth traits were found to be less affected by food quality and had less variation. Exploring trait variation and potential plasticity in organisms is increasingly important to consider as a potential mechanism for population persistence given the fluctuations in environmental stressors we are currently experiencing.

The foraging behaviour of species determines their diet and, therefore, also emergent food-web structure. Optimal foraging theory (OFT) has previously been applied to understand the emergence of food-web structure through a consumer-centric consideration of diet choice. However, the resource-centric viewpoint, where species adjust their behaviour to reduce the risk of predation, has not been considered. We develop a mechanistic model that merges metabolic theory with OFT to incorporate the effect of predation risk on diet choice to assemble food webs. This 'predation-risk-compromise' (PR) model better captures the nestedness and modularity of empirical food webs relative to the classical optimal foraging model. Specifically, compared with optimal foraging alone, risk-mitigated foraging leads to more-nested but less-modular webs by broadening the diet of consumers at intermediate trophic levels. Thus, predation risk significantly affects food-web structure by constraining species' ability to forage optimally, and needs to be considered in future work.

Temporal variation in demographic processes can greatly impact population dynamics. Perturbations of statistical coefficients that describe demographic rates within matrix models have, for example, revealed that stochastic population growth rates (log(λs)) of fast life histories are more sensitive to temporal autocorrelation of environmental conditions than those of slow life histories. Yet, we know little about the mechanisms that drive such patterns. Here, we used a mechanistic, functional trait approach to examine the functional pathways by which a typical fast life history species, the macrodetrivore Orchestia gammarellus, and a typical slow life history species, the reef manta ray Manta alfredi, differ in their sensitivity to environmental autocorrelation if (a) growth and reproduction are described mechanistically by functional traits that adhere to the principle of energy conservation, and if (b) demographic variation is determined by temporal autocorrelation in food conditions. Opposite to previous findings, we found that O. gammarellus log(λs) was most sensitive to the frequency of good food conditions, likely because reproduction traits, which directly impact population growth, were most influential to log(λs). Manta alfredi log(λs) was instead most sensitive to temporal autocorrelation, likely because growth parameters, which impact population growth indirectly, were most influential to log(λs). This differential sensitivity to functional traits likely also explains why we found that O. gammarellus mean body size decreased (due to increased reproduction) but M. alfredi mean body size increased (due to increased individual growth) as food conditions became more favorable. Increasing demographic stochasticity under constant food conditions decreased O. gammarellus mean body size and increased log(λs) due to increased reproduction, whereas M. alfredi mean body and log(λs) decreased, likely due to decreased individual growth. Our findings signify the importance of integrating functional traits into demographic models as this provides mechanistic understanding of how environmental and demographic stochasticity affects population dynamics in stochastic environments.

Abalone (Haliotis spp.) are commercially important marine shellfish species worldwide. Knowledge about the physiology of abalone that impacts life-history traits is important for a better understanding of the biology of the species and the impact of stressful husbandry procedures at different seasons. The present study quantified the seasonal and diurnal variations in four physiological parameters of the European species Haliotis tuberculata, i.e. carbon aerial and aquatic respiration, calcification and excretion rates, and the effect of prolonged aerial exposure upon abalone aerial respiration. We also investigated the effect of individual size upon these physiological parameters. Aquatic respiration and calcification rates showed an allometric relationship with biomass. All parameters showed lower rates in cool season and higher rates in warmer season. Temperature was assumed to be the primary driver of the reported seasonal variability in physiological parameters, although reproductive needs and nutrition may also contribute to the observed patterns. Importantly, abalone did not stop calcifying in winter, and calcified more at night than during the day. Abalone did not respire more underwater at night-time than at daytime, however they excreted more overnight. The low air:aquatic ratio (0.2) is likely to be an energy-saving strategy for emerged H. tuberculata individuals. This study highlights the temporal heterogeneity in physiological rates of H. tuberculata, which constitutes a species recently domesticated in Europe.

Aim Body size is a master trait with significant ecological importance. Seasonal changes in body size within diverse ectothermic species can result from different environmental conditions experienced during ontogeny in subsequent generations. Whilst intraspecific changes in adult size have been well studied under controlled experimental conditions and across geographical ranges, comprehensive analyses of temporal changes are lacking, and there remains considerable unexplained variation in body size responses within aquatic taxa. Using planktonic copepods as an exemplar taxon, we quantify variation in adult body mass within seasonally varying marine and freshwater environments. We describe how size variation relates to temperature, food concentration (chlorophyll-a) and life-history characteristics, including feeding strategy. Location Global. Methods Using a meta-analytic approach we extract quantitative data from published literature on seasonal size responses of copepods. We analyse competing models to determine the best predictors of these responses, and compare the relative importance of temperature and chlorophyll-a concentration in explaining variation in body size. Results We quantify 140 seasonal size responses from 33 different global locations, representing 48 planktonic copepod species from four taxonomic orders. We find that temperature (r2 = 0.50), rather than food (r2 = 0.22), is the dominant explanatory variable of changes in adult body size across seasons. A striking outcome is that calanoid copepods, which utilize feeding currents to capture prey, exhibit a four-fold greater reduction in adult body mass per °C (−3.66%) compared with cyclopoid copepods (−0.91%), which are ambush feeders. By contrast, species body size or reproductive strategy did not explain variation in the seasonal temperature–size response. Main conclusions Our findings lead us to suggest that feeding strategies may play a significant role in dictating the magnitude of seasonal temperature–size responses in copepods, with potential implications for other ectotherms with diverse feeding methods. Seasonal temperature–size responses were typically much more variable than responses in laboratory studies that provided excess food, suggesting that field conditions modify the temperature–size response.

Planktivorous and benthivorous fish have been documented to influence the density and size structure of their prey communities in lakes. We hypothesized that piscivorous fish modify their prey fish communities in the same way and sought to find evidence for such predation effects from a comparison across 356 lakes located in nine European ecoregions. We categorized individual fish as being piscivore, nonpiscivore, or prey of piscivores, depending on species and individual size. We calculated piscivore, nonpiscivore, and piscivore prey densities, respectively, and fit linear abundance size spectra (SS) on lake-specific piscivore, nonpiscivore, and piscivore-prey size distributions. Multiple linear regressions were calculated to quantify the effect of piscivore density and SS slopes on nonpiscivore and piscivore-prey densities and SS slopes by accounting for potentially confounding factors arising from lake morphometry, productivity, and local air temperature. Piscivore density correlated positively with piscivore-prey density but was uncorrelated with density of nonpiscivores. Across a subset of 76 lakes for which SS slopes of piscivores were statistically significant, SS slopes of piscivores were uncorrelated with SS slopes of either nonpiscivores or piscivore prey. However, densities of piscivores, nonpiscivores, or piscivore prey were a significant negative predictor of SS slopes of the respective groups. Our analyses suggest that direct predation effects by piscivorous fish on density and size structure of prey fish communities are weak in European lakes, likely caused by low predator–prey size ratios and the resulting size refuges for prey fish. In contrast, competition may substantially contribute to between-lake variability in fish density and size.

00001 WOS:000389304800009; International audience; Climate change is inducing deep modifications in local communities worldwide as a consequence of individualistic species range shifts. Understanding how complex interaction networks will be reorganized under climate change represents a major challenge in the fields of ecology and biogeography. However, forecasting the potential effects of climate change on local communities, and more particularly on food-web structure, requires the consideration of highly structuring processes, such as trophic interactions. A major breakthrough is therefore expected by combining predictive models integrating habitat selection processes, the physiological limits of marine species and their trophic interactions. In this study, we forecasted the potential impacts of climate change on the local food-web structure of the highly threatened Gulf of Gabes ecosystem located in the south of the Mediterranean Sea. We coupled the climatic envelope and habitat models to an allometric niche food web model, hence taking into account the different processes acting at regional (climate) and local scales (habitat selection and trophic interactions). Our projections under the A2 climate change scenario showed that future food webs would be composed of smaller species with fewer links, resulting in a decrease of connectance, generality, vulnerability and mean trophic level of communities and an increase of the average path length, which may have large consequences on ecosystem functioning. The unified framework presented here, by connecting food-web ecology, biogeography and seascape ecology, allows the exploration of spatial aspects of interspecific interactions under climate change and improves our current understanding of climate change impacts on local marine food webs.

OBJECTIVES: The aims of this study were to develop a population pharmacokinetic model for intravenous paracetamol in preterm and term neonates and to assess the generalizability of the model by testing its predictive performance in an external dataset. METHODS: Nonlinear mixed-effects models were constructed from paracetamol concentration-time data in NONMEM 7.2. Potential covariates included body weight, gestational age, postnatal age, postmenstrual age, sex, race, total bilirubin, and estimated glomerular filtration rate. An external dataset was used to test the predictive performance of the model through calculation of bias, precision, and normalized prediction distribution errors. RESULTS: The model-building dataset included 260 observations from 35 neonates with a mean gestational age of 33.6 weeks [standard deviation (SD) 6.6]. Data were well-described by a one-compartment model with first-order elimination. Weight predicted paracetamol clearance and volume of distribution, which were estimated as 0.348 L/h (5.5 % relative standard error; 30.8 % coefficient of variation) and 2.46 L (3.5 % relative standard error; 14.3 % coefficient of variation), respectively, at the mean subject weight of 2.30 kg. An external evaluation was performed on an independent dataset that included 436 observations from 60 neonates with a mean gestational age of 35.6 weeks (SD 4.3). The median prediction error was 10.1 % [95 % confidence interval (CI) 6.1-14.3] and the median absolute prediction error was 25.3 % (95 % CI 23.1-28.1). CONCLUSIONS: Weight predicted intravenous paracetamol pharmacokinetics in neonates ranging from extreme preterm to full-term gestational status. External evaluation suggested that these findings should be generalizable to other similar patient populations. ispartof: Clinical Pharmacokinetics vol:55 issue:1 pages:107-119 ispartof: location:Switzerland status: published

Pre-adult density-associated alterations in the composition of storage lipids may affect the cell membrane fatty acid profile (mainly phospholipids), membrane integrity, and cell function. The present study evaluated the impact of pre-adult density conditions, sex, and the selection regime on the composition of phospholipid fatty acids and lifespan of Drosophila melanogaster. The phospholipid profile of adult flies developed under larval crowding contained a higher proportion of polyunsaturated fatty acids, lower proportion of monounsaturated fatty acids, and greater risk of peroxidation. There was also a negative correlation between the peroxidation index (PI) and longevity. The longevity-selected females showed a lower PI compared with control lines under both densities. The present results indicate that pre-adult density may play a significant role in the lifespan of adult flies by altering the composition of phospholipids and shaping cell membrane bilayers with different susceptibilities to peroxidation. (C) 2015 Elsevier Inc. All rights reserved.

Currently, there is much debate on the genetic architecture of quantitative traits in wild populations. Is trait variation influenced by many genes of small effect or by a few genes of major effect? Where is additive genetic variation located in the genome? Do the same loci cause similar phenotypic variation in different populations? Great tits (Parus major) have been studied extensively in long‐term studies across Europe and consequently are considered an ecological ‘model organism’. Recently, genomic resources have been developed for the great tit, including a custom SNP chip and genetic linkage map. In this study, we used a suite of approaches to investigate the genetic architecture of eight quantitative traits in two long‐term study populations of great tits—one in the Netherlands and the other in the United Kingdom. Overall, we found little evidence for the presence of genes of large effects in either population. Instead, traits appeared to be influenced by many genes of small effect, with conservative estimates of the number of contributing loci ranging from 31 to 310. Despite concordance between population‐specific heritabilities, we found no evidence for the presence of loci having similar effects in both populations. While population‐specific genetic architectures are possible, an undetected shared architecture cannot be rejected because of limited power to map loci of small and moderate effects. This study is one of few examples of genetic architecture analysis in replicated wild populations and highlights some of the challenges and limitations researchers will face when attempting similar molecular quantitative genetic studies in free‐living populations.

Boreal forests have been intensively managed, influencing the spatiotemporal occurrence of dead wood, and leading to changes in saproxylic species assemblages. Some particular traits, such as habitat specialization, can be expected to make species sensitive to alterations in the amount, dynamics and heterogeneity of dead-wood habitats. We compared the saproxylic beetle assemblages of 320 dead standing Scots pines within 52 pine forest stands in three regions in Finland and Russia with contrasting forest-use history. We used the joint species distribution model of Hierarchical Modelling of Species Communities (HMSC) to analyze how the beetle communities respond to alteration of forest structure. We applied scenario simulations to examine relationships between selected species traits and environmental gradients. Our results show that tree-level characteristics were the most important variables shaping the community composition in dead standing pines, but that also the characteristics of the forest stand as well as the larger-scale landscape context affected assemblage composition. Most importantly, managed forest stands and managed forest landscapes had lost species that are specialized in their resource use. The generalist species thriving in managed forest stands and managed forest landscapes were able to utilize dead wood of small diameter and man-made dead wood types, such as cut stumps and logging residues. We conclude that forest management not only reduces the amount of resources for saproxylic beetles locally, but has also landscape-level effects so that the most vulnerable species with specialized resource use and short-lived substrates can be lost also from remnant natural forest patches embedded in managed landscapes. peerReviewed

Understanding the role of climatic variation on biodiversity is of chief importance due to the ongoing biodiversity loss and climate change. Freshwaters, one of the most threatened ecosystems in the world, offer a valuable context to study biodiversity patterns of distinct organism groups in relation to climatic variation. In the Tibetan Plateau biodiversity hotspot - Hengduan Mountain region, we studied the effects of climate and local physico-chemical factors on stream microorganisms (i.e. bacteria) and macroorganisms (i.e. macroinvertebrates) in two parallel catchments with contrasting precipitation and temperature, that is, the Nujiang and Lancang Rivers. Diversities and community structures were better explained by climatic and local environmental variables in the drier and colder catchment and at higher elevations, than in the warmer and wetter conditions and at lower elevations. This suggests that communities may be more strongly assembled by deterministic processes in the former, comparatively harsher conditions, compared to the latter, more benign conditions. Macroinvertebrates were more strongly affected by climatic and local environmental factors compared to bacteria, but the diversities and community structures of the two groups showed spatially similar responses to overall abiotic variation, being especially evident with their community structures' responses to climate. Furthermore, bacterial and macroinvertebrate diversities were positively correlated in the drier and colder catchment, implying that these biologically and ecologically distinct organism groups are likely to be driven by similar processes in areas with such climatic conditions. We conclude that changes in climatic and local environmental conditions may affect the diversity of macroorganisms more strongly than that of microorganisms, at least in subtropical mountainous stream ecosystems studied here, but simultaneous responses of both groups to environmental changes can also be expected.

The ongoing down-sizing of the global mammal communities is assumed to have subsequent effects on mutualistic species communities. Dung beetles co-evolved with large-sized animals since millennia and depend on the megafauna feces of an appropriate size. Mammal community down-sizing as a result of past and ongoing megafauna losses is therefore likely to result in a down-sizing of dung beetle communities. However, empirical evidence for this co-down-sizing is lacking especially on larger spatial scales and over extended periods of time. Here, we show a significant down-sizing of European dung beetle assemblages over the last 53 000 years by relating Quaternary fossil records with trait information on body size of beetles. This significant down-sizing of dung beetle communities was thereby not linear, but characterized by a weak decrease until the early Holocene but a strong acceleration in the recent pre-history, from 6-7000 years BP onwards. This acceleration of down-sizing coincides with the completion of the Quaternary megafauna extinction and the start of major shifts in human agricultural land-use. In contrast, assemblage mean body size of non-coprophagous scarabids as well as ground beetles - two groups of beetles with no or weak relations to megafauna - was observed to increase towards the present with an acceleration of body size increase coinciding with the onset of late-glacial warming (14 200 years BP). In summary, the observed late-Quaternary down-sizing of European dung beetle communities is consistent with an effect of pre-historic megafauna losses, and not with the coincident general warming. Ongoing down-sizing of mammal communities is therefore likely to result in further down-sizing of dung beetle assemblages, with potential effects on their important role for nutrient cycling and secondary seed dispersal in natural and extensive agro-ecosystems. Future nature management initiatives could halt or even reverse this functional diversity loss via effective protection or restoration of megafauna communities.

In oviparous species, the embryonic environmentparticularly temperaturecan alter phenotype and survival of an individual by affecting its size as well as its metabolic rate. Previous studies have shown that incubation temperatures can affect sex ratio in birds; specifically, low incubation temperatures were shown to produce a male-biased sex ratio in zebra finches (Taeniopygia guttata) possibly because of a higher pre- or postnatal mortality rate in females. We hypothesized that sexes respond differently to suboptimal incubation temperature, leading to a male-biased sex ratio. To test this hypothesis, zebra finch eggs were incubated at 36.1 degrees, 37.5 degrees, or 38.5 degrees C and hatching success, hatchling mass, residual yolk mass, and pectoralis mass were measured. We found that while hatchling mass was similar between the sexes at 37.5 degrees C, female hatchlings were heavier at 36.1 degrees C, and male hatchlings were heavier at 38.5 degrees C. Pectoralis muscle mass was similar between the sexes at 36.1 degrees C; however, at 37.5 degrees C, female pectoralis mass was heavier at hatching than that of males. Females at 37.5 degrees C also had lower residual yolk at hatching compared with males, reflecting a higher use of energy by female embryos compared with male embryos at this temperature. In contrast, residual yolk was similar between the sexes at 36.1 degrees and 38.5 degrees C. Our results suggest that there are sex differences in how incubation temperature alters organ mass and yolk energy reserve; this can lead to a difference in survival at different incubation temperatures between the sexes. Taken together with previous studies showing that females alter incubation behavior with ambient temperature, rising ambient temperatures could impact phenotype and survival of avian offspring in a sex-specific manner.

Group living animals invariably risk resource competition. Cooperation in foraging, however, may benefit individuals in groups by facilitating an increase in dietary niche. To test this, we performed a comparative study of social and solitary spider species. Three independently derived social species of Stegodyphus (Eresidae) occupy semi-arid savannas and overlap with three solitary congeners. We estimated potential prey availability in the environment and prey acquisition by spiders in their capture webs. We calculated dietary niche width (prey size) and breadth (taxonomic range) to compare resource use for these six species, and investigated the relationships between group size and average individual capture web production, prey biomass intake rate and variance in biomass intake. Cooperative foraging increased dietary niche width and breadth by foraging opportunistically, including both larger prey and a wider taxonomic range of prey in the diet. Individual capture web production decreased with increasing group size, indicating energetic benefits of cooperation, and variance in individual intake rate was reduced. However, individual biomass intake also decreased with increasing group size. While cooperative foraging did not completely offset resource competition among group members, it may contribute to sustaining larger groups by reducing costs of web production, increasing the dietary niche and reducing the variance in prey capture.

In many species, the natural distribution of material resources important for reproduction can profoundly impact reproductive success among individuals and, hence, the opportunity and intensity of sexual selection. Here, we report on a field-based experiment investigating the effects of nest aggregation on sexual selection in a fish, the sand goby Pomatoschistus minutus. We found that the distribution of potential nests (sparse versus aggregated nest treatments) affected patterns of nest colonization and reproductive success. Specifically, in the treatment with aggregated nesting resources, a greater proportion of nests remained unoccupied by sand goby males. Although the size of nesting males did not differ between treatments, eggs accumulated more rapidly when nests were sparsely distributed. We found that the opportunity for selection decreased over time with the accumulation of eggs in the nests in both the aggregated and sparse treatments. Moreover, the effect of male size on reproductive success was influenced by an interaction between nest distribution and time, with the selection gradient being highest right after nest colonization when nests were aggregated, while the opposite pattern was observed in the sparse nest treatment. Such findings highlight the vital role that environmental and social factors can play in determining the importance of male phenotypic traits (in this case, male size). More broadly, our results also underscore how the natural distribution of resources, both in space and time, can impact the strength of sexual selection acting on wild animal populations.

[Departement_IRSTEA]Eaux [TR1_IRSTEA]QUASARE [ADD1_IRSTEA]Systèmes aquatiques soumis à des pressions multiples; International audience; Body size, coupled with abundance and taxonomy, may help to understand the mechanisms shaping community structure. Since the body size of fish is closely related to their trophic niche, size diversity (based on individual body size) of fish communities may capture intraspecific variations in fish trophic niches that are not detected by species diversity. Thus, the relationship between size diversity and species diversity may help to integrate variation at both intraspecific and interspecific levels. We studied the relationship between species diversity and size diversity as a measure of the degree of overlap in size among species and thereby the potential overlap in niches in a community. We hypothesized that the relationship between size diversity and species would be different across the European continent due to different levels of size overlap in fish communities. The data were derived from samplings of fish communities using standardised benthic gill nets in 363 lakes. At the continental scale, size diversity increased with species diversity; at the ecoregion scale, the slope of the relation changed across the continent, with the greatest mismatch occurring in northern Europe where communities comprised only one or a few species, but each of which exhibited a great range in size. There was an increase in slope towards the south with significant relations for four out of six ecoregions. The steeper size diversity-species diversity slope at lower latitudes is attributable to a lower overlap in fish size and thus likely to finer niche separation. Our results also suggest that size diversity is not a strong surrogate for species diversity in European lake fish communities. Thus, particularly in fish communities composed of few species, measuring size diversity may help to detect potential functional variation which may be neglected by measuring species diversity alone.

The extant diversity and rich fossil record of cetaceans provides an extraordinary evolutionary context for investigating the relationship between form, function and ecology. The transition from terrestrial to marine ecosystems is associated with a complex suite of morphological and physiological adaptations that were required for a fully aquatic mammalian life history. Two specific functional innovations that characterize the two great clades of cetaceans, echolocation in toothed whales (Odontoceti) and filter feeding in baleen whales (Mysticeti), provide a powerful comparative framework for integrative studies. Both clades exhibit gigantism in multiple species, but we posit that large body size may have evolved for different reasons and in response to different ecosystem conditions. Although these foraging adaptations have been studied using a combination of experimental and tagging studies, the precise functional drivers and consequences of morphological change within and among these lineages remain less understood. Future studies that focus at the interface of physiology, ecology and paleontology will help elucidate how cetaceans became the largest predators in aquatic ecosystems worldwide.

Body size is intrinsically linked to metabolic rate and life-history traits, and is a crucial determinant of food webs and community dynamics 1,2. The increased temperatures associated with the urban-heat-island effect result in increased metabolic costs and are expected to drive shifts to smaller body sizes 3. Urban environments are, however, also characterized by substantial habitat fragmentation 4 , which favours mobile species. Here, using a replicated, spatially nested sampling design across ten animal taxonomic groups, we show that urban communities generally consist of smaller species. In addition, although we show urban warming for three habitat types and associated reduced community-weighted mean body sizes for four taxa, three taxa display a shift to larger species along the urbanization gradients. Our results show that the general trend towards smaller-sized species is overruled by filtering for larger species when there is positive covariation between size and dispersal, a process that can mitigate the low connectivity of ecological resources in urban settings 5. We thus demonstrate that the urban-heat-island effect and urban habitat fragmentation are associated with contrasting community-level shifts in body size that critically depend on the association between body size and dispersal. Because body size determines the structure and dynamics of ecological networks 1 , such shifts may affect urban ecosystem function. Body size is a fundamental species trait relating to space use and key life-history features such as longevity and fecundity 6. It also drives interspecific relationships, thus affecting ecological network dynamics 1. Size-biased species loss has profound effects on ecosystem function 7,8. Ectotherms rely on ambient conditions to achieve operational body temperatures 9. Because higher ambient temperature increases metabolic rates and the associated costs for a given body size 2 , global climatic warming is expected to drive shifts to communities consisting of smaller species 3. Our planet is urbanizing quickly 10 , which is a primary example of human-induced rapid environmental change. Cities are urban heat islands characterized by increased temperatures that are decades ahead of global averages 11. Not only are cities warmer than surrounding areas, but they also experience extensive fragmentation of (semi-)natural habitats , and both of these effects increase with percentage built-up cover (BUC; a proxy for urbanization) 12,13. This provides an opportunity to study the opposing effects of size-dependent thermal tolerance and dispersal capacity, as larger body size favours dispersal in some, but not all, taxa. Here we test the hypothesis that urbanization causes shifts in community level body size, and that these shifts are dictated by the community specific association between body size and dispersal. We generally expect the urban-heat-island effect to drive shifts to species with smaller body sizes in communities of ectothermic species, in line with Atkinson's temperature-size rule 14. For taxa characterized by a positive association between body size and dispersal, however, we also expect a filtering in favour of larger-bodied species associated with habitat fragmentation 5,15. Filtering for increased mobility has been demonstrated for urban ground beetle and plant communities 16,17. Hence, for taxa characterized by a positive body-size-dispersal link, we predict that the general community-level pattern of smaller species with increasing urbanization may be neutralized or even reversed. To test our hypothesis, we engaged in an analysis of community-level shifts in body size across a broad range of both terrestrial and aquatic taxa along the same systematically sampled urbanization gradients. We studied the direction of change of community-level body size in ten taxa using a replicated, highly standardized and nested sampling design that covers urbanization gradients at seven spatial scales (50-3,200 m radii; Fig. 1). We sampled each taxon at up to 81 sites, sampling 95,001 individuals from 702 species, with species-specific body size varying by a factor of 400 (0.2-80 mm; Extended Data Table 1). Three of the ten groups are characterized by a positive association between body size and dispersal capacity (see Extended Data Table 1). We show that the local temperature of pond, grassland and woodland habitats significantly increases with urbanization (linear mixed regression models, P

Sirtuin 1 (SIRT1) is an energy-sensing protein, which may affect tumorigenesis. We used SIRT1 variants as time-independent indicators of SIRT1 involvement in carcinogenesis and we studied two tagging SIRT1 variants in relation to colorectal cancer (CRC) risk. We also evaluated known energy balance-related CRC risk factors within SIRT1 genotype strata. The Netherlands Cohort Study includes 120,852 individuals and has 20.3 years follow-up (case-cohort: nsubcohort = 5000; nCRC cases = 4667). At baseline, participants self-reported weight, weight at age 20, height, trouser/skirt size reflecting waist circumference, physical activity, and early life energy restriction. SIRT1 rs12778366 and rs10997870 were genotyped in toenail DNA available for ~75% of the cohort. Sex- and subsite-specific Cox hazard ratios (HRs) showed that the rs12778366 CC versus TT genotype decreased CRC and colon cancer risks in women (HRCRC = 0.53, 95% confidence interval: 0.30–0.94) but not men. Multiplicative interactions were observed between SIRT1 variants and energy balance-related factors in relation to CRC endpoints, but the direction of associations was not always conform expectation nor specific to one genotype stratum. In conclusion, these results support SIRT1 involvement in colon cancer development in women. No conclusions could be made regarding a modifying effect of SIRT1 variants on associations between energy balance-related factors and CRC risk.

Changes in zooplankton community structureand function were analyzed in 24 lakes covering awide salinity gradient (from 0.5 to 115 g l-1) in asemiarid region in northwest China. We hypothesizedthat species richness (S), species diversity (H), functionaldiversity (FD), biomass, and size of zooplanktonwould decrease with increasing salinity. We found thatS, H, and FD did decrease with increasing salinity,whereas zooplankton sizes, size range, and biomassesdid not. In fact, the sizes of microcrustaceans weremainly regulated by the abundance of small fish.Besides the impoverishment of FD, the zooplanktonfunctional groups also varied along the salinitygradient. A shift occurred from selective raptorial tomore generalist microphagous rotifers, from selectiveto more generalist filter feeder cladocerans, and fromdominance of microphagous herbivorous copepods tomicrophagous carnivores. Our study indicates that theongoing salinization of lakes with climate warmingwill result in important changes in the zooplankton,affecting not only the structure but also the functioningof this community. A weakened top-down control byzooplankton on phytoplankton at moderate highsalinities may be an indirect consequence, leading toa worsening of eutrophication symptoms. Loss of fishat high salinities may, however, counteract this effect. Fil: Gutierrez, Marìa Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Tavsanoglu, Ülkü Nihan. Limnology Laboratory, Department Of Biology; Turquía Fil: Vidal, Nicolas. Universidad de la República; Uruguay Fil: Yu, Jinlei. State Key Laboratory Of Lake Science And Environment; China Fil: Teixeira-de Mello, Franco. Universidad de la República; Uruguay Fil: Aye Idil Çakiroglu. Biofluids And Cardiovascular Engineering Laboratory; Turquía Fil: He, Hu. State Key Laboratory Of Lake Science And Environment; China Fil: Liu, Zhengwen. State Key Laboratory Of Lake Science And Environment; China Fil: Jeppesen, Erik. University Aarhus; Dinamarca

Species that span large latitudinal gradients face strong differences in voltinism and in winter conditions within their range. Latitudinal gradients in winter survival and especially their underlying mechanisms and association with voltinism patterns are poorly studied. We tested in the damselfly Enallagma cyathigerum whether high-latitude populations were better in dealing with the longer winters compared to central- and low-latitude populations and whether this was associated with changes in voltinism. We thereby evaluated whether higher initial levels and/or lower reductions during winter of energy storage (measured as fat content) and investment in immune function [measured as the activity of phenoloxidase (PO)], and/or stronger compensatory responses in food intake contributed to the higher winter survival in high-latitude populations. To this end, we simulated a long high-latitude winter at 4 °C under manipulated food conditions. Across food levels, winter survival was highest in Swedish larvae, intermediate in Belgian larvae, and lowest in Spanish larvae, indicating latitude-specific thermal adaptation that could be partly linked to differences in voltinism. The semi-voltine Swedish larvae were growing slower before winter and as a result accumulated the highest fat content and PO activity when the winter started compared to the univoltine, faster growing Belgian, and Spanish larvae. Fat content and PO activity declined during the winter, yet equally across latitudes, and were not buffered by compensatory food intake. Our data identified possible underlying physiological mechanisms of winter survival and support the hypothesis that widespread latitude-associated voltinism shifts may be a selective factor contributing to latitudinal shifts in winter survival. ispartof: OECOLOGIA vol:186 issue:4 pages:919-929 ispartof: location:Germany status: published

1. Human activities have caused global changes of atmospheric chemistry resulting in increased temperature especially in the colder regions of the northern hemisphere. Since warming of the environment can have drastic effects on terrestrial ecosys-tems it is important to experimentally evaluate the extent of such effects in long-term field-based experiments. In this study we make use of both recent (short-term) and long-term geothermal warming of Icelandic soils to examine the responses of Collembola, an ecologically important group of soil invertebrates, to warming. 2. On the basis of metabolic scaling theory, we hypothesized that species of small size would be more successful in warmed soils than species of larger size. Further we expected that top-soil-dwelling species would benefit more from warming than deep-soil-dwelling species. In order to test these hypotheses we sampled Collembola along replicated gradients of increasing temperature in areas that had been heated for about 6 years and more than 50 years respectively. Collembola were identified to species level, counted and the community-weighted mean trait scores for six functional and ecological traits were calculated. 3. Results show that both short-term and long-term soil warming caused a shift to-wards a higher relative abundance of species with small body size. Furthermore, abundance of top-soil-dwelling Collembola tended to increase after short-term warming, but the opposite was observed after long-term warming.4. Using trait-based diversity indices (FRic and RaoQ), we show that functional rich-ness and diversity of Collembola communities was significantly reduced (almost halved) as a result of short-term soil warming to about 10°C above normal, but this effect was not detected in plots equally warmed for more than 50 years. This in-dicates that the functional diversity of Collembola communities have high resil-ience towards soil warming in a long-term perspective., The authors are indebted to E. Jørgensen and Z. Gavor for their excellent technical assistance in Collembola extraction and identi-fication. Four anonymous reviewers are thanked for relevant and constructive comments to earlier drafts of the manuscript. M.H. was supported by a grant from the Danish Research Council (Grant no. DFF- 4002- 00384) and a Skou senior fellowship at AIAS. N.L. was supported by the Research Foundation – Flanders with a FWO as-pirant grant (Grant no. 11G1615N) and B.D.S. by Icelandic Research Council (Grant no. 163272-051). This work contributes also to the SNS funded Nordic CAR-ES III project and the ClimMani COST Action (ES1308)., Pre-print

Body size is a fundamental trait known to allometrically scale with metabolic rate and therefore a key determinant of individual development, life history, and consequently fitness. In spatially structured environments, movement is an equally important driver of fitness. Because movement is tightly coupled with body size, we expect habitat fragmentation to induce a strong selection pressure on size variation across and within species. Changes in body size distributions are then, in turn, expected to alter food web dynamics. However, no consensus has been reached on how spatial isolation and resource growth affect consumer body size distributions. Our aim was to investigate how these two factors shape the body size distribution of consumers under scenarios of size‐dependent and size‐independent consumer movement by applying a mechanistic, individual‐based resource–consumer model. We also assessed the consequences of altered body size distributions for important ecosystem traits such as resource abundance and consumer stability. Finally, we determined those factors that explain most variation in size distributions. We demonstrate that decreasing connectivity and resource growth select for communities (or populations) consisting of larger species (or individuals) due to strong selection for the ability to move over longer distances if the movement is size‐dependent. When including size‐dependent movement, intermediate levels of connectivity result in increases in local size diversity. Due to this elevated functional diversity, resource uptake is maximized at the metapopulation or metacommunity level. At these intermediate levels of connectivity, size‐dependent movement explains most of the observed variation in size distributions. Interestingly, local and spatial stability of consumer biomass is lowest when isolation and resource growth are high. Finally, we highlight that size‐dependent movement is of vital importance for the survival of populations or communities within highly fragmented landscapes. Our results demonstrate that considering size‐dependent movement is essential to understand how habitat fragmentation and resource growth shape body size distributions—and the resulting metapopulation or metacommunity dynamics—of consumers.

Why the rate of metabolism varies (scales) in regular, but diverse ways with body size is a perennial, incompletely resolved question in biology. In this article, I discuss several examples of the recent rediscovery and (or) revival of specific metabolic scaling relationships and explanations for them previously published during the nearly 200-year history of allometric studies. I carry out this discussion in the context of the four major modal mechanisms highlighted by the contextual multimodal theory (CMT) that I published in this journal four years ago. These mechanisms include metabolically important processes and their effects that relate to surface area, resource transport, system (body) composition, and resource demand. In so doing, I show that no one mechanism can completely explain the broad diversity of metabolic scaling relationships that exists. Multi-mechanistic models are required, several of which I discuss. Successfully developing a truly general theory of biological scaling requires the consideration of multiple hypotheses, causal mechanisms and scaling relationships, and their integration in a context-dependent way. A full awareness of the rich history of allometric studies, an openness to multiple perspectives, and incisive experimental and comparative tests can help this important quest.

Publisher's version (útgefin grein), Global warming is predicted to significantly alter species physiology, biotic interactions and thus ecosystem functioning, as a consequence of coexisting species exhibiting a wide range of thermal sensitivities. There is, however, a dearth of research examining warming impacts on natural communities. Here, we used a natural warming experiment in Iceland to investigate the changes in above‐ground terrestrial plant and invertebrate communities along a soil temperature gradient (10°C–30°C). The α‐diversity of plants and invertebrates decreased with increasing soil temperature, driven by decreasing plant species richness and increasing dominance of certain invertebrate species in warmer habitats. There was also greater species turnover in both plant and invertebrate communities with increasing pairwise temperature difference between sites. There was no effect of temperature on percentage cover of vegetation at the community level, driven by contrasting effects at the population level. There was a reduction in the mean body mass and an increase in the total abundance of the invertebrate community, resulting in no overall change in community biomass. There were contrasting effects of temperature on the population abundance of various invertebrate species, which could be explained by differential thermal tolerances and metabolic requirements, or may have been mediated by changes in plant community composition. Our study provides an important baseline from which the effect of changing environmental conditions on terrestrial communities can be tracked. It also contributes to our understanding of why community‐level studies of warming impacts are imperative if we are to disentangle the contrasting thermal responses of individual populations., We acknowledge the funding support of NERC (NE/L011840/1, NE/M020843/1), the British Ecological Society (4009-4884, SR16/1152, 7283/5350), the Royal Society (RG140601), the recruitment fund of the University of Iceland and the Finnish Cultural Foundation.

For hundreds of millions of years, large vertebrates (megafauna) have inhabited most of the ecosystems on our planet. During the late Quaternary, notably during the Late Pleistocene and the early Holocene, Earth experienced a rapid extinction of large, terrestrial vertebrates. While much attention has been paid to understanding the causes of this massive megafauna extinction, less attention has been given to understanding the impacts of loss of megafauna on other organisms with whom they interacted. In this review, we discuss how the loss of megafauna disrupted and reshaped ecological interactions, and explore the ecological consequences of the ongoing decline of large vertebrates. Numerous late Quaternary extinct species of predators, parasites, commensals and mutualistic partners were associated with megafauna and were probably lost due to their strict dependence upon them (co-extinctions). Moreover, many extant species have megafauna-adapted traits that provided evolutionary benefits under past megafauna-rich conditions, but are now of no or limited use (anachronisms). Morphological evolution and behavioural changes allowed some of these species partially to overcome the absence of megafauna. Although the extinction of megafauna led to a number of co-extinction events, several species that likely co-evolved with megafauna established new interactions with humans and their domestic animals. Species that were highly specialized in interactions with megafauna, such as large predators, specialized parasites, and large commensalists (e.g. scavengers, dung beetles), and could not adapt to new hosts or prey were more likely to die out. Partners that were less megafauna dependent persisted because of behavioural plasticity or by shifting their dependency to humans via domestication, facilitation or pathogen spill-over, or through interactions with domestic megafauna. We argue that the ongoing extinction of the extant megafauna in the Anthropocene will catalyse another wave of co-extinctions due to the enormous diversity of key ecological interactions and functional roles provided by the megafauna., M.G. and J‐C.S. thank the Aarhus University Research Foundation for a guest researcher grant to sponsor M.G. at Aarhus University. J‐C.S. considers this work a contribution to his Carlsberg Foundation Semper Ardens project MegaPast2Future (CF16‐0005) and to his VILLUM Investigator project ‘Biodiversity Dynamics in a Changing World’ funded by VILLUM FONDEN. M.M. and P.J. were supported by the Severo Ochoa Program for Centres of Excellence in R+D+I (SEV‐2012‐0262) and M.M. by a Ramón y Cajal (RYC‐2015‐19231) grant. M.G. and P.R.G. have a fellowship from Conselho Nacional de Desenvolvimento Científico (CNPq, 300241/2010‐0). M.G. and M.M.P. thank São Paulo Research Foundation (FAPESP, 2014/01986‐0, 2013/22016‐6) for financial support.

1. Kleptoparasitic and parasitoid insects are expected to be particularly sensitive to changes in habitat availability due to their high trophic position and small population sizes compared with their hosts, but there are only few quantitative studies on their population changes. 2. Here, we studied the distribution and abundance of 48 kleptoparasitic and parasitoid species of cuckoo wasps (Chrysididae) and eight selected host species recorded in Finland from 1840 to 2015 based on an extensive survey of entomological collections. Population trends were assessed by studying changes in occupancy in 10 9 10 km grid squares between two study periods, 1840-1967 and 1968-2015. 3. Statistically significant decreases in occurrence were found for 11 cuckoo wasp species and one host species, while significant increases were not observed for any species. Trends of cuckoo wasps and their hosts were positively correlated, and changes were generally stronger in cuckoo wasps than in their hosts. 4. In a comparative analysis of species traits, abundance, body size and nesting type of host were related to occurrence changes of cuckoo wasps. Scarce and small species that use above ground-nesting hosts declined more than abundant and large species that use ground-nesting hosts. 5. Cuckoo wasp species dependent on dead wood are more vulnerable to changes in the environment than species associated with open sandy habitats. While both groups of species have probably suffered from habitat loss, the emergence of secondary habitats may have benefitted species living in sandy areas and compensated for the negative impact of habitat destruction.

We analysed changes in the abundance, biomass and cell size of the microbial food web community (bacteria, heterotrophicnanoflagellates, ciliates) at contrasting nutrient concentrations and temperatures during a simulated heat wave. We used 24mesocosms mimicking shallow lakes in which two nutrient levels (unenriched and enriched by adding nitrogen and phosphorus)and three different temperature scenarios (ambient, IPCC A2 scenario and A2+%50) are simulated (4 replicates of each).Experiments using the mesocosms have been running un-interrupted since 2003. A 1-month heat wave was imitated by anextra 5◦C increase in the previously heated mesocosms (from 1st July to 1st August 2014). Changes in water temperatureinduced within a few days a strong effect on the microbial food web functioning, demonstrating a quick response of microbialcommunities to the changes in environment, due to their short generation times. Warming and nutrients showed synergisticeffects. Microbial assemblages of heterotrophic nanoflagellates and ciliates responded positively to the heating, the increasebeing largest in the enriched mesocosms. The results indicate that warming and nutrients in combination can set off complexinteractions in the microbial food web functioning. This work was supported by MARS project (ManagingAquatic ecosystems and water Resources under multipleStress, EU 7th Framework Programme, contract no.: 603378)and by institutional grant IUT 21-2 of the Estonian Min-istry of Education and Research. The Danish group wasalso supported by PROGNOS (Predicting in-lake RespOnsesto chanGe using Near real time mOdelS – Water JointProgramme Initiative) and AQUACOSM (Network of Lead-ing European AQUAtic MesoCOSM Facilities ConnectingMountains to Oceans from the Arctic to the Mediterranean),the latter also supporting the Turkish group. Yu Cao issupported by NSF-China (31500296) and CSC (The ChinaScholarship Council). This work was supported by MARS project (ManagingAquatic ecosystems and water Resources under multipleStress, EU 7th Framework Programme, contract no.: 603378)and by institutional grant IUT 21-2 of the Estonian Min-istry of Education and Research. The Danish group wasalso supported by PROGNOS (Predicting in-lake RespOnsesto chanGe using Near real time mOdelS – Water JointProgramme Initiative) and AQUACOSM (Network of Lead-ing European AQUAtic MesoCOSM Facilities ConnectingMountains to Oceans from the Arctic to the Mediterranean),the latter also supporting the Turkish group. Yu Cao issupported by NSF-China (31500296) and CSC (The ChinaScholarship Council).

Human activities can generate a wide variety of direct and indirect effects on animals, which can manifest as environmental and genetic stressors. Several phenotypic markers have been proposed as indicators of these stressful conditions but have displayed contrasting results, depending, among others, on the phenotypic trait measured. Knowing the worldwide decline of multiple bumblebee species, it is important to understand these stressors and link them with the drivers of decline. We assessed the impact of several stressors (i.e. natural toxin-, parasite-, thermic- and inbreeding- stress) on both wing shape and size and their variability as well as their directional and fluctuating asymmetries. The total data set includes 650 individuals of Bombus terrestris (Hymenoptera: Apidae). Overall wing size and shape were affected by all the tested stressors. Except for the sinigrin (e.g. glucosinolate) stress, each stress implies a decrease of wing size. Size variance was affected by several stressors, contrary to shape variance that was affected by none of them. Although wing size directional and fluctuating asymmetries were significantly affected by sinigrin, parasites and high temperatures, neither directional nor fluctuating shape asymmetry was significantly affected by any tested stressor. Parasites and high temperatures led to the strongest phenotype modifications. Overall size and shape were the most sensitive morphological traits, which contrasts with the common view that fluctuating asymmetry is the major phenotypic marker of stress.

Sexual size dimorphism (SSD) is common in birds and has been linked to various selective forces. Nevertheless, the question of how and when the sexes start to differentiate from each other is poorly studied. This is a critical knowledge gap, as sex differences in growth may cause different responses to similar ecological conditions. In this study, we describe the sex-specific growth - based on body mass and five morphometric measurements - of 56 captive Black-tailed Godwit Limosa limosa limosa chicks raised under adlibitum food conditions, and conclude that all six growth curves are sex-specific. Females are the larger sex in terms of body mass and skeletal body size. To test whether sex-specific growth leads to sex-specific susceptibility to environmental conditions, we compared the age-specific sizes of male and female chicks in the wild with those of Black-tailed Godwits reared in captivity. We then tested for a relationship between residual growth and relative hatching date, age, sex and habitat type in which the wild chicks were born. Early-hatched chicks were relatively bigger and in better condition than late-hatched chicks, but body condition and size were not affected by natal habitat type. Female chicks deviated more negatively from the sex-specific growth curves than male chicks for body mass and total-head length. This suggests that the growth of the larger females is more susceptible to limiting environmental conditions. On average, the deviations of wild chicks from the predicted growth curves were negative for all measurements, which suggests that conditions are limiting in the current agricultural landscape. We argue that in estimating growth curves for sexually dimorphic species, it is critical first to make accurate sex and age determinations.

International audience; Understanding how changes in temperature affect interspecific competition is critical for predicting changes in ecological communities with global warming. Here we develop a theoretical model that links interspecific differences in the temperature-dependence of resource acquisition and growth to the outcome of pairwise competition in phytoplankton. We parameterised our model with these metabolic traits derived from six species of freshwater phytoplankton and tested its ability to predict the outcome of competition in all pairwise combinations of the species in a factorial experiment, manipulating temperature and nutrient availability. The model correctly predicted the outcome of competition in 72% of the pairwise experiments, with competitive advantage determined by difference in thermal sensitivity of growth rates of the two species. These results demonstrate that metabolic traits play a key role in determining how changes in temperature influence interspecific competition and lay the foundation for mechanistically predicting the effects of warming in complex, multi-species communities.

International audience; Responses of ecosystems to modifications of their environmental conditions are usually considered in terms of biodiversity or function. Maybe because they represent a hidden part of ecosystems, responses of ecological interactions are rarely studied. A more comprehensive view of the processes underlying the restructuring of food webs under environmental gradients appears crucial to understand how ecosystems functionalities are altered. We address this general issue in an experiment where trophic interactions are reorganized under a gradient of top–down effects (predation pressure) and bottom–up effects (nutrient availability). Unimodal relationships of species diversity are pervasive in ecology; we extend this principle to food-web topology: in our study, most topological descriptor values peak at intermediate predation intensity. The same unimodal pattern holds for network complexity, measured by entropy and scaled entropy (a measure independent of species diversity). Moreover, food web complexity is maximized at higher fish abundance when nutrient availability is increased. We infer that whereas in absence of top predators, a mechanism of competitive exclusion takes place, and indirect facilitation process underlies systems with a moderate predation pressure. These results highlight the importance of the dynamic reorganization of trophic links in response to bottom–up and top–down effects. Interaction between bottom–up and top–down forces argue for multifactorial studies of ecological effects

Earlier menarche has been related to shorter height and greater obesity-related anthropometric dimensions and blood pressure in women. Boys and girls with earlier maternal menarcheal age (MMA) have shown greater height and body mass index (BMI) in childhood.To analyse associations of menarcheal age with their own and their children's anthropometric dimensions and blood pressure.The sample consisted of 493 women and their children (aged 2-19 years) from Greater Bilbao (Basque Country, Spain). For both generations there is information on 19 anthropometric dimensions, blood pressure and socio-demographic characteristics. Linear regressions adjusted for different covariates were used to analyse the associations.Menarcheal age in women showed the greatest positive associations with iliospinal height and ectomorphy and negative associations with BMI, sum of six skin-folds, endomorphy and mesomorphy. Boys with earlier MMA had greater body heights and breadths, particularly iliospinal height and biacromial breadth (0.10 z-score/year; p 0.05). In girls, earlier MMA predicted greater sitting height, biepicondylar humerus breadth, weight and sum of four circumferences (0.07-0.09 z-score/year; p 0.05). However, there was some evidence that MMA was positively associated with body heights, ectomorphy and blood pressure in girls aged ≥12.Children with earlier MMA tend to have greater anthropometric dimensions. Adolescent growth spurt might affect these relationships, at least in girls.

In the face of ongoing habitat fragmentation, species–area relationships (SARs) have gained renewed interest and are increasingly used to set conservation priorities. An important question is how large habitat areas need to be to optimize biodiversity conservation. The relationship between area and species richness is explained by colonization–extinction dynamics, whereby smaller sites harbor smaller populations, which are more prone to extinction than the larger populations sustained by larger sites. These colonization–extinction dynamics are predicted to vary with trophic rank, habitat affinity, and dispersal ability of the species. However, empirical evidence for the effect of these species characteristics on SARs remains inconclusive.In this study we used carabid beetle data from 58 calcareous grassland sites to investigate how calcareous grassland area affects species richness and activity density for species differing in trophic rank, habitat affinity, and dispersal ability. In addition, we investigated how SARs are affected by the availability of additional calcareous grassland in the surrounding landscape.Beetle species richness and activity density increased with calcareous grassland area for zoophagous species that are specialists for dry grasslands and, to a lesser extent, for zoophagous habitat generalists. Phytophagous species and zoophagous forest and wet-grassland specialists were not affected by calcareous grassland area. The dependence of species on large single sites increased with decreasing dispersal ability for species already vulnerable to calcareous grassland area. Additional calcareous grassland in the landscape had a positive effect on local species richness of both dry-grassland specialists and generalists, but this effect was restricted to a few hundred meters.Our results demonstrate that SARs are affected by trophic rank, habitat affinity, and dispersal ability. These species characteristics do not operate independently, but should be viewed in concert. In addition, species' responses depend on the landscape context. Our study suggests that the impact of habitat area on trophic interactions may be larger than previously anticipated. In small habitat fragments surrounded by a hostile matrix, food chains may be strongly disrupted. This highlights the need to conserve continuous calcareous grassland patches of at least several hectares in size.Read More: http://www.esajournals.org/doi/abs/10.1890/14-0082.1

There is recent evidence from laboratory experiments and analysis of livestock populations that not only the phenotype itself, but also its environmental variance, is under genetic control. Little is known about the relationships between the environmental variance of one trait and mean levels of other traits, however. A genetic covariance between these is expected to lead to nonlinearity between them, for example between birth weight and survival of piglets, where animals of extreme weights have lower survival. The objectives were to derive this nonlinear relationship analytically using multiple regression and apply it to data on piglet birth weight and survival. This study provides a framework to study such nonlinear relationships caused by genetic covariance of environmental variance of one trait and the mean of the other. It is shown that positions of phenotypic and genetic optima may differ and that genetic relationships are likely to be more curvilinear than phenotypic relationships, dependent mainly on the environmental correlation between these traits. Genetic correlations may change if the population means change relative to the optimal phenotypes. Data of piglet birth weight and survival show that the presence of nonlinearity can be partly explained by the genetic covariance between environmental variance of birth weight and survival. The framework developed can be used to assess effects of artificial and natural selection on means and variances of traits and the statistical method presented can be used to estimate trade-offs between environmental variance of one trait and mean levels of others.

Global change analyses usually consider biodiversity as a global asset that needs to be preserved. Biodiversity is frequently analysed mainly as a response variable affected by diverse environmental drivers. However, recent studies highlight that gradients of biodiversity are associated with gradual changes in the distribution of key dominant functional groups characterized by distinctive traits and stoichiometry, which in turn often define the rates of ecosystem processes and nutrient cycling. Moreover, pervasive links have been reported between biodiversity, food web structure, ecosystem function and species stoichiometry. Here we review current global stoichiometric gradients and how future distributional shifts in key functional groups may in turn influence basic ecosystem functions (production, nutrient cycling, decomposition) and therefore could exert a feedback effect on stoichiometric gradients. The C-N-P stoichiometry of most primary producers (phytoplankton, algae, plants) has been linked to functional trait continua (i.e. to major axes of phenotypic variation observed in inter-specific analyses of multiple traits). In contrast, the C-N-P stoichiometry of higher-level consumers remains less precisely quantified in many taxonomic groups. We show that significant links are observed between trait continua across trophic levels. In spite of recent advances, the future reciprocal feedbacks between key functional groups, biodiversity and ecosystem functions remain largely uncertain. The reported evidence, however, highlights the key role of stoichiometric traits and suggests the need of a progressive shift towards an ecosystemic and stoichiometric perspective in global biodiversity analyses. (C) 2014 Elsevier GmbH. All rights reserved.

Objective: To evaluate the effect of chest size on coronary calcium score (CCS) as assessed with new-generation CT systems from 4 major vendors.Methods: An anthropomorphic, small-sized (300 x 200 mm) chest phantom containing 100 small calcifications (diameters, 0.5-2.0 mm) was evaluated with and without an extension ring on state-of-the-art CT systems from 4 vendors. The extension ring was used to mimic a patient with a large chest size (400 x 300 mm). Image acquisition was repeated 5 times with small translations and/or rotations. Routine clinical acquisition and reconstruction protocols for small and large patients were used. CCS was quantified as Agatston and mass scores with vendor software.Results: The small-sized phantom resulted in median (interquartiles) Agatston scores of 10 (9-35), 136 (123-146), 34 (30-37), and 87 (85-89) for Philips, GE, Siemens, and Toshiba, respectively. Mass scores were 4 mg (3-9 mg), 23 mg (21-27 mg), 8 mg (8-9 mg), and 20 mg (20-20 mg), respectively. Adding the extension ring resulted in reduced Agatston scores for all vendors (17%-48%) and mass.scores for 2 vendors (11%-49%). Median Agatston scores decreased to 9 (5-10), 79 (60-80), 27 (24-32), and 45 (29-53) units, and median mass scores remained similar for Philips at 4 mg (4-6 mg) and Siemens at 8 mg (7-8 mg) and decreased for the other vendors to 13 mg (11-14 mg) and 10 mg (8-13 mg), respectively.Conclusion: This multivendor phantom study showed that CCS can be underestimated up to 50% (49%-66%) for Agatston scores and 49% (36%-59%) for mass scores at a larger chest size, which may be relevant for women and large patients. However, CCS underestimation by chest size differs considerably by vendor. (C) 2015 Society of Cardiovascular Computed Tomography. All rights reserved.

Among species with variable numbers of individuals contributing to offspring care, an individual's investment strategy should depend upon both the size of the breeding group and the relative contributions of each carer. Existing theoretical work on carer investment rules has, however, largely focused on biparental care, and on modelling offspring provisioning in isolation from other stages of investment. Consequently, there has been little exploration of how maternal investment prior to birth might be expected to influence carer provisioning decisions after birth, and how these should be modified by the number of carers present. In particular, it is unclear whether mothers should increase or decrease their investment in each offspring under favourable rearing conditions, and whether this differs under alternative assumptions about the consequences of being ‘high quality’ at birth. We develop a game-theoretical model of cooperative care that incorporates female control of prebirth investment, and allow increased maternal investment to either substitute for later investment (giving offspring a ‘head start’) or raise the value of later investment (a ‘silver spoon’). We show that mothers reduce prebirth investment under better rearing conditions (more helpers) when investment is substitutable, leading to concealed helper effects. In contrast, when maternal prebirth investment primes offspring to benefit more from postbirth care, mothers should take advantage of good care environments by investing more in offspring both before and after birth. These results provide novel mechanisms to explain contrasting patterns of maternal investment across cooperative breeders.