Trade-offs In Traits Research Articles

Chemical mutagenesis and thermal selection of coral photosymbionts induce adaptation to heat stress with trait trade-offs.

Despite the relevance of heat-evolved microalgal endosymbionts to coral reef restoration, to date, few Symbiodiniaceae strains have been thermally enhanced via experimental evolution. Here, we investigated whether the thermal tolerance of Symbiodiniaceae can be increased through chemical mutagenesis followed by thermal selection. Strains of Durusdinium trenchii, Fugacium kawagutii and Symbiodinium pilosum were exposed to ethyl methanesulfonate to induce random mutagenesis, and then underwent thermal selection at high temperature (31/33°C). After 4.6-5 years of experimental evolution, the in vitro thermal tolerance of these strains was assessed via reciprocal transplant experiments to ambient (27°C) and elevated (31/35°C) temperatures. Growth, photosynthetic efficiency, oxidative stress and nutrient use were measured to compare thermal tolerance between strains. Heat-evolved D. trenchii, F. kawagutii and S. pilosum strains all exhibited increased photosynthetic efficiency under thermal stress. However, trade-offs in growth rates were observed for the heat-evolved D. trenchii lineage at both ambient and elevated temperatures. Reduced phosphate and nitrate uptake rates in F. kawagutii and S. pilosum heat-evolved lineages, respectively, suggest alterations in nutrition resource usage and allocation processes may have occurred. Increased phosphate uptake rates of the heat-evolved D.trenchii strain indicate that experimental evolution resulted in further trade-offs in this species. These findings deepen our understanding of the physiological responses of Symbiodiniaceae cultures to thermal selection and their capacity to adapt to elevated temperatures. The new heat-evolved Symbiodiniaceae developed here may be beneficial for coral reef restoration efforts if their enhanced thermal tolerance can be conferred in hospite.

Trade-offs and synergies of plant traits co-drive efficient nitrogen use in intercropping systems

ContextNitrogen (N) enrichment increases aboveground net primary productivity, but causes a loss of plant diversity and a decline in ecosystem stability. Diverse systems that enhance the N-use efficiency help achieve sustainable development goals. Functional traits have been used to predict ecosystem functions in diverse systems. However, few studies considered both the effect of functional traits and evaluated the relationship between traits and N acquisition in intercropping. ObjectiveThe aim of this study was to evaluate the relationships between functional traits resulting from interspecific interactions and determine relationships between functional traits and N acquisition of intercropping systems. MethodsBased on a four-year N-manipulation field experiment, we measured 10 functional traits related to light interception and nutrient-use efficiency in different systems (maize (Zea mays L.), peanut (Arachis hypogaea L.), soybean (Glycine max L. Merrill.) monocultures, and maize/peanut and maize/soybean intercrops) at the pre-tasseling stage of maize, calculated the crude protein yield and aboveground N content at harvest time. ResultsThe maize grain N concentration was increased by N application, and it increased by intercropping in legumes. Both maize/soybean and maize/peanut intercropping systems increased crude protein productivity. Synergies among plant functional traits of maize allowed maize to establish its dominance, which resulted in greater N acquisition and crude protein yield of intercrops. Trade-offs among plant functional traits (between root traits and shoot traits of legumes) show strategies of legumes in response to interspecific competition. The specific leaf area of the legume was a key trait and affected interspecific interactions. This N-use advantage of intercropping was directly influenced by the aboveground functional traits of the system (community-weighted mean values of functional traits), but indirectly affected by belowground functional traits of the system. Conclusions and significanceOur study highlights greater N uptake of the intercropping system and suggests that intercropping can be used to increase the quality of crop products via enhancing crude protein production. The synergy and trade-offs in plant functional traits together enhance efficient N use in the intercropping systems. These findings help to better understand the underlying mechanisms that determine efficient resource use in diverse cropping systems and have implications for the sustainable management of food-production systems.

Geographic variation in the life history of lane snapper Lutjanus synagris, with new insights from the warm edge of its distribution.

Research on life-history variations in widely distributed fish species is needed to understand global warming impacts on populations and to improve fisheries management advice. The lane snapper Lutjanus synagris (Linnaeus, 1758) is commercially important to fisheries in the Western Central Atlantic, where spread information on its life-history traits is available. We studied growth, age, reproduction and mortality of lane snapper in the Guatemalan Caribbean, the warmest part of its distribution range, and collated the new information with published data in a latitudinal analysis extending between 18°S and 30°N. Longevity was estimated at 11 years, and von Bertalanffy growth parameters were asymptotic length (Linf) 45.6 and 42.2 cm for females and males, respectively, the growth coefficient (K) was 0.1 year-1 and the theoretical age at zero length (t0 ) was -4.4 years. Lane snapper grew slowest in April, prior to the rainy season, and at the onset of the reproductive season, which lasted from May to October. Fifty percent of female and male lane snappers matured at 23 and 17 cm, corresponding to 3.5 and 2.4 years of age respectively. A regional multivariate analysis found seawater temperature to be an important driver of life-history variation. Lane snapper lifespan was shorter at the warm edge of its distribution range, and maximum size and peak reproductive investment were negatively related to sea surface temperature. The trade-offs in lane snapper life-history traits and phenology likely enhance its fitness to differing environments. Interpolation from the present regional estimates to less-studied regions of the Caribbean is useful for preliminary understanding of reaction norms and harvest potentials.

Identification and validation of a major quantitative trait locus for spike length and compactness in the wheat (Triticum aestivum L.) line Chuanyu12D7.

Spike length (SL) and spike compactness (SC) are crucial traits related to wheat (Triticum aestivum L.) yield potential. In this study, a backcrossed inbred lines (BILs) population segregating for SL/SC was developed by using a commercial variety chuanyu25 as recurrent parent and a backbone parent Chuanyu12D7. Bulked segregant analysis (BSA) combined with the Wheat 660K SNP array was performed to conduct quantitative trait locus (QTL) mapping. A major and stable SL/SC QTL (designated as QSl/Sc.cib-2D.1) was identified on chromosome 2DS, explaining 45.63-59.72% of the phenotypic variation. QSl/Sc.cib-2D.1 was mapped to a 102.29-Kb interval by flanking SNPs AX-110276364 and AX-111593853 using a BC4F2:3 population. Since QSl/Sc.cib-2D.1 is linked to the Rht8 gene, their additive effects on plant type and spike type were analysed. Remarkably, the superior allele of QSl/Sc.cib-2D.1 combined with Rht8 can increase SL and TGW, and decrese SC without any apparent trade-offs in other yield-related traits. In addition, the closely linked kompetitive allele-specific PCR (KASP) markers of this locus were developed for marker-assisted selection (MAS) breeding. Four genes within the physical interval were considered as potential candidates based on expression patterns as well as orthologous gene functions. These results laid the foundation for map-based cloning of the gene(s) underlying QSl/Sc.cib-2D.1 and its potential application in wheat ideotype breeding.

Functional trait trade-offs define plant population stability across different biomes.

Ecological theory posits that temporal stability patterns in plant populations are associated with differences in species' ecological strategies. However, empirical evidence is lacking about which traits, or trade-offs, underlie species stability, especially across different biomes. We compiled a worldwide collection of long-term permanent vegetation records (greater than 7000 plots from 78 datasets) from a large range of habitats which we combined with existing trait databases. We tested whether the observed inter-annual variability in species abundance (coefficient of variation) was related to multiple individual traits. We found that populations with greater leaf dry matter content and seed mass were more stable over time. Despite the variability explained by these traits being low, their effect was consistent across different datasets. Other traits played a significant, albeit weaker, role in species stability, and the inclusion of multi-variate axes or phylogeny did not substantially modify nor improve predictions. These results provide empirical evidence and highlight the relevance of specific ecological trade-offs, i.e. in different resource-use and dispersal strategies, for plant populations stability across multiple biomes. Further research is, however, necessary to integrate and evaluate the role of other specific traits, often not available in databases, and intraspecific trait variability in modulating species stability.

Partial protection from fluctuating selection leads to evolution towards wider population size fluctuation and a novel mechanism of balancing selection.

When a population is partially protected from fluctuating selection, as when a seed bank is present, variance in fitness will be reduced and reproductive success of the population will be promoted. This study further investigates the effect of such a 'refuge' from fluctuating selection using a mathematical model that couples demographic and evolutionary dynamics. While alleles that cause smaller fluctuations in population density should be positively selected according to classical theoretic predictions, this study finds the opposite: alleles that increase the amplitude of population size fluctuation are positively selected if population density is weakly regulated. Under strong density regulation with a constant carrying capacity, long-term maintenance of polymorphism caused by the storage effect emerges. However, if the carrying capacity of the population is oscillating, mutant alleles whose fitness fluctuates in the same direction as population size are positively selected, eventually reaching fixation or intermediate frequencies that oscillate over time. This oscillatory polymorphism, which requires fitness fluctuations that can arise with simple trade-offs in life-history traits, is a novel form of balancing selection. These results highlight the importance of allowing joint demographic and population genetic changes in models, the failure of which prevents the discovery of novel eco-evolutionary dynamics.

Mechanistic Models of Trophic Interactions: Opportunities for Species Richness and Challenges for Modern Coexistence Theory.

AbstractMany potential mechanisms promote species coexistence, but we know little about their relative importance. To compare multiple mechanisms, we modeled a two-trophic planktonic food web based on mechanistic species interactions and empirically measured species traits. We simulated thousands of possible communities under realistic and altered interaction strengths to assess the relative importance of three potential drivers of phytoplankton and zooplankton species richness: resource-mediated coexistence mechanisms, predator-prey interactions, and trait trade-offs. Next, we computed niche and fitness differences of competing zooplankton to obtain a deeper understanding of how these mechanisms determine species richness. We found that predator-prey interactions were the most important driver of phytoplankton and zooplankton species richness and that large zooplankton fitness differences were associated with low species richness, but zooplankton niche differences were not associated with species richness. However, for many communities we could not apply modern coexistence theory to compute niche and fitness differences of zooplankton because of conceptual issues with the invasion growth rates arising from trophic interactions. We therefore need to expand modern coexistence theory to fully investigate multitrophic-level communities.

The Shift in Key Functional Traits Caused by Precipitation under Nitrogen and Phosphorus Deposition Drives Biomass Change in Leymus chinensis.

The trade-offs between key functional traits in plants have a decisive impact on biomass production. However, how precipitation and nutrient deposition affect the trade-offs in traits and, ultimately, productivity is still unclear. In the present study, a mesocosm experiment was conducted to explore the relationships between biomass production and the aboveground and belowground key functional traits and their trade-offs under changes in precipitation and nutrient depositions in Leymus chinensis, a monodominant perennial rhizome grass widespread in the eastern Eurasian steppe. Our results showed that moisture is the key factor regulating the effect of nitrogen (N) and phosphorus (P) deposition on increased biomass production. Under conditions of average precipitation, water use efficiency (WUE) was the key trait determining the biomass of L. chinensis. There were obvious trade-offs between WUE and leaf area, specific leaf area, leaf thickness, and leaf dry matter. Conversely, under increasing precipitation, the effect of restricted soil water on leaf traits was relieved; the key limiting trait changed from WUE to plant height. These findings indicate that the shift of fundamental traits of photosynthetic carbon gain induced by precipitation under N and P deposition is the key ecological driving mechanism for the biomass production of typical dominant species in semi-arid grassland.

Implementation of trait-based ozone plant sensitivity in the Yale Interactive terrestrial Biosphere model v1.0 to assess global vegetation damage

Abstract. A major limitation in modeling global ozone (O3) vegetation damage has long been the reliance on empirical O3 sensitivity parameters derived from a limited number of species and applied at the level of plant functional types (PFTs), which ignore the large interspecific variations within the same PFT. Here, we present a major advance in large-scale assessments of O3 plant injury by linking the trait leaf mass per area (LMA) and plant O3 sensitivity in a broad and global perspective. Application of the new approach and a global LMA map in a dynamic global vegetation model reasonably represents the observed interspecific responses to O3 with a unified sensitivity parameter for all plant species. Simulations suggest a contemporary global mean reduction of 4.8 % in gross primary productivity by O3, with a range of 1.1 %–12.6 % for varied PFTs. Hotspots with damage >10 % are found in agricultural areas in the eastern US, western Europe, eastern China, and India, accompanied by moderate to high levels of surface O3. Furthermore, we simulate the distribution of plant sensitivity to O3, which is highly linked with the inherent leaf trait trade-off strategies of plants, revealing high risks for fast-growing species with low LMA, such as crops, grasses, and deciduous trees.

Mechanism of Terrestrial Plant Community Assembly under Different Intensities of Anthropogenic Disturbance in Dianchi Lakeside

A lakeside is a functional transition zone that connects the lake aquatic ecosystem and the land ecosystem. Understanding the community assembly mechanism is crucial for regional ecological restoration, habitat management, and biodiversity conservation. However, research on the terrestrial plant community assembly in lakesides under anthropogenic disturbance is still lacking. The present study used phylogeny and functional traits to assess the community assembly of three habitat types with different anthropogenic disturbances in Dianchi lakeside. The factors that influenced the community assembly were also explored. Results indicated that the phylogenetic signals of all the examined functional traits of the dominant species were weak, suggesting that the traits were convergent. The community phylogenetic and functional structures of the different habitat types showed random patterns. Thus, the assembly of terrestrial plant communities in the three habitat types was driven by competitive exclusion and neutral processes in Dianchi lakeside. The trait trade-off strategies of species in the different habitats varied with the different habitat types. Anthropogenic disturbance played an important role in the process of community assembly. The present study provides a scientific basis for the assessment and management of ecological restoration in Dianchi lakeside and other plateau lakes and enriches the knowledge on the community assembly mechanism of disturbed plant communities.

Root traits in response to frequent fires: Implications for belowground carbon dynamics in fire-prone savannas.

Predicting how belowground carbon storage reflects changes in aboveground vegetation biomass is an unresolved challenge in most ecosystems. This is especially true for fire-prone savannas, where frequent fires shape the fraction of carbon allocated to root traits for post-fire vegetation recovery. Here I review evidence on how root traits may respond to frequent fires and propose to leverage root traits to infer belowground carbon dynamics in fire-prone savannas. Evidently, we still lack an understanding of trade-offs in root acquisitive vs. conservative traits in response to frequent fires, nor have we determined which root traits are functionally important to mediate belowground carbon dynamics in a frequently burned environment. Focusing research efforts along these topics should improve our understanding of savanna carbon cycling under future changes in fire regimes.

Soil resources and functional trait trade-offs determine species biomass stocks and productivity in a tropical dry forest

Previous studies have shown that environmental conditions and plant attributes determine biomass stocks and productivity across multiple tropical forests. However, it is less clear how these factors act at local scales. We evaluated how the spatial variation of soil resource availability (soil nutrient and water content) and plant functional traits determine species biomass stocks and productivity in a Colombian tropical dry forest, based on spatially explicit soil sampling and an intensive plant trait characterization of 89 species in three 1-ha permanent plots with similar climate and floristic composition. Within each plot, we measured nine soil variables and ten functional traits and quantified forest biomass stocks and productivity for 10,161 individual trees in a period of 3 years. The soil resources where species were located and their functional traits had coordinated effects on the spatial distribution of forest biomass stocks across the plots. The highest biomass stocks were concentrated on nutrient-rich soils with low water availability and were dominated by conservative species with dense tissues and low hydraulic failure risk, probably because they are able to better cope with water limitation. Most of the remaining forest biomass stocks were found in nutrient-poor soils with high water availability and were dominated by acquisitive species. Sites with nutrient-rich soils and low water availability increased biomass survival but also mortality; however, the presence of conservative species in these sites also increased biomass survival, decreased mortality, and led to biomass accumulation, probably because their strong and hydraulically secure tissues are able to deal with water limitation for nutrient absorption during dry seasons. Interestingly, soil resources and functional traits had no effects on biomass recruitment. We conclude that strong coordinated effects of soil resources and functional traits determine local biomass processes of tropical dry forests with a central role of conservative trait species types, whereby these species promote community assembly and functioning but are also vulnerable to potential changes in water availability. Thus, conservation and restoration actions should pay special attention to soil and plant functional trait trade-offs to improve management practices in these threatened forests.

Height and crown allometries and their relationship with functional traits: An example from a subtropical wet forest.

Forest tree communities are largely structured by interactions between phenotypes and their environments. Functional traits have been popularized as providing key insights into plant functional tradeoffs. Similarly, tree crown-stem diameter and tree height-stem diameter allometric relationships are likely to be strongly coordinated with functional trait tradeoff axes. Specifically, species with functional traits indicative of conservative strategies (i.e., dense wood, heavy seeds) should be related to tree architectures that have lower heights and wider crowns for a given stem diameter. For example, shade-tolerant species in tropical forests are typically characterized as having dense wood, large seeds, and relatively broad crowns at early ontogenetic stages. Here, we focus on 14 dominant dicot tree species in a tropical forest. We utilized hierarchical Bayesian models to characterize species-specific height and crown size allometric parameters. We sampled from the posterior distributions for these parameters and correlated them with six functional traits. We also characterize the expected height and crown size for a series of reference stem diameters to quantify the relationship between traits and tree architecture across size classes. We find little interspecific variation in allometric slopes, but clear variation in allometric intercepts. Allometeric height intercepts were negatively correlated with wood density and crown size intercepts were positively related to wood density and seed mass and negatively related to leaf percent phosphorus. Thus, interspecific variation in tree architecture is generated by interspecific variation in allometric intercepts and not slopes. These intercepts could be predicted using a handful of functional traits where conservative traits were indicative of trees that are relatively short and have larger crown sizes. This demonstrates a coordination of tropical tree life histories that can be characterized simultaneously with functional traits and tree allometries.

Woody plant adaptations to multiple abiotic stressors: Where are we?

Interacting abiotic stresses exert a fundamental selective pressure on the adaptive syndromes of long-living organisms such as woody plants. However, general patterns and mechanisms describing woody plant adaptations to tolerate multiple abiotic stressors are yet to emerge. This hampers our ability to build predictive frameworks foreseeing species responses to stochastic changes in abiotic stress regimes due to climate change. With this Virtual Special Issue (VSI), we aimed to summarize what we know, and what we do not know, about woody plant adaptations to achieve tolerance to multiple abiotic limitations. To this end, we brought together studies exploring ecological or ecophysiological perspectives on woody plant adaptations to tolerate multiple abiotic stresses. Ecological studies suggest patterns associating trait trade-offs, climate, and biotic interactions with woody plants’ multi-stress tolerance. Ecophysiological studies point to traits and conceptual frameworks that might explain some processes underpinning woody plant multi-stress tolerance. Here, we first revised the definitions of stress and stress tolerance used in ecological and ecophysiological research, providing a nomenclature of tolerance that could be used to unify definitions across research fields. Then, we summarized the main theories and evidence on woody plant adaptations to tolerate multiple abiotic stresses. Finally, we introduced the ecological and ecophysiological perspectives on this matter and placed the contributions to this VSI within the current state of the art. Altogether, this VSI allowed us to identify the lack of large-scale integration of patterns and processes describing woody plant adaptations to multiple abiotic stresses as a major gap in this field.

Influence of environmental factors on biodiversity, abundance and the distribution pattern of dinoflagellates and ciliates during spring and summer in coastal waters of Algeria (southwestern Mediterranean Sea)

Abstract The objective of this study was to assess the distribution patterns of dinoflagellates and ciliates communities during planktonic bloom and post-bloom development periods, in relation to environmental parameters. Their distribution was studied during spring and summer 2012, in coastal waters of Algeria at six sampling stations (four sampling layers). Overall, 116 species were identified, including 98 dinoflagellates. The species richness of microzooplankton was higher in summer (81 species: 67 dinoflagellates, seven tintinnids and seven ciliates) than in spring (76 species: 72 dinoflagellates, three naked ciliates and one tintinnid). Significant difference in total abundances was observed between spring (median = 145 ind l−1) and summer (median = 90 ind l−1) but no significance (P > 0.05, Mann–Whitney test) in Shannon–Wiener (H′spring: 3.31 bits ind−1; H′summer: 3.70 bits ind−1) and evenness (Espring: 0.77; Esummer: 0.84) indices. The ciliate average abundance was higher in summer (11.3 ind l−1) than in spring (1.95 ind l−1), whereas dinoflagellate average abundance was lower in summer (127.92 ind l−1) than spring (190.19 ind l−1). Non-metric multidimensional scaling was used to identify different sample assemblages. It showed that temperature and salinity influenced the distribution pattern in the canonical correspondence analysis followed by chlorophyll a, silicate and nitrate concentrations. Our framework provides insight regarding trait trade off with implications for feedbacks to ecosystems, aiming to bridge the gap of plankton community ecology in Algeria. It elaborates a taxonomic list of dinoflagellates and ciliates in the marine pelagic ecosystem and performs their ecological characterization in their environment.

Soil microbial trait-based strategies drive the storage and stability of the soil carbon pool in Robinia pseudoacacia plantations

Soil microorganisms play an essential role in soil carbon sequestration and stability in forest ecosystems. However, how trade-offs in distinct microbial traits affect soil carbon storage and stability remains largely unknown, especially for forest soils that stock significant amounts of organic carbon. Here, we assessed the influences of the chronosequence of Robinia pseudoacacia (8, 18, and 30 years) on soil organic carbon (SOC) fractions and further explored the specific roles of microbial taxa in regulating soil carbon sequestration on the Loess Plateau via high-throughput sequencing techniques and analysis of co-occurrence networks and assembly processes. The results showed that the concentrations of soil easily oxidizable carbon (EOC), recalcitrant organic carbon (ROC), and SOC storage increased with stand age. However, the dissolved organic carbon (DOC) and microbial biomass carbon (MBC) concentrations increased from 8 years to 18 years and then decreased after 30 years. Stand age significantly affected the soil bacterial and fungal structures and diversity. Stochastic processes, especially dispersal limitation, were the main assembly processes affecting the bacterial and fungal communities. Soil pH, DOC and the N:P ratio drove bacterial assembly. However, fungal assembly was not affected by soil properties. Moreover, network analysis showed that three major bacterial modules and one major fungal module (Bac_Mod 1, 3, 4 and Fun_Mod 2) showed strong relationships with soil carbon storage and were considered soil carbon pool-associated modules. These modules based on the co-occurrence network analysis were composed of microbial taxa with different taxonomic and functional traits. Both random forest and correlation analyses indicated that increases or decreases in these modules were strongly correlated to variations in SOC fractions. These results demonstrated that with R. pseudoacacia plantation development, the recalcitrant-related module attributed to SOC became more stable.

Variations in phenotypic plasticity in a cosmopolitan copepod species across latitudinal hydrographic gradients

Studies assessing latitudinal variations in habitat conditions and phenotypic plasticity among populations yield evidence of the mechanisms governing differentiation in the potential to adapt to current/future habitat changes. The cosmopolitan copepod species Acartia tonsa thrives across ocean clines delimiting Seasonal (30–40° S) and Permanent (10–30° S) Upwelling coastal provinces established during the middle–late Pliocene (3.6–1.8 Ma) alongshore the South East Pacific (SEP), nowadays exhibiting contrasting variability features related to several ocean drivers (temperature, salinity, pH, and food availability). Latitudinal variation across the range of environmental conditions of the coastal provinces can contribute toward shaping divergent A. tonsa’s phenotypes, for example, through specific patterns of phenotypic plasticity in morphological and physiological traits and tolerance to environmental drivers. With the aim of contributing to the understanding of these adaptive processes in a relatively little studied oceanic region, here we compared the expression of parental (i.e., adult size, egg production, and ingestion rate) and offspring (i.e., egg size) traits in relation to variation in environmental habitat conditions across different cohorts of two distant (> 15° latitude) A. tonsa populations inhabiting estuarine and upwelling habitats located in the Seasonal and Permanent Upwelling province, respectively. Mean conditions and ranges of variability in the habitat conditions and phenotypic plasticity of parental and offspring traits within and among cohorts of A. tonsa populations varied significantly across the different examined regions (i.e., Seasonal vs. Permanent). We also found significant differences in the coupling of habitat variability and trait expression, suggesting that the differences in trait expressions might be related to habitat variability. The phenotypic divergence was translated to cohort-related patterns of trait trade-offs regulating reproduction and tolerance of egg production efficiency that can jointly determine the level of plasticity, genetic structure, or local adaptation. The current findings provide novel evidence of how divergent phenotypes might sustain A. tonsa populations across variable coastal provinces of the SEP.

The effects of different temperatures in mercury toxicity to the terrestrial isopod Porcellionides pruinosus

Climate changes and metal contamination are pervasive stressors for soil ecosystems. Mercury (Hg), one of the most toxic metals, has been reported to interact with temperature. However, compared to aquatic biota, little is known about how temperature affects Hg toxicity and bioaccumulation to soil organisms. Here, toxicity and bioaccumulation experiments were replicated at 15 °C, 20 °C, and 25 °C to understand how sub-optimal temperatures affect the toxicokinetics and toxicodynamics of Hg via soil. Genotoxicity and energy reserves were also assessed to disclose potential trade-offs in life-history traits. Results underpin the complexity of temperature-Hg interactions. Survival was determined mainly by toxicokinetics, but toxicodynamics also played a significant role in defining survival probability during early stages. The processes determining survival probability were faster at 25 °C: General Unified Threshold of Survival (GUTS) model identified an earlier/steeper decline in survival, compared to 20 °C or 15 °C, but it also approached the threshold faster. Despite potentiation of Hg genotoxicity, temperature promoted faster detoxification, either increasing toxicokinetics rates or damage repair mechanisms. This metabolism-driven increase in detoxification led to higher depletion of energy reserves and likely triggered stress response pathways. This work emphasized the need for comprehensive experimental approaches that can integrate the multiple processes involved in temperature-metal interactions.

Growth and reproduction in the land snail Allopeas gracile (Hutton 1834): a laboratory appraisal

ABSTRACT The growth and reproduction of the graceful awl snail Allopeas gracile (Hutton 1834) (Gastropoda: Subulinidae) were evaluated in the laboratory. Observations on single individual and multiple individuals showed similar growth pattern fitted with the von Bertalanffy growth model. A fecundity schedule of the snail was constructed using the daily reproductive outputs of the snails in cohort and in isolated state. The net reproductive rate (R0) and the finite rate of increase (λ) of single individuals (R0 = 124.33 ± 14.67 SE, λ = 1.03 ± 0.003 SE) were lower than the individuals reared in cohort (R0 = 774.55 ± 147.49 SE, λ = 1.115 ± 0.006 SE). The generation time (Tc) of individuals in competition was 107.89 ± 7.92 SE days, while single individuals had longer generation time of 199.39 ± 7.24 SE days. The longevity, the shell size and the shell length, body weight and the fecundity of A. gracile exhibited correspondences as well as provided evidences of the tradeoff in the life history traits. Information on the growth and reproduction of the snail A. gracile will therefore be suitable to assess the life history feature and serves as an input for framing the strategies for its population regulation.

Hemiepiphytic figs kill their host trees: acquiring phosphorus is a driving factor.

Hemiepiphytic figs killing their host trees is an ecological process unique to the tropics. Yet the benefits and adaptive strategies of their special life history remain poorly understood. We compared leaf phosphorus (P) content data of figs and palms worldwide, and functional traits and substrate P content of hemiepiphytic figs (Ficus tinctoria), their host palm and nonhemiepiphytic conspecifics at different growth stages in a common garden. We found that leaf P content of hemiepiphytic figs and their host palms significantly decreased when they were competing for soil resources, but that of hemiepiphytic figs recovered after host death. P availability in the canopy humus and soil decreased significantly with the growth of hemiepiphytic figs. Functional trait trade-offs of hemiepiphytic figs enabled them to adapt to the P shortage while competing with their hosts. From the common garden to a global scale, the P competition caused by high P demand of figs may be a general phenomenon. Our results suggest that P competition is an important factor causing host death, except for mechanically damaging and shading hosts. Killing hosts benefits hemiepiphytic figs by reducing interspecific P competition and better acquiring P resources in the P-deficient tropics, thereby linking the life history strategy of hemiepiphytic figs to the widespread P shortage in tropical soils.