Reaction Norms Research Articles

Urbanization alters plastic responses in the common dandelion Taraxacum officinale.

Urban environments expose species to contrasting selection pressures relative to rural areas due to altered microclimatic conditions, habitat fragmentation, and changes in species interactions. To improve our understanding on how urbanization impacts selection through biotic interactions, we assessed differences in plant defense and tolerance, dispersal, and flowering phenology of a common plant species (Taraxacum officinale) along an urbanization gradient and their reaction norms in response to a biotic stressor (i.e., herbivory). We raised plants from 45 lines collected along an urbanization gradient under common garden conditions and assessed the impact of herbivory on plant growth (i.e., aboveground biomass), dispersal capacity (i.e., seed morphology), and plant phenology (i.e., early seed production) by exposing half of our plants to two events of herbivory (i.e., grazing by locusts). Independent from their genetic background, all plants consistently increased their resistance to herbivores by which the second exposure to locusts resulted in lower levels of damage suffered. Herbivory had consistent effects on seed pappus length, with seeds showing a longer pappus (and, hence, increased dispersal capacities) regardless of urbanization level. Aboveground plant biomass was neither affected by urbanization nor herbivore presence. In contrast to consistent responses in plant defenses and pappus length, plant fitness did vary between lines. Urban lines had a reduced early seed production following herbivory while rural and suburban lines did not show any plastic response. Our results show that herbivory affects plant phenotypes but more importantly that differences in herbivory reaction norms exist between urban and rural populations.

Modelling population dynamics based on experimental trials with genetically modified (RIDL) mosquitoes

Recently, the RIDL-SIT technology has been field-tested for control of Aedes aegypti. The technique consists of releasing genetically modified mosquitoes carrying a “lethal gene”. In 2016 the World Health Organization (WHO) and the Pan-American Health Organization (PAHO) recommended to their constituent countries to test the new technologies proposed to control Aedes aegypti populations. However, issues concerning effectiveness and ecological impact have not been thoroughly studied so far. In order to study these issues, we develop an ecological model. It presents interdependent dynamics of mosquito populations and food in a homogeneous setting. Mosquito populations are described in a stochastic compartmental setup, in terms of reaction norms depending on the available food in the environment. The development of the model allows us to indicate some critical biological knowledge that is missing and could (should) be produced. Hybridisation levels, release numbers during and after intervention and population recovery time after the intervention as a function of intervention duration and target are calculated under different hypotheses with regard to the fitness of hybrids and compared with two field studies of actual interventions. This minimal model should serve as a basis for detailed models when the necessary information to construct them is produced. For the time being, the model shows that nature will not clean non-lethal introgressed genes.

Larger bacterial populations evolve heavier fitness trade-offs and undergo greater ecological specialization.

Evolutionary studies over the last several decades have invoked fitness trade-offs to explain why species prefer some environments to others. However, the effects of population size on trade-offs and ecological specialization remain largely unknown. To complicate matters, trade-offs themselves have been visualized in multiple ways in the literature. Thus, it is not clear how population size can affect the various aspects of trade-offs. To address these issues, we conducted experimental evolution with Escherichia coli populations of two different sizes in two nutritionally limited environments, and studied fitness trade-offs from three different perspectives. We found that larger populations evolved greater fitness trade-offs, regardless of how trade-offs are conceptualized. Moreover, although larger populations adapted more to their selection conditions, they also became more maladapted to other environments, ultimately paying heavier costs of adaptation. To enhance the generalizability of our results, we further investigated the evolution of ecological specialization across six different environmental pairs, and found that larger populations specialized more frequently and evolved consistently steeper reaction norms of fitness. This is the first study to demonstrate a relationship between population size and fitness trade-offs, and the results are important in understanding the population genetics of ecological specialization and vulnerability to environmental changes.

The geometry of reaction norms yields insights on classical fitness functions for Great Lakes salmon.

Life history theory examines how characteristics of organisms, such as age and size at maturity, may vary through natural selection as evolutionary responses that optimize fitness. Here we ask how predictions of age and size at maturity differ for the three classical fitness functions–intrinsic rate of natural increase r, net reproductive rate R0, and reproductive value Vx−for semelparous species. We show that different choices of fitness functions can lead to very different predictions of species behavior. In one’s efforts to understand an organism’s behavior and to develop effective conservation and management policies, the choice of fitness function matters. The central ingredient of our approach is the maturation reaction norm (MRN), which describes how optimal age and size at maturation vary with growth rate or mortality rate. We develop a practical geometric construction of MRNs that allows us to include different growth functions (linear growth and nonlinear von Bertalanffy growth in length) and develop two-dimensional MRNs useful for quantifying growth-mortality trade-offs. We relate our approach to Beverton-Holt life history invariants and to the Stearns-Koella categorization of MRNs. We conclude with a detailed discussion of life history parameters for Great Lakes Chinook Salmon and demonstrate that age and size at maturity are consistent with predictions using R0 (but not r or Vx) as the underlying fitness function.

Recent advances on the estimation of the thermal reaction norm for sex ratios.

Temperature-dependent sex determination, or TSD, is a widespread phenomenon in reptiles. The shape of the relationship between constant incubation temperature and sex ratio defines the TSD pattern. The TSD pattern is considered a life-history parameter important for conservation because the wider the range of temperatures producing both sexes, the more resilient the species is to climate change impacts. We review the different published equations and methodologies that have been used to model TSD patterns. We describe a new flexible model that allows for an asymmetrical pattern around the pivotal temperature, which is the constant temperature producing both sexes in equal proportions. We show that Metropolis-Hastings with Markov chain produced by a Monte Carlo process has many advantages compared to maximum likelihood and is preferred. Finally, we apply the models to results from incubation experiments using eggs from the marine turtle Lepidochelys olivacea originating in Northeast Indian, East Pacific, and West Atlantic Regional Management Units (RMUs) and find large differences in pivotal temperatures but not in transitional ranges of temperatures.

The power and limitations of gene expression pathway analyses toward predicting population response to environmental stressors.

Rapid environmental changes impact the global distribution and abundance of species, highlighting the urgency to understand and predict how populations will respond. The analysis of differentially expressed genes has elucidated areas of the genome involved in adaptive divergence to past and present environmental change. Such studies however have been hampered by large numbers of differentially expressed genes and limited knowledge of how these genes work in conjunction with each other. Recent methods (broadly termed “pathway analyses”) have emerged that aim to group genes that behave in a coordinated fashion to a factor of interest. These methods aid in functional annotation and uncovering biological pathways, thereby collapsing complex datasets into more manageable units, providing more nuanced understandings of both the organism‐level effects of modified gene expression, and the targets of adaptive divergence. Here, we reanalyze a dataset that investigated temperature‐induced changes in gene expression in marine‐adapted and freshwater‐adapted threespine stickleback (Gasterosteus aculeatus), using Weighted Gene Co‐expression Network Analysis (WGCNA) with PANTHER Gene Ontology (GO)‐Slim overrepresentation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. Six modules exhibited a conserved response and six a divergent response between marine and freshwater stickleback when acclimated to 7°C or 22°C. One divergent module showed freshwater‐specific response to temperature, and the remaining divergent modules showed differences in height of reaction norms. PPARAa, a transcription factor that regulates fatty acid metabolism and has been implicated in adaptive divergence, was located in a module that had higher expression at 7°C and in freshwater stickleback. This updated methodology revealed patterns that were not found in the original publication. Although such methods hold promise toward predicting population response to environmental stressors, many limitations remain, particularly with regard to module expression representation, database resources, and cross‐database integration.

Variability approaching the thermal limits can drive diatom community dynamics

AbstractOrganismal distributions are largely mediated by temperature, suggesting thermal trait variability plays a key role in defining species' niches. We employed a trait‐based approach to better understand how inter‐ and intraspecific thermal trait variability could explain diatom community dynamics using 24 strains from 5 species in the diatom genus Skeletonema, isolated from Narragansett Bay (NBay), where this genus can comprise up to 99% of the microplankton. Strain‐specific thermal reaction norms were generated using growth rates obtained at temperatures ranging from −2°C to 36°C. Comparison of thermal reaction norms revealed inter‐ and intraspecific similarities in the thermal optima, but significant differences approaching the thermal limits. Cellular elemental composition was determined for two thermally differentiated species and again, the most variation occurred approaching the thermal limits. To determine the potential impact of interspecific variability on community composition, a species succession model was formulated utilizing each species' empirically determined thermal reaction norm and historical temperature data from NBay. Seasonal succession in the modeled community resembled the timing of species occurrence in the field, but not species' relative abundance. The model correctly predicted the timing of the dominant winter–spring species, Skeletonema marinoi, within 0–14 d of its observed peak occurrence in the field. Interspecific variability approaching the thermal limits provides an alternative mechanism for temporal diatom succession, leads to altered cellular elemental composition, and thus has the potential to influence carbon flux and nutrient cycling, suggesting that growth approaching the thermal limits be incorporated into both empirical and modeling efforts in the future.

Multigenerational exposure to elevated temperatures leads to a reduction in standard metabolic rate in the wild.

In light of global climate change, there is a pressing need to understand and predict the capacity of populations to respond to rising temperatures. Metabolic rate is a key trait that is likely to influence the ability to cope with climate change. Yet, empirical and theoretical work on metabolic rate responses to temperature changes has so far produced mixed results and conflicting predictions.Our study addresses this issue using a novel approach of comparing fish populations in geothermally warmed lakes and adjacent ambient‐temperature lakes in Iceland. This unique ‘natural experiment’ provides repeated and independent examples of populations experiencing contrasting thermal environments for many generations over a small geographic scale, thereby avoiding the confounding factors associated with latitudinal or elevational comparisons. Using Icelandic sticklebacks from three warm and three cold habitats, we measured individual metabolic rates across a range of acclimation temperatures to obtain reaction norms for each population.We found a general pattern for a lower standard metabolic rate (SMR) in sticklebacks from warm habitats when measured at a common temperature, as predicted by Krogh's rule. Metabolic rate differences between warm‐ and cold‐habitat sticklebacks were more pronounced at more extreme acclimation temperatures, suggesting the release of cryptic genetic variation upon exposure to novel conditions, which can reveal hidden evolutionary potential. We also found a stronger divergence in metabolic rate between thermal habitats in allopatry than sympatry, indicating that gene flow may constrain physiological adaptation when dispersal between warm and cold habitats is possible.In sum, our study suggests that fish may diverge toward a lower SMR in a warming world, but this might depend on connectivity and gene flow between different thermal habitats. A free Plain Language Summary can be found within the Supporting Information of this article.

Transgenerational plasticity of inducible defences: Combined effects of grand-parental, parental and current environments.

Phenotypic plasticity can occur across generations (transgenerational plasticity) when environments experienced by the previous generations influenced offspring phenotype. The evolutionary importance of transgenerational plasticity, especially regarding within‐generational plasticity, is a currently hot topic in the plasticity framework. How long an environmental effect can persist across generations and whether multigenerational effects are cumulative are primordial—for the evolutionary significance of transgenerational plasticity—but still unresolved questions. In this study, we investigated how the grand‐parental, parental and offspring exposures to predation cues shape the predator‐induced defences of offspring in the Physa acuta snail. We expected that the offspring phenotypes result from a three‐way interaction among grand‐parental, parental and offspring environments. We exposed three generations of snails without and with predator cues according to a full factorial design and measured offspring inducible defences. We found that both grand‐parental and parental exposures to predator cues impacted offspring antipredator defences, but their effects were not cumulative and depended on the defences considered. We also highlighted that the grand‐parental environment did alter reaction norms of offspring shell thickness, demonstrating an interaction between the grand‐parental transgenerational plasticity and the within‐generational plasticity. We concluded that the effects of multigenerational exposure to predator cues resulted on complex offspring phenotypic patterns which are difficult to relate to adaptive antipredator advantages.

Genotype-environment interaction for age at first calving in Holstein cows in Brazil

Dairy cattle production is distributed throughout the Brazilian regions. However, Brazilian producing regions are different in air temperature and humidity, diet, birth season, and other factors that may alter the reproductive performances of cows. The age of the cow at first calving (AFC) is a good indicator of sexual precocity since it shows the beginning of the female reproductive life and has a great influence on cow replacement costs. Researches on genotype-environment interaction (GEI) show the importance of using specific bulls for the different production systems in Brazil since most semen used in the country is imported. The objective of this work was to evaluate GEI for AFC in Holstein cows in Brazil, using reaction norms. The statistical models used were the standard animal model, which disregards the GEI, and hierarchical reaction norm models with homoscedastic (HRNMHO) and heteroscedastic (HRNMHE) residual variance, and one (HRNMHO1S and HRNMHE1S) and two (HRNMHO2S and HRNMHE2S) steps. HRNMHO1S presented better fit to the data, with lower heritability for environments with lower AFC, and higher heritability for environments with higher AFC. The GEI found was complex, with a reclassification of bulls, denoting the importance of considering GEI for evaluation and selection of bulls for different production levels. The reduction of AFC is possible when using breeding bulls adapted to the tropical and subtropical conditions of Brazil.

A novel GIS-based tool to reveal spatial trends in reaction norm: upland rice case study

The upland rice crop system located within Brazilian savannas and Amazon Rainforest is the largest rainfed rice growing area in Latin America. To develop and release higher yield and adapted cultivars for this large region, the upland rice breeders need to conduct multiple-location trials aiming to model the genotype × location (G × L) and evaluate the germplasm yield adaptability. Here we hypothesize that regional patterns of G × L across this extensive region can be modeled by integrating factorial regression models with a geographic information system (GIS). Two sets of advanced yield trials from different germplasm pool were used in this study. From GIS tools, we collect and process geographic covariates and produce thematic maps of yield adaptability. One advantage of the methodology is that adaptability can be dissected into genotypic-sensibility coefficients related to the reaction norm for the geographic gradient. Then, breeders can discriminate different types of adaptability over a region, such as responsiveness for elevation, longitudinal or latitudinal adaptation, identifying possible ideotypes to solve current adaptation gaps for target regions. We observed that about of 53–59% of the G × L effects are due to predictable geographic-related factors. However, the upland rice germplasm is better adapted to higher elevations (> 700 m), which may indicate limitations in cultivar development because these regions do not represent the current upland rice growing region. We suggest to exploit geographic-related factors by increasing breeding efforts for northern and western Brazil environments located at lower elevations (< 300 m) and Equador’s near latitudes (2° S–2° N).

From individuals to populations: How intraspecific competition shapes thermal reaction norms

Abstract Most ectotherms follow the temperature‐size rule (TSR): in cold environments individuals grow slowly but reach a large asymptotic length. Intraspecific competition can induce plastic changes of growth rate and asymptotic length and competition may itself be modulated by temperature. Our aim was to disentangle the joint effects of temperature and intraspecific competition on growth rate and asymptotic length. We used two distinct clonal lineages of the Collembola Folsomia candida, to describe thermal reaction norms of growth rate, asymptotic length and reproduction over six temperatures between 6 and 29°C. In parallel, we measured the long‐term size structure and dynamics of springtail populations reared under the same temperatures to measure growth rates and asymptotic lengths in populations and to quantify the joint effects of competition and temperature on these traits. We show that intraspecific competition modulates the temperature‐size rule. In dense populations there is a direct negative effect of temperature on asymptotic length, but there is no temperature dependence of the growth rate, the dominant factor regulating growth being competition. The two lineages responded differently to the joint effects of temperature and competition on growth and asymptotic size and these genetic differences have marked effects on population structure along our temperature gradient. Our results reinforce the idea that the TSR of ectotherms can be modulated by biotic and abiotic stressors when studied in non‐optimal laboratory experiments. Untangling complex interactions between the environment and demography will help to understand how growth trajectories respond to environmental change and how climate change may influence population size structure. A free Plain Language Summary can be found within the Supporting Information of this article.

High differentiation in functional traits but similar phenotypic plasticity in populations of a soil specialist along a climatic gradient.

Plants experiencing contrasting environmental conditions may accommodate such heterogeneity by expressing phenotypic plasticity, evolving local adaptation or a combination of both. We investigated patterns of genetic differentiation and plasticity in response to drought in populations of the gypsum specialist Lepidium subulatum. We created an outdoor common garden with rain exclusion structures using 60 maternal progenies from four distinct populations that substantially differ in climatic conditions. We characterized fitness, life history and functional plasticity in response to two contrasting treatments that realistically reflect soil moisture variation in gypsum habitats. We also assessed neutral genetic variation and population structure using microsatellite markers. In response to water stress, plants from all populations flowered earlier, increased allocation to root tissues and advanced leaf senescence, consistent with a drought escape strategy. Remarkably, these probably adaptive responses were common to all populations, as shown by the lack of population × environment interaction for almost all functional traits. This generally common pattern of response was consistent with substantial neutral genetic variation and large differences in population trait means. However, such population-level trait variation was not related to climatic conditions at the sites of origin. Our results show that, rather than ecotypes specialized to local climatic conditions, these populations are composed of highly plastic, general-purpose genotypes in relation to climatic heterogeneity. The strikingly similar patterns of plasticity among populations, despite substantial site of origin differences in climate, suggest past selection on a common norm of reaction due to similarly high levels of variation within sites. It is thus likely that plasticity will have a prevalent role in the response of this soil specialist to further environmental change.

When to diapause or not to diapause? Winter predictability is not the answer

A recommendation of: Jens Joschinski and Dries Bonte Diapause is not selected as a bet-hedging strategy in insects: a meta-analysis of reaction norm shapes 10.1101/752881

Constitutive and Plastic Gene Expression Variation Associated with Desiccation Resistance Differences in the Drosophila americana Species Group.

Stress response mechanisms are ubiquitous and important for adaptation to heterogenous environments and could be based on constitutive or plastic responses to environmental stressors. Here we quantify constitutive and plastic gene expression differences under ambient and desiccation stress treatments, in males and females of three species of Drosophila known to differ in desiccation resistance. Drosophila novamexicana survives desiccation trials significantly longer than the two subspecies of Drosophila americana, consistent with its natural species range in the desert southwest USA. We found that desiccation stress reduces global expression differences between species—likely because many general stress response mechanisms are shared among species—but that all species showed plastic expression changes at hundreds of loci during desiccation. Nonetheless, D. novamexicana had the fewest genes with significant plastic expression changes, despite having the highest desiccation resistance. Of the genes that were significantly differentially expressed between species—either within each treatment (>200 loci), constitutively regardless of treatment (36 loci), or with different species-specific plasticity (26 loci)—GO analysis did not find significant enrichment of any major gene pathways or broader functions associated with desiccation stress. Taken together, these data indicate that if gene expression changes contribute to differential desiccation resistance between species, these differences are likely shaped by a relatively small set of influential genes rather than broad genome-wide differentiation in stress response mechanisms. Finally, among the set of genes with the greatest between-species plasticity, we identified an interesting set of immune-response genes with consistent but opposing reaction norms between sexes, whose potential functional role in sex-specific mechanisms of desiccation resistance remains to be determined.

Repeatability of behavior and physiology: No impact of reproductive investment

Animals have well-documented individual differences in their behaviour, including in their response to stressful stimuli. The physiological bases for the repeatability of these traits has been the focus of much research in recent years, in an attempt to explain the mechanistic drivers for behavioral syndromes. Whilst a range of studies have demonstrated repeatable individual differences in physiological traits, little is known about potential trade-offs between reproductive investment and the physiological responses to subsequent stressors. We therefore sought to test the behavioral and physiological responses of male zebra finches (Taeniopygia guttata) to a novel environment, quantifying a series of repeated “temporal reaction norms” before and after reproduction. Given that reproductive investment is costly both in time and energy, it is likely to affect expression of behavioral and physiological traits. We hypothesised that reproductive investment would impact the consistency of these temporal reaction norms. Specifically, we predicted that individuals which invested more in reproduction would show altered rates of habituation to a stressful stimulus. Therefore, we quantified temporal reaction norm components (i.e., intercept and slope) of two behaviours and metabolic rate (MR) within and among individuals before and after a breeding season. We found that individuals consistently differed in how their locomotor and feeding activity increased upon introduction into a novel environment and also how their MR decreased after being handled and confined within the metabolic chamber. We also found that the slope of the feeding activity reaction norm was negatively correlated with stress-induced corticosterone levels at the within-individual level. Finally, in contrast to our prediction, we found that neither the intercept nor slope of the reaction norms were influenced by the reproductive effort (the number of fledglings produced) displayed by individual males. This suggests that the substantial individual variation in the expression of physiological and behavioural traits is not plastic with respect to the immediate consequences of reproductive investment. This study is the first quantification of metabolic rate reaction norms and their relationships with fitness, which represents an important first step towards understanding the evolutionary significance of instantaneous habituation to stressful and novel situations.

Morphological and physiological plasticity in seedlings of Araucaria angustifolia and Cabralea canjerana is related to plant establishment performance in the rainforest

High phenotypic plasticity is an important characteristic that should have a tree species that is going to be used to restore degraded rainforests, as those are stressful and changing environments. Quantifying phenotypic plasticity is necessary to compare species and populations. At least 17 different indexes have been employed to measure phenotypic plasticity and most of them were analyzed in pot experiments. However, no studies that evaluate the degree of coincidence between plasticity indexes were applied in pot and field experiments. The aim of this work is to determine the importance of species acclimation and plasticity to the establishment of planted trees for rainforest restoration. We estimated and compared the plasticity and robustness in plants of Araucaria angustifolia and Cabralea canjerana acclimated to full sun and canopy shade in pots, with the slope of the reaction norm. Then, we described the plasticity in a continuum of coverage gradients in rainforest gaps, with environmentally standardized plasticity index for individual distances (ESPIid). Finally, we analyzed the relationship between plasticity and growth performance. C.canjerana had higher plasticity and robustness than A.angustifolia, both in the pot experiment and in the gap experiment. The light-demanding species had lower plasticity than the intermediate shade-tolerant species. The slope of the reaction norm and the ESPIid gave similar qualitative results in the comparison of the species. In C.canjerana, the trait with higher plasticity in the gaps was specific leaf area, which was the better predictor of height 42-months after planting. On the other hand, the prediction of A.angustifolia growth was better fitted with incident light. Growth in A.angustifolia, a species with low plasticity, can be predicted with environmental variables, while growth in C.canjerana, a species with high plasticity, is better predicted with plant traits. The species with higher plasticity in morpho-physiological traits established in all the microenvironments within the gaps, with high growth rate. Survivor of the species with low plasticity was lower in shaded microenvironments than in the positions with higher radiation and light-limited its growth in the gaps. Knowing the plasticity and acclimation capacity of the native species is crucial to choose the better places to plant trees in rainforest restoration and to enhance performance of the young plants.

Genomic reaction norm models exploiting genotype×environment interaction on sexual precocity indicator traits in Nellore cattle.

Brazilian beef cattle are raised predominantly on pasture in a wide range of environments. In this scenario, genotype by environment (G×E) interaction isan important source of phenotypic variation in the reproductive traits. Hence, the evaluation of G×E interactions for heifer's early pregnancy (HP) and scrotal circumference (SC) traits in Nellore cattle, belonging to three breeding programs, was carried out to determine the animal's sensitivity to the environmental conditions (EC). The dataset consisted of 85874 records for HP and 151553 records for SC, from which 1800 heifers and 3343 young bulls were genotyped with the BovineHD BeadChip. Genotypic information for 826 sires was also used in the analyses. EC levels were based on the contemporary group solutions for yearling body weight. Linear reaction norm models (RNM), using pedigree information (RNM_A) or pedigree and genomic information (RNM_H), were used to infer G×E interactions. Two validation schemes were used to assess the predictive ability, with the following training populations: (a) forward scheme-dataset was split based on year of birth from 2008 for HP and from 2011 for SC; and (b) environment-specific scheme-low EC (-3.0 and -1.5) and high EC (1.5 and 3.0). The inclusion of the H matrix in RNM increased the genetic variance of the intercept and slope by 18.55 and 23.00% on average respectively, and provided genetic parameter estimates that were more accurate than those considering pedigree only. The same trend was observed for heritability estimates, which were 0.28-0.56 for SC and 0.26-0.49 for HP, using RNM_H, and 0.26-0.52 for SC and 0.22-0.45 for HP, using RNM_A. The lowest correlation observed between unfavorable (-3.0) and favorable (3.0) EC levels were 0.30 for HP and -0.12 for SC, indicating the presence of G×E interaction. The G×E interaction effect implied differences in animals' genetic merit and re-ranking of animals on different environmental conditions. SNP marker-environment interaction was detected for Nellore sexual precocity indicator traits with changes in effect and variance across EC levels. The RNM_H captured G×E interaction effects better than RNM_A and improved the predictive ability by around 14.04% for SC and 21.31% for HP. Using the forward scheme increased the overall predictive ability for SC (20.55%) and HP (11.06%) compared with the environment-specific scheme. The results suggest that the inclusion of genomic information combined with the pedigree to assess the G×E interaction leads to more accurate variance components and genetic parameter estimates.

Long-term changes in the maturation and growth of Cape Cod/Gulf of Maine yellowtail flounder Limanda ferruginea

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 633:169-180 (2020) - DOI: https://doi.org/10.3354/meps13175 Long-term changes in the maturation and growth of Cape Cod/Gulf of Maine yellowtail flounder Limanda ferruginea Gregory R. DeCelles1,*, Tiffany Vidal1,2 1Massachusetts Division of Marine Fisheries, Resource Assessment and Monitoring Program, New Bedford, MA 02744, USA 2The Pacific Community, BP D5, 98848 Noumea, New Caledonia *Corresponding author: gregory.decelles@mass.gov ABSTRACT: Yellowtail flounder Limanda ferruginea in the Gulf of Maine have been harvested by commercial fisheries since the 1930s, and the most recent stock assessment estimated that from 1985 to 2016 fishing mortality rates exceeded the fishing mortality reference point (F40%) in all but one year. The objective of this study was to understand changes in the maturation and growth of Cape Cod/Gulf of Maine yellowtail flounder by examining fisheries-independent data from cohorts produced over a 38 yr period (1976 to 2014). Maturity ogives demonstrated that the length and age at 50% maturity declined for cohorts throughout that time period. Probabilistic maturation reaction norms (PMRNs), which describe the probability that an immature individual will become mature at a certain age and size class, demonstrated a shift towards maturation at younger ages and smaller sizes. For age 3 female and male yellowtail flounder, the size at which the probability of becoming mature was 0.5 declined from 30.8 and 26.0 cm to 23.9 and 16.4 cm, respectively. Using von Bertalanffy growth curves, a decrease in asymptotic length (L×) and an increase in the growth rate (K) was estimated for both sexes. Taken together, these life history changes are suggestive of fisheries-induced evolution. However, although the PMRN approach is designed to account for phenotypic plasticity associated with growth and survival, further work is needed to determine whether other factors (e.g. temperature and body condition) could be responsible for the changes in maturation observed in this study. KEY WORDS: PMRN · Limanda ferruginea · Fisheries-induced evolution · Maturation · Von Bertalanffy Full text in pdf format PreviousNextCite this article as: DeCelles GR, Vidal T (2020) Long-term changes in the maturation and growth of Cape Cod/Gulf of Maine yellowtail flounder Limanda ferruginea. Mar Ecol Prog Ser 633:169-180. https://doi.org/10.3354/meps13175 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 633. Online publication date: January 09, 2020 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2020 Inter-Research.

Trade-offs between host tolerances to different pathogens in plant-virus interactions.

Although accumulating evidence indicates that tolerance is a plant defence strategy against pathogens as widespread as resistance, how plants evolve tolerance is poorly understood. Theory predicts that hosts will evolve to maximize tolerance or resistance, but not both. Remarkably, most experimental works failed in finding this trade-off. We tested the hypothesis that the evolution of tolerance to one virus is traded-off against tolerance to others, rather than against resistance and identified the associated mechanisms. To do so, we challenged eighteen Arabidopsis thaliana genotypes with Turnip mosaic virus (TuMV) and Cucumber mosaic virus (CMV). We characterized plant life-history trait modifications associated with reduced effects of TuMV and CMV on plant seed production (fecundity tolerance) and life period (mortality tolerance), both measured as a norm of reaction across viral loads (range tolerance). Also, we analysed resistance-tolerance and tolerance-tolerance trade-offs. Results indicate that tolerance to TuMV is associated with changes in the length of the pre-reproductive and reproductive periods, and tolerance to CMV with resource reallocation from growth to reproduction; and that tolerance to TuMV is traded-off against tolerance to CMV in a virulence-dependent manner. Thus, this work provides novel insights on the mechanisms of plant tolerance and highlights the importance of considering the combined effect of different pathogens to understand how plant defences evolve.