Life in fluctuating environments

Predictable patterns within the kelp forest can indirectly create temporary refugia from ocean acidification

Kelps are recognized for providing many ecosystem services in coastal areas and considered in ocean acidification (OA) mitigation. However, assessing OA modification requires an understanding of the multiple parameters involved in carbonate chemistry, especially in highly dynamic systems. We studied the effects of sugar kelp (Saccharina latissima) on an experimental farm at the north end of Hood Canal, Washington-a low retentive coastal system. In this field mesocosm study, two oyster species (Magallana gigas, Ostrea lurida) were exposed at locations in the mid, edge, and outside the kelp array. The Hood Head Sugar Kelp Farm Model outputs were used to identify dominating factors in spatial and temporal kelp dynamics, while wavelet spectrum analyses helped in understanding predictability patterns. This was linked to the measured biological responses (dissolution, growth, isotopes) of the exposed organisms. Positioned in an area of high (sub)-diel tidal fluxes with low retention potential, there were no measurable alterations of the seawater pH at the study site, demonstrating that the kelp array could not induce a direct mitigating effect against OA. However, beneficial responses in calcifiers were still observed, which are linked to two causes: increased pH predictability and improved provisioning through kelp-derived particulate organic resource utilization and as such, kelp improved habitat suitability and indirectly created refugia against OA. This study can serve as an analogue for many coastal bay habitats where prevailing physical forcing drives chemical changes. Future macrophyte studies that investigate OA mitigating effects should focus also on the importance of predictability patterns, which can additionally improve the conditions for marine calcifiers and ecosystem services vulnerable to or compromised by OA, including aquaculture sustainability.

Insights from single-strain and mixed culture experiments on the effects of heatwaves on freshwater flagellates

The increasing frequency and intensity of heatwaves driven by climate change significantly impact microbial communities in freshwater habitats, particularly eukaryotic microorganisms. Heterotrophic nanoflagellates are important bacterivorous grazers and play a crucial role in aquatic food webs, influencing the morphological and taxonomic structure of bacterial communities. This study investigates the responses of three flagellate taxa to heatwave conditions through single-strain and mixed culture experiments, highlighting the impact of both biotic and abiotic factors on functional redundancy between morphologically similar protist species under thermal stress. Our results indicate that temperature can significantly impact growth and community composition. However, density-dependent factors also had a significant impact. In sum, stabilizing effects due to functional redundancy may be pronounced as long as density-dependent factors play a minor role and can be overshadowed when flagellate abundances increase.

Bacteria face trade-offs in the decomposition of complex biopolymers

Although depolymerization of complex carbohydrates is a growth-limiting bottleneck for microbial decomposers, we still lack understanding about how the production of different types of extracellular enzymes affect individual microbes and in turn the performance of whole decomposer communities. In this work we use a theoretical model to evaluate the potential trade-offs faced by microorganisms in biopolymer decomposition which arise due to the varied biochemistry of different depolymerizing enzyme classes. We specifically consider two broad classes of depolymerizing extracellular enzymes, which are widespread across microbial taxa: exo-enzymes that cleave small units from the ends of polymer chains and endo-enzymes that act at random positions generating degradation products of varied sizes. Our results demonstrate a fundamental trade-off in the production of these enzymes, which is independent of system's complexity and which appears solely from the intrinsically different temporal depolymerization dynamics. As a consequence, specialists that produce either exo- or only endo-enzymes limit their growth to high or low substrate conditions, respectively. Conversely, generalists that produce both enzymes in an optimal ratio expand their niche and benefit from the synergy between the two enzymes. Finally, our results show that, in spatially-explicit environments, consortia composed of endo- and exo-specialists can only exist under oligotrophic conditions. In summary, our analysis demonstrates that the (evolutionary or ecological) selection of a depolymerization pathway will affect microbial fitness under low or high substrate conditions, with impacts on the ecological dynamics of microbial communities. It provides a possible explanation why many polysaccharide degraders in nature show the genetic potential to produce both of these enzyme classes.

Effects of experimental canopy openness on wood-inhabiting fungal fruiting diversity across succession

While the succession of terrestrial plant communities is well studied, less is known about succession on dead wood, especially how it is affected by environmental factors. While temperate forests face increasing canopy mortality, which causes considerable changes in microclimates, it remains unclear how canopy openness affects fungal succession. Here, we used a large real-world experiment to study the effect of closed and opened canopy on treatment-based alpha and beta fungal fruiting diversity. We found increasing diversity in early and decreasing diversity at later stages of succession under both canopies, with a stronger decrease under open canopies. However, the slopes of the diversity versus time relationships did not differ significantly between canopy treatments. The community dissimilarity remained mainly stable between canopies at ca. 25% of species exclusively associated with either canopy treatment. Species exclusive in either canopy treatment showed very low number of occupied objects compared to species occurring in both treatments. Our study showed that canopy loss subtly affected fungal fruiting succession on dead wood, suggesting that most species in the local species pool are specialized or can tolerate variable conditions. Our study indicates that the fruiting of the fungal community on dead wood is resilient against the predicted increase in canopy loss in temperate forests.

Phenotypic memory in quorum sensing

Quorum sensing (QS) is a regulatory mechanism used by bacteria to coordinate group behavior in response to high cell densities. During QS, cells monitor the concentration of external signals, known as autoinducers, as a proxy for cell density. QS often involves positive feedback loops, leading to the upregulation of genes associated with QS signal production and detection. This results in distinct steady-state concentrations of QS-related molecules in QS-ON and QS-OFF states. Due to the slow decay rates of biomolecules such as proteins, even after removal of the initial stimuli, cells can retain elevated levels of QS-associated biomolecules for extended periods of time. This persistence of biomolecules after the removal of the initial stimuli has the potential to impact the response to future stimuli, indicating a memory of past exposure. This phenomenon, which is a consequence of the carry-over of biomolecules rather than genetic inheritance, is known as "phenotypic" memory. This theoretical study aims to investigate the presence of phenotypic memory in QS and the conditions that influence this memory. Numerical simulations based on ordinary differential equations and analytical modeling were used to study gene expression in response to sudden changes in cell density and extracellular signal concentrations. The model examined the effect of various cellular parameters on the strength of QS memory and the impact on gene regulatory dynamics. The findings revealed that QS memory has a transient effect on the expression of QS-responsive genes. These consequences of QS memory depend strongly on how cell density was perturbed, as well as various cellular parameters, including the Fold Change in the expression of QS-regulated genes, the autoinducer synthesis rate, the autoinducer threshold required for activation, and the cell growth rate.

Stochastic Gene Expression in Proliferating Cells: Differing Noise Intensity in Single-Cell and Population Perspectives

Random fluctuations (noise) in gene expression can be studied from two complementary perspectives: following expression in a single cell over time or comparing expression between cells in a proliferating population at a given time. Here, we systematically investigated scenarios where both perspectives lead to different levels of noise in a given gene product. We first consider a stable protein, whose concentration is diluted by cellular growth, and the protein inhibits growth at high concentrations, establishing a positive feedback loop. For a stochastic model with molecular bursting of gene products, we analytically predict and contrast the steady-state distributions of protein concentration in both frameworks. Although positive feedback amplifies the noise in expression, this amplification is much higher in the population framework compared to following a single cell over time. We also study other processes that lead to different noise levels even in the absence of such dilution-based feedback. When considering randomness in the partitioning of molecules between daughters during mitosis, we find that in the single-cell perspective, the noise in protein concentration is independent of noise in the cell cycle duration. In contrast, partitioning noise is amplified in the population perspective by increasing randomness in cell-cycle time. Overall, our results show that the commonly used single-cell framework that does not account for proliferating cells can, in some cases, underestimate the noise in gene product levels. These results have important implications for studying the inter-cellular variation of different stress-related expression programs across cell types that are known to inhibit cellular growth.

Global distribution and environmental correlates of marine bioturbation

The activities of marine sediment-dwelling invertebrates play a fundamental role in mediating major biogeochemical cycles and have profoundly shaped the evolution of marine systems. Yet there remains a paucity of global marine data describing bioturbation intensities and mixed layer depths and interrogating how these vary with multiple environmental and ecological factors at a system scale. We applied an ensemble of tree-based machine learning techniques to resolve a global map and determine the environmental and ecological correlates most closely associated with bioturbation. We find that bioturbation intensity and the depth of the sediment mixed layer each reflect different associations with a consortium of environmental and ecological parameters, and that bioturbation intensities are much more readily predicted than sediment mixed layer depths from these correlates. Furthermore, we find that the bioturbation intensity, the depth of the sediment mixed layer, and their environmental and ecological correlates differ between shallow marine and open-ocean settings. Our findings provide new insights into the importance of potential drivers of ancient sediment mixing recorded by geologic archives. These results also highlight that climate change may, in the near future, drive shifts in bioturbation and reciprocal fundamental changes in benthic functioning.

Predicting organismal response to marine heatwaves using dynamic thermal tolerance landscape models

Marine heatwaves (MHWs) can cause thermal stress in marine organisms, experienced as extreme 'pulses' against the gradual trend of anthropogenic warming. When thermal stress exceeds organismal capacity to maintain homeostasis, organism survival becomes time-limited and can result in mass mortality events. Current methods of detecting and categorizing MHWs rely on statistical analysis of historic climatology and do not consider biological effects as a basis of MHW severity. The re-emergence of ectotherm thermal tolerance landscape models provides a physiological framework for assessing the lethal effects of MHWs by accounting for both the magnitude and duration of extreme heat events. Here, we used a simulation approach to understand the effects of a suite of MHW profiles on organism survival probability across (1) three thermal tolerance adaptive strategies, (2) interannual temperature variation and (3) seasonal timing of MHWs. We identified survival isoclines across MHW magnitude and duration where acute (short duration-high magnitude) and chronic (long duration-low magnitude) events had equivalent lethal effects on marine organisms. While most research attention has focused on chronic MHW events, we show similar lethal effects can be experienced by more common but neglected acute marine heat spikes. Critically, a statistical definition of MHWs does not accurately categorize biological mortality. By letting organism responses define the extremeness of a MHW event, we can build a mechanistic understanding of MHW effects from a physiological basis. Organism responses can then be transferred across scales of ecological organization and better predict marine ecosystem shifts to MHWs.

Modelling dynamics between free-living amoebae and bacteria

Free-living amoebae (FLA) serve as hosts for a variety of endosymbionts, which are microorganisms that reside and multiply within the FLA. Some of these endosymbionts pose a pathogenic threat to humans, animals, or both. The symbiotic relationship with FLA not only offers these microorganisms protection but also enhances their survival outside their hosts and assists in their dispersal across diverse habitats, thereby escalating disease transmission. This review is intended to offer an exhaustive overview of the existing mathematical models that have been applied to understand the dynamics of FLA, especially concerning their interactions with bacteria. An extensive literature review was conducted across Google Scholar, PubMed, and Scopus databases to identify mathematical models that describe the dynamics of interactions between FLA and bacteria, as published in peer-reviewed scientific journals. The literature search revealed several FLA-bacteria model systems, including Pseudomonas aeruginosa, Pasteurella multocida, and Legionella spp. Although the published mathematical models account for significant system dynamics such as predator-prey relationships and non-linear growth rates, they generally overlook spatial and temporal heterogeneity in environmental conditions, such as temperature, and population diversity. Future mathematical models will need to incorporate these factors to enhance our understanding of FLA-bacteria dynamics and to provide valuable insights for future risk assessment and disease control measures.

Heat shocks during egg incubation led to developmental, morphological, and behavioral differences in Arctic charr (Salvelinus alpinus)

Temperature variation is affecting fish biodiversity worldwide, causing changes in geographic distribution, phenotypic structure, and even species extinction. Incubation is a critical stage for stenothermic species, which are vulnerable to large temperature fluctuations, and its effects on the phenotype at later developmental stages are understudied, despite the fact that the phenotype being essential for organism ecology and evolution. In this study, we tested the effects of heat shocks during the embryonic period on the phenotype of Arctic charr (Salvelinus alpinus). We repeatedly quantified multiple phenotypic traits, including morphology, development, and behavior, over a period of 4 months, from hatching to juvenile stage in individuals that had experienced heat shocks (+ 5°C on 24 h, seven times) during their embryonic stage and those that had not. We found that heat shocks led to smaller body size at hatching and a lower sociability. Interestingly, these effects weakened throughout the development of individuals and even reversed in the case of body size. We also found an accelerated growth rate and a higher body condition in the presence of heat shocks. Our study provides evidence that heat shocks experienced during incubation can have long-lasting effects on an individual's phenotype. This highlights the importance of the incubation phase for the development of ectothermic organisms and suggests that temperature fluctuations may have significant ecological and evolutionary implications for Arctic charr. Given the predicted increase in extreme events and the unpredictability of temperature fluctuations, it is critical to further investigate their effects on development by examining fluctuations that vary in frequency and intensity.

Rapid adaptation of cellular metabolic rate to the MicroRNA complements of mammals and its relevance to the evolution of endothermy

The metabolic efficiency of mammalian cells depends on the attenuation of intrinsic translation noise by microRNAs. We devised a metric of cellular metabolic rate (cMR), rMR/Mexp optimally fit to the number of microRNA families (mirFam), that is robust to variation in mass and sensitive to body temperature (Tb), consistent with the heat dissipation limit theory of Speakman and Król (2010). Using mirFam as predictor, an Ornstein-Uhlenbeck process of stabilizing selection, with an adaptive shift at the divergence of Boreoeutheria, accounted for 95% of the variation in cMR across mammals. Branchwise rates of evolution of cMR, mirFam and Tb concurrently increased 6- to 7-fold at the divergence of Boreoeutheria, independent of mass. Cellular MR variation across placental mammals was also predicted by the sum of model conserved microRNA-target interactions, revealing an unexpected degree of integration of the microRNA-target apparatus into the energy economy of the mammalian cell.

Preparing Collared Peccary (Pecari tajacu Linnaeus, 1758) for Reintroduction into the Wild: A Screening for Parasites and Hemopathogens of a Captive Population

The reintroduction of captive animals to the wild helps restore endangered species, but it risks pathogen transmission, harming wild populations. Such transmission can impact the genetic diversity and long-term viability of these populations. This study assessed parasite diversity and load in captive Pecari tajacu, a species native to the Americas and culturally significant to Brazilian indigenous culture, prior to reintroduction. Samples from 24 peccaries were analyzed for ectoparasites, hemopathogens, and stool parasites with direct and molecular analysis. Findings showed that various parasites were present. Two peccaries (8.3%) were infested by the adult tick Amblyomma sculptum. Six (25.0%) tested positive for Trypanosoma evansi, four (16.7%) for hemobacteria of the family Anaplasmataceae, twelve (50.0%) for hemotropic Mycoplasma, and seven (29.2%) for Leishmania braziliensis. Stool samples indicated multiple parasites, with sixteen (66.7%) peccaries infected by Strongylida order parasites, Spiruridae in three (12.5%), and Ascaris suum in one (4.2%) animal. Cysts of Balantidium sp. were found in twenty (83.3%), Entamoeba polecki in five (20.8%), and Iodamoeba bütschlii in two (8.3%) peccaries. To our current knowledge, this is the first global report of Leishmania braziliensis, Iodamoeba bütschlii, and Entamoeba polecki in P. tajacu, irrespective of the environment, including both captivity and wild conditions. Some of these parasites are common in domestic animals, and others are zoonotic, indicating potential interspecies pathogen transmission.

Pairing lab and field studies to predict thermal performance of wild fish

In thermally variable ecosystems, temperatures can change extensively on hourly and seasonal timescales requiring ectotherms to possess a broad thermal tolerance (critical thermal minima [CTmin] and maxima [CTmax]). However, whether fish acclimate in the laboratory similarly as they acclimatize in the field under comparable thermal variation is unclear. We used temperature data from a tidal salt marsh to design 21-day lab-acclimation treatments (static: 12, 17, 22, 27 °C; daily variation with mean 22 °C: i) range 17-27 °C, ii) range 17-27 °C with irregular extremes within 12-32 °C). We compared thermal limits in lab-acclimated and field-acclimatized eurythermal arrow goby (Clevelandia ios). Variable temperature-acclimated and acclimatized fish had similar CTmin and CTmax. Notably, arrow gobies showed rapid plasticity in their absolute thermal tolerance within one tidal cycle. The daily mean and max temperatures experienced were positively related to CTmax and CTmin, respectively. This study demonstrates that ecologically informed lab acclimation treatments can yield tolerance results that are applicable to wild fish.

Ecosystem feedbacks constrain the effect of day-to-day weather variability on land-atmosphere carbon exchange

Whole-ecosystem interactions and feedbacks constrain ecosystem responses to environmental change. The effects of these constraints on responses to climate trends and extreme weather events have been well studied. Here we examine how these constraints respond to changes in day-to-day weather variability without changing the long-term mean weather. Although environmental variability is recognized as a critical factor affecting ecological function, the effects of climate change on day-to-day weather variability and the resultant impacts on ecosystem function are still poorly understood. Changes in weather variability can alter the mean rates of individual ecological processes because many processes respond non-linearly to environmental drivers. We assessed how these individual-process responses to changes in day-to-day weather variability interact with one another at an ecosystem level. We examine responses of arctic tundra to changes in weather variability using stochastic simulations of daily temperature, precipitation, and light to drive a biogeochemical model. Changes in weather variability altered ecosystem carbon, nitrogen, and phosphorus stocks and cycling rates in our model. However, responses of some processes (e.g., respiration) were inconsistent with expectations because ecosystem feedbacks can moderate, or even reverse, direct process responses to weather variability. More weather variability led to greater carbon losses from land to atmosphere; less variability led to higher carbon sequestration on land. The magnitude of modeled ecosystem response to weather variability was comparable to that predicted for the effects of climate mean trends by the end of the century.

Stability of consumer-resource interactions in periodic environments

Periodic fluctuations in abiotic conditions are ubiquitous across a range of temporal scales and regulate the structure and function of ecosystems through dynamic biotic responses that are adapted to these external forces. Research has suggested that certain environmental signatures may play a crucial role in the maintenance of biodiversity and the stability of food webs, while others argue that coupled oscillators ought to promote chaos. As such, numerous uncertainties remain regarding the intersection of temporal environmental patterns and biological responses, and we lack a general understanding of the implications for food web stability. Alarmingly, global change is altering the nature of both environmental rhythms and biological rates. Here, we develop a general theory for how continuous periodic variation in productivity, across temporal scales, influences the stability of consumer-resource interactions: a fundamental building block of food webs. Our results suggest that consumer-resource dynamics under environmental forcing are highly complex and depend on asymmetries in both the speed of forcing relative to underlying dynamics and in local stability properties. These asymmetries allow for environmentally driven stabilization under fast forcing, relative to underlying dynamics, as well as extremely complex and unstable dynamics at slower periodicities. Our results also suggest that changes in naturally occurring periodicities from climate change may lead to precipitous shifts in dynamics and stability.

Light cues induce protective anticipation of environmental water loss in terrestrial bacteria

The ecological significance of light perception in nonphotosynthetic bacteria remains largely elusive. In terrestrial environments, diurnal oscillations in light are often temporally coupled to other environmental changes, including increased temperature and evaporation. Here, we report that light functions as an anticipatory cue that triggers protective adaptations to tolerate a future rapid loss of environmental water. We demonstrate this photo-anticipatory stress tolerance in leaf-associated Pseudomonas syringae pv. syringae (Pss) and other plant- and soil-associated pseudomonads. We found that light influences the expression of 30% of the Pss genome, indicating that light is a global regulatory signal, and this signaling occurs almost entirely via a bacteriophytochrome photoreceptor that senses red, far-red, and blue wavelengths. Bacteriophytochrome-mediated light control disproportionally up-regulates water-stress adaptation functions and confers enhanced fitness when cells encounter light prior to water limitation. Given the rapid speed at which water can evaporate from leaf surfaces, such anticipatory activation of a protective response enhances fitness beyond that of a reactive stress response alone, with recurring diurnal wet-dry cycles likely further amplifying the fitness advantage over time. These findings demonstrate that nonphotosynthetic bacteria can use light as a cue to mount an adaptive anticipatory response against a physiologically unrelated but ecologically coupled stress.

Seasonal specialization drives divergent population dynamics in two closely related butterflies

Seasons impose different selection pressures on organisms through contrasting environmental conditions. How such seasonal evolutionary conflict is resolved in organisms whose lives span across seasons remains underexplored. Through field experiments, laboratory work, and citizen science data analyses, we investigate this question using two closely related butterflies (Pieris rapae and P. napi). Superficially, the two butterflies appear highly ecologically similar. Yet, the citizen science data reveal that their fitness is partitioned differently across seasons. Pieris rapae have higher population growth during the summer season but lower overwintering success than do P. napi. We show that these differences correspond to the physiology and behavior of the butterflies. Pieris rapae outperform P. napi at high temperatures in several growth season traits, reflected in microclimate choice by ovipositing wild females. Instead, P. rapae have higher winter mortality than do P. napi. We conclude that the difference in population dynamics between the two butterflies is driven by seasonal specialization, manifested as strategies that maximize gains during growth seasons and minimize harm during adverse seasons, respectively.

Metabolic and transcriptional responses demonstrating enhanced thermal tolerance in domesticated abalone

Global warming threatens aquatic systems and organisms. Many studies have focused on the vulnerability and stress responses of aquaculture organisms to future thermal conditions. However, it may be of more practical significance to reveal their acclimation potential and mechanisms. In this study, the physiological, metabolic, and transcriptional responses to long-term temperature acclimation of northern and southern populations of Pacific abalone Haliotis discus hannai, a commercially important gastropod sensitive to environmental changes, were compared. This study conducted two common-garden experiments, including a thermostatic experiment in the lab and an aquaculture experiment on the farm. The abalone population cultured in warmer southern waters was tolerant of ongoing high temperatures, whereas the abalone population originally cultured in cooler northern waters exhibited vulnerability to high temperatures but could enhance its thermal tolerance through the process of natural selection in warmer southern waters. This difference was linked to divergence in the metabolic and transcriptional processes of the two populations. The tolerant population exhibited a greater capacity for carbohydrate and amino acid metabolism regulation and energy redistribution to cope with heat stress. This capacity may have been selected for, and accumulated, over many generations because the tolerant population originated from the intolerant population over two decades ago. This work provides insight into the vulnerability and acclimation potential of abalone to heat stress and discloses the molecular and metabolic traits underlying this phenomenon. Future research on the ability of abalone and other commercial shellfish species to acclimate to global warming should take this potential into account.

Disturbance of primary producer communities disrupts the thermal limits of the associated aquatic fauna

Environmental fluctuation forms a framework of variability within which species have evolved. Environmental fluctuation includes predictability, such as diel cycles of aquatic oxygen fluctuation driven by primary producers. Oxygen availability and fluctuation shape the physiological responses of aquatic animals to warming, so that, in theory, oxygen fluctuation could influence their thermal ecology. We describe annual oxygen variability in agricultural drainage channels and show that disruption of oxygen fluctuation through dredging of plants reduces the thermal tolerance of freshwater animals. We compared the temperature responses of snails, amphipods, leeches and mussels exposed to either natural oxygen fluctuation or constant oxygen in situ under different acclimation periods. Oxygen saturation in channel water ranged from c. 0 % saturation at night to >300 % during the day. Temperature showed normal seasonal variation and was almost synchronous with daily oxygen fluctuation. A dredging event in 2020 dramatically reduced dissolved oxygen variability and the correlation between oxygen and temperature was lost. The tolerance of invertebrates to thermal stress was significantly lower when natural fluctuation in oxygen availability was reduced and decoupled from temperature. This highlights the importance of natural cycles of variability and the need to include finer scale effects, including indirect biological effects, in modelling the ecosystem-level consequences of climate change. Furthermore, restoration and management of primary producers in aquatic habitats could be important to improve the thermal protection of aquatic invertebrates and their resistance to environmental variation imposed by climate change.

The fitness value of ecological information in a variable world

Information processing is increasingly recognized as a fundamental component of life in variable environments, including the evolved use of environmental cues, biomolecular networks, and social learning. Despite this, ecology lacks a quantitative framework for understanding how population, community, and ecosystem dynamics depend on information processing. Here, we review the rationale and evidence for 'fitness value of information' (FVOI), and synthesize theoretical work in ecology, information theory, and probability behind this general mathematical framework. The FVOI quantifies how species' per capita population growth rates can depend on the use of information in their environment. FVOI is a breakthrough approach to linking information processing and ecological and evolutionary outcomes in a changing environment, addressing longstanding questions about how information mediates the effects of environmental change and species interactions.

Enzyme adaptation to habitat thermal legacy shapes the thermal plasticity of marine microbiomes

Microbial communities respond to temperature with physiological adaptation and compositional turnover. Whether thermal selection of enzymes explains marine microbiome plasticity in response to temperature remains unresolved. By quantifying the thermal behaviour of seven functionally-independent enzyme classes (esterase, extradiol dioxygenase, phosphatase, beta-galactosidase, nuclease, transaminase, and aldo-keto reductase) in native proteomes of marine sediment microbiomes from the Irish Sea to the southern Red Sea, we record a significant effect of the mean annual temperature (MAT) on enzyme response in all cases. Activity and stability profiles of 228 esterases and 5 extradiol dioxygenases from sediment and seawater across 70 locations worldwide validate this thermal pattern. Modelling the esterase phase transition temperature as a measure of structural flexibility confirms the observed relationship with MAT. Furthermore, when considering temperature variability in sites with non-significantly different MATs, the broadest range of enzyme thermal behaviour and the highest growth plasticity of the enriched heterotrophic bacteria occur in samples with the widest annual thermal variability. These results indicate that temperature-driven enzyme selection shapes microbiome thermal plasticity and that thermal variability finely tunes such processes and should be considered alongside MAT in forecasting microbial community thermal response.

Effects of thermal fluctuations on biological processes: a meta-analysis of experiments manipulating thermal variability

Thermal variability is a key driver of ecological processes, affecting organisms and populations across multiple temporal scales. Despite the ubiquity of variation, biologists lack a quantitative synthesis of the observed ecological consequences of thermal variability across a wide range of taxa, phenotypic traits and experimental designs. Here, we conduct a meta-analysis to investigate how properties of organisms, their experienced thermal regime and whether thermal variability is experienced in either the past (prior to an assay) or present (during the assay) affect performance relative to the performance of organisms experiencing constant thermal environments. Our results-which draw upon 1712 effect sizes from 75 studies-indicate that the effects of thermal variability are not unidirectional and become more negative as mean temperature and fluctuation range increase. Exposure to variation in the past decreases performance to a greater extent than variation experienced in the present and increases the costs to performance more than diminishing benefits across a broad set of empirical studies. Further, we identify life-history attributes that predictably modify the ecological response to variation. Our findings demonstrate that effects of thermal variability on performance are context-dependent, yet negative outcomes may be heightened in warmer, more variable climates.

Looking to the past to understand the future: linking evolutionary modes of response with functional and life history traits in variable environments

In a variable world, plants must have strategies to deal with environmental conditions as they change. Understanding these strategies is critical since climate change not only affects mean conditions but also affects variability and predictability of those conditions. Doing so requires identifying how functional and life history traits interact throughout the life cycle to drive responses, as well as exploring how past variability will shape future responses. Here, I highlight relevant life history theory for predicting strategies in relation to the nature of environmental variability, relate theory to empirical studies integrating functional and life history traits to understand responses, and identify key areas for future research that will facilitate the application of this understanding toward predicting responses to climate change.

Gradistics: An underappreciated dimension in evolutionary space

The growth of complexity is an unsolved and underappreciated problem. We consider possible causes of this growth, hypotheses testing, molecular mechanisms, complexity measures, cases of simplification, and significance for biomedicine. We focus on a general ability of regulation, which is based on the growing information storage and processing capacities, as the main proxy of complexity. Natural selection is indifferent to complexity. However, complexification can be inferred from the same first principle, on which natural selection is founded. Natural selection depends on potentially unlimited reproduction under limited environmental conditions. Because of the demographic pressure, the simple ecological niches become fulfilled and diversified (due to species splitting and divergence). Diversification increases complexity of biocenoses. After the filling and diversification of simple niches, the more complex niches can arise. This is the 'atomic orbitals' (AO) model. Complexity has many shortcomings but it has an advantage. This advantage is ability to regulatory adaptation, including behavioral, formed in the evolution by means of genetic adaptation. Regulatory adaptation is much faster than genetic one because it is based on the information previously accumulated via genetic adaptation and learning. Regulatory adaptation further increases complexity of biocenoses. This is the 'regulatory advantage' (RA) model. The comparison of both models allows testable predictions. We focus on the animal evolution because of the appearance of higher regulatory level (nervous system), which is absent in other lineages, and relevance to humans (including biomedical aspects).

Spatiotemporal thermal variation drives diversity trends in experimental landscapes

Temperature is a fundamental driver of species' vital rates and thus coexistence, extinctions and community composition. While temperature is neither static in space nor in time, little work has incorporated spatiotemporal dynamics into community-level investigations of thermal variation. We conducted a microcosm experiment using ciliate protozoa to test the effects of temperatures fluctuating synchronously or asynchronously on communities in two-patch landscapes connected by short or long corridors. We monitored the abundance of each species for 4 weeks-equivalent to ~28 generations-measuring the effects of four temperature regimes and two corridor lengths on community diversity and composition. While corridor length significantly altered the trajectory of diversity change in the communities, this did not result in different community structures at the end of the experiment. The type of thermal variation significantly affected both the temporal dynamics of diversity change and final community composition, with synchronous fluctuation causing deterministic extinctions that were consistent across replicates and spatial variation causing the greatest diversity declines. Our results suggest that the presence and type of thermal variation can play an important role in structuring ecological communities, especially when it interacts with dispersal between habitat patches.

Current and lagged climate affects phenology across diverse taxonomic groups

The timing of life events (phenology) can be influenced by climate. Studies from around the world tell us that climate cues and species' responses can vary greatly. If variation in climate effects on phenology is strong within a single ecosystem, climate change could lead to ecological disruption, but detailed data from diverse taxa within a single ecosystem are rare. We collated first sighting and median activity within a high-elevation environment for plants, insects, birds, mammals and an amphibian across 45 years (1975-2020). We related 10 812 phenological events to climate data to determine the relative importance of climate effects on species' phenologies. We demonstrate significant variation in climate-phenology linkage across taxa in a single ecosystem. Both current and prior climate predicted changes in phenology. Taxa responded to some cues similarly, such as snowmelt date and spring temperatures; other cues affected phenology differently. For example, prior summer precipitation had no effect on most plants, delayed first activity of some insects, but advanced activity of the amphibian, some mammals, and birds. Comparing phenological responses of taxa at a single location, we find that important cues often differ among taxa, suggesting that changes to climate may disrupt synchrony of timing among taxa.

Age-specific sensitivity analysis of stable, stochastic and transient growth for stage-classified populations

Sensitivity analysis in ecology and evolution is a valuable guide to rank demographic parameters depending on their relevance to population growth. Here, we propose a method to make the sensitivity analysis of population growth for matrix models solely classified by stage more fine-grained by considering the effect of age-specific parameters. The method applies to stable population growth, the stochastic growth rate, and transient growth. The method yields expressions for the sensitivity of stable population growth to age-specific survival and fecundity from which general properties are derived about the pattern of age-specific selective forces molding senescence in stage-classified populations.

Long term environmental variability modulates the epigenetics of maternal traits of kelp crabs in the coast of Chile

The methylation of DNA is an environmentally inducible epigenetic mechanism reflecting the short-term ecological and environmental background of populations. Marine invertebrate populations, which spread along a latitudinal cline, are particularly suitable for profiling DNA methylation, due to the heterogenous environmental conditions experienced. We used the MSAP (Methylation Sensitive Amplified Polymorphism) technique to investigate the natural variation in DNA methylation of different female's tissues (muscle, gonads, and gills) and early-stage eggs from five populations of the kelp crab Taliepus dentatus, distributed along a latitudinal cline in the coast of Chile. We assessed whether, (1) the distribution of DNA methylation profiles can be associated with the temporal variability of long term (18 years) climatologies (sea surface temperature, turbidity and productivity) and (2) the epigenetic diversity of eggs is related to the population-level phenotypic variability of several maternal investment traits (egg volume, egg weight, egg lipids and fecundity). The DNA methylation of eggs correlated positively and negatively with the long term variability in productivity and sea surface temperature, respectively. Furthermore, the diversity of DNA methylation of eggs correlated positively with the population-level phenotypic variability of several maternal investment traits, suggesting a key role of epigenetic mechanisms in generating phenotypic variability at population level for this species. We provide evidence of a strong link between the temporal variability of long term climatologies with the epigenetic profiles of key early ontogenetic traits associated with the maternal investment of kelp crabs. These modulating mechanisms can hence contribute early to phenotypic variability at population levels in response to local and past environmental fluctuation.

Schindler's legacy: from eutrophic lakes to the phosphorus utilization strategies of cyanobacteria

David Schindler and his colleagues pioneered studies in the 1970s on the role of phosphorus in stimulating cyanobacterial blooms in North American lakes. Our understanding of the nuances of phosphorus utilization by cyanobacteria has evolved since that time. We review the phosphorus utilization strategies used by cyanobacteria, such as use of organic forms, alternation between passive and active uptake, and luxury storage. While many aspects of physiological responses to phosphorus of cyanobacteria have been measured, our understanding of the critical processes that drive species diversity, adaptation and competition remains limited. We identify persistent critical knowledge gaps, particularly on the adaptation of cyanobacteria to low nutrient concentrations. We propose that traditional discipline-specific studies be adapted and expanded to encompass innovative new methodologies and take advantage of interdisciplinary opportunities among physiologists, molecular biologists, and modellers, to advance our understanding and prediction of toxic cyanobacteria, and ultimately to mitigate the occurrence of blooms.

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.

Mild temperatures differentiate while extreme temperatures unify gene expression profiles among populations of Dicosmoecus gilvipes in California

Accurately predicting the effects of future warming on aquatic ectotherms requires an understanding how thermal history, including average temperature and variation, affects populations of the same species. However, many laboratory studies simplify the thermal environment to focus on specific organismal responses and sacrifice environmental realism. Here, we paired laboratory-based transcriptomic RNA-seq analysis to identify thermally responsive genes with NanoString analysis of a subset of those genes to characterize natural field-based variation in thermal physiology among populations. We tested gene expression responses of three populations of field-acclimatized larval caddisflies (Dicosmoecus gilvipes) from streams in different eco-regions (mountain, valley, and coast) following exposure to current and future summertime temperatures. We hypothesized that distinct thermal histories across eco-regions could differentiate populations at baseline “control” levels of gene expression, as well as gene expression changes in response to daily warming and heat shock. Population-specific patterns of gene expression were apparent under the control and daily warming conditions suggesting that local acclimatization or local adaptation may differentiate populations, while responses to extreme temperatures were similar across populations, indicating that response to thermal stress is canalized. Underlying gene co-expression patterns in the daily warming and heat shock treatments were different, demonstrating the distinct physiological mechanisms involved with thermal acclimatization and response to thermal stress. These results highlight the importance and limitations of studies of the thermal biology of wild-caught organisms in their natural environment, and provide an important resource for researchers of caddisflies and aquatic insects in general.

Experimental Evolution Shows Body Size Decrease in Response to Hypoxia, with a Complex Effect on Plastic Size Response to Temperature

AbstractThere is a scientific debate whether oxygen concentration may be a factor driving the pattern of size decrease at higher temperature. Central to this debate is the fact that oxygen availability relative to demand for living organisms decreases with increasing temperature. We examined whether rotifers Lecane inermis exposed to hypoxic conditions would evolve smaller sizes than rotifers exposed to normoxic conditions, using experimental evolution with the same fluctuating temperature but differentiated by three regimes of oxygen availability: normoxia, hypoxia throughout the whole thermal range, and hypoxia only at the highest temperature. Immediately after the six-month experiment (more than 90 generations), we tested the plasticity of size responses to temperature in three post-evolution groups, and we related these responses to fitness. The results show that normoxic rotifers had evolved significantly larger sizes than two hypoxic rotifer groups, which were similar in size. All three groups displayed similar plastic body size reductions in response to warming over the range of temperatures they were exposed to during the period of experimental evolution, but they showed different and complex responses at two temperatures below this range. Any type of plastic response to different temperatures resulted in a similar fitness pattern across post-evolution groups. We conclude that (i) these rotifers showed a genetic basis for the pattern of size decrease following evolution under both temperature-dependent and temperature-independent hypoxia; and (ii) plastic body size responds consistently to temperatures that are within the thermal range that the rotifers experienced during their evolutionary history, but responses become more noisy at novel temperatures, suggesting the importance of evolutionary responses to reliable environmental cues.

Insufficient reporting of experimental variables as a cause for nonreproducibility in animal physiology? A case study

Nonreproducibility in scientific investigations has been explained by inadequately reporting methodology, honest error, and even misconduct. We hypothesized that, within the field of animal physiology, the most parsimonious explanation for nonreproducibility is inadequate reporting of key methodological details. We further hypothesized that implementation of relatively recently released reporting guidelines has positively impacted journal article quality, as measured by completeness of the methodology descriptions. We analyzed 84 research articles published in five primarily organismal animal physiology journals in 2008-2010 (generally before current guidelines) and 2018-2020. Compliance for reporting 34 variables referring to biology, experiments, and data collection was assessed. Reporting compliance was just ∼61% in 2008-2010, rising only slightly to 67.5% for 2018-2020. Only 21% of the reported variables showed significant differences across the period from 2008-2020. We conclude that, despite attempts by societies and journals to promote greater reporting compliance, such efforts have so far been relatively unsuccessful in the field of animal physiology.

Net effect of environmental fluctuations in multiple global-change drivers across the tree of life

Jensen's inequality predicts that the response of any given system to average constant conditions is different from its average response to varying ones. Environmental fluctuations in abiotic conditions are pervasive on Earth; yet until recently, most ecological research has addressed the effects of multiple environmental drivers by assuming constant conditions. One could thus expect to find significant deviations in the magnitude of their effects on ecosystems when environmental fluctuations are considered. Drawing on experimental studies published during the last 30 years reporting more than 950 response ratios (n = 5,700), we present a comprehensive analysis of the role that environmental fluctuations play across the tree of life. In contrast to the predominance of interactive effects of global-change drivers reported in the literature, our results show that their cumulative effects were additive (58%), synergistic (26%), and antagonistic (16%) when environmental fluctuations were present. However, the dominant type of interaction varied by trophic level (autotrophs: interactive; heterotrophs: additive) and phylogenetic group (additive in Animalia; additive and positive antagonism in Chromista; negative antagonism and synergism in Plantae). In addition, we identify the need to tackle how complex communities respond to fluctuating environments, widening the phylogenetic and biogeographic ranges considered, and to consider other drivers beyond warming and acidification as well as longer timescales. Environmental fluctuations must be taken into account in experimental and modeling studies as well as conservation plans to better predict the nature, magnitude, and direction of the impacts of global change on organisms and ecosystems.

The Pace of Life: Metabolic Energy, Biological Time, and Life History

New biophysical theory and electronic databases raise the prospect of deriving fundamental rules of life, a conceptual framework for how the structures and functions of molecules, cells and individual organisms give rise to emergent patterns and processes of ecology, evolution and biodiversity. This framework is very general, applying across taxa of animals from 10-10 g protists to 108 g whales, and across environments from deserts and abyssal depths to rain forests and coral reefs. It has several hallmarks: 1) Energy is the ultimate limiting resource for organisms and the currency of biological fitness. 2) Most organisms are nearly equally fit, because in each generation at steady state they transfer an equal quantity of energy (22.4 kJ/g) and biomass (1 g/g) to surviving offspring. This is the equal fitness paradigm (EFP) of Brown et al. (2018). 3) The enormous diversity of life histories is due largely to variation in metabolic rates (e.g., energy uptake and expenditure via assimilation, respiration and production) and biological times (e.g., generation time). As in standard allometric and metabolic theory, most physiological and life history traits scale approximately as quarter-power functions of body mass, m (rates as ∼m-1/4 and times as ∼m1/4), and as exponential functions of temperature. 4) Time is the fourth dimension of life. Generation time is the pace of life. 5) There is, however, considerable variation not accounted for by the above scalings and existing theories. Much of this "unexplained" variation is due to natural selection on life history traits to adapt the biological times of generations to the clock times of geochronological environmental cycles. 7) Most work on biological scaling and metabolic ecology has focused on respiration rate. The emerging synthesis applies conceptual foundations of energetics and the EFP to shift the focus to production rate and generation time.

A framework to understand the role of biological time in responses to fluctuating climate drivers

Understanding biological responses to environmental fluctuations (e.g. heatwaves) is a critical goal in ecology. Biological responses (e.g. survival) are usually measured with respect to different time reference frames, i.e. at specific chronological times (e.g. at specific dates) or biological times (e.g. at reproduction). Measuring responses on the biological frame is central to understand how environmental fluctuation modifies fitness and population persistence. We use a framework, based on partial differential equations (PDEs) to explore how responses to the time scale and magnitude of fluctuations in environmental variables (= drivers) depend on the choice of reference frame. The PDEs and simulations enabled us to identify different components, responsible for the phenological and eco-physiological effects of each driver on the response. The PDEs also highlight the conditions when the choice of reference frame affects the sensitivity of the response to a driver and the type of join effect of two drivers (additive or interactive) on the response. Experiments highlighted the importance of studying how environmental fluctuations affect biological time keeping mechanisms, to develop mechanistic models. Our main result, that the effect of the environmental fluctuations on the response depends on the scale used to measure time, applies to both field and laboratory conditions. In addition, our approach, applied to experimental conditions, can helps us quantify how biological time mediates the response of organisms to environmental fluctuations.

Natural Analogues in pH Variability and Predictability across the Coastal Pacific Estuaries: Extrapolation of the Increased Oyster Dissolution under Increased pH Amplitude and Low Predictability Related to Ocean Acidification

Coastal-estuarine habitats are rapidly changing due to global climate change, with impacts influenced by the variability of carbonate chemistry conditions. However, our understanding of the responses of ecologically and economically important calcifiers to pH variability and temporal variation is limited, particularly with respect to shell-building processes. We investigated the mechanisms driving biomineralogical and physiological responses in juveniles of introduced (Pacific; Crassostrea gigas) and native (Olympia; Ostrea lurida) oysters under flow-through experimental conditions over a six-week period that simulate current and future conditions: static control and low pH (8.0 and 7.7); low pH with fluctuating (24-h) amplitude (7.7 ± 0.2 and 7.7 ± 0.5); and high-frequency (12-h) fluctuating (8.0 ± 0.2) treatment. The oysters showed physiological tolerance in vital processes, including calcification, respiration, clearance, and survival. However, shell dissolution significantly increased with larger amplitudes of pH variability compared to static pH conditions, attributable to the longer cumulative exposure to lower pH conditions, with the dissolution threshold of pH 7.7 with 0.2 amplitude. Moreover, the high-frequency treatment triggered significantly greater dissolution, likely because of the oyster's inability to respond to the unpredictable frequency of variations. The experimental findings were extrapolated to provide context for conditions existing in several Pacific coastal estuaries, with time series analyses demonstrating unique signatures of pH predictability and variability in these habitats, indicating potentially benefiting effects on fitness in these habitats. These implications are crucial for evaluating the suitability of coastal habitats for aquaculture, adaptation, and carbon dioxide removal strategies.

Intraspecific variability in thermal tolerance: a case study with coastal cutthroat trout

Fish physiological performance is directly regulated by their thermal environment. Intraspecific comparisons are essential to ascertain the vulnerability of fish populations to climate change and to identify which populations may be more susceptible to extirpation and which may be more resilient to continued warming. In this study, we sought to evaluate how thermal performance varies in coastal cutthroat trout (Oncorhynchus clarki clarki) across four distinct watersheds in OR, USA. Specifically, we measured oxygen consumption rates in trout from the four watersheds with variable hydrologic and thermal regimes, comparing three ecologically relevant temperature treatments (ambient, annual maximum and novel warm). Coastal cutthroat trout displayed considerable intraspecific variability in physiological performance and thermal tolerance across the four watersheds. Thermal tolerance matched the historical experience: the coastal watersheds experiencing warmer ambient temperatures had higher critical thermal tolerance compared with the interior, cooler Willamette watersheds. Physiological performance varied across all four watersheds and there was evidence of a trade-off between high aerobic performance and broad thermal tolerance. Given the evidence of climate regime shifts across the globe, the uncertainty in both the rate and extent of warming and species responses in the near and long term, a more nuanced approach to the management and conservation of native fish species must be considered.

Coupled changes in pH, temperature, and dissolved oxygen impact the physiology and ecology of herbivorous kelp forest grazers

Understanding species' responses to upwelling may be especially important in light of ongoing environmental change. Upwelling frequency and intensity are expected to increase in the future, while ocean acidification and deoxygenation are expected to decrease the pH and dissolved oxygen (DO) of upwelled waters. However, the acute effects of a single upwelling event and the integrated effects of multiple upwelling events on marine organisms are poorly understood. Here, we use in situ measurements of pH, temperature, and DO to characterize the covariance of environmental conditions within upwelling-dominated kelp forest ecosystems. We then test the effects of acute (0-3 days) and chronic (1-3 months) upwelling on the performance of two species of kelp forest grazers, the echinoderm, Mesocentrotus franciscanus, and the gastropod, Promartynia pulligo. We exposed organisms to static conditions in a regression design to determine the shape of the relationship between upwelling and performance and provide insights into the potential effects in a variable environment. We found that respiration, grazing, growth, and net calcification decline linearly with increasing upwelling intensity for M. francicanus over both acute and chronic timescales. Promartynia pulligo exhibited decreased respiration, grazing, and net calcification with increased upwelling intensity after chronic exposure, but we did not detect an effect over acute timescales or on growth after chronic exposure. Given the highly correlated nature of pH, temperature, and DO in the California Current, our results suggest the relationship between upwelling intensity and growth in the 3-month trial could potentially be used to estimate growth integrated over long-term dynamic oceanographic conditions for M. franciscanus. Together, these results indicate current exposure to upwelling may reduce species performance and predicted future increases in upwelling frequency and intensity could affect ecosystem function by modifying the ecological roles of key species.

Temporal variation may have diverse impacts on range limits

Environmental fluctuations are pervasive in nature, but the influence of non-directional temporal variation on range limits has received scant attention. We synthesize insights from the literature and use simple models to make conceptual points about the potentially wide range of ecological and evolutionary effects of temporal variation on range limits. Because organisms respond nonlinearly to environmental conditions, temporal variation can directionally alter long-term growth rates, either to shrink or to expand ranges. We illustrate this diversity of outcomes with a model of competition along a mortality gradient. Temporal variation can permit transitions between alternative states, potentially facilitating range expansion. We show this for variation in dispersal, using simple source-sink population models (with strong Allee effects, or with gene flow hampering local adaptation). Temporal variation enhances extinction risk owing to demographic stochasticity, rare events, and loss of genetic variation, all tending to shrink ranges. However, specific adaptations to exploit variation (including dispersal) may permit larger ranges than in similar but constant environments. Grappling with temporal variation is essential both to understand eco-evolutionary dynamics at range limits and to guide conservation and management strategies. This article is part of the theme issue 'Species' ranges in the face of changing environments (Part II)'.

Flood-Pulse Variability and Climate Change Effects Increase Uncertainty in Fish Yields: Revisiting Narratives of Declining Fish Catches in India’s Ganga River

River-floodplains support a significant number of small-scale capture fisheries despite having undergone degradation due to human modification of river flows by dams, pollution, and climate change. River fish production is underpinned by the annual flood-pulse and associated environmental changes that act as cues for spawning and dispersal for most species. However, studies on fish stock declines have focused more on overfishing than on hydroclimatic variability. Therefore, understanding how changes in flood-pulse variability influence fishing effort and yields is critical to inform adaptive fisheries’ management. We investigated hydroclimatic factors driving flood-pulse variability and fish catch–effort dynamics in India’s Ganga River over two decades (2000–2020). We compiled fishers’ narratives of changing fish catches through semi-structured interviews to compare them with our observed trends. Flood amplitude showed increasing variability, longer duration, and earlier rise timings, linked to La Niña and El Niño phases. Catches per unit effort were correlated with total yield and effort but did not decline as fishers thought, despite overall declines in yield over time. Hydroclimatic variability was a more significant driver of changing yields than local fishing pressure. Rising uncertainty in fisheries’ production, in response to increasing flood-pulse variability and altered flows in the Gangetic Plains, may be affecting fishing behaviour and underlying resource conflicts.

Over a decade of field physiology reveals life-history specific strategies to drought in garter snakes (Thamnophis legans)

Changing climates and severe weather events can affect population viability. Individuals need to buffer such negative fitness consequences through physiological plasticity. Whether certain life-history strategies are more conducive to surviving changing climates is unknown, but theory predicts that strategies prioritizing maintenance and survival over current reproduction should be better able to withstand such change. We tested this hypothesis in a meta-population of garter snakes having naturally occurring variation in life-history strategies. We tested whether slow pace-of-life (POL) animals, that prioritize survival over reproduction, are more resilient than fast POL animals as measured by several physiological biomarkers. From 2006 to 2019, which included two multi-year droughts, baseline and stress-induced reactivity of plasma corticosterone and glucose varied annually with directionalities consistent with life-history theory. Slow POL animals exhibited higher baseline corticosterone and lower baseline glucose, relative to fast POL animals. These patterns were also observed in stress-induced measures; thus, reactivity was equivalent between ecotypes. However, in drought years, measures of corticosterone did not differ between different life histories. Immune cell distribution showed annual variation independent of drought or life history. These persistent physiological patterns form a backdrop to several extirpations of fast POL populations, suggesting a limited physiological toolkit to surviving periods of extreme drought.

Habitability Is Binary, But It Is Used by Astrobiologists to Encompass Continuous Ecological Questions

The term "habitability" is pervasive throughout the space sciences and astrobiology literature and is broadly used to describe an environment's ability to support life. Here, we argue that, while it is fundamentally a binary matter whether an organism can persist in an environment or not, these binary assessments lead to continuous ecological measurements that are often collected under the umbrella term "habitability" by astrobiologists. Although the use of habitability in this way has provided a framework for those studying the potential of environments to support life, including comparative analyses between terrestrial and extraterrestrial environments, it can also generate confusion and limit interdisciplinary understanding. Namely, differing ecological metrics used as proxies for habitability can yield differing conclusions depending upon the metrics chosen. Therefore, we suggest that in this continuous sense, the terms habitable and habitability lose meaning unless the specific scientific question and biological metric chosen to address it are defined. As a corollary, the search for universal single metrics to make habitability assessments is not to be encouraged, and as we argue, attempting to do so would oversimply analyses of the ability of environments to support life.

Seed banks alter metacommunity diversity: The interactive effects of competition, dispersal and dormancy

Dispersal and dormancy are two common strategies allowing for species persistence and the maintenance of biodiversity in variable environments. However, theory and empirical tests of spatial diversity patterns tend to examine either mechanism in isolation. Here, we developed a stochastic, spatially explicit metacommunity model incorporating seed banks with varying germination and survival rates. We found that dormancy and dispersal had interactive, nonlinear effects on the maintenance and distribution of metacommunity diversity. Seed banks promoted local diversity when seed survival was high and maintained regional diversity through interactions with dispersal. The benefits of seed banks for regional diversity were largest when dispersal was high or intermediate, depending on whether local competition was equal or stabilising. Our study shows that classic predictions for how dispersal affects metacommunity diversity can be strongly influenced by dormancy. Together, these results emphasise the need to consider both temporal and spatial processes when predicting multi-scale patterns of diversity.

Biogeochemical extremes and compound events in the ocean

The ocean is warming, losing oxygen and being acidified, primarily as a result of anthropogenic carbon emissions. With ocean warming, acidification and deoxygenation projected to increase for decades, extreme events, such as marine heatwaves, will intensify, occur more often, persist for longer periods of time and extend over larger regions. Nevertheless, our understanding of oceanic extreme events that are associated with warming, low oxygen concentrations or high acidity, as well as their impacts on marine ecosystems, remains limited. Compound events-that is, multiple extreme events that occur simultaneously or in close sequence-are of particular concern, as their individual effects may interact synergistically. Here we assess patterns and trends in open ocean extremes based on the existing literature as well as global and regional model simulations. Furthermore, we discuss the potential impacts of individual and compound extremes on marine organisms and ecosystems. We propose a pathway to improve the understanding of extreme events and the capacity of marine life to respond to them. The conditions exhibited by present extreme events may be a harbinger of what may become normal in the future. As a consequence, pursuing this research effort may also help us to better understand the responses of marine organisms and ecosystems to future climate change.