Robby Stoks

A key goal of predictive ecology is to understand how global warming affects ectotherm growth and development. Researchers often rear organisms under constant temperature and photoperiod regimes, raising the question of whether responses under these simplified conditions reflect those in realistic, seasonally varying environments. We examined key life-history traits of the damselfly Lestes sponsa across six combinations of constant and seasonal temperatures and photoperiod regimes, simulating present-day and future climates with a projected 4°C warming. Trait responses differed qualitatively and quantitatively among treatments. Mass and development responses to warming shifted direction depending on regime. For example, the response in mass to warming was reversed between constant (decrease) and seasonal varying (increase) conditions. In addition, developmental synchrony was stronger under seasonal photoperiods, and the temperature–size rule held only under constant conditions. Our results highlight that incorporating seasonal variation is crucial for developing a realistic framework for predicting species' responses to climate change.

Invasive alien (IA) predators can disrupt predator-prey interactions and alter prey phenotypes. However, how their effects differ from those of native predators remains poorly understood. Additionally, it is unclear to what extent these impacts interact with environmental factors such as warming and photoperiod. To address these gaps, two complementary experiments were performed in the damselfly Ischnura elegans to test the effects of predator chemical cues (control, native noble crayfish, and IA spinycheek crayfish) in combination with (Experiment 1) temperature (ambient vs. warming) and short- and long-term predator cue exposure or (Experiment 2) photoperiod imposing different seasonal time constraints (early vs. late season). Effects on life-history (survival and growth rate), physiological (immune function measured as phenoloxidase (PO) activity and fat content), and behavioral (boldness and feeding rate) traits were subsequently quantified. In Experiment 1, responses to IA spinycheek crayfish cues differed from those induced by native noble crayfish cues across all trait types, with predator-specific responses strongly dependent on temperature. Following short-term exposure, predator-specific differences in boldness and PO activity were evident at ambient temperature but weakened under warming. Following long-term exposure, survival was lower under IA spinycheek than under native noble crayfish cues, whereas under warming, growth rate was lower following exposure to native noble crayfish cues than in the control, with the IA spinycheek treatment intermediate. In Experiment 2, the late photoperiod increased predator-specific differentiation in growth rate and boldness, primarily through stronger responses to native noble crayfish cues. The results broadly support the naïve prey hypothesis but show that responses to native and IA predators are not determined by predator novelty alone. Abiotic conditions, represented here by temperature and photoperiod, can modulate predator-specific plasticity, highlighting the importance of environmental context when predicting prey responses to biological invasions under climate change.

Warming is increasingly recognized to magnify the toxicity of chemicals. Yet, limited understanding of the underlying physiological mechanisms constrains our ability to predict these interactions between warming and toxicants, and how these may evolve under global climate change scenarios. Here, a common-garden experiment was conducted with two resurrected subpopulations of Daphna magna, separated by ca. 40 years in time, of which the recent subpopulation evolved a higher heat tolerance. Daphnia were exposed to low (150 µg L-1) and high (300 µg L-1) zinc levels across a large thermal gradient (12 °C - 30 °C). After 96-h exposure, bioenergetic traits, oxidative damage to lipids and hemoglobin levels were quantified. Both zinc levels caused stronger reductions in net energy budget at higher temperatures in both subpopulations. At the highest temperature, low zinc reduced energy consumption in the old subpopulation, whereas the recent subpopulation evolved an increased energy consumption, resulting in a greater decline in the net energy budget. Across treatment groups, survival correlated positively with the net energy budget, and negatively with oxidative damage, while the hemoglobin levels correlated positively with the acute heat tolerance. These findings suggest reductions in the net energy budget to be a key driver of the widespread phenomenon whereby toxicants become more lethal at higher temperatures, and reductions in hemoglobin to contribute to the toxicant-induced declines in heat tolerance. Overall, our study underscores the importance of incorporating physiological mechanisms to understand and predict the current and future sensitivity of organisms to contaminants under ongoing climate change.

Accurately predicting species’ responses to climate change requires an understanding of the drivers of their thermal limits. Despite rapid warming of freshwater ecosystems worldwide, we still lack a global perspective on how upper thermal limits (UTLs) vary among aquatic insects, what constrains these limits, and how they contribute to species vulnerability. Here, we compiled a global dataset encompassing 423 aquatic insect species to test the effects of environmental conditions, organismal traits, acclimation history, and phylogenic relationships on patterns of heat tolerance. Maximum habitat temperatures were positively correlated with UTLs supporting the Climate Extremes Hypothesis, and insects relying exclusively on dissolved oxygen had the lowest UTLs supporting the Oxygen- and Capacity-Limited Thermal Tolerance hypothesis. Functional traits also explained substantial variation in UTLs; those that feed via scraping and shredding exhibited some of the lowest UTLs. Laboratory acclimation methods further influenced UTL estimates. Short-term exposure to higher acclimation temperatures increased UTLs, but longer exposure led to decreased heat tolerance. Finally, warming tolerance, i.e., the difference between UTL and the maximum habitat temperature) varied with breathing mode. Across latitude, warming tolerances were lowest for obligate dissolved oxygen-breathers but increased more rapidly in insects that can access terrestrial air. Collectively, these patterns indicate that oxygen is a key mechanism shaping thermal vulnerability in aquatic insects.

More and more data on species traits are being collected and made openly available. Despite these efforts, effective syntheses of trait data to comprehend how species respond to and affect their environment are hampered by inadequate standards for publishing the data and the associated metadata, which limits the interoperability and reuse of data across studies. We have developed ShareTrait ( https://sharetrait.org/ ), a novel initiative that consolidates individual‐level trait data and associated metadata in an interoperable and reusable format, enabling standardised and integrated use. As a proof‐of‐concept, we initially focus on three core traits of ectotherms: metabolic rate, development time and fecundity. These traits, measurable in almost all animals, are fundamental to an organism’s overall fitness. ShareTrait enables researchers to share their (meta)data with the research community. To date, researchers from diverse fields have contributed 28,692 individual‐level data records to ShareTrait. These records originated from 45 datasets and are just the tip of the iceberg of existing data, highlighting the potential of ShareTrait to be a valuable community resource for meta‐analyses and comparative approaches. Future directions of ShareTrait will focus on accumulating more records, expanding to cover more traits, including those measurable at the population level, and partnering with journals in relevant fields (ecology, physiology, evolution) to make sharing standardised trait data part of the standard publication process. We envision ShareTrait, along with its digital infrastructure and comprehensive metadata, to be a catalyst for collating trait data across species. ShareTrait can streamline research efforts, minimise duplication and empower researchers to explore patterns and broader ecological, evolutionary and physiological questions among taxa (e.g. via meta‐analyses and comparative approaches). This way, ShareTrait will unlock new frontiers in trait‐based approaches, enhancing our understanding of species–environment relationships. Read the free Plain Language Summary for this article on the Journal blog.

Latitudinal patterns in fitness‐related traits within species are receiving increased attention as these inform how high‐latitude populations may evolve in response to global warming. The underlying mechanisms for these latitudinal trait patterns remain poorly understood, and recently the gut microbiome has been suggested to be a potentially important proximate driver of these patterns. We investigated the novel idea of whether the gut microbiome drives latitudinal differences in immune function and pathogen load. To test this idea, we performed a reciprocal gut microbiome transplant between slow‐paced, high‐latitude (southern Sweden) and fast‐paced, low‐latitude (southern France) populations of Ischnura elegans damselflies. The transplants were conducted in the laboratory between high‐ and low‐latitude larvae, at both a colder and warmer thermal regime, whereafter larvae were exposed to Escherichia coli, a widespread pathogenic bacterium in aquatic ecosystems. During the experiment, larval mortality, growth rate, phenoloxidase (PO) level (a measure of immune function), E. coli burden (a measure of pathogen load) and the gut microbiome diversity (α‐diversity) and community compositions (β‐diversity) were analysed. Exposure to the pathogen increased mortality, especially under warming. Our results confirmed latitude‐associated thermal adaptation and a faster pace of life of the low‐latitude larvae, which was associated with a lower immune function (lower activity of PO), consistent with previous findings and now showed this to be linked to a higher pathogen load (higher E. coli body burden). Moreover, our results provided the first experimental evidence that the gut microbiome causally contributed to latitudinal differences in the host's immune function and pathogen load. As latitudinal patterns in the microbiome are widespread, this may be an important yet ignored proximate driver of the latitudinal patterns in immune function and pathogen load.

Dragonflies (Odonata) are ancient and familiar insects with a deep and strong cultural association with humans. They have an aquatic larval stage and an aerial adult stage, meaning that they respond to ecological conditions in both freshwater and the adjacent land surface. Currently, 16% of dragonflies are threatened. Overall, they face several threats, especially habitat loss, landscape transformation, pollution, altered hydrology, spread of invasive alien species, as well as certain geographic‐specific threats. Overarching these threats, which can be interactive with each other, is the issue of global climate change and attendant extreme weather events. While many localised and habitat specialist species are under extreme threat, some other dragonfly species, mostly habitat generalists, benefit from certain moderate human activities, especially the creation of high‐quality artificial ponds. As well‐researched insects, dragonflies play an important role in the protection of freshwater and riparian ecosystems. Dragonfly assemblages have great value as sentinels of both deteriorating environmental conditions and ecosystem recovery following restoration. While similar findings on both threats and conservation actions are emerging across the world, certain ecosystems require targeted approaches. Above all, dragonflies must be included more widely in general biodiversity conservation activities and policies. Overall, dragonflies are important targets, tools and model organisms for conservation action, and they can act as potential surrogates for other taxa that also depend on high water and riparian zone quality. While research has paved the way to address these challenges, including the use of new technologies, we now urge that dragonflies be included more strongly in policy and management associated with both freshwater and adjacent terrestrial realms. This inclusion is especially effective as dragonflies have great appeal to a diverse community of people from odonatologists (citizen and professional) through to policymakers and managers, all of whom can employ dragonflies to contribute more to freshwater‐associated conservation. Finally, we propose an action plan focusing on five action points that address opportunities, and we suggest where dragonflies can play a greater role in freshwater/riparian zone conservation more widely across the world.

Invasive alien (IA) predators pose significant threats to native ecosystems, often leading to profound impacts on prey species through both direct and non-consumptive effects (NCE). This study focused on the NCE of predator-induced stress from one native crayfish species, noble (Astacus astacus), compared to one alien danube crayfish (Pontastacus leptodactylus) and two IA crayfish species, signal (Pacifastacus leniusculus) and spinycheek crayfish (Faxonius limosus), on the native damselfly Ischnura elegans. We investigated the direct crayfish cue effect on egg traits as well as potential carry-over effects from the egg stage to the larval stage. We hypothesised that native crayfish cues would lead to more pronounced negative effects on prey traits compared to alien and IA crayfish, due to an evolutionary history of interaction and recognition of these threats. Unexpectedly, compared to native crayfish cues, alien and IA crayfish cues caused significantly higher egg mortality and prolonged developmental times, particularly cues from danube and signal crayfish, while cues from spinycheek crayfish had weaker, yet, still significant effects. Hatching synchrony was reduced and this to the same extent by the cues of all four crayfish species. Notably, cues from both alien and IA crayfish species caused significant carry-over effects, resulting in reduced larval survival, mass and fat content, which were more pronounced for danube and signal crayfish. Native crayfish cues did not induce carry-over effects, suggesting that I. elegans may have evolved a degree of resilience against this predator or that native crayfish produce chemical cues that do not cause a strong antipredator response. Our findings underscore the importance of considering immediate and carry over effects of crayfish on prey traits across multiple life stages, particularly in the context of biological invasions.