Sylvain Pincebourde

1. Most plant species are genetically differentiated among populations, often reflected by phenotypic trait variation that corresponds to local adaptation. Yet the strength of local adaptation and heritable contribution to phenotypic traits vary across traits, species, and environments. Additionally, climate change is rapidly altering environmental conditions, and the climate may shift faster than populations can adapt or track the change via dispersal, resulting in adaptive lags. However, it remains unclear how widespread such adaptive lags are across plant species. 2. We focused on Hordeum murinum , an annual ruderal grass widespread in Europe. We combined continental-scale in situ measurements of 2070 plants across 207 populations with common garden experiments across two contrasting climates and two soil types to disentangle heritable variation from phenotypic plasticity and assess potential adaptive lags under climate change. 3. We found that heritable variation was pronounced in developmental traits, particularly flowering time and plant height, while seed weight, reproductive investment and SLA showed intermediate heritable contribution, and flag leaf area and total biomass were primarily plastic. Heritable trait variation was strongly associated with temperature at the populations’ origin, and trait clines were consistent with in situ patterns, suggesting that temperature is the main driver of genetic differentiation in H. murinum . However, we detected that fitness peaked in populations originating from warmer climates, indicating that evolutionary responses may not keep pace with rapid environmental shifts. 4. Synthesis: Our results highlight that H. murinum harbors substantial heritable variation, shaped primarily by temperature. However, the pace of evolutionary change may be insufficient to track ongoing climate change, leaving populations potentially vulnerable to future environmental conditions.

Background and Aims: Plant functional traits link environmental conditions to plant performance and adaptation. Growing evidence suggests that intraspecific trait variation can be as important as differences between species, yet large intraspecific studies of in situ variation remain rare. Most studies have focused on plant morphological traits, whereas the concentrations of elemental nutrients in seeds have received much less attention so far. Methods: We conducted a large-scale in situ study of the widespread annual ruderal grass Hordeum murinum. We sampled 2070 individuals from 207 populations across a large part of its native range in Europe and North Africa. We measured seed ripening phenology and growth-related traits in situ and analysed concentrations of elemental nutrients in the seeds. Key Results: We found that H. murinum grew larger, produced seeds later and had heavier seeds in colder and wetter regions. Plants growing in denser vegetation were taller and produced heavier seeds but formed fewer spikes. Concentrations of elemental nutrients in the seed generally declined with seed weight and were driven primarily by climatic variables, whereas soil conditions had only minor effects on plant traits and seed nutrients. Population identity explained a substantial proportion of trait variation, indicating a possible genetic component. Conclusions: Our findings provide a comprehensive view of how H. murinum responds to environmental gradients across its European distribution. Climatic variables, particularly temperature, are key drivers of reproductive timing and concentrations of elemental nutrients in the seed, whereas local environmental conditions, such as biotic pressures, are more important for growth-related traits. Together, these patterns indicate that H. murinum modulates its growth and reproductive investment along environmental gradients, balancing phenology, stress tolerance and limited competitive capacity.

Natural microcosms are those such as galls, flowers, splashpools and lichen patches that form uniquely circumscribed systems, whose boundaries may be difficult to physically and physiologically define. Yet, unlike artificial microcosms that are assembled within petri plates, outdoor or indoor tanks, natural microcosms contain a full complement of organismal diversity within intricate food webs thus constituting functional natural ecosystems. Their small size and smaller number of organisms inhabiting them make many natural microcosms amenable to experimentation and utilization of techniques including sophisticated labelling, stoichiometry, genomics and transcriptomics to answer fundamental aspects of species ecology, ecosystem functioning, nutrient flows and physiological responses to climate change. Many natural microcosms of the same type occur over wide latitudinal extents and can therefore be used to investigate large-scale climatic impacts. Some microcosms exhibit internal gradients of temperature and oxygenation saturation resulting in different abiotic conditions within microcosms. Thus, an individual microcosm type can offer insights into physiological adaptations such as thermal tolerance. Organisms that inhabit ephemeral microcosms must also have efficient dispersal or dormancy strategies contributing to organism survival. The ephemerality of the microcosm may contribute to organism specialization versus generalization. Microlandscape ecology and microcosm stoichiometry are other new research areas that microcosms offer. This article is part of the theme issue ‘Life in natural microcosms’.

Microclimates within microcosms are often stated to shelter occupants from adverse conditions, yet our limited knowledge narrows our ability to estimate the vulnerability to warming of species exploiting them. We characterized the microclimate temperature of the floral chamber of a thermogenic plant that produces heat in the context of pollination syndrome. Pollinators (Psychoda moth flies) of Arum italicum are trapped within the floral chamber for 24 h, thereby potentially exposing insects to dangerous temperatures. We report a strong temperature gradient across the floral chamber. We propose two hypotheses for the role of this temperature gradient in the pollination syndrome depending on environmental context. Under moderate conditions, the system relies on the exact position of the thermogenic organ to discourage insects from escaping the chamber, while temperature at the bottom of the chamber corresponds to the moth fly’s preferred temperature, motivating the insect to remain there long enough to get covered by pollen. Under extreme conditions, the floral chamber may provide a thermal reward to avoid the Psychoda fly from reaching its thermal limits. Our comprehensive mechanistic analysis of the microclimate in a thermogenic flower highlights the importance of coevolutionary trajectories between temperature regulation by plants and their pollinators’ thermal biology. This article is part of the theme issue ‘Life in natural microcosms’.

The transition from aquatic to terrestrial life exposed organisms to novel thermal and hydric challenges. In terrestrial isopods, these pressures drove key adaptations in their aerial respiratory system, including the evolution of pseudotracheae (0, 2 or 5 pairs depending on species). However, the functional consequences of these respiratory adaptations for heat and desiccation tolerance remain unclear. We quantified these tolerances in five species differing in pseudotracheae number to test whether a higher number confers higher physiological limits. Heat tolerance was assessed using the thermal death time framework, and desiccation tolerance was tested at 34°C under three relative humidity levels. Species with pseudotracheae showed higher tolerance to both heat and desiccation, supporting their role in terrestrial adaptation. Yet, at low humidity, the 5-pair species was more sensitive than the 2-pair species, suggesting that other morpho-behavioral traits such as volvation also shape desiccation tolerance. Our study highlights the functional role of pseudotracheae in the transition between aquatic and terrestrial environments by improving physiological limits.

Insect research remains hindered by limited data availability and fragmented knowledge compared to other, better-documented taxonomic groups. Yet, both the macroecological and the insect research communities highlight the need to integrate large-scale ecological trait datasets for insects. Insects and humans are interconnected through diverse relationships, ranging from beneficial interactions, such as the use of insects as nutritional resources, to adverse impacts, including their role in to the emergence and spread of biological invasions. Understanding the traits of insects associated with human use, movement and impact is therefore important for linking insects to ecosystem function and global change. We present AnthropInsect , one of the largest database on insect traits to date, which uniquely includes variables describing human-insect associations. AnthropInsect describes species through 35 variables grouped into five categories: (i) taxonomic descriptors; (ii) ecological descriptors (native bioregions and habitat); (iii) human-insect associations (edibility and invasive status); (iv) functional traits (behavior, morphology, life history and feeding); (v) and macroecological descriptors of native-range geography and climate. AnthropInsect currently includes 5867 species across six major orders: Coleoptera, Lepidoptera, Hemiptera, Hymenoptera, Orthoptera and Blattodea. Data extracted from peer-reviewed, grey literature and from existing databases were standardized and validated with expert knowledge to ensure accuracy. By providing traits data with information on insect–human interactions, this rigorously curated resource supports global research in entomology, ecology, conservation, and global change.

Polyphagous insects rely on multiple cues to choose oviposition sites, including substrate temperature and nutritional quality, which often do not coincide. We examined how females of the invasive fly Drosophila suzukii make oviposition decisions when temperature and nutrition mismatch, and whether infection with the symbiotic bacterium Wolbachia influences these choices. We first quantified female performance (egg number, offspring development time, survival and mass) on four fruit purees at three ambient temperatures. We then assessed oviposition preferences when either substrate temperature or fruit quality varied independently. Finally, we conducted multi-choice experiments combining thermal and nutritional cues to test which most strongly drives oviposition. Both temperature and fruit quality affected offspring performance. Although females did not always choose the most favourable fruit, they consistently prioritised thermally optimal sites, even when these were nutritionally suboptimal. This behaviour gave partial support to the preference–performance hypothesis, which mainly held for temperature – the factor with the strongest effect on offspring development and survival in no-choice tests. Wolbachia infection enhanced offspring survival and reduced development time. It also altered oviposition patterns, leading to a more even distribution of eggs across fruit, though females maintained their preference for thermally favourable sites. Our findings suggest that the invasive success of D. suzukii could partly result from its capacity to select oviposition sites that maximise offspring performance under variable conditions. More broadly, they highlight the need to study behavioural decisions under conflicting environmental constraints to understand how behavioural flexibility contributes to individual fitness and population persistence in changing environments.

Plant functional traits link environmental conditions to plant performance and adaptation. Growing evidence shows that in-situ intraspecific trait variation can be as important as differences between species, yet large intraspecific datasets measured in situ are rare. While most studies focused on plant morphological traits, contents of elemental nutrients in the seeds received much less attention so far. We conducted a large-scale in-situ study of the widespread ruderal grass Hordeum murinum . We sampled 2070 individuals from 207 populations from a large part of the native range in Europe and Northern Africa. In-situ, we measured seed ripening phenology and morphological traits, and analyzed the content of elemental nutrients in the seeds. We found that Hordeum murinum grew larger, produced seeds later, and had heavier seeds in colder and wetter areas. Plants in denser vegetation were taller with heavier seeds but formed fewer spikes. Seed nutrient content generally declined with seed weight and was mainly driven by climate. Soil conditions had only minor effects on plant traits and seed nutrients. Population identity explained much of the variation, indicating a possible genetic component. Synthesis : Our findings provide a comprehensive view of Hordeum murinum responding to environmental gradients across its European distribution. Climatic variables, especially temperature, are key drivers for reproductive success and seed nutrient content, while local environments, such as biotic pressures, are more critical for growth-related traits. These patterns indicate that H. murinum modulates its growth and reproductive investment along environmental gradients, balancing phenology, stress tolerance, and limited competitive capacity.

Extreme heat events are expected to increase under global climate change, which may depress the abundance of most insect species, including agricultural pests. However, here our experimental observations show that the behavioural plasticity within fine-scale microhabitats, which is often neglected in pest damage and crop loss predictions, can buffer the exposure to simulated extreme high temperatures in a small pest aphid species. As expected, this buffering effect promotes aphid population growth in our lab experiments. Our model predictions further suggest that this buffering effect can aggravate pest damage and wheat yield losses globally during 1977-2017 (8.7 million tons/year, accounting for ~1.2% of global production), assuming a moderate initial pest density if no pesticides are applied. This estimated yield-loss aggravation may even worsen faster ( + 2.6% per year) than the reported increase of global wheat production ( + 2.0% per year) under warming. More than 4/5 countries may undergo increasingly aggravated losses, including most of the countries with the largest wheat production, particularly serious for less developed countries. Global food security will be greatly challenged, considering many other pest insects may also cause aggravated crop loss via buffering climate impacts through behavioural plasticity.