Environmental stochasticity impacts population dynamics and their viability. As such, understanding how organisms cope with this variability is crucial. Here, we investigate demographic buffering, the ability of populations to maintain stable growth despite environmental fluctuations. We integrate well-established stochastic and deterministic approaches to investigate characteristics of demographic buffering, analysing stochastic elasticities and self-second derivatives of deterministic population growth rate. We test the hypothesis that buffered species exhibit low stochastic elasticity to temporal variability and signs of concave selection (i.e. negative second derivatives of population growth rate with respect to demographic processes), reducing variance in key demographic processes. Analysing 43 natural populations of 37 mammal species, we find limited support for this hypothesis. Indeed, while primates often show low stochastic elasticity, concave selection is less prevalent than expected. Our findings highlight the complex and dynamic relationship between demographic processes, environmental variability, and selection pressures in determining population persistence.

Current global changes are driving many species towards extinction, making the early detection of threatened species a priority for efficient conservation actions. However, the threat status of many species remains unknown because we lack primary data (e.g., population trends), and using ecological indicator traits such as range size is not always straightforward. Recently, the idea has emerged to link species’ current threat status to macroevolutionary indicators, e.g., rates of extinction, diversification or niche evolution. However, to fully utilise this approach, we need to understand the underlying assumptions and when they are valid; namely, in which cases macroevolutionary indicators can be used as proxies for extinction-promoting characteristics, such as small range size, narrow niche breadth or low evolutionary potential. Here, we assess current understanding of the assumptions underlying the relationship between macroevolutionary indices and contemporary extinction risk. We find that only past extinction rates can be reliable predictors of current extinction risk. Assumptions underlying relationships between current extinction risk and diversification and niche evolution rates were only supported in specific circumstances and should be tested on a case-by-case basis. When intermediate assumptions are validated, macroevolutionary indicators could be promising tools complementing trait-based approaches in identifying vulnerable species.

Climate change is increasing extreme heating events and the potential for disease outbreaks. Whether hosts can adapt to infection with rising temperatures is important for forecasting species persistence. We tested whether warming -- at different host life-stages -- affects the ecological and evolutionary dynamics of resistance in Caenhorabditis elegans infected by a wild bacterial pathogen. We competed genotypes across 10 passages and tracked the spread of resistance in the population. Infection and prolonged warming strongly selected for the resistant genotype. Warming during host development induced plastic defenses against infection, reducing the selective pressure for costly genetic-based resistance. Resistance was lost under ambient temperatures and periodic warming. Selection for resistance was likely weakened at ambient temperatures by the dilution effect, whereby resistant genotype reduced pathogen transmission. Evolutionary dynamics of resistance depend on the balance among pathogen virulence, costs of genetic-based resistance, the dilution effect, and plastic defenses induced by temperature stress.

Insect pollinators are essential for the health and resilience of terrestrial ecosystems, delivering key ecosystem services in the face of anthropogenic disturbance. Urbanisation may be a key threat to pollinator diversity and abundance. However, the scale of the threat remains unknown due to an overwhelming research emphasis on bees and a lack of comparative studies of hyper-diverse taxa such as nocturnal moths. Consequently, the question of which pollinator groups will be more affected by urbanisation remains unknown, and the habitat features that support key taxa remain controversial. We conducted the first large-scale assessment of the negative effects of increasing urbanisation on the diversity of bee, hoverfly and nocturnal moths across three cities. We report up to a 43% reduction in species richness along replicated urbanisation gradients, suggesting that a wide range of pollinators are limited due to abiotic stresses and limited resources in urban environments. Landscape mapping indicated that these effects are driven by the reduction of tree cover and semi-natural habitat; however, the specific landscape drivers were taxon-specific, suggesting that urban insect conservation depends on the preservation or expansion of habitat features specific to different threatened taxa. In the first empirical comparison of three major pollinator taxa, we show that, relative to bees, moths and hoverflies are particularly sensitive to urbanisation, and we highlight the importance of including these frequently overlooked pollinator groups when assessing the biodiversity impacts of environmental change.

Exposure to environmentally-transmitted parasites should increase with population density due to accumulation of infective parasites in space. However, resource competition also increases with density, lowering immunity and increasing susceptibility, offering an alternative pathway for density-dependent infection. To test the relationships between these two processes and parasitism, we examined associations between host density, resource availability, immunity, and counts of three common helminth parasites using a long-term study of red deer. We found evidence that immunity increased with resource availability while parasite counts declined with immunity. We also found that greater density correlated with reduced resource availability, and while density was positively associated with both strongyle and tissue worm burdens, resource availability was independently and negatively associated with the same burdens. Our results support separate roles of density-dependent exposure and susceptibility in driving infection, providing evidence that resource competition is an important driver of infection, exacerbating effects of density-dependent increases in exposure.

Restricted space use patterns are common in mobile organisms, yet an understanding of how such patterns are developed is lacking. We conceptualize the settlement process of home range formation as the discovery of patches and subsequent decision to return to them. We then test how forage quality and landscape structure influence this process. Using 5 years of data from reintroduced bison (n = 10), we found patch discovery was influenced by landscape structure, with lower traveling costs, larger patch size, and higher patch connectivity facilitating patch discovery. Once discovered, areas of high-quality were more likely incorporated into regular space use, especially if an individual had recently visited relatively high-quality areas. Overall, landscape structure mainly influenced patch discovery, while forage quality underlined space use refinement. Our work provides a mechanistic understanding of home range development, elucidating the iterative process of settlement as a function of both landscape structure and habitat quality.

Ecologists increasingly use complex models to predict and understand ecological systems and their responses to external drivers or anthropogenic pressures. A persistent challenge in this context is quantifying and reducing uncertainty in model inputs, parameters and structure, and understanding their implications for model predictions. Three major methodological fields have emerged in this context: sensitivity analysis, uncertainty analysis and model calibration. These three methods are a integral part of any modelling or forecasting process, but the corresponding literature is often scattered, and distinct terminology and definitions are used in different methodological and scientific contexts. Here, we review and connect these three fields and discuss best practices for their practical implementation with a focus on complex ecological models. We classify relevant types of uncertainty, discuss the complementary roles of sensitivity and uncertainty analyses, give an overview of available calibration methods, and emphasise the importance of effective communication of uncertainty. We conclude that using state-of-the-art methods for understanding model behaviour as well as consistently accounting for all uncertainties is essential for correctly understanding model predictions and thus forms the basis for a responsible use of models in ecological decision making.

Species coexistence is shaped by a range of biotic and abiotic factors. Beyond predation, parasitism, and competition, one species may interfere with another's reproduction to induce sexual exclusion from a habitat. Here, we test for reproductive interference from inter-species mating between sympatric nematodes Caenorhabditis macrosperma and C. nouraguensis. Higher intrinsic population growth of C. nouraguensis arises from greater reproductive output by both sexes, predicting it to be superior in resource competition. Mate discrimination between species is incomplete, however, with inter-species mating errors reducing lifespan and reproductive fitness of female C. nouraguensis only. These asymmetric costs arise within hours, due to ectopic migration of C. macrosperma's giant sperm cells. We modelled the population dynamic impacts of reproductive interference, then confirmed rapid sexual exclusion in mixed-species communities with multi-generation experiments. These findings demonstrate the profound ecological implications of reproductive interference for demographic parameters and species coexistence through a cell-mediated mechanism of inter-species harm.

It is well established that heterogeneities in host susceptibility and infectiousness affect transmission, and are typically assumed to be pre-determined traits. However, they may arise dynamically during the transmission process. Specifically, while infectiousness may be an inherent trait of the recipient (‘recipient-dependent’), it may instead be determined by the donor host that infected them (‘donor-dependent’). We investigated how the effects of heterogeneities on transmission are affected by these contrasting scenarios by analysing two ‘Susceptible-Infected’ models for three metrics: the basic reproduction number (R0), changes in heterogeneity, and equilibrium host abundance. We show that the primary driver of R0 differs between the two scenarios: covariance between susceptibility and infectiousness for recipient-dependent, versus maximum infectiousness for donor-dependent. Consequences for equilibrium host abundance also differed, but changes in heterogeneity did not. Our results show that these scenarios change epidemiological dynamics and should be considered when exploring the consequences of host heterogeneity on transmission.

Spillback – where non-native species increase the prevalence of native pathogens – is an important mechanism by which non-natives species may contribute to the emergence of zoonoses. However, spillback is rarely directly demonstrated because it is difficult to disentangle from confounding factors which correlate with non-native species abundance and native pathogen prevalence. Here, we capitalise on 25 independent, quasi-experimental releases of non-native pheasants (Phasianus colchicus) to compare vector abundance and native pathogen prevalence between sites with similar local conditions but different non-native densities. Questing adult (but not nymph) Ixodes ricinus were more abundant in woods where pheasants are released compared to control woods, and Borrelia sp. (the causative agent of Lyme disease) prevalence in questing nymphs and adults was 2.5 times higher, with a particularly strong effect on Borrelia garinii. This work provides direct evidence that non-native species can amplify zoonotic pathogens via spillback in an ecologically meaningful context.

Woodland creation is crucial for nature recovery and achieving net-zero goals. Although habitat creation to improve connectivity is assumed to benefit biodiversity, this has not been extensively quantified across multiple taxa and landscapes. Focusing on the UK, where woodland cover is low (13%), we analysed species occurrence records from citizen science for over 800 broadleaf woodland-associated invertebrate species from 15 taxa in relation to woodland cover and connectivity. Overall, we found that increased connectivity positively impacts the occurrence of these woodland-associated species (effect of connectivity across species, when accounting for the positive effect of woodland cover = 0.122). The benefits of connectivity varied considerably among these taxa: 49% of species showed a significant positive effect, while for 7% it was significantly negative. Our findings emphasise the biodiversity gains from increasing woodland cover and connectivity and highlight the importance of spatial targeting and landscape context in restoration efforts.

Freezing tolerance plays a pivotal role in shaping the distribution and diversification of organisms. We investigated the dynamics of adaptation to climate and potential trade-offs between stem freezing tolerance and growth rate in 48 Quercus species. Species from colder regions exhibited higher freezing tolerance, lower growth rates and higher winter-acclimation potential than species from warmer climates. Despite an evolutionary lag, freezing tolerance in oaks is closely aligned with its optimal state. Deciduous species showed marked variability in freezing tolerance across their broad climatic range while evergreen species, confined to warm climates, displayed low freezing tolerance. Annual growth rates were constrained in all deciduous species but those that evolved in warm latitudes lost freezing tolerance precluding a trade-off between freezing tolerance and growth. We provide evidence that capacity to adapt to a wide range of thermal environments was critical to adaptive radiation and current dominance of the North American oaks.

Dispersal is a fundamental process driving many ecological patterns. During transfer, species often make large-scale displacements resulting in significant energetic losses with implications for fitness and survival, however generalising these losses across different taxonomic groups is challenging. We developed a bioenergetic dispersal model based on fundamental processes derived from species traits. By balancing energy storage and energy loss during active dispersal, our mechanistic model can quantify energetic expenditures depending on landscape configuration and the species in focus. Moreover, it can be used to predict the maximum dispersal capacity of animals, which we compare with recorded maximum dispersal distances (n = 1571). Due to its foundation in bioenergetics it can easily be integrated into various ecological models, such as food-web and meta-community models. Furthermore, as dispersal is integral to ecological research, the quantification of dispersal capacities provides valuable insight into landscape connectivity, species persistence, and distribution patterns with implications for conservation research.

It remains challenging to understand why natural food webs are remarkably stable despite pronounced variability in environmental factors and population densities. We analysed the dynamics in the structure and stability of the pelagic food web of Lake Constance using seven years of high-frequency observations of biomasses and production, leading to 59 seasonally resolved quantitative food web descriptions. We analysed the dynamics in asymptotic food web stability using maximum loop weight, which revealed mechanisms governing stability. Maximum loop weight showed a recurrent seasonal pattern while indicating consistently high stability despite pronounced dynamics in biomasses and fluxes. This arose from rewiring of the food web structure along seasons, which counteracted destabilization by enhanced productivity. The rewiring originated from energetic constraints within loops and how loops were embedded into food web structure. The stabilizing dynamics originated from the counter-acting effect between high metabolic activity and competitiveness/susceptibility to predation within a diverse grazer community.

With many species interacting in nature, determining which describe community dynamics is nontrivial. By applying a new Bayesian-sparse modelling approach to an extensive field survey, we assessed the importance of interactions from con- and hetero-specific plants, pollinators, and insect herbivores on plant performance. We compared the inclusion of the interaction effects as aggregate "generic" terms versus specific terms. We found that a continuum of positive to negative interactions, containing mostly generic but a few strong specific interactions, was sufficient to describe variation in plant performance. While interactions with herbivores and conspecifics varied from weakly negative to weakly positive, heterospecific plants mainly promoted competition and pollinators facilitated plants. The consistency of these empirical findings over three years suggests that a broad resolution, including the generic effects of guilds and a few specific groups rather than all pairwise and high-order interactions, can accurately describe species variation in plant performance across natural communities.

Understanding the drivers of spatially and temporally correlated (synchronous) fluctuations in abundance is a fundamental challenge in ecology and conservation. Synchronous fluctuations in different demographic rates can potentially drive or dampen abundance synchrony, but demographic synchrony is generally poorly understood. Using long-term count and demographic data for breeding land-birds at sites across Europe, we show that the strength and scale of synchrony are greatest in productivity, followed by adult survival rates and then counts. However, count fluctuations are more synchronous with survival than with productivity. Despite migratory and resident species having similar periodicities of count synchrony, synchrony in both demographic rates was more common over long-timescales in resident species and short-timescales in migrant species. These findings suggest local impacts of synchronous fluctuations in adult survival rates on count synchrony, potentially dampening effects of large-scale synchrony in productivity, and that the environmental drivers of synchrony may differ between residents and migrants.

Animals disperse the seeds of 60-90% of trees in tropical rainforests, which are among the most structurally complex ecosystems on Earth. Here, we investigated how 3D rainforest structure influences the movements of large, frugivorous birds and resulting spatial patterns of seed dispersal. We GPS-tracked white-thighed (Bycanistes albotibialis) and black-casqued hornbills (Ceratogymna atrata) in southern Cameroon and found that both species preferred areas of greater canopy height, and white-thighed hornbill preferred areas of greater vertical complexity. In addition, 33% of the hornbills preferred areas close to canopy gaps, while 16.7% and 27.8% avoided large and small gaps, respectively. White-thighed hornbills avoided swamp habitats, while black-casqued preferred them during the hottest temperatures. We mapped spatial probabilities of seed dispersal by hornbills, showing that 3D structural attributes shape this ecological process by influencing hornbill behavior. These results provide evidence of a possible feedback loop between rainforest vegetation structure and seed dispersal by animals.

Rapid evolution contributes to plant invasion success. Previous studies have rarely considered the coevolution of multidimensional traits in invasive plants. We compared multiple traits related to growth, fecundity, and herbivore palatability of the widespread invader Spartina alterniflora in its native (US) and introduced (China) families across large geographic scales. Of 18 tested variables, ten revealed genetic-based differences between native and introduced ranges, and nine exhibited latitudinal clines within the introduced range. Introduced families compared to natives exhibited superior syndromes with larger growth, higher fecundity, and lower palatability, which were linked to provenance climates and could enhance plant competitiveness and spread. We conclude that within only 40 years since its introduction to China, Spartina has evolved an integrated ecological strategy to enhance invasiveness under climate selective pressure, making it the most successful invader along China’s coast. Our study underscores the importance of considering multivariate traits to understand plant invasion success.