Journal of Animal Ecology最新文献

Since 1990, Mediterranean striped dolphins, Stenella coeruleoalba, have suffered two mass mortality events caused by the dolphin morbillivirus (DMV), but the population-level impact is unknown because abundance estimates are spatio-temporally sparse. This study investigates whether data from epibionts of striped dolphins-the barnacle Xenobalanus globicipitis, the cyamid Syncyamus aequus, and the copepod Pennella balaenoptera, with different life cycles and degrees of specificity-could provide indirect evidence on host population dynamics. To address this question, we combined empirical and theoretical approaches. First, we used Generalized Additive Models (GAMs) to examine occurrence trends of the three epibiotic species over the period 1980-2023 for both striped dolphins and other sympatric cetacean species that did not suffer DMV outbreaks. Second, we developed a two-step theoretical modeling approach to investigate the epidemiology of these DMV outbreaks (SIR model) and to link dolphin population abundance shifts with the epibiont trends observed empirically (mechanistic model). The SIR model provided coarse estimates of the impact of DMV on the striped dolphin population under two scenarios with varying virus-induced mortality and duration of the infectious period. These estimates were then used to simulate the effect of dolphin population shifts on its epibionts through mechanistic models. Models indicated that DMV-induced shifts in striped dolphin population dynamics have cascading effects on the population abundance of X. globicipitis and S. aequus, whereas the population of the less host-specific P. balaenoptera was unaffected. Together, long-term trends in the occurrence of host-specific epibionts can serve as an indicator of host abundance shifts.

Home range (HR) is a key indicator of animal spatial ecology. HR size, shape, location and habitat composition reflect both species' ecological requirements and their responses to anthropogenic stressors. Felidae, a charismatic taxon, faces escalating threats mainly due to habitat degradation and human-wildlife conflict. Understanding the ecological and anthropogenic drivers of HR size variation is therefore critical for their conservation. To address this gap and explore these factors at a global scale for the entire taxon, we used the HomeRange database-a global database with HR values across 960 different mammal species-complemented with about 20% additional records, to compile 1137 individual HR size estimates from 29 out of 40 recognized wild felid species. We applied generalized linear mixed models to assess the influence of intrinsic, methodological, ecological and anthropogenic factors on space use. HR size was shaped by multiple drivers. It increased with body mass (0.94 ± 0.16; p < 10^-8) and was larger in males than in females (0.51 ± 0.07; p < 10^-13), consistent with higher energy demands and sex-specific reproductive strategies. HR size decreased with increasing productivity (-0.37 ± 0.07; p < 10^-7) and felid richness (-0.24 ± 0.10; p = 0.02), suggesting reduced spatial requirements in resource-rich areas and under interspecific competition. HR size also decreased with increasing croplands (HR: -0.50 ± 0.14; p < 10^-3) and pastures (HR: -0.16 ± 0.07; p = 0.02)-both human footprint proxies-which may reflect multiple causes such as anthropogenic food sources, habitat loss or movement restriction from infrastructures associated with agriculture. Our results reinforce the role of well-known established HR size's predictors such as body mass, sex and primary productivity while highlighting the impact of less frequently investigated factors (i.e. felid richness and agricultural land-use). Our findings emphasize the importance of incorporating a broad range of biological, environmental and methodological predictors when studying space use across a taxonomic group. Our approach provides novel insights into habitat requirements and the effects of anthropogenic pressures, which can ultimately lead to improved conservation strategies for felids.

Some animals exhibit large-amplitude fluctuations with periods close to their generation length. These fluctuations can be caused by seasonal environmental influences, scheduled pesticide applications, or ecological factors such as intraspecific regulation and consumer-resource interactions. While theory provides various mechanisms for how environmental and ecological factors might generate generational fluctuations, there has never been a field experiment testing the relative contributions of seasonal demographic synchronisation and intraspecific regulation to generation cycles in natural populations. The smaller tea tortrix, Adoxophyes honmai, is a serious pest of tea plants and a temperate multivoltine insect that undergoes 3-5 large-amplitude generation cycles each year under natural conditions in Japan. Theory suggests that these fluctuations may represent limit cycles driven by asymmetric intraspecific interference, where older larvae directly affect younger ones. However, in the field, these populations also experience strong seasonality and periodic insecticide applications that are thought to either generate or modify these fluctuations. We conducted a replicated field-cage experiment on the tortrix populations to manipulate the initial degree of stage synchrony and the timing of introduction. The experiment included four treatments contrasting pulsed versus continuous age structures at the onset of spring, along with two introduction timings separated by 20 days (approximately half a generation time). We minimised artificial interventions, such as harvesting and insecticide application, as well as the effect of natural enemies while allowing meteorological influences during the season. To compare the field-cage experiment results with theoretical predictions, we constructed an age-structured population model featuring asymmetric larval interference. We executed simulations using the same introduction scenarios as in the field-cage experiment. We observed the emergence of clear generational cycles in all treatments of the field-cage even in the absence of any initial demographic synchrony. This suggests an internal mechanism regulating population cycles, possibly intraspecific interference. However, the generational cycles in the field-cage were synchronised across treatments and with outer field populations. The results from the field-cage experiment and simulation analyses indicate that external environmental factors, such as precipitation, acted as a pacemaker for the generational cycles created by the internal regulatory mechanism.

Environmental stochasticity poses significant challenges to population persistence. A key mechanism thought to buffer populations against such variability is demographic buffering-the ability of a population to stabilise growth despite temporal fluctuations in survival, development or reproduction. However, empirical tests of demographic buffering remain limited and often yield conflicting results. Here, we propose an integrative demographic framework that combines two complementary approaches to identify demographic buffering: (1) stochastic elasticities, which quantify the sensitivity of long-term stochastic growth rates (λ_s) to variance in demographic processes, and (2) second-order derivatives of deterministic growth (λ₁), which indicate whether selection acts to reduce or amplify variance in vital rates. Applying this framework to 43 natural populations across 37 mammalian species, we position each species along a variance continuum and assess whether those with low stochastic elasticities-suggestive of buffering-also exhibit signs of concave selection on key demographic processes. While most primates and a few other long-lived mammals occupy the buffered end of the continuum, only one species-the Columbian ground squirrel-exhibits strong support for our hypothesis, with key vital rates both critical for λ₁ and under concave selection. In contrast, primates, despite showing low stochastic elasticities, often show convex or absent second-order effects on their most influential vital rates, indicating a mismatch between ecological buffering and evolutionary constraint. Our findings suggest that demographic buffering is more dynamic and context dependent than previously recognised. Selection does not consistently act to reduce variance in key demographic processes, even in species where population growth appears robust to environmental variability. This decoupling implies that evolutionary and ecological signals of buffering may not always align. Our framework offers a new lens to dissect the demographic and selective processes underpinning resilience, providing a scalable tool for exploring demographic strategies across taxa. Future work integrating phylogenetic context, trait covariation and environmental drivers will be essential to understand the adaptive value of demographic buffering under global change.

Theoretical and empirical studies agree that populations harbour extensive among-individual variation in phenotypic plasticity, but the mechanisms generating and maintaining this variation are often unknown. Endocrine systems, which can change plastically in response to environmental variation, may be shaped by natural selection, but their evolution requires heritable variation. It is currently unknown if endocrine plasticity in response to environmental challenges is heritable. We investigated this question in house sparrows, Passer domesticus, by testing glucocorticoid responsiveness to food restriction. We alternated restricted (70% of individual daily food intake) and adequate (110%) treatments twice, drawing blood samples at the end of each treatment. Based on glucocorticoid responsiveness, we classified individuals into high-plasticity, low-plasticity and medium (control) groups by selecting the 20 most responsive, least responsive and random individuals, respectively. We transferred these groups into separate aviaries and let them reproduce. In the next generation, we measured hormonal responsiveness using identical methods. Using a cross-foster design and quantitative genetic models, we partitioned the heritability of glucocorticoid responsiveness into genetic and environmental components. We found moderate heritability (h² > 30%) of glucocorticoid plasticity in response to food availability. The environmental and residual variances of glucocorticoid responsiveness were smaller than those for the intercept. Our findings provide empirical evidence for the existence of heritable individual variation in glucocorticoid plasticity, highlighting its potential to evolve under natural selection, particularly in dynamic and rapidly changing environments.

Wild bees are widely distributed and effective pollinators, yet they face significant threats such as degradation of forests. Forest restoration has been advocated as a strategy to mitigate these threats and stabilize biodiversity. However, there is a lack of understanding of the ecological consequences of forest restoration on bee diversity, particularly regarding interactions with tree diversity and microenvironment. Using data from the world's largest tree diversity experiment (BEF-China), this study examines how tree species richness, canopy cover, understorey vegetation, and microclimatic conditions affect bee diversity in the context of forest restoration. Our analysis of bee diversity data (8341 individuals from 79 species) revealed that these biotic factors had distinct effects on three dimensions of bee diversity. Specifically, canopy cover had a negative effect on bee taxonomic diversity but a positive effect on phylogenetic and functional diversity. However, these patterns were reversed when the cover of understorey vegetation was accounted for. Moreover, tree species richness exerted an indirect influence on bee diversity through understorey microenvironment. Our findings provide nuance into how tree species richness shapes bee communities via vegetation cover and microclimate, which is informative on habitat characteristics in forest restoration and conservation that better enable the safeguarding of pollinators.

Migratory birds often navigate inhospitable barriers (e.g. oceans, deserts) during migration. Barrier crossings are frequently associated with increased rates of mortality and likely impose selective pressures on migratory species that shape their behaviour and distribution. Therefore, understanding how weather conditions influence the behaviour of migratory birds at a major barrier can provide insight into the adaptive evolution of long-distance migrations involving barrier crossings and how changing climatic conditions might affect migratory species in the future. We used light-level geolocator data from 89 individual Vermivora warblers to identify the weather conditions associated with individuals initiating barrier-crossing flights across the Gulf of Mexico (i.e. 'trans-Gulf flights') during both autumn and spring migrations from 2013 to 2017. Weather conditions associated with the initiation trans-Gulf flights differed between autumn and spring. In autumn, the initiation of trans-Gulf flights was positively associated with favourable wind conditions and temperature but negatively associated with relative humidity and 24-h change in barometric pressure. During spring migration, the initiation of trans-Gulf flights was negatively associated with surface-level relative humidity and barometric pressure but not associated with wind conditions. We found that the frequency of days with weather conditions associated with a high-predicted probability of Vermivora warblers initiating trans-Gulf flights varied geographically (range 0%-58% of days). Distinct breeding populations of golden-winged warblers (V. chrysoptera) with strong migratory connectivity between breeding and non-breeding regions exhibited weak migratory connectivity and overlapped extensively during migration immediately prior to initiating trans-Gulf flights. Breeding populations of blue-winged warblers (V. cyanoptera) exhibited weak migratory connectivity and co-occurred during both autumn and spring migrations and during the non-breeding period. The weak migratory connectivity that we observed in Vermivora warblers prior to crossing the Gulf of Mexico may be shaped by shared evolutionary responses to consistent synoptic weather conditions in the region. Predicted future climate conditions including increased humidity and more frequent and/or severe storms may decrease the favourability of conditions associated with initiating trans-Gulf flights during spring migration for Vermivora warblers, which could negatively affect populations.

Temperature is a key ecological factor influencing biological processes across various levels of biological organization. At the individual level, temperature changes often impact life-history traits. The Temperature-Size Rule predicts lower body mass at higher temperatures, whereas the Metabolic Theory of Ecology predicts faster growth rates and shorter development times with rising temperature via its effects on metabolism. Butterflies, a highly diverse group distributed worldwide, often exhibit plastic responses to differences in ambient temperature. As such, climate change may potentially impact their life history traits, population dynamics and interactions. We conducted a Bayesian multilevel meta-regression of 71 studies published between 1960 and 2024, encompassing 673 effect sizes, to assess the impact of temperature variation on butterfly growth rate, development time and body mass across ontogenetic stages and sexes. Our meta-analysis reveals that rising temperatures markedly accelerate growth and shorten development time in butterflies at a rate of ca. 10%/Δ°C, while body mass is comparatively only weakly affected. These temperature effects on growth and development are consistent across sexes and life stages and are largely independent of evolutionary history, suggesting a basis in fundamental biochemical constraints. These patterns highlight the potential for climate change to reshape butterfly life cycles, population dynamics and ecological interactions.

Research Highlight: Monitoring the restoration process can help us understand the relationships between plants and animals. By manipulating the habitat, researchers can evaluate how changes in plant community influence the diversity and distribution of associated fauna. Yet, the mechanisms shaping pollinators' diversity in response to forest attributes remain poorly understood. The study by Xie et al. (2025) demonstrates how tree richness and forest canopy cover influence pollinator communities by mediating floral resource availability in the understory and modifying microclimatic conditions within the forest. The authors found that tree richness increases canopy cover and consequently changes the microclimatic conditions within the forest, which, in turn, reshapes the niche space available for bee communities. Such findings are fundamental because they reveal how changes in one component of biodiversity cascade into others. Such mechanistic insights are also crucial for scaling up biodiversity assessments using remote sensing and for guiding restoration strategies that move beyond vegetation recovery to the restoration of ecosystem functions.

Understanding the drivers of seasonal disease outbreaks remains a fundamental challenge in disease ecology. Periodic outbreaks can be driven by several seasonally varying factors, including pulses of susceptible individuals through births, changes in host behaviour and social aggregation and variation in host immunity. However, when these potential drivers overlap temporally, isolating their relative contributions to outbreak patterns becomes challenging. We studied Hendra virus, a zoonotic pathogen with seasonal spillovers from bats to horses and humans. Multiple seasonal factors have been hypothesized to drive Hendra virus transmission, including food shortages, birth pulses and changes in host aggregation, but their temporal overlap has made identifying primary drivers difficult. We conducted a 4-year longitudinal study of Pteropus bats to test whether seasonal birth pulses and the resulting influx of susceptible juveniles drive Hendra virus transmission. Using a Bayesian ageing model, we aged sexually immature bats and placed them into birth cohorts. We used our age predictions to model how viral shedding and antibody responses changed as bats aged. We tracked Bartonella spp. Infection-a bacterial pathogen requiring close contact for transmission-as an indicator of transmission opportunities within each cohort for comparison. We found no evidence that seasonal birth pulses of immunologically naïve juveniles drove Hendra virus transmission. Two out of three cohorts showed substantially reduced maternal antibody transfer compared to the 2018 cohort, with seroprevalence near zero at our earliest sampling timepoints and showed no clear evidence of synchronized seroconversion. Furthermore, Bartonella infection rates were consistent across cohorts, indicating that opportunities for pathogen transmission remained consistent across cohorts despite varying viral shedding patterns. Our findings demonstrate that birth pulses alone cannot explain observed patterns of Hendra virus outbreaks. These results highlight the importance of using multiple lines of evidence to evaluate competing mechanisms underlying seasonal disease dynamics, particularly when potential drivers coincide temporally.