Journal of Animal Ecology最新文献

Challenging events in the environment that are both predictable (e.g. seasonal patterns in breeding activities) and unpredictable (e.g. predator encounter) are known to induce a glucocorticoid response that facilitates metabolic requirements during the challenge. Given its role in mobilizing energy, glucocorticoid levels can influence the nutritional ecology of an individual by shifting dietary intake or retention patterns, but this relationship has not been tested in free-ranging vertebrates. Using a tropical lizard species (Psammophilus dorsalis) as a model system, we tested whether the elemental composition of dietary intake and excretion (faecal samples) varies with stress-induced corticosterone levels in males and females across different seasons. From free-ranging lizards in the wild, we measured levels of stress-induced corticosterone and glucose in blood and determined diet composition from gut-flushing. Elemental composition of the diet was determined by analysing the carbon and nitrogen content of identified prey Orders caught from the wild. We also collected faecal samples and estimated their elemental composition. We found that stress-induced corticosterone levels varied across seasons, with the lowest levels during the breeding season for both males and females. Despite high variation in corticosterone responsiveness, lizards did not shift the elemental composition of their diets and maintained an intake carbon:nitrogen ratio of 4.56. We did, however, find a negative correlation between stress-induced corticosterone levels and faecal elemental composition, suggesting selective retention of both carbon and nitrogen in individuals that have higher corticosterone responsiveness. This study highlights the interplay between corticosterone responsiveness and nutritional ecology, challenging the existing links in literature and illustrating how free-ranging animals, such as lizards, adjust the elemental composition of excretion and not dietary intakes as a potential strategy to modulate natural physiological and ecological challenges.

Ecosystem engineering is a facilitative interaction that generates bottom-up extrinsic variability that may increase species coexistence, particularly along a stress/disturbance gradient. American alligators (Alligator mississippiensis) create and maintain 'alligator ponds' that serve as dry-season refuges for other animals. During seasonal water recession, these ponds present an opportunity to examine predictions of the stress-gradient (SGH) and intermediate disturbance hypotheses (IDH). To test the assumption that engineering would facilitate species coexistence in ponds along a stress gradient (seasonal drying), we modelled fish catch-per-unit-effort (CPUE) in ponds and marshes using a long-term dataset (1997-2022). Stomach contents (n = 1677 from 46 species) and stable isotopes of carbon and nitrogen (n = 3978 representing 91 taxa) from 2018 to 2019 were used to evaluate effects of engineering on trophic dynamics. We quantified diets, trophic niche areas, trophic positions and basal-resource use among habitats and between seasons. As environmental stress increases, we used seasonal changes in trophic niche areas as a proxy for competition to examine SGH and IDH. Across long-term data, fish CPUE increased by a factor of 12 in alligator ponds as the marsh dried. This validates the assumption that ponds are an important dry-season refuge. We found that 73% of diet shifts occurred during the dry season but that diets differed among habitats in only 11% of comparisons. From wet season to dry season, both stomach contents and stable isotopes revealed changes in niche areas. Direction of change depended on trophic guild but was opposite between stable-isotope and stomach-content niches, except for detritivores. Stomach-content niches generally increased suggesting decreased competition in the dry season consistent with existing theory, but stable-isotope niches yielded the opposite. This may result from a temporal mismatch with stomach contents reflecting diets over hours, while stable isotopes integrate diet over weeks. Consumptive effects may have a stronger effect than competition on niche areas over longer time intervals. Overall, our results demonstrated that alligators ameliorated dry-season stress by engineering deep-water habitats and altering food-web dynamics. We propose that ecosystem engineers facilitate coexistence at intermediate values of stress/disturbance consistent with predictions of both the SGH and IDH.

The relationship of plant diversity and several ecosystem functions strengthens over time. This suggests that the restructuring of biotic interactions in the process of a community's assembly and the associated changes in function differ between species-rich and species-poor communities. An important component of these changes is the feedback between plant and soil community history. In this study, we examined the interactive effects of plant richness and community history on the trophic functions of the soil fauna community. We hypothesized that experimental removal of either soil or plant community history would diminish the positive effects of plant richness on the multitrophic functions of the soil food web, compared to mature communities. We tested this hypothesis in a long-term grassland biodiversity experiment by comparing plots across three treatments (without plant history, without plant and soil history, controls with ~20 years of plot-specific community history). We found that the relationship between plant richness and below-ground multitrophic functionality is indeed stronger in communities with shared plant and soil community history. Our findings indicate that anthropogenic disturbance can impact the functioning of the soil community through the loss of plant species but also by preventing feedbacks that develop in the process of community assembly.

The evolution of sociality is one of the major evolutionary transitions in the history of life and a key step in this transition is the occurrence of kin associations. Yet, the question of what demographic processes and environmental factors generate kin-structured populations and drive kin-directed cooperation remains open. In this review, we synthesise 30 years of studies of the long-tailed tit Aegithalos caudatus, which has a kin-selected cooperative breeding system with redirected help: failed breeders may help to raise offspring of conspecifics, typically relatives, breeding nearby. We describe the use of ecological, demographic, genetic and behavioural approaches to reveal: (a) how kin-structured populations (here 'kin neighbourhoods') arise; (b) why the prevalence of cooperation varies among populations and individuals; and (c) how variation in dispersal and opportunities for cooperation influence individual fitness. The kin neighbourhoods of long-tailed tits arise from three processes. First, natal dispersal is limited and sex-biased so many individuals, especially males, recruit as breeders close to their natal site. Second, neither dispersal nor migration necessarily disrupts kin associations because long-tailed tits often move with close relatives. Third, a small effective population size driven by high nest predation rates enhances within-population relatedness. Together, these processes set the scene for kin-directed helping behaviour by causing spatial clustering of relatives. The prevalence of cooperation within kin neighbourhoods depends on several factors, both at the population-level (annual nest predation rate and length of the breeding season) and individual-level (relatedness, familiarity, sex and condition). However, limited information on prior social association and the reliability of kin discrimination cues hampers our current understanding of individual helping decisions. Finally, variation in dispersal within and between sexes affects the probability of interacting with kin, the likelihood of cooperation, and accrual of the direct and indirect components of inclusive fitness. We use this comprehensive understanding of the factors driving cooperative behaviour in long-tailed tits to highlight gaps in knowledge and suggest future avenues for research in this system, and to make general inferences about the role of dispersal, demography and kinship in social evolution.

Whilst efficient movement through space is thought to increase the fitness of long-distance migrants, evidence that selection acts upon such traits remains elusive. Here, using 228 migratory tracks collected from 102 adult breeding common terns (Sterna hirundo) aged 3-22 years, we find evidence that older terns navigate more efficiently than younger terns and that efficient navigation leads to a reduced migration duration and earlier arrival at the breeding and wintering grounds. We additionally find that the age-specificity of navigational efficiency in adult breeding birds cannot be explained by within-individual change with age (i.e. learning), suggesting the selective disappearance of less navigationally efficient individuals. This suggests that, at least in common terns, learning of navigational skills may be largely absent in adulthood, and limited to the pre-breeding phase of life where tracking is more difficult. We propose that selection might explain parts of the age-specificity of navigational performance observed in migratory taxa more generally; discuss the causes and evolutionary implications of variation in navigational traits and the selective agents acting upon them; and highlight the necessity of longitudinal studies when considering changes in behaviour with age.

For similar species to co-occur in places where resources are limited, they need to adopt strategies that partition resources to reduce competition. Our understanding of the mechanisms behind resource partitioning among sympatric marine predators is evolving, but we lack a clear understanding of how environmental change is impacting these dynamics. We investigated spatial and trophic resource partitioning among three sympatric seabirds with contrasting biological characteristics: greater crested terns Thalasseus bergii (efficient flyer, limited diver, and preference for high quality forage fish), little penguins Eudyptula minor (flightless, efficient diver, and preference for high quality forage fish) and silver gulls Chroicocephalus novaehollandiae (efficient flyer, limited diver and generalist diet). We investigated interannual variability in resource partitioning in relation to environmental variability in a climate change hotspot influenced by the warm and intensifying East Australian Current (EAC). Sampling was conducted from 2012 to 2014 during the austral summer breeding season of seabirds at Montague Island, Australia. Daily seabird movements were monitored using GPS trackers and feather tissues were collected and processed for stable isotope analysis (δ¹⁵N and δ¹³C). Generalised Linear Mixed Models were used to assess how changes in oceanographic conditions influenced space use for each species. Schoener's D and Bayesian mixing models were used to respectively investigate the levels of yearly inter-specific environmental and trophic niche overlaps. Crested terns and little penguins were less likely to be observed in warm, saline EAC waters and crested terns and silver gulls had smaller foraging areas on days when more than 30% of available habitat was classified as EAC origin. All species preferred areas with low variability in sea surface temperature (<0.5°C). Terns and penguins occupied similar marine trophic levels, with penguins having larger isotopic niche spaces in 2014 when the EAC was more dominant in the study area. Gulls occupied the lowest trophic level, with the widest niche and lowest interannual variability in niche area. As the EAC intensifies along the southeast coast of Australia under climate change, interspecific competition for resources may increase, with the greatest impacts on species like little penguins that have relatively restricted foraging ranges. This study suggests that species-specific biological traits and behavioural plasticity should be accounted for when predicting the effects of climate change on marine species.

Understanding insect behaviour and its underlying drivers is vital for interpreting changes in local biodiversity and predicting future trends. Conventional insect traps are typically limited to assess the composition of local insect communities over longer time periods and provide only limited insights into the effects of abiotic factors, such as light on species activity. Achieving finer temporal resolution is labour-intensive or only possible under laboratory conditions. Here, we demonstrate that time-controlled insect sampling using an automated Malaise trap in combination with metabarcoding allows for the observation and documentation of taxon-specific activity patterns. Furthermore, these recorded activity patterns can provide valuable insights into the underlying ecological processes. Insect activity curves, derived from predicted detection numbers using generalised linear latent variable models, reveal distinct differences in activity patterns at higher and lower taxonomic level. While our findings align with existing literature, they also reveal that the activity patterns of some species are more complex than previously known. Additionally, a comparison of the assessed activity patterns across taxa suggest potential, previously undescribed parasitoid-host relationships. Within taxonomic groups, we observe variations in both the timing and duration of activity patterns, which can be linked to differences in mating strategies among closely related species. By capturing circadian rhythms of insect activity through time-controlled bulk sampling, we can expand our knowledge on species behaviour, ecology and temporal interactions. This contributes significantly to the advancement of chronoecology, allowing for further exploration of the roles of species and benefits in natural and anthropogenic ecosystems, alongside their potentially significant threat.

Marine heatwaves are increasingly common due to human-induced climate change. Under prolonged thermal stress on coral reefs, corals can undergo bleaching, leading to mass coral mortality and large-scale changes in benthic community composition. While coral mortality has clear, negative impacts on the body condition and populations of coral-dependent fish species, the mechanisms that drive these changes remain poorly resolved. Specifically, little is known about the effects of coral bleaching on (1) the nutritional quality of corals, (2) nutrient acquisition in coral-feeding butterflyfishes and (3) fish dietary selectivity and potential supplementary consumption of non-coral prey. Here, we evaluate the response of obligate coral-feeding butterflyfishes to a mass coral bleaching event in French Polynesia, which resulted in high coral mortality and a 50% decline in obligate corallivore density. We examine benthic and butterflyfish community composition over two decades, including a mass bleaching event in 2019 and multiple prior disturbances. We couple these data with surveys of butterflyfish feeding selectivity, high-resolution molecular assays of gut contents and nutrient acquisition before, during and after the bleaching event. Contrary to previous studies, obligate corallivores did not strongly alter their feeding preferences for different coral genera in response to bleaching. They did not increase their consumption of non-corals in response to coral mortality, and hard corals continued to dominate their diets (>90%). Instead, butterflyfishes targeted partially bleached corals that were likely releasing nutrient-rich mucus, and they avoided fully bleached and dead corals that were likely nutrient-depleted. Moreover, after bleaching, butterflyfishes exhibit reduced nitrogen assimilation, indicating that coral stress may adversely impact butterflyfish nutrient acquisition. Coupled with the increasing frequency of recurrent bleaching events, severe, long-term nutritional impacts of coral bleaching on butterflyfish populations may jeopardize the persistence of coral-feeding fishes in the future.

Global trends in marine turtle nesting numbers vary by region, influenced by environmental or anthropogenic factors. Our study investigates the potential role of past temperature fluctuations on these trends, particularly whether warmer beaches are linked to increased nesting due to higher female production (since sea turtles have temperature-dependent sex determination). We selected the loggerhead turtle (Caretta caretta) due to its wide distribution, strong philopatry and vulnerability to environmental changes. We compiled nest counts per year on 35 globally significant rookeries, analysing trends at regional and individual beach levels. We compiled air (CHELSA) and land surface (MODIS) temperature data sets spanning the last four decades (1979-2023) for each location. To analyse temporal trends in nest counts and temperatures, we used generalised additive models and Mann-Kendall trend tests. Additionally, we correlated nest counts with lagged air temperature variables. We found significant warming at 33 nesting locations, 23 of which also showed significant increases in nest counts. Our results suggest that rising temperatures may be boosting nest numbers in regions of the Caribbean, Atlantic Ocean and Mediterranean (sites in Cayman, Mexico, Brazil, Cyprus and Turkey). Furthermore, while some regions temporarily benefit, continued warming could precipitate long-term population declines. This regional variability helps predict species responses to climate change, with the general global increase in nest counts already indicating short-term warming effects. Nesting count trends might reflect a combination of natural ecological phenomena, conservation efforts, and warming effects. Long-term studies are needed to assess global trends in the sex ratio of hatchlings and the extent to which feminisation is driving nest numbers.

Population matrix models are routinely used to study the demography of wild populations and to guide management choices. When vital rates are unknown for a specific population or life history stage, researchers often replace them with estimates from other populations of the same species. Such 'hybrid' matrices might ignore among-population life history variation and lead to incorrect inferences. In this study, we examined the real-world effect of using hybrid matrices on demographic inference and management decisions, using a large dataset on yellow-bellied toad (Bombina variegata) populations, an amphibian species whose life history depends on human land use. We estimated stage-specific survival and recruitment for 18 populations across different habitat types. We then assessed how estimated population growth rates and elasticities changed when population-specific vital rates were replaced by estimates from other populations, chosen randomly or based on habitat, demographic or geographic proximity. The use of hybrid matrices mixing demographic estimates from different populations and habitats biased predictions. The mean bias was relatively minor even when sampling randomly across all populations, because our large dataset represented the whole range of life histories and errors cancelled out on average. However, borrowing estimates from geographically close or demographically similar populations substantially reduced the risk of extreme errors. Borrowing from populations from similar habitat types could also reduce bias, but results varied depending on the exact habitat types concerned. Our study illustrates how habitat-specific among-population variation in life history affects the reliability of population matrices commonly used in evolutionary demography, ecology and conservation. When the use of hybrid population matrices cannot be avoided, their creation can be informed by additional information about ecological or demographic patterns, helping reduce bias. When such information is not available, we recommend that studies should consider the whole space of parameter estimates (the complete range of estimates available), thus transparently describing the true uncertainty surrounding demographic estimates.