Through depositing waste products, animals influence the spatial distribution of elements across landscapes. Yet the relationship between animal movement and element distribution remains poorly characterized. We developed a spatially explicit agent-based model to test how migratory versus resident red deer (Cervus elaphus) influence nitrogen redistribution across an alpine landscape in the Central-Eastern Italian Alps. Specifically, we asked how both local-scale and landscape-scale movement alter the spatial extent and magnitude of nitrogen deposition. We parameterized our model with GPS telemetry from 2021 to 2024 and remotely sensed vegetation data. We simulated four different scenarios which allowed us to disentangle the relative effects of large-scale (migration persisting) and fine-scale (resident behaviour) movement: (i) mixed migratory-resident (300 deer), (ii) fully resident (300 deer), (iii) reduced resident (150 deer) and (iv) reduced migratory (150 deer). The potential for nitrogen intake, assimilation, and excretion occurred hourly across a seasonally dynamic landscape. Across all scenarios, tree cover density and slope consistently emerged as positive predictors of nitrogen transport. Thus, regardless of resident or migratory status, red deer act as mediators of local element transport. Similarly, proximity to roads/trails reduced nitrogen inputs and created closed systems, indicating that barriers constrain both local and landscape-scale element transport. Migration substantially expanded the spatial extent of nitrogen redistribution and enabled the upward movement of elements, both locally upslope and into higher elevation habitats, effectively transporting elements against gravitational forces. Consequently, the loss of migration is likely to weaken these large-scale element linkages and reduce associated ecosystem functions. Our results demonstrate that different animal movement patterns play distinct and complementary roles in connecting element pools across landscapes. While both resident and migrant foraging redistribute elements locally, migratory movements link lowland and alpine habitats, expanding the spatial reach of element redistribution. Thus, loss of migration not only reduces the spatial extent of element distribution but also alters the topographic pathways through which elements are cycled. These findings highlight the broader ecosystem consequences of declining animal movement extent, and migration in particular, and underscore the importance of conserving behavioural diversity to maintain element heterogeneity and ecosystem functioning in mountain systems.
Mutualistic networks provide essential contributions to long-term ecosystem functioning and food security, but Anthropocene stressors continue to alter their structure and size. Previous theoretical approaches produce conflicting predictions for how network features influence dynamical stability, which is the ability to return to the original state after a disturbance. The main methods, which are random matrix models and conventional differential equation models, face certain limitations, including difficulties in incorporating some biological details or explicit parameterization. An alternative approach is given by Generalized Modelling, which combines both high efficiency with high biological realism, but has not been applied to plant-animal mutualistic networks prior to this study. Here, we develop a Generalized Model for mutualism that allows the mathematically rigorous and highly efficient analysis of dynamical stability for many network replicates ( ∼ 10 5 per data point). The model incorporates important biological mechanisms that are known to influence stability behaviour, such as animal competition for limited plant resources and saturating mutualistic benefits, without the need for explicit parameterization. Using simulated network structures we find increasing dynamical stability with increasing complexity as measured by the product of species richness and connectance. We are able to explain this effect mechanistically: While mutualistic interactions do represent destabilizing positive feedbacks, the strengths of those feedbacks weaken with increasing complexity because mutualistic dependencies as given by the Jacobian matrix elements in the off-diagonal blocks decrease. We further show that the effect of nestedness on the dynamical stability of simulated networks is negligible compared to the effect of connectance and species richness. Additionally, we find similar relationships between network features and dynamical stability for 160 empirical networks as an input for our model, highlighting the robustness of our findings. As Anthropocene stressors lead to species and interaction loss, our model results predict a corresponding loss in dynamical stability if network complexity is decreased, highlighting the urgency of conservation strategies that preserve network complexity.
Population growth depends upon individual survival and reproduction, but do drivers of individual reproductive success scale up to population recruitment? Factors affecting individuals may have little effect on population dynamics if individuals within a population experience different conditions. When seasonal resource availability is unpredictable and breeding season long, average conditions over a breeding cycle may poorly reflect the environment experienced by many individuals. We compared the drivers of individual reproductive success and population recruitment in an asynchronously breeding large herbivore, the eastern grey kangaroo (Macropus giganteus). We analysed 18 years of individual-based data using multivariate hierarchical Bayesian models to first identify the causal mechanisms relating population density, environmental conditions and maternal traits to individual success. We then assessed whether the drivers of individual reproductive success scaled up to determine population recruitment. Most maternal and environmental covariates strongly influenced individual reproductive success, with distinct effects on juvenile survival before and after pouch exit. Maternal traits had a greater influence in the pouch, whereas environmental conditions became increasingly important once young exited the pouch. Most drivers of individual reproductive success did not affect population recruitment. Recruitment increased with population density and mean body condition of adult females. Weather harshness had a weak positive effect on recruitment, which appeared independent of female age structure, previous recruitment or forage. Most drivers of individual reproductive success did not scale up to population recruitment. Birth asynchrony could buffer population recruitment against environmental variation such that variables affecting individual reproduction have little impact at the population level. Large herbivores that reproduce asynchronously may therefore be more resilient to environmental variability than synchronous breeders.
Global warming affects organismal performance across biological levels, from molecular processes to complex behaviours. Ectotherms are particularly vulnerable to thermal stress, as their body temperature critically depends on ambient environmental conditions. Warming may affect their foraging behaviour and/or their activity patterns. Here, we experimentally investigated the effects of acute and chronic thermal stresses on foraging by an ectotherm species. Social insects are important ecosystem engineers. Colony survival and growth depend on successful foraging, and colonies are more susceptible to warming when they are young and have fewer workers. We investigate how heat intensity and exposure duration influence foraging dynamics and survivorship in young colonies of the Lasius niger ant. Using laboratory assays, we studied the effects of acute heat stress by exposing foragers to short (10 min) and intermediate (1 h) heat pulses of 25°C (control), 30°C, 35°C and 40°C. Furthermore, we investigated the effects of chronic heat stress by rearing colonies at 25°C:20°C (day:night, control conditions) or 35°C:30°C (heat stress) for 2 weeks. After heat exposure, we recorded the latency to initiate foraging, the number of foraging visits and individual and colony survival between treatments. We hypothesized that ants could cope with relatively low and relatively short heat shocks, but not with high or long heat exposures. We found that prolonged and high heat exposure indeed increased the mortality of foragers and colonies, increased the delay before foraging, and decreased the number of foraging trips. Reduced foraging capacity in young colonies is likely to have strong fitness consequences. The establishment of colonies is dependent on the rapid acquisition of resources to sustain exponential growth. Any slowdown in resource intake can limit colony development and prolong the duration of the incipient (newly founded) and vulnerable stage, ultimately reducing the likelihood of successful establishment.
Social dominance shapes group structure and the collective behaviour of gregarious animals. Senescence, the progressive physiological deterioration associated with ageing, may influence behaviour, including social dominance, while reproductive roles may lead to different onset times or rates of senescence between the sexes. However, how ageing shapes sex differences in sociality remains poorly understood, largely due to the scarcity of long-term studies comparing male and female social behaviour. To address this gap of knowledge, we monitored dominance hierarchies during foraging in an ageing, semi-natural population of adult common waxbills (Estrilda astrild). Our study lasted 5 years, which is more than most adult waxbills would live in the wild, to facilitate detecting effects of senescence. At the onset of the study, sex differences in dominance were negligible but became pronounced with ageing during breeding seasons. In contrast, sex differences remained weak during non-breeding seasons. Females showed stronger longitudinal and seasonal changes in dominance than males, whose dominance patterns remained more consistent across breeding and non-breeding periods. Nonetheless, social dominance also increased, on average, as the number of years until death decreased. Although sex differences in animal sociality are often thought of as largely fixed, our findings reveal a dynamic pattern in which sex differences in dominance emerge with ageing and are context-dependent, varying across breeding seasons. Overall, our results suggest that senescence and seasonal context shape sociality later in life.
Understanding how climate warming reshapes animal life histories is crucial for assessing population persistence and evolutionary trajectories. This is particularly important in ectotherms, whose physiology, performance and, ultimately, fitness are strongly influenced by environmental temperature. Because climate warming can alter key life-history traits such as growth and survival, its effects may differ between sexes, potentially generating divergent organismal responses and long-term consequences. Identifying the mechanisms underlying these sex-specific patterns is therefore essential for explaining how ectotherms cope with warming environments. To determine whether climate warming induces sex-specific life-history responses and to elucidate physiological mechanisms underlying these responses, we conducted a longitudinal experiment in which toad-headed agamas (Phrynocephalus przewalskii) were exposed to simulated higher temperatures under seminatural conditions. We specifically monitored growth, survival, telomere dynamics, telomerase expression and oxidative status throughout development. Males exposed to elevated temperatures showed accelerated growth and a slight reduction in survival, whereas females showed no detectable changes in growth or survival. This suggests divergent sex-specific responses in life history to warming. At the physiological level, warming did not lead to telomere shortening; instead, the telomere length increased over time in both sexes. This was accompanied by a transient up-regulation of telomerase expression in rapidly growing males, which could contribute to the maintenance of the telomere during accelerated growth. However, telomerase expression declined at the end of the experiment in both sexes exposed to warming. Finally, warming increased lipid oxidative damage in both sexes despite activation of antioxidant responses at elevated temperatures. Our results show that climate warming can reshape sex-specific life-history trajectories without necessarily inducing telomere shortening, challenging the expectation that faster growth under thermal stress is inevitably associated with telomere erosion. However, warming can still impose physiological costs with potential long-term consequences for organismal health, as indicated by elevated oxidative damage. Our findings highlight the importance of integrating sex-specific life-history responses with physiological mechanisms to improve predictions of species responses to climate change.
Urbanisation acts as a non-random filter of biodiversity, often resulting in less diverse communities dominated by a subset of species with particular traits. These patterns have led to the expectation that urban environments may promote biotic homogenisation, yielding taxonomically or functionally similar communities across cities, relative to their surrounding natural ecosystems. Here, we evaluated whether the non-random filtering of biodiversity by urbanisation results in the homogenisation of bird communities across three environmental conditions (i.e. natural ecosystems, urban greenspaces, urban sites) in three biogeographically distinct Mexican cities. Assuming an urban-driven filtering process (i.e. an overall decline in native species richness from natural ecosystems into the urban matrix, with possible additions of exotic species), we formulated scenario-based expectations to disentangle urban filtering from biotic homogenisation, predicting whether filtering results in locally distinct urban communities, or additionally, convergent filtering across cities drives cross-city homogenisation. We quantified taxonomic and functional richness (alpha diversity) and compositional dissimilarity (beta diversity) across natural ecosystems, urban greenspaces and urban sites to evaluate whether only filtering occurred or if such process has additionally led to context-dependent convergence in community composition across cities, which could indicate homogenisation. We analysed taxonomic and functional approaches using incidence- and abundance-based metrics to assess compositional variation within and among cities. We recorded 131 bird species, of which only a handful were shared across urban conditions in all three cities. Bird communities showed strong taxonomic and functional differentiation among cities, with greater similarity within the studied environmental conditions per city region than across cities, indicating that urbanisation filters species locally, with no clear evidence of cross-city convergence in community composition. Our findings indicate that urbanisation filters species locally, simplifying communities, yet avian assemblages remain more similar within the three environmental conditions per city region than across the three surveyed cities in Mexico. Notably, widespread and abundant urban-associated species contribute to increased similarity within urban assemblages but do not result in cross-city convergence. This challenges the notion that urbanisation causes homogenisation (at least across the three studied Mexican cities and their surrounding natural ecosystems, which belong to highly distinct biogeographic regions) and highlights the predominant influence of regional species pools and local environmental contexts in shaping urban avifaunas.
Urban environments impose novel selective pressures that can drive rapid phenotypic and genetic change in wild populations. While previous studies have focused on broad urban-rural contrasts or cross-city comparisons, less is known about how phenotypic traits vary across fine spatial scales within cities, where environmental gradients and geographic features may create localized heterogeneity. We studied spatial variation in coat colour morph of the eastern grey squirrel (Sciurus carolinensis) across the Montreal Metropolitan Area, focusing on grey and melanic morphs, the latter of which is caused by an incompletely dominant MC1R mutation. We conducted standardized scan sampling surveys across 197 parks and supplemented this data with citizen science observations from iNaturalist and SquirrelMapper. As an archipelago segmented by major waterways, Montreal exhibits a spatial mosaic where phenotypic gradients are partitioned by physical barriers. We examined variation in melanism in relation to urbanization, local environmental conditions (e.g. temperature and canopy cover) and geographic structure. Unlike patterns in many cities where melanism peaks in urban cores, melanism in Montreal was generally negatively correlated with urbanization, but the strength and direction of urban-rural clines varied sharply across the city's complex island landscape. Abrupt shifts in morph frequency corresponded with major waterways, including the Saint-Lawrence River and its tributaries, suggesting that rivers might act as partial barriers to dispersal which partition the landscape into distinct phenotypic regions. Consistent with the thermoregulatory advantages of melanism, melanic morph frequency increased most in areas with cooler winter temperatures and higher canopy cover. Structural equation modelling revealed that urbanization indirectly suppresses melanism by altering these two variables. Our results suggest that phenotypic patterns within cities are not uniform but are instead shaped by fine-scale environmental heterogeneity and geographic barriers, highlighting the need to move beyond simple urban-rural contrasts when predicting phenotypic variation in urban populations.
Marine heatwaves are increasing in frequency and intensity worldwide and represent a growing threat to coastal ecosystems and the animals inhabiting them. The vulnerability of marine species to these events depends on several factors, including upper thermal tolerance, the thermal sensitivity of physiological performance, and the capacity for rapid physiological acclimation. We examined upper thermal tolerance and short-term acclimation capacity in 10 mobile macroinvertebrate species inhabiting shallow coastal ecosystems in the Northeast Atlantic. Individuals were exposed either to ambient thermal conditions at 15°C or to a simulated short-term marine heatwave of 5 days at 5°C above ambient temperature. We then measured critical thermal maxima (CTmax) to quantify thermal limits and acclimation responses. Across species, CTmax increased significantly following heatwave exposure, showing that these coastal invertebrates can undergo rapid physiological adjustment. However, the magnitude of the acclimation response was modest, indicating that short-term plasticity provides only limited protection against acute thermal extremes. These limited acclimation responses suggest that some coastal invertebrates may remain vulnerable to intensifying marine heatwaves, particularly taxa with narrow thermal safety margins. Our findings provide an ecologically relevant assessment of thermal performance in coastal invertebrates and contribute to predictions of how nearshore communities may respond to accelerating ocean warming.
Shifting breeding phenology is a widespread response to global warming in ectothermic species such as reptiles, with considerable impacts on reproductive success and population dynamics. Thus, understanding causes and consequences of plasticity and microevolution in breeding phenology is important for determining vulnerability to climate change. Here, we study environmental and individual determinants of breeding phenology, its heritability and the temporal variation of selection on parturition date using a 31-year monitoring of a wild, viviparous population of common lizards (Zootoca vivipara). Warmer daily maximum temperatures during the post-winter activity advanced parturition dates and larger females gave birth earlier, but warmer temperatures also reduced size-related phenological variability. Parturition dates were repeatable but weakly heritable, suggesting that inter-individual consistency of parturition dates may be related to non-heritable factors such as home range quality, nutritional condition or behaviour. In addition, we found evidence for a directional selection towards earlier parturition without fluctuation in time. This study highlights the strong inter-annual thermal plasticity coupled with a limited adaptive potential of breeding phenology in the common lizard. In future, warmer conditions, the interplay between such plasticity and a selection apparently independent from environmental fluctuations would thus essentially depend on the yet unknown costs of thermal plasticity.
Range expansions are driven by a host of eco-evolutionary mechanisms, with consequences for individual fitness, population dynamics and ecosystem function. Processes at the range front are particularly important in determining rates of expansion and resulting distributions. Species recolonisations are a subset of range expansions which have become a global conservation priority, with a key goal to maximise the rate of spatial recovery. However, this is limited by a poor understanding of the underlying patterns expected during recolonisations and their mechanistic drivers. We address this knowledge gap using a unique long-term dataset, comprising nesting records across 54 years of recolonisation by Osprey Pandion haliaetus in Northern Scotland. We investigate spatiotemporal variation in rates of expansion and the role of conspecifics in determining patterns of settlement, including the distribution and density of nests. Spatial expansion in most years was minimal, relying heavily on long-distance dispersal of rare pioneering individuals beyond the breeding range to drive substantial recovery and thus exhibiting a stratified diffusion pattern. The distribution of nests was consequently non-random, with strong clustering into distinct subpopulations. Our findings suggest that recolonisations follow similar patterns of expansion to biological invasions, highlighting opportunities to combine knowledge across two key areas of ecological research. We also emphasise the disproportionate role of male Ospreys in restricting patterns and rates of breeding range expansion under female-biased dispersal. Adapting conservation management accordingly could accelerate species restoration, including wider application of interventions like artificial nest provisioning and translocations to facilitate long-distance dispersal.
Green sea turtles (Chelonia mydas) are globally distributed and use tropical and subtropical beaches for nesting. Green turtles exhibit temperature-dependent sex determination (TSD), a mechanism by which incubation temperature during a critical developmental window determines offspring sex. As global temperatures rise, many nesting populations could be producing increasingly female-biased sex ratios, raising concerns about long-term population viability. Our ability to assess demographic risks has been hindered by the absence of validated models that accurately convert field-recorded nest temperatures into sex ratios. In this study, we combine high-resolution temperature data from 62 monitored nests with known hatchling sex ratios (n = 594 individuals) to develop and validate a predictive model for sex ratio in green turtles. We developed several methodological innovations to study the impact of temperature-dependent sex determination (TSD) under natural conditions. First, we developed a novel approach to quantify spatial temperature heterogeneity (H, range between the 2.5th and 97.5th percentiles of the pairwise differences of nest temperatures recorded at the same time) on a nesting beach. The median heterogeneity of the beach is 1.58°C (95% credible interval: 1.52-1.64°C). Second, using a Bayesian mixed-model framework and experimental data from 1480 embryos incubated at constant temperatures under different moisture conditions, we detected genetic and/or maternal differences among clutches in the thermal sensitivity of sex ratio estimates, but no effect of Regional Management Units (RMU). Third, we fitted nine models to estimate field sex ratios; the best-performing model combined a thermal reaction norm of sexualization with a sensitivity function across the thermosensitive period (TSP), showing that both the timing and magnitude of temperature exposure influence sex determination. Our results indicate that males can be produced even under apparent female-producing conditions, due to temperature heterogeneity, temporal autocorrelation of nest temperatures that increased sex ratio variance and non-linear sensitivity to male-producing temperatures. This study establishes a new standard for predicting sex ratios in reptiles with TSD, offering critical insights for population assessments and adaptive conservation planning under changing climatic conditions.
Parasites routinely persist in seasonal systems while infecting multiple host species. An important question for parasite control is whether parasite persistence is driven by particular host species, specific times of year or their interaction. We have few empirically tractable models to answer this question. We develop a data-driven model that partitions species-specific and temporal drivers of parasite persistence from commonly collected surveillance data. Leveraging standard epidemiological theory, our approach demonstrates a novel way to link time-varying fluctuations in species-level contributions to parasite persistence directly to time-integrated parasite persistence in the community as a whole, while using real-world field data that is tractable to obtain. We applied our approach to 3 years of parasite surveillance data in seasonal amphibian communities persisting with the fungal pathogen Batrachochytrium dendrobatidis (Bd). We asked three questions: (i) Do amphibians trade-off in their contributions to Bd persistence across the year? (ii) What host characteristics, such as seasonally fluctuating host density or host competence, drive these trade-offs? and (iii) what are the relative contributions of species compared to periods of high transmission for enzootic Bd persistence? We found that the identity of the amphibian species driving Bd persistence was highly variable through time. Specifically, temporal variability in host density and less so variability in host competence drove the temporal variation in species' contributions to persistence. Moreover, our model identified two distinct mechanisms of Bd persistence: (i) spillover dynamics from a dominant maintenance species and (ii) temporally asynchronous, but equal, contributions of host species to persistence. In both cases, species-targeted interventions were as effective or more effective than temporal control for reducing the capacity of Bd to persist. Broadly, our results demonstrate that species contributions to parasite persistence can have strong, asynchronous temporal variability, potentially limiting the effectiveness of targeted seasonal parasite control. Our model is designed to link closely with standard parasite surveillance data and is broadly applicable to other host-parasite systems where it can partition who, when and what drive parasite persistence in multi-host seasonal communities.
Mutualistic interactions between species form complex networks that shape evolutionary and ecological processes. Traditionally, these networks have been studied at the species level, with species abundance and traits proposed as key structuring mechanisms. However, such approaches often fail to explain commonly observed network structural patterns, which have consequences for community stability and functioning. This limitation may stem from overlooking fine-scale interactions between individuals, the actual network building blocks. By shifting the focus from species to individuals, here we aim to better understand the mechanisms shaping mutualistic networks using plant-pollinator assemblages. To do so, we combined field data on pollinator visitation to individual plants and agent-based models (ABMs) within a Bayesian framework. We found that explaining a key network structural pattern, the pollinator community degree distributions, required accounting for species abundances, distinct pollinator behaviours, and plant spatial configurations. These factors determined the probability of interactions between individuals and altogether explained a substantial portion of the degree distribution variation even without including specific trait-matching mechanisms. Nevertheless, our predictive ability varied across different flowering stages, highlighting that distinct mechanisms operate across time. By integrating empirical data with individual-based modelling, we were able to capture details of interactions occurring in the real world, revealing how fine-scale processes shape community-wide network structure and offering new insights into the emergence of complex ecological networks.
Animal populations are exposed to environmental variation through yearly and seasonal fluctuations, as well as human-induced rapid environmental change. Social behaviour has received growing attention as a potentially important but underappreciated mechanism for resilience to environmental changes. Social interactions shape access to resources, information, protection from predators and opportunities for reproduction. They can also influence how individuals experience and respond to environmental stressors, which relates to the concept of social buffering, a pattern where sociality attenuates the detrimental effects of stressors on individual and population fitness. Such ideas have typically been examined using biogeographic analyses to test whether social living is more prevalent in harsh environments. However, there may also be variation in social behaviour within populations and within an individual's lifespan that serves to maintain or even enhance fitness during environmental changes. In this Special Feature, we present a collection of contributions examining the role of social interactions in maintaining fitness in the face of adverse effects across mammal, reptile and insect species. These studies were conducted under laboratory and field conditions and in response to a wide range of ecological factors, including predation risk, food abundance and interspecific competition. Collectively, we see that social behaviour interacts with environmental variation through multiple pathways, and these behavioural adjustments can have consequences for individual fitness and scale up to affect population performance. Lastly, we offer suggestions for future research directions to address remaining knowledge gaps and advance our understanding of the links between environmental variation, social behaviour, fitness outcomes and population persistence. Such work has the potential to provide valuable insights for management and conservation efforts, which is critically important in a rapidly changing world.
Ecotones between major biomes represent strong ecological gradients and offer valuable opportunities to investigate the processes structuring biological communities. The ecotone between the Cerrado and the Atlantic Forest is one of the most extensive and biodiverse transition zones in South America. Here, we investigated the assembly processes of bat communities across the Cerrado-Atlantic Forest ecotone, contrasting the predictions of environmental filtering, competitive exclusion, and neutral assembly using a coevolutionary community assembly framework. We also evaluated how environmental and historical variables influence patterns of phylogenetic beta diversity and tested whether abrupt changes in community composition occur along the gradient from the ecotone towards the core areas of both biomes. We found that environmental filtering was better supported than competitive exclusion and neutral models in structuring bat communities within the ecotone. Variation in phylogenetic beta diversity was primarily explained by environmental variables, particularly precipitation seasonality, annual precipitation, annual temperature range, and canopy height. An abrupt change in phylogenetic beta diversity was detected from the ecotone towards the core of the Cerrado biome, whereas no comparable shift was observed towards the Atlantic Forest, indicating that distinct assembly processes operate along gradients associated with these two megadiverse biomes. Our results highlight the dominant role of environmental filtering in shaping bat communities in the Cerrado-Atlantic Forest ecotone and emphasise the importance of accounting for coevolutionary processes when interpreting community assembly patterns in Neotropical biodiversity hotspots.
Animals play an important role in elemental cycles that underpin ecosystem functioning through their foraging, movement and waste excretion. Yet animals also play a distinct but often overlooked role in the cycling of trace elements by incorporating potentially scarce trace elements into their tissues and returning significant quantities to the local environment when their carcasses decompose. This gap in our understanding of trace element cycling through animal decomposition means we lack a complete picture of the fundamental zoogeochemical processes that integrate animals within landscapes. Here, we present a perspective on the role large animals play in linking trace elemental cycles from local to landscape scales during their lives (via accumulation and excretion) and after their death (via carcass decomposition). We highlight how large vertebrates, and their decomposition, can redistribute trace elements across spatial scales and may serve as tools for managing trace elemental cycling and enhancing landscape heterogeneity.
Ungulates play vital roles in ecological systems, shaping plant biomass and diversity via herbivory and impacting soil properties through zoogeochemical cycling. As ungulate communities fluctuate worldwide, the extent to which wild ungulates and domestic livestock can play similar ecological roles is an increasingly vital - and fraught - question. Here, we synthesized the literature directly comparing wild and domestic ungulate effects on plants and soil nutrients. We investigated the intrinsic and extrinsic mechanisms researchers identified as driving similarities and differences in ecosystem responses to wild and domestic ungulates, and qualitatively assessed the direction and relative strength of species' impacts within shared environments. We found that surprisingly few studies directly compare the effects of wild and domestic ungulates, and even fewer explicitly consider the mechanisms underlying observed outcomes. Qualitative synthesis suggested that wild and domestic ungulate effects on ecological variables differed in intensity rather than direction, with domestic ungulates exhibiting greater effects on ecosystem responses, perhaps due to their greater densities. More intentional study of the intrinsic and extrinsic factors underlying ungulate effects on ecosystems, and particularly on below-ground processes, is necessary for a more complete understanding of the functional interchangeability - or irreplaceability - of wild and domestic ungulates in a rapidly changing world.
Reptile behavioural ecology and regulatory behaviours have long been interpreted primarily through the lens of thermoregulation. However, basking and shuttling also expose animals to ultraviolet (UV) radiation necessary for vitamin D3 synthesis and other fitness-relevant processes. Here, I adapt a standard thermoregulation framework to UV data to test whether lizards actively regulate UV exposure in nature. Using field observations, operative models, laboratory preference trials and custom-built UV data loggers, I quantified the effectiveness of UV regulation and thermoregulation by ornate tree lizards (Urosaurus ornatus) across contrasting microhabitats (trees vs. snags). Lizards consistently preferred low UV exposures despite high environmental variation, particularly on snags. While U. ornatus thermoregulated equally well in both microhabitats, lizards were far more effective at UV regulation in trees than in snags. This difference likely reflects structural contrasts, as trees offer finer mosaics of sun and shade, whereas snags often impose unavoidable full-sun exposure during basking. My results provide field evidence that wild lizards actively regulate their UV exposure. They further suggest that, for U. ornatus at least, the physiological consequences of microhabitat selection depend more strongly on UV conditions than on thermal conditions. Recognising UV regulation as a fundamental component of reptile homeostasis alongside thermoregulation, together with the trade-offs between these regulatory demands, will broaden our understanding of reptile physiology and ecology and provide a stronger basis for predicting their ecological and evolutionary responses to environmental change.
Ecological stability is fundamental to sustaining ecosystem functioning amid accelerating global environmental change. Both theoretical and empirical evidence suggest that biological diversity and composition influence species asynchrony and species stability within individual trophic levels, thereby contributing to greater temporal stability at the community level. Nonetheless, it remains unclear whether and how these stabilizing factors are integrated across trophic levels to determine multitrophic stability. In this study, using 3 years of community data collected approximately 10 years after the manipulation of plant diversity in a grassland biodiversity experiment, we used structural equation models to assess how species richness, functional composition, species asynchrony and species stability within plant, herbivore and predator communities were associated with multitrophic stability. We quantified multitrophic stability in two complementary ways: an averaging approach, based on the overall mean stability across trophic levels, and a multiple-threshold approach, based on how many trophic levels maintained high stability concurrently. This framework allowed us to examine whether key predictors of multitrophic stability were shared between the two metrics or differed depending on the metric used. Asynchrony among species within each trophic group typically contributed to enhanced community stability. At the multitrophic level, analyses using the averaging approach revealed that average multitrophic stability was positively associated with herbivore species asynchrony and richness, predator functional composition and predator species asynchrony, with herbivore species asynchrony showing a particularly strong positive relationship. Similarly, employing the multiple threshold approach, which evaluated how many trophic levels exceeded 50%, 60%, 70% or 80% of the maximum stability, further identified herbivore species asynchrony as a significant positive predictor at 70% and 80% stability thresholds. Herbivore species richness, by contrast, showed threshold-dependent effects, with positive indirect effects at the 70% and 80% thresholds but negative direct effects at the 50% and 70% thresholds, potentially attributable to diminished plant community stability. Our findings suggest that multitrophic stability across plants, herbivores and predators is most closely associated with the compensatory dynamics of the intermediate consumer trophic level-specifically, herbivores-highlighting this trophic level as a key contributor to buffering temporal fluctuations in multitrophic communities.
