Ecosphere最新文献

Bird migration is a fascinating behavioral phenomenon on earth, with annual movements along migratory routes forming complex migration networks. Stopovers, which serve as fuel stations for migratory birds, are critical to the success of long-distance migrations. However, there is growing concern that stopover habitat has been converted and degraded due to intense human disturbances, which severely threaten migratory populations. New remote automated approaches for collecting data, such as passive acoustic monitoring (PAM) technology, provide a promising avenue for the continuous measurement of vocally active species. In this study, we applied PAM to monitor migrating birds in the stopovers of the Jingxin wetland in China, aiming to explore the activity and habitat use of migratory species through soundscape and deep learning approaches. We collected acoustic data from October 16, 2022, to December 15, 2022 (autumn migration season) and from February 19, 2023, to April 28, 2023 (spring migration season) across three habitats: degraded wetland, farmland, and forest. We applied multilabel classification via the ResNet50 convolutional neural network (CNN) to identify a total of 2.45 million 10-s audio clips collected. Our results revealed that the 1–2-kHz vocal signals of Anatidae dominated the soundscapes of the two migratory periods. Two automated measures—compound acoustic indices and a CNN-derived migratory bird activity—reflected avian habitat use gradients and diel patterns in two migratory periods, with the compound indices model explaining 52% and 47% of the variation in migratory intensity, respectively. Furthermore, farmland is the most intensively utilized habitat by migratory species because of the food resources available. This novel use of combining reproducible acoustic data with deep learning can be used to track the temporal changes and spatial distribution of avian migrants effectively and highlights the importance of agricultural ecosystem management at dominated-human stopover sites. Managers should consider using cost-effective acoustic sensors for long-term monitoring of avian movements and for refining conservation practices in a rapidly changing world.

Competition between carnivores and scavengers can alter predation rates and foraging behavior, shaping the effects of predation on complex community dynamics. The perceived risks of conflict and resource loss may influence a predator's response to competitive pressure, but these behaviors can be difficult to infer through traditional field methods. We collected two datasets on predation and foraging behavior to capture spatiotemporal patterns of predation by cougars (Puma concolor) and their response to scavenging by black bears (Ursus americanus). We used feeding-site investigations (n = 2325) to model handling and search time. Bears displaced cougars and reduced handling time at <10% of foraging locations, but they did not affect search time between subsequent foraging events. We also used motion-triggered cameras (n = 144) to assess how cougars allocate their time while at cached carcasses, such as how much time they spend feeding compared to other behaviors. Cougars exhibited limited predictive behaviors (e.g., increased vigilance or caching) in response to higher local bear density. Environmental covariates influenced cougar behavior at their kills more strongly than did the presence of bears. Our results suggest that the mere presence of bears has little effect on cougar predation behavior where these species co-occur at moderate densities and there is abundant prey. This research highlights how outcomes of carnivore competition may differ across a range of environmental pressures; thus, understanding context-specific inference about competition among large predators is critical for long-term persistence and ecological function of complex multi-predator systems.

Global change factors, such as anthropogenic nitrogen (N) enrichment, have been shown to have diverse and widespread effects on plants and ecosystem functioning, including effects on intraspecific trait variation. Plant symbionts such as Epichloë amarillans (Epichloë, hereafter), are ubiquitous and can have substantial effects on host traits and fitness, yet little is known about how they interact with global change factors to affect host growth. We used an in situ, long-term experiment to examine the functional traits and population-level productivity of both Epichloë-inoculated and sham-inoculated Ammophila breviligulata (American beachgrass, Ammophila hereafter) plants experiencing three levels of N enrichment. We found that Epichloë and N enrichment shifted Ammophila functional traits toward a faster, more acquisitive growth strategy at the tiller level. At the population level, we found that Ammophila biomass was 43% lower in Epichloë-inoculated plots than in sham-inoculated plots under conditions of low N enrichment. When plots were exposed to high N enrichment, however, this pattern was reversed, with Epichloë-inoculated Ammophila plots having 30% greater biomass than sham-inoculated plots. We demonstrate that a fungal endophyte and N enrichment had significant direct effects on intraspecific trait variation in a dominant grass species, while their interaction impacted population-level biomass in complex ways that were not immediately obvious from tiller-level trait measures. Examining plant-microbe interactions along with clonal traits and demography may be important for linking individual-level functional traits with population-level effects on ecosystem processes under conditions of global change.

The Arctic is warming nearly four times faster than the global average, but the rate of change is not uniform across the region. Wide-ranging Arctic species are exposed to variable environmental conditions across their range, but it remains unclear how different climate change regimes are affecting populations within the same species that have become exposed to different conditions and how each population may respond in the future. In this study, we investigated how environmental changes in the Greenland Sea (GS) have influenced foraging behavior and diet of GS hooded seals (Cystophora cristata) over recent decades, and evaluated how future climate scenarios may affect them. We then compared these findings with recently published results on hooded seals from the Northwest Atlantic (NWA) stock, placing them in the broader context of Arctic ecosystem dynamics. Specifically, we analyzed changes in (1) foraging distribution and habitat use based on a two-decade tracking time series (1992–1993 and 2007–2008) from GS hooded seals and (2) diet, using carbon and nitrogen stable isotopes from blubber samples collected in 2007 and 2022. We also projected future suitable foraging habitats under the SSP5-8.5 climate scenario. Our results show that while GS hooded seals have maintained consistent habitat preferences and diets over the past two decades, their foraging areas have shifted eastward, rather than northward as was seen for the NWA seals—despite northward shifts in their breeding and molting grounds. Suitable foraging habitats of the future are projected to expand and continue shifting eastward. This pattern is unexpected for an ice-associated Arctic species, and contrasts projections for the NWA stock. Although it is uncertain whether hooded seals possess sufficient behavioral or physiological plasticity to cope with future climate-driven changes, our findings underscore the importance of considering population-level behavioral heterogeneity when assessing species-wide responses to environmental change.

Understanding predator–prey relationships is fundamental to our knowledge of the stability and resilience of ecological systems. These dynamics are shaped by both ecological factors, like interaction strength, and anthropogenic factors, like harvest intensity, which can have large-scale implications for community structure. However, few studies have focused on the combined impact of these effects and their contribution to phenomena like prey release within two-species frameworks. In this study, we investigate the interactive impact of interaction strength and harvest pressure on two trophic levels in a predator–prey system using a mathematical modeling approach. Our results reveal that interaction strength plays a crucial role in shaping population dynamics, with high interaction strength leading to a predator-dominated system and low interaction strength enabling coexistence between species. The addition of predator harvest into the system reveals complex and counterintuitive behavior not seen in unharvested systems, likely due to the destabilizing impacts of harvest at some interaction strengths. Specifically, the inclusion of harvest on the predator can induce a range of behaviors, such as prey release and predator decline, that alter the equilibrium abundance of both predator and prey populations. Interestingly, predator–prey systems with intermediate to high interaction strengths achieve maximum total abundance with low harvest levels rather than in scenarios with no harvest pressure, as prey populations benefit greatly from reduced predation mortality associated with predator harvest. We gain insights into the complex interplay between predator–prey interactions and human activities in shaping community composition and abundances across trophic levels. This study provides potential mechanisms that may explain the observed variation in numerical prey release in trophically complex systems in which predators and prey are both extracted, like coral reef fisheries. Results highlight the need for resource management to consider the wide range of factors that shape ecosystem dynamics to develop effective strategies that safeguard the long-term health of complex ecosystems and the human communities that they support.

Positive interactions among non-native species can drive invasional meltdowns to the detriment of native biota. Here, we assessed whether targeted control of aquatic invasive species (AIS) can benefit native species by eliminating synergies among invaders. We did so by monitoring changes in the abundance of native and non-native benthic invertebrates following the targeted removal of non-native fish and crustaceans in 10 streams on the island of Oʻahu (Hawaiʻi, USA). Benthic invertebrate sampling was conducted in paired control reaches and removal reaches in each stream immediately following removals, one month following removals, and then at 2- to 3-month intervals for 16 months. Temporal variations in the abundance, composition, and diversity of the native and non-native invertebrates were compared among streams and between treatment reaches using multivariate data visualization and mixed-effects models. We observed both seasonal shifts in overall community composition and treatment-specific effects on the abundance of common taxa that were mediated by the number of AIS fish removed. Most notably, as removal of non-native poeciliid fish increased, we observed concordant decreases (−32 ± 13% mean ± SE) in non-native caddisfly (Cheumatopsyche analis) and increases (122 ± 69%) in partially native chironomid midges in the treatment reaches relative to the control reaches. Our results provide experimental evidence supporting the hypothesis that predation by introduced poeciliids on midges indirectly facilitates non-native caddisfly populations via competitive release. Our findings indicate that removal of poeciliids allows midges to outcompete non-native caddisflies and increase their abundance. Our study illustrates that targeted removal of non-native species can have cascading negative effects on other introduced taxa. Understanding trophic relationships among invasive and native species can thus enhance management efforts by maximizing benefits to native species relative to effort and cost.

Animals in northern environments contend with seasonally variable resources and have evolved life histories to cope with the flush of nutrients in summer and scarcity in winter. Ungulates cope with seasonal variation in resources by accreting fat stores when resources are plentiful during the growing season and then mobilizing these stores to meet nutritional requirements when resources are more limited during winter. While this generalization makes sense, previous work has suggested that caribou (Rangifer tarandus spp.) may break this rule; however, previous works have suffered various limitations that leave this question unanswered. As part of a larger study to understand the role of nutrition as a potential factor limiting the Mulchatna Caribou Herd (MCH) in southwestern Alaska, we initiated a longitudinal study in which we captured the same individual caribou twice annually in autumn and late winter. We aimed to test the hypothesis that winter nutrition limited the MCH and predicted that caribou would lose fat between late autumn and late winter. During captures, we determined body fat percentage of lactating, adult females using validated ultrasonography and manual palpation techniques, and determined pregnancy status in late winter using transabdominal ultrasonography. Repeated measures indicated lactating females gained body fat over winter, averaging ~2.8 percentage points from 6.1% ± 0.1% (mean ± SE) in autumn to 8.9% ± 0.4% in late winter (z = 5.425, p < 0.001), with maximum individual gains of up to 8.5 percentage points. Our findings provide empirical support for overwinter gains in fat among caribou and indicate that winter nutrition is not limiting the MCH. Our findings illustrate the value of longitudinal studies in ecology, have implications for research designs for studies of nutrition in northern ungulates, and highlight important considerations for caribou relative to unique nutritional aspects of their life history.

Urban green spaces are key sites for protecting and supporting biodiversity, providing new perspectives and solutions for ecological conservation and urban management. This study reviews empirical research on terrestrial fauna biodiversity in urban green spaces, with 121 studies included in this review. The content covers current research trends and the mechanisms of drivers for biodiversity. First, the research trend results show that the research areas are mainly concentrated in economically developed regions; the main species studied are birds and insects; the biodiversity response variables are mostly focused on species richness and diversity, and the exploration of community functional structure indicators is still insufficient; species monitoring mainly relies on non-interventional methods, and long-term monitoring and experimental research are scarce; research on landscape drivers primarily focuses on the independent effects of individual variables, with limited exploration of their synergies and interactions; the effect of drivers mainly focuses on positive and negative correlations, with little research on the applicability threshold of this relationship. Second, regarding landscape driving mechanisms, the drivers of fauna biodiversity in urban green spaces involve 23 landscape variables in four aspects; there are significant differences in the trends of sensitive landscape drivers across different animal groups and biodiversity indicators. This finding is valuable for more targeted conservation of specific target groups and biodiversity levels. Our research results emphasize the important role of urban green spaces in maintaining biodiversity, suggesting that through scientific and reasonable spatial layout and management, their ecological conservation and service functions can be largely exerted while meeting human usage.

Effective conservation management relies on accessing and integrating various forms of evidence regarding the potential effects of management interventions. Here, we aim to identify key management options to enhance habitat suitability and mitigate threats for grassland and farmland birds in the Central Plains of Thailand, a key area for open-country birds in the region, using a Bayesian Belief Network (BBN) approach. We selected eight at-risk passerine landbird species as focal taxa and developed up to nine scenarios to assess the potential impacts on the area of available suitable habitat for each species under different management options: a status quo scenario depicting the current situation, a future scenario if no action is taken, and up to seven scenarios each with management options. Three options focused on improving and/or maintaining habitat suitability, and the other four targeted threat mitigation. We then sought the best combination of management options, based on results from the above scenarios. The models predicted that each species would respond differently to each option depending on their ecological niches. If no action is taken in the near future, the highest quality habitats for all species were predicted to decrease from the current situation, with some species facing substantial habitat loss. For example, the globally Vulnerable Manchurian reed warbler Acrocephalus tangorum was predicted to lose nearly all of its highest suitability habitats (a 93% decline). The best conservation strategy involved implementing multiple management options, with tax incentives playing a particularly important role—and being the most effective measure for four species and the second most effective for the remaining four. Species-specific responses varied; two species required fewer interventions, while others needed multiple concurrent management strategies. For instance, the highest suitability areas for the Manchurian reed warbler and Oriental skylark Alauda gulgula reached an asymptote when two management options were applied together, whereas species like the long-tailed shrike Lanius schach required four interventions simultaneously. Our study underscores the advantages of this BBN approach for prioritizing optimal management strategies before implementation. It is adaptable for various decision-making processes and can be applied to other species and agricultural systems, particularly those lacking baseline data.

Habitat modification is the main threat to biodiversity, but other causes are involved, such as climate change or pollution. To optimize conservation efforts, it is crucial to determine their respective contributions. An effective approach to disentangle causalities is to set up comparative or experimental monitoring in the field. In a temperate forest classified as an integral nature reserve, left unexploited, tree growth led to canopy closure and the progressive disappearance of semi-open woodlands and associated thermophilic species. Past logging provided a semi-experimental setting with contrasting patches in terms of canopy closure. A long-term capture–mark–recapture study of two snake species (1995–2021), one thermophilic and the other less so, revealed which demographic parameters were affected and established a link between habitat closure and population decline. For the most thermophilic species (Hierophis viridiflavus), rapid increases in canopy cover drastically reduced the survival probability of very young individuals, neonates and snakes a few months old, likely by depriving them of essential thermophilic prey (i.e., small lizards). Juveniles and adults that feed mainly on rodents and less on thermophilic lizards were less affected. For the least thermophilic snake species (Zamenis longissimus) where all age groups feed on rodents, habitat closure had no major effect on survival. Importantly, open woodlands remained favorable for both species. Although closing habitat was detrimental to H. viridiflavus, we predict that the survival of Z. longissimus will also drop as the forest closure approaches 100%. Canopy closure and the disappearance of shrubby habitats are the main factors responsible for the decline of forest snakes. A lack of management in temperate forests may not be the best option to maintain healthy reptile populations.