Ecological Applications最新文献

Bees are focal pollinators, essential for maintaining biodiversity and crop production. Thus, reports of high annual honey bee colony losses and population declines among many wild bees in different parts of the world are of major concern. The spread of viruses is highlighted as a potential threat to bee communities. Viruses infect a wide range of bee species and can be transmitted interspecifically through shared floral resources. Therefore, the role of flowers as hubs of bee virus transmission requires a community ecology perspective. Here, we investigate local and landscape-scale characteristics of floral communities potentially associated with the spread of viruses in the solitary Andrena spp. (mining bees). We surveyed 14 sites in a Mediterranean agroecosystem with varying local densities of honey bee (Apis mellifera) foragers and diversity of flowering species and assessed the prevalence of four common Hymenoptera-associated viruses (deformed wing virus [DWV], black queen cell virus [BQCV], sacbrood virus [SBV], and Lake Sinai virus-2 [LSV-2]) in co-foraging honey bees and mining bees. We found that the probability of virus presence in mining bees was generally associated with the diversity and composition of the local (site level) floral community, and with floral resource availability at the landscape scale (up to 1000-m range). In addition, SBV and DWV prevalence in mining bees were positively related to the density of SBV-infected, and total honey bee foragers, respectively. These findings demonstrate the focal role that the floral community at multiple spatial scales, and co-foraging pollinator species, may play in virus spread and, potentially, pollinator health.

Expanding urbanization introduces various environmental stressors, such as artificial light at night, anthropogenic noise, and human presence. Although these stressors are commonly blamed for biodiversity decline, urban development also coincides with severe habitat transformations, leading to the loss of natural habitats and key ecological features essential for diverse biota. How these environmental changes interact to shape urban biodiversity remains unresolved, posing substantial challenges for conservation policies. Here, we address this issue using multilevel structural equation modeling (MSEM) across 90 wooded green spaces in Kraków, Poland, focusing on local communities of birds (28 species) and bats (5 genera). We found that environmental stressors are widespread correlates of bird and bat occurrences but also strongly correlate with habitat degradation, reflected in reduced green space size and diminished availability of structural features, such as deadwood, tree cavities, and epiphytes—critical resources for these taxa. In MSEM predictions, environmental stressors primarily affected communities indirectly by driving habitat changes. Secondarily, stressors acted as both direct and indirect predictors for some taxa (combined within a single model), though purely direct effects were rare and often co-occurred with habitat effects. Overall, habitat alterations were more significant drivers of taxon loss than stressors, with green space size, crown or lying deadwood, tree cavities, and epiphytic plants emerging as the most critical features for supporting biodiversity. Habitat degradation was primarily correlated with human presence, less strongly with light, and only weakly with noise levels. However, the direct effects of each were similarly rare and could be either positive or negative. Our findings suggest that the seemingly prominent effects of human-associated stressors on biodiversity may often be artifacts of coinciding habitat degradation, with habitat loss and the removal of nuanced habitat features playing a more direct and critical role. While reducing noise, light, and restricting human activity might be effective conservation strategies for some species, they are insufficient without preserving habitat remnants and fostering structural diversity to resemble that of natural ecosystems. These habitat-centric approaches are keystones that should be prioritized, offering a promising roadmap to reconcile human well-being with biodiversity preservation in future sustainable cities.

Grazing is the common agricultural land-use in mountain regions. It is of high socioeconomic importance but also essential for conservation as extensive mountain pastures are hotspots of biodiversity. Climate change is causing earlier growing seasons, prompting earlier livestock turnout. The effects of grazing on biodiversity, however, may differ depending on the time of the year, yet our understanding of these effects is limited. Here, we evaluate how short-term effects of different livestock turnouts affect taxonomic, phylogenetic, and functional diversity of pollinators (wild bees and butterflies) and phytophagous insects (leafhoppers) as well as plant–insect interactions on eight mountain pastures in the northern Alps, Germany. At each pasture, we established three grazing treatments including an ungrazed control, early and late livestock turnout. We sampled wild bees and butterflies during two and leafhoppers during one growing season twice a year (summer onset and summer peak). To account for effects of grazing through changes in vegetation, we surveyed vegetation characteristics, such as the number of inflorescences and sward height. Early-grazing plots had lower wild bee and leafhopper diversity during summer onset, but this pattern shifted later in the season after grazing had stopped. During summer peak, wild bee diversity was higher at early-grazing plots than at late-grazing plots and structural equation modeling indicated that this could be partly explained by a higher number of inflorescences. Phylogenetic network diversity of wild bee– and leafhopper–plant networks was higher at late than at early-grazing plots. Our study shows that grazing in general, and also the timing of grazing, affects vegetation characteristics, insect diversity, and plant–insect interactions in mountain pastures. Effects of grazing on insect diversity were mostly positive, which supports the notion that extensive grazing is important to maintain insect diversity in mountain pastures below the timberline. Although negative effects of early livestock turnout treatments occurred, they disappeared and even turned positive later in the season. Thus, earlier livestock turnout does not appear to threaten insect diversity in mountain pastures, but further research is needed to understand long-term effects.

The Anthropocene is defined by rapid environmental changes such as biological invasions and shifting disturbance regimes that threaten native species. Understanding the drivers of endangerment for species facing multiple simultaneous threats is challenging without experimental methods. Here, we examined the relative and combined effects of severe wildfires and an early-stage barred owl (Strix varia) invasion on an assemblage of three native forest owl species in the Sierra Nevada, California, USA, leveraging manipulative (lethal barred owl removals) and natural (severe wildfires) experiments and a regional passive acoustic monitoring program from 2018 to 2023. Wildfires reduced flammulated owl (Psiloscops flammeolus) occupancy by 71% in severely burned areas (sites experiencing near-complete high-severity fire) for at least 3 years postfire but did not affect great horned (Bubo virginianus) or northern pygmy owl (Glaucidium californicum) occupancy. Because flammulated owls have small home ranges and an insectivorous diet that depends on nearby mature forest foraging habitat and secondary-cavity nest sites, they showed a strong negative response to extensive high-severity burn areas that eliminate these resources. Flammulated owl occupancy increased approximately twofold from 0.09 (85% CI: 0.03, 0.20) to 0.18 (85% CI: 0.07, 0.36) following lethal barred owl removals (with only 4% posterior distribution overlap), but removals did not affect the other two native species. Despite evidence of habitat segregation between barred owls and the native species, where barred owls typically occupied intermediate-to-late seral forests in flatter, lower elevation areas, this niche partitioning was insufficient to prevent nonconsumptive or predatory effects on flammulated owls. In contrast, the resilience of great horned and pygmy owls may have stemmed from their larger body size and diurnal activity, respectively, suggesting that life history mediates forest owl vulnerability to invasive barred owls. The negative effects of barred owls on flammulated owls, even during the early invasion stage, coupled with well-documented effects on other small, nocturnal forest owl species in regions with high barred owl densities, reinforce the conservation value of proactive invasive species management. Our study demonstrates the power of regional-scale experimentation, facilitated by bioacoustic monitoring, for understanding biological community responses—mediated by species' life history—to rapid environmental changes.

Conservation scientists have long used population viability analysis (PVA) on species count data to quantify critical decline risk, thereby informing conservation actions. These assessments typically focus on a single species rather than assemblages and assume that risk is consistent within a given life stage (e.g., across the different seasons or months of a year). However, assessing risk at overly broad temporal or spatial scales may obscure diverging population declines between predators and prey, potentially disrupting biotic interactions. In this study, we used time-series-based PVA for age-0 forage fishes and their potential zooplankton prey for each month of the year in the San Francisco Estuary, over 1995–2023 (N = 175 time series). The PVA were parameterized using Multivariate Autoregressive (MAR) models that estimate long-term population trends and variability (i.e., process error) for each population. We found widespread negative population trends across fish species (56.8%) and observed that critical decline risk is often higher in months when species peak in abundance compared to “shoulder” months. Although current decline risk is somewhat balanced between predators and their prey (mean 23.7% for fish and 21.1% for zooplankton), our time-series models indicate trophic levels are poised to diverge over the next 10 years, with fish generally accumulating risk faster than their prey. Additionally, zooplankton showed 11.2% higher uncertainty about their near-term critical decline risk relative to fish. These observations suggest strong, previously unreported potential for future trophic mismatches. Our results underscore the need to assess risk over finer temporal scales within and across trophic levels to better understand vulnerability, and thus inform conservation of imperiled species. Our approach is transferable and highlights the benefits of time-series-based PVA to understand risk of food-web collapse in the face of climate-induced phenological shifts.

Coastal subarctic systems are inhabited by bivalve and gastropods, which due to their lifecycle and longevity are reliable indicators of ecological alterations in the environment. Recent laboratory studies have shown that young life stages of invertebrates perceive natural sounds, and their settlement, behavior, and fitness could be altered by anthropogenic noise. Through a field study conducted on two sites differing by their noise pollution level (pristine [PS] or anthropized [AS]), we tested whether the distances (from 25 to 890 m) of anthropogenic noises might affect the diversity and early recruitment of multiple species in pristine and anthropized sites using artificial collectors moored on transects. Overall, environmental conditions (except sound levels) were homogeneous through the transects. The acoustic scenario differed between the PS (vessel noise, 132–138 dB re 1 μPa² s) and AS (mix of pile driving and vessel noise, >140 dB re 1 μPa² s) sites, with the AS site experiencing a higher level of sound exposure than the PS site. Species richness fluctuated with distance from the noise, but only in the anthropized site. Regarding species diversity and evenness, they varied with distance and month at both sites, displaying a clear negative effect of anthropogenic noises and shifting species composition. Specific early recruitment responses were observed for each species to anthropogenic noise, but with a different pattern for each site due to variations in sound pressure and exposure levels. The findings of our field study document, for the first time, that controlled anthropogenic noise emission leads to ecological shifts in community structure and population metrics of benthopelagic marine invertebrate species. To avoid disruptions in community structure and recruitment, we recommend that a noise threshold level for invertebrates should be below 140 dB re 1 μPa² s.

Global changes in disturbance regimes are reshaping ecosystems, driving shifts in species composition, diversity, and community structure. On islands, these effects are often pronounced due to their unique ecological contexts, including high levels of endemism and vulnerability to invasive species. Using three decades of longitudinal data, we examined vegetation dynamics on Santa Cruz Island, California (SCI), following the removal of feral ungulates, focusing on the interplay of convergence, divergence, and hierarchical complexity in community assembly. Specifically, we asked: (1) To what degree has species composition diverged within communities since ungulate removal? (2) Is there evidence of convergence in species composition among vegetation communities? Our analyses revealed patterns of divergence and convergence influenced by historical grazing intensity and local site variability. Divergence was most pronounced in grassland and fennel-dominated communities, where invasive species continued to dominate or alternate trajectories emerged. Conversely, convergence was observed among woody communities (e.g., coastal scrub, chaparral), characterized by increases in native shrub and tree cover. These shifts demonstrate the role of hierarchical complexity in ecological recovery, with local-scale processes such as competition and priority effects interacting with larger scale drivers like climate variability and disturbance legacies. Novel and hybrid ecosystems emerged in many areas, reflecting the interplay between native and invasive species because of a history of extreme disturbance. These findings demonstrate the challenges of managing ecological recovery in systems influenced by multiple perturbations. As global pressures on ecosystems increase, understanding the hierarchical dynamics of convergence and divergence offers critical insights for setting realistic conservation goals and managing biodiversity in recovering landscapes.

The conservation of native bees and other pollinators is an important consideration for the future of urban sustainability. Parks, urban gardens, cemeteries, and other green spaces can provide habitat space for both native and non-native pollinators in cities. These publicly managed green spaces are not evenly distributed across otherwise inhospitable urban landscapes. Buildings and other human-made structures could act as barriers to the movement of pollinators, especially in highly built-up cities. Little is known about how bees navigate cities, and finding suitable habitat in urban ecosystems may be particularly difficult for native solitary bees, which have small foraging ranges. In this study, we utilized open GIS data as well as open-source software (Quantum GIS and Python) to model the shortest flight paths between parks and other public green spaces in New York City, New York, USA. We also used open light detection and ranging (LiDAR) data to assess plausible pollinator habitat in New York City parks. We found that the majority of straight-line (Euclidean) paths between parks intersected at least one building and that shortest paths around buildings were generally 20% longer than their Euclidean equivalent. We found that most managed properties alone, or within connected clusters, did not have sufficient plausible pollinator habitat to support pollinators with medium foraging distances, which include most solitary native bees. Our findings suggest limited connectivity and potential barriers between managed properties in New York City. Increasing pollinator habitat within smaller managed properties and building green roofs on shorter buildings and establishing stepping stone habitats like tree pits and vacant lots could increase overall green space connectivity. This technique for assessing connectivity between green spaces utilizes open data and tools that can be used by conservationists, planners, and policymakers to explore questions related to supporting pollinators or other species of interest in urban landscapes.

Restoring a low-intensity, frequent-fire regime in fire-prone forests offers a promising natural climate solution. Management interventions that include prescribed fire and/or mechanical treatments have effectively reduced fire hazards in the Western United States, yet concerns remain regarding their impact on forest carbon storage. This study used results from a long-term, replicated field experiment to assess the impacts of a restored disturbance regime on carbon dynamics in a Sierra Nevada, mixed conifer forest. The carbon consequences of the treatments were compared to a dynamic baseline of untreated controls (Control). After 19 years of wildfire mitigation, all treated stands stored less carbon than Control, but a larger proportion was sequestered in wildfire-resistant pools (i.e., large trees or fire-resistant species). Notably, only the most intensive treatment regime—thinning, mastication, and prescribed fire (Mech+Fire)—became a net carbon source by Year 20 (−60 MgC/ha). Annual average net ecosystem productivity (NEP) in Control and prescribed fire-only (Fire, 5.6–5.8 MgC/ha/year) more than doubled that of the mechanical treatments (2.0–2.1 MgC/ha/year). Moreover, temporal trends diverged. By the 3rd post-fire interval, the live vegetation carbon accumulation stalled in Control (0.9 ± 1.0 MgC/ha/year, mean ± SE) and accelerated in Fire (6.6 ± 1.2 MgC/ha/year). In contrast, surface fuel recovery was initially faster in Fire but slowed significantly by the 3rd interval, suggesting that the increased productivity under a frequent-fire regime does not necessarily lead to rapid surface fuel buildup once the regime is established. A simulated wildfire in Year 20 killed 6×–16× more live tree carbon in Control (46% mortality). Still, Control maintained the highest post-fire carbon storage. Despite the inherent carbon costs of wildfire mitigation, our 20-year study highlights management pathways that minimize the trade-off between wildfire hazard and carbon storage in Sierra Nevada mixed conifer forests.

Recreation (i.e., hiking and biking) and hunting can occur simultaneously in time and space, and both sources of disturbance affect wildlife behavior, leading to reactions resembling anti-predator behavior. However, the additive effects of lethal and non-lethal human disturbances on wildlife are only beginning to be understood, and research on the impact of hunting on non-target species is limited. Recreation and hunting commonly co-occur in areas where wildlife is present, and understanding their combined effects on wildlife behavior is crucial for protected area management. Using records from 122 camera traps placed along trails and in surrounding forests, we assessed the effect of varying intensities of hunting and recreation over space and time on the temporal activity of red deer (Cervus elaphus), roe deer (Capreolus capreolus), wild boar (Sus scrofa), red fox (Vulpes vulpes), and Eurasian lynx (Lynx lynx) in the Bavarian Forest National Park, Germany. We documented the relative abundance of these species on trails versus in forests and applied Bayesian models to assess how hunting and recreation influenced wildlife nocturnality. Our results suggest that hunting is a strong driver behind wildlife temporal behavior. Hunting amplified avoidance of non-lethal recreation and potentially impacts species interactions. Red deer exhibited the most pronounced temporal avoidance of both hunting and recreational activity, increasing nocturnality and trail avoidance as these disturbances increased. Red deer were more diurnal in the non-hunting zone and decreased nocturnal activity with increasing distance from the hunting zone. Wild boar and non-hunted species exhibited moderate or negligible responses. However, high hunting effort led to species not targeted by hunting (roe deer and red fox) increasing their temporal avoidance of recreational activities, with wild boar and roe deer avoiding trails more strongly. In the context of protected area management, our results suggest that strictly reducing hunting in space and time while concentrating recreation in certain areas to create disturbance-free habitat year-round has great potential to reduce the temporal avoidance of humans by wildlife, thereby fostering nature conservation goals by protecting natural processes.