Ecosphere最新文献

A characteristic feature of Earth's drylands is the patchy nature of the vegetation, often referred to as a two-phase mosaic landscape, comprised of a homogenous matrix containing distinctive vegetated patches. The latter are considered vital for ecosystem functioning as they provide refuge to biota from unsuitable conditions. Ground-living (epigeic) and foliage arthropods contribute to dryland biodiversity patterns and processes, but little is known of how their richness, abundance, and composition varies between patches and the matrix in these systems. Throughout the Succulent Karoo, South Africa, such patches (earthen mounds referred to as heuweltjies) are hotspots for both floral and faunal diversity. We investigate how epigeic and foliage-dwelling arthropod species richness, abundance, and community composition respond to heuweltjie patch characteristics, particularly isolation (distance to nearest neighbor, average distance to nearest neighbor, patch density), size (area), and quality (average plant height, dead plant cover, leaf litter cover, termite frass) during a severe drought. Patch isolation and quality were significantly correlated with arthropod richness, abundance, and community composition. More specifically, average proximity of sampled heuweltjies to other neighboring heuweltjies, termite frass, and vegetation structure (height, leaf litter and dead plant cover) were key determinants for epigeic and foliage-dwelling arthropods' species richness, abundance, and community composition. The uniqueness of these mounds as landscape features increases niche and microhabitat availability for arthropods. This emphasizes their importance as promoters of landscape heterogeneity and highlight heuweltjies as key to the spatial distribution of arthropod assemblages in the Succulent Karoo.

Habitat fragmentation and host community composition are implicated as key drivers of changing tick populations and tick-borne pathogen dynamics, altering infection risk through coupled socioecological pathways that mediate interactions between tick vectors, vertebrate hosts, and humans. Patterns of host diversity may be particularly idiosyncratic across urbanized landscapes, due to trade-offs between extreme fragmentation that reduces habitat suitability and access, and human activities that artificially increase resource availability for wildlife. We used camera and hair trap surveys and tick sampling to identify links between landscape composition and configuration, the mammalian host community, and the presence of three tick vector species at a human–wildlife interface in New York City, an emerging area within an endemic region for several tick-borne diseases. We found that human infrastructures, such as the presence of fences in yards, could affect mammal host community composition by changing the “hardness” of edges between urban greenspaces and residential areas. We identified yard- and broader landscape-level features associated with the presence of urban mammal species, and identified cascading effects of host community composition on tick distribution in yards, suggesting management implications for the mitigation of human exposure to tick-borne pathogens. In particular, we identified a possible role of ubiquitous mesomammals, such as raccoons (Procyon lotor), in transporting Amblyomma americanum ticks between parks and neighboring residential yards, and confirmed the key role of white-tailed deer (Odocoileus virginianus) for introducing Ixodes scapularis ticks into yards. Our results challenge assumptions that biodiversity loss in human-modified areas always increases the risk for tick-borne diseases. Instead, we found many residential sites had higher mammal species richness and higher detection of low reservoir competent (“dilution”) hosts for Borrelia burgdorferi, such as opossums (Didelphis virginiana), than paired forested greenspaces. Our study highlights the importance of disentangling the mechanisms mediating tick-borne disease hazard as a critical first step toward reducing urban tick-borne disease risk.

A major threat to small mammalian carnivore populations is human-induced land use change, but conservation and management are inhibited by limited knowledge about their ecology and natural history. To fill a key knowledge gap of the western spotted skunk (Spilogale gracilis), we investigated their spatial ecology at the landscape and home range scale in the temperate rainforests of the Oregon Cascades during 2017–2019. For the landscape scale analysis, we used detections of western spotted skunks at 112 baited camera traps and fitted a dynamic occupancy model to investigate spatial distribution and drivers of inter-seasonal and inter-annual changes in occupancy. Concurrently, we radio-collared 25 spotted skunks (9 female, 16 male) and collected 1583 relocations. Using continuous-time movement models, we estimated large home range sizes for both male and female spotted skunks, relative to their body mass, and highly overlapping home ranges that indicated a lack of territoriality. Using these home ranges, we fitted a resource selection function using environmental covariates that we assigned to various hypotheses such as resources, predator avoidance, thermal tolerance, and disturbance. Overall, western spotted skunks were widely distributed across our study area (seasonal occupancy up to 63.7 ± 5.3%) and highly detectable (weekly detection probability = 41.2%). At both spatial scales, spotted skunks selected wetter areas and local valleys, which we attributed to areas with more food resources. At the home range scale, spotted skunks selected locations with lower predation risk and areas surrounded by more previously logged forests. In this montane environment, inter-seasonal contractions in the spatial distributions of spotted skunks were strongly driven by their response to cold temperature and accumulated snow. This was especially evident when seasonal occupancy declined significantly following a severe heavy snow event in February 2019. Given that there is little information available on the natural history of the western spotted skunk, these results provide essential information about their ecology to focus future monitoring efforts and may help identify potential threats (e.g., forest management, severe snow events, or wildfires) to this species.

Many wildlife species vary habitat selection across space, time, and behavior to maximize rewards and minimize risk. Multi-scale research approaches that identify variation in wildlife habitat selection can highlight not only habitat preferences and risk tolerance but also movement strategies that afford coexistence or cause conflict with humans. Here, we examined how anthropogenic and natural features influenced coyote (Canis latrans) habitat selection in a mixed-use, agricultural landscape in Mendocino County, California, USA. We used resource selection functions and hidden Markov models to test whether coyote selection for anthropogenic and natural features varied by time of day or by behavioral state (resting, foraging, and traveling). We found that coyotes avoided development, but, contrary to our expectations, coyotes selected for roads, agriculture, and areas with risk of human encounter and rifle use regardless of diel period or behavioral state. While traveling, coyotes increased selection for roads and avoided ruggedness, indicating that unpaved roads may enhance connectivity for coyotes in mixed-use landscapes. Finally, we found that coyotes selected for mountain lion habitat when resting and at night, signifying that risk from natural predators was not a factor in habitat selection at coarse scales. Coyote habitat selection for places and times associated with human activity, without variation across scales, signals a potential for conflict if coyotes are perceived by people as a nuisance.

Long-term, large-scale monitoring of wildlife populations is an integral part of conservation research and management. However, some traditional monitoring protocols lack the information needed to account for sources of measurement error in data analyses. Ignoring measurement error, such as partial availability, imperfect detection, and species misidentification, can lead to mischaracterizations of population states and processes. Accounting for measurement error is key to robust monitoring of populations, which can inform a wide variety of decisions, including harvest, habitat restoration, and determination of the legal status of species. We undertook an effort to retroactively minimize bias in a large-scale, long-term monitoring program for marine birds in the Salish Sea, Washington, USA, by conducting an auxiliary study to jointly estimate components of measurement error. We built a novel model in a Bayesian framework that simultaneously harnessed human observer and photographic data types to produce estimates necessary to correct for the effects of partial availability, imperfect detection, and species misidentification. Across all 31 species identified in photographs, both observers had instances of undercounting and overcounting birds but tended to undercount (observers undercounted totals across all species on 69.3%–78.9% of transects). We estimated species-specific correction factors that can be used to correct both historical and future counts from the Salish Sea survey, which has been running since 1992. Our novel modeling framework can be applied in other multispecies monitoring contexts where minimal photographic data can be collected for the purposes of correcting for measurement error in large-scale, long-term datasets.

The C₄ Poaceae are a diverse group in terms of both evolutionary lineage and biochemistry. There is a distinct pattern in the distribution of C₄ grass groups with aridity; however, the mechanistic basis for this distribution is not well understood. Additionally, few studies have investigated the functional strategies of co-occurring C₄ grass species for dealing with aridity in their natural environments. We explored the coordination of leaf-level gas exchange, water use, and morphology among five co-occurring semiarid C₄ grasses belonging to divergent clades, biochemical subtypes, and size classes at three sites along a natural aridity gradient. More specifically, we measured predawn and midday water potential, stomatal conductance, water use efficiency, and photosynthesis. Leaf tissue was also collected for the analysis of stable isotopes of carbon and oxygen as well as for measurement of specific leaf area (SLA) and leaf width. Species differences in responsiveness of stomata to changes in vapor pressure deficit (VPD) were also assessed. It was expected that NAD-me species would maintain higher rates of photosynthesis, higher water use efficiency, and have more responsive stomata than other co-occurring species based on observed biogeographic patterns and past greenhouse studies. We found that Aristidoideae and Chloridoideae NAD-me-type grasses had greater stomatal sensitivity to VPD, consistent with a more isohydric strategy. However, midgrasses had both greater apparent water access and water use efficiency, regardless of subtype or lineage. PCK-type species had less responsive stomata and maintained lower levels of photosynthesis with increasing aridity. There were strong interspecific differences in δ¹³C, leaf width, and SLA; however, these were not significantly correlated with water use efficiency. C₄ grasses in our study did not fit discretely into functional groups as defined by lineage, biochemistry, or size class. Interspecific differences, evolutionary legacy, and biochemical pathway are likely to interact to determine water use and photosynthetic strategies of these plants. Control of water loss via highly responsive stomata may form the basis for dominance of certain C₄ grass groups in arid environments. These findings build on our understanding of contrasting strategies of C₄ grasses for dealing with aridity in their natural environments.

Climate-driven ecosystem shifts occur through turnover in the foundation species which structure the landscape. Therefore, to predict the fate of areas undergoing climate-driven ecosystem shifts, one approach is to characterize ecological and evolutionary responses of foundation species along dynamic environmental gradients. One such gradient is the ecotone between tidal marshes and maritime forests in coastal areas of the US Mid-Atlantic region where accelerated sea-level rise and coastal storms of increased frequency and intensity are driving forest dieback and inland marsh migration. Mid-Atlantic tidal marshes are structured by marsh grasses which act as foundation species, and these grasses exhibit trait variation across their distribution from established marsh interior to their inland migration front. We conducted a reciprocal transplant experiment with Spartina patens, a dominant high marsh grass and foundation species, between established populations in the high marsh and range edge populations in the forest understory at three Mid-Atlantic sites. We monitored environmental conditions in marsh and forest understory habitats, measured plant traits (above- and belowground biomass, specific leaf area, leaf N and C concentrations) in transplanted and reference non-transplanted individuals, and used microsatellite markers to determine the genetic identity of transplants to quantify clonality between habitats and sites. Individuals transplanted into the forest understory exhibited a plastic shift in resource allocation to aboveground structures associated with light acquisition, with shifts in transplants making them more morphologically similar to reference individuals sampled from the forest habitat. Clonal diversity and genetic distance among transplants were relatively high at two of three sites, but individuals at all sites exhibited trans-habitat plasticity regardless of clonal diversity or a lack thereof. Individuals grown in the forest understory showed lower vegetative and reproductive fitness. Nevertheless, the trait plasticity exhibited by this species allowed individuals from the forest that were transplanted into the marsh to recoup significant biomass in only a single growing season. We predict high plasticity will facilitate the persistence of colonizing S. patens individuals under suboptimal forest shade conditions until forest dieback increases light availability, ultimately promoting continued inland migration of this foundation species under sea-level rise.

Restoring ecological dynamics is a key objective of conservation translocations. Exemplarily, reconnecting the reintroduced alpine populations with native Pyrenean populations through re-establishing locally extinct populations in between, in the Causses and the Pre-Alps, is a major goal for the long-term conservation of Bearded Vultures in Europe. Understanding Bearded Vultures' post-release movements and foraging behavior is critical to understanding the settlement of newly restored populations and to supporting conservation measures. The telemetric monitoring of 43 translocated and wild-born juveniles allowed us to investigate whether differences exist in post-release movements and foraging behavior during the first year of life between reintroduced and native populations. Medium- and long-distance exploration movements start during the spring following fledging for both translocated and wild-born individuals. However, birds translocated in the most distant release site (Causses) exhibited greater exploration distances with no clear directional movement pattern, had smaller home ranges, and had a stronger preference for supplementary feeding stations than those from other populations. Although some birds translocated in the Pre-Alps displayed similar behaviors, the pattern is not as strong as in the Causses, likely because of the proximity to the breeding populations reintroduced in the Alps or differences in the number and management of supplementary feeding stations. Preference for supplementary feeding stations (SFS) mostly occurred in the Pre-Alps and the native populations, but was lower in the Causses. Seasonal variations in SFS preference were consistent among populations, with a peak in the first spring following fledging. Beyond documenting post-release movements in Bearded Vultures, we suggest better accounting for the demographic consequences of behaviors to track conservation translocation effectiveness, at both local and regional scales.

An accurate depiction of wildfire, harvesting, and insect outbreak disturbances is essential for sustainable ecosystem management of forests in Canada. Even though the advent of temporally consistent 30-m resolution Landsat data has enabled the detailed mapping of forest disturbances in Canada from 1985 onward, the disturbance record prior to 1985 remains sparse. This study aimed to extend the existing pre-1985 disturbance history record by mapping wildfire, harvest, and insect outbreaks in Canadian forests between 1965 and 1984. Our geospatial data processing methodology relied on multilayer perceptrons (MLP) trained on spectral recovery signatures to map and age these disturbances. Our model detected approximately 4.8, 7.3, and 3.8 million ha of burnt, harvested, and insect-ravaged forest areas, respectively, that were absent from national and provincial disturbance databases and forest inventories. Results were validated using both internal and external validation datasets. Our disturbance detection methodology was highly effective, with an internal validation kappa score of 0.91 and an external score of 0.81. The fire and harvest age disturbance MLPs, whose predictions can also be used as a proxy of forest stand age, performed adequately on the internal (fire R² = 0.675; root mean squared error [RMSE] = 4.42; harvest R² = 0.723; RMSE = 3.17) and external validation datasets (fire R² = 0.242; RMSE = 4.69; harvest R² = 0.257; RMSE = 5.46), outperforming existing forest age disturbance products. Finally, we relied on several open data products, such as provincial forest inventories, to correct our disturbance type and year prediction whenever these more reliable, but incomplete, data sources were available. Specific years were not assigned to insect outbreaks due to the lack of dependable training and validation data. We also illustrate how extending the existing forest disturbance record by 20 years may provide a more in-depth understanding of landscape-disturbance dynamics with a case study of the 2023 Canadian wildfire season.

Understanding the mechanisms underlying viable seed production of perennial bunchgrasses is critical to improving restoration and conservation success in Great Basin sagebrush steppe rangelands. We studied the effects of pre- and post-anthesis flag-leaf removal and post-anthesis seed-head shading on reproductive effort in two important rangeland restoration species, the exotic crested wheatgrass (Agropyron cristatum) and native squirreltail (Elymus elymoides). Flag-leaf removal had distinct, species-specific effects on seed filling. Pre-anthesis flag-leaf removal in crested wheatgrass reduced the proportion of filled seeds, while post-anthesis removal did not. In contrast, squirreltail increased filled seed proportions regardless of flag-leaf removal timing. Neither flag-leaf removal treatment affected seed quality, as quantified by seed-specific mass (in grams per square meter), which significantly reduced with seed-head shading in both species. Seed-head shading reduced total propagule production (unfilled + filled seeds) in crested wheatgrass but increased it in squirreltail, possibly due to our shading method protecting from seed-head herbivory or high-light stress. Flag-leaf removal in the squirreltail also induced a negative shading effect on filled seed area, mass, and specific mass. These findings suggest flag leaves can modulate reproductive effort outside of seed provisioning, either by maintaining pre-fertilized seed viability, as in crested wheatgrass, or acting as a competitive sink to the fully emerged seed-head, as in squirreltail. Moreover, this study demonstrates photosynthetic activity by the seed-head itself is critical to the expression of seed quality traits important to seedling establishment success of semiarid perennial bunchgrasses.