Ecosphere最新文献

Infectious diseases can cause considerable mortality in vertebrate populations, especially when a new pathogen emerges. Quantifying the impact of diseases on wild populations and dissecting the underlying mechanisms requires longitudinal individual monitoring combining demographic and epidemiologic data. Such longitudinal population studies are rare. Rabbit hemorrhagic disease (RHD) is one of the main causes of the decline in European wild rabbit (Oryctolagus cuniculus) populations. A new genotype of RHD virus (RHDV), called RHDV2 or GI.2, emerged in 2010, posing a new threat to previously weakened populations, particularly as this virus can infect individuals already immune to classical RHDV strains. Taking advantage of intensive monitoring from 2009 to 2014 by physical captures and microchip detections of a semi-captive population of rabbits, we finely assessed the demographic impact of an initial RHDV2 outbreak that occurred in the population and identified the most affected demographic parameters. A multi-event modeling analysis revealed decreased survival in both juveniles and adults in 2011 and 2012, suggesting an RHDV2 outbreak for two consecutive years. The short-term survival benefit of vaccination against classical RHDV strains only during these years, and the recovery of carcasses with RHDV2 detection, supported this hypothesis. Variations in population vaccination coverage also explain the difference in adult survival between the two years of the outbreak. And the transient protective effect of vaccination could explain the prolonged duration of the outbreak. A brief episode of myxomatosis in 2011 seems to have had only a limited impact on the population. During outbreak years, in individuals not recently vaccinated, monthly juvenile survival crashed (0.55), and annual adult survival was three times lower than in normal years (0.21 vs. 0.69). The combination of successive juvenile and adult survival estimates for unvaccinated rabbits during the outbreak years resulted in a very low recruitment rate in the breeding population. Finally, RHDV2 outbreaks appear to have caused mortalities comparable to those caused by older classical RHDV strains and may have a strong demographic impact on wild populations of European rabbit. This work highlights the importance of long-term observational and experimental studies to better understand the impact of epidemics on animal populations.

Studies of lake ice phenology have historically relied on limited in situ data. Relatively few observations exist for ice out and fewer still for ice in, both of which are necessary to determine the temporal extent of ice cover. Satellite data provide an opportunity to better document patterns of ice phenology across landscapes and relate them to the climatological drivers behind changing ice phenology. We developed a model, the Cumulative Sum Method (CSM), that uses daytime and nighttime surface temperature observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on board the Earth-observing Aqua satellite to approximate ice in (the onset of ice cover) and ice out from training datasets of 13 and 58 Maine lakes, respectively, during the 2002/2003 through 2017/2018 ice seasons. Ice in was signaled by reaching a threshold of cumulative negative degrees following the first day of the season below 0°C. Ice out was signaled by reaching a threshold of cumulative positive degrees following the first day of the year above 0°C. The comparison of observed and remotely sensed ice-in dates showed relative agreement with a correlation coefficient of 0.71 and a mean absolute error (MAE) of 9.8 days. Ice-out approximations had a correlation coefficient of 0.67 and an MAE of 8.8 days. Lakes smaller in surface area and nearer the Atlantic coast had the greatest error in approximation. Application of the CSM to 20 additional lakes in Maine produced a comparable ice-out MAE of 8.9 days. Ice-out model performance was weaker for the warmest years; there was a larger MAE of 12.0 days when the model was applied to the years 2019–2023 for the original 58 lakes. The development of this model, which utilizes daily satellite data, demonstrates the promise of remote sensing for quantifying ice phenology over short, temporal scales, and wider geographic regions than can be observed in situ, and allows exploration of the influence of surface temperature patterns on the process and timing of ice in and ice out.

Effective management and mitigation of multiple human impacts on marine ecosystems require accurate knowledge of the spatial patterns of human activities and their overlap with vulnerable habitats. Cumulative impact (CI) mapping combines spatial information and the intensity of human activities with the spatial extent of habitats and their vulnerabilities to those stressors into an intuitive relative CI score that can inform marine spatial planning processes and ecosystem-based management. Here, we mapped potential CIs of 45 human activities from five sectors (climate change, land-based, marine-based, coastal, commercial fishing) on 21 habitats in Atlantic Canada's Scotian Shelf bioregion. We applied an uncertainty and sensitivity analysis to assess the robustness of results and identify hot and cold spots of CIs. Nearly the entire Scotian Shelf bioregion experiences the CIs of human activities, and high CIs were frequently associated with multiple stressors. CIs varied widely across habitats: CI scores in habitats >30 m deep were dominated by climate change and commercial fishing, while nearshore habitats were influenced by a much wider range of activities across all five sectors. When standardized by area, coastal habitats had among the highest CI scores, highlighting the intensity of multiple stressors in these habitats despite their relatively small spatial extent and emphasizing the importance of a multisector approach when managing coastal ecosystems. Robust hot spots of CIs (i.e., areas with high CI scores that were insensitive to alternative modeling assumptions and simulated data quality issues) occurred mostly in coastal areas where multiple high-intensity activities overlapped with highly vulnerable biogenic habitats. In contrast, robust cold spots of CI mostly occurred offshore. Overall, our results emphasize the need to consider CIs in management and protection and demonstrates that, in many areas, targeting only one activity will be insufficient to reduce overall human impact. The CI map will be useful to highlight areas in need of protection from multiple human impacts, provide information for ecological indicator development, and establish a baseline of the current state of human use in the bioregion.

The factors that enable the coexistence of closely related species remain a major question in ecology, particularly in human-disturbed habitats. The effects of anthropogenic disturbance and interspecific competition can exacerbate the decline in populations of competing species. The adoption of different strategies in responding to anthropogenic disturbances and competitive avoidances may create opportunities for competing species to coexist. However, few studies have explored how disturbance and competition interact to shape species coexistence. In this study, we conducted long-term and large-scale camera trap surveys comprising 540 sampling sites from 2017 to 2021 at Xishuangbanna, southwestern China, and deployed a spatiotemporal analysis framework to determine the effect of anthropogenic disturbances and competitive avoidances on the coexistence of three sympatric macaque species: Assamese macaque (Macaca assamensis; MA), northern pig-tailed macaque (M. leonina; ML), and rhesus macaque (M. mulatta; MM). Macaque species exhibited diverse responses to different types of anthropogenic disturbances. The occurrence probability of MM was positively associated with distance to road and relative abundance of human occurrence, and negatively associated with distance to cropland, which reduces the likelihood of sympatry between MM and the other two species due to their opposing responses to road, cropland, and human occurrence. Conversely, the similar responses to road and cropland increase the sympatry between MA and ML. Three macaque species did not avoid each other through shifting space use or their overall daily activity pattern. However, they delayed using the shared site after other species used it to avoid confrontation. We provide evidence that (1) the spatial co-occurrence pattern of sympatric macaque species was determined by anthropogenic disturbances rather than by competitive spatial avoidance and (2) fine-scale temporary avoidance is the strategy to alleviate their interspecific competition. These results enhance our understanding of the underlying mechanisms leading to species coexistence of nonhuman primates in human-disturbed habitats.

Foraging for wild resources links urban citizens to nature and biodiversity while providing resources important for local livelihoods and culture. However, the abundance and distributional (in)equity of forageable urban tree resources have rarely been examined. Consequently, this study assessed the abundance of forageable street trees and their distribution in Lagos metropolis, Nigeria. During a survey of 32 randomly selected wards across 16 local government areas (LGAs) in the metropolis, 4017 street trees from 46 species were enumerated. The LGA with the highest number of street trees was Ikeja, with 818 trees, while Lagos Island had the lowest count, with two trees. This disparity in tree numbers could be attributed to variations in human population density within each LGA. Ninety-four percent of the street trees surveyed had at least one documented use and 76% had two, making them potentially forageable. However, the most common species had relatively low forageability scores. Only 5.6% of the total street tree population was rated as highly forageable, with a usability score of at least 11 out of 15. The most forageable street trees were fruit trees and non-native species. The forageable street trees in the LGAs showed a significant disparity in their distribution, as evidenced by a Gini coefficient of 0.81. Overall, richer neighborhoods had a higher street tree abundance, richness, and forageability potential. To meet greening and foraging goals and address the current inequitable distribution, we suggest allocating more funds for greening, particularly in low-income neighborhoods. Further research should evaluate forageable species from other sites to acquire a detailed understanding of the distribution and abundance of forageable resources in Lagos metropolis.

Darwin's naturalization conundrum posits that the alien species either succeed in the introduced region because they are phylogenetically related to the native species and thus tend to have niches similar to those of native species, or they are phylogenetically dissimilar to native species and thus occupy unfilled niches. This conundrum has received a lot of attention, but the findings regarding these two hypotheses have been contradictory. To reconcile the two seemingly contradictory hypotheses, we assessed the phylogenetic relationship of a highly widespread and invasive species, Anthemis cotula L. (focal species), separately with the native species and all its co-occurring species (including native and non-native species) along an elevation gradient. Our results show that the abundance of A. cotula declined continuously with an increase in elevation and with an increase in the number of both all co-occurring and native species only. The phylogenetic distance between the focal species and the native species based on weighted mean pairwise distance (MPD_aw) declined with elevation as well as native species richness. Our study also revealed that soil nutrients strongly influence the abundance of A. cotula; however, their effect on the phylogenetic distance between the focal and other species is negligible. These findings suggest a strong role of microecological factors and spatial heterogeneity in the abundance distributions of invasive species and community assembly. Thus, it could be concluded that the phylogenetic relationship of A. cotula with co-occurring all or only native species varies with elevation and species richness, adding another layer of complexity to the resolution of Darwin's naturalization conundrum.

In recent years, motivated by widespread declines in wild bees, ecologists have prioritized learning about patterns of wild bee communities across the landscape at the expense of learning about the population-level mechanisms driving those patterns. In this essay, we seek to revitalize the tradition of studying wild bee populations in a way that both contributes key knowledge for bee conservation and builds a strong conceptual understanding of the processes underpinning bee populations. We address two widespread concerns about investing in population-level research. First, that population-level studies are too conceptually narrow to provide broad inference. If population-level studies are couched in general ecological theory, then findings from a single species can be generalized to many. We highlight how wild bees would make excellent candidates for exploring five areas of general ideas in population ecology, including nutritional ecology, drivers of vital rates, phenology and voltinism, habitat selection, and movement. Second, we address the concern that methods for studying bees at the population level are too difficult to implement. Methods for conducting population-level studies of bees—specifically, identifying living bees in the field and studying individuals throughout their life cycles—are feasible to implement at the scales appropriate for answering population-level questions, for example, a few species at a few sites. To facilitate adoption of these ideas, we developed an online field guide (www.watchingbees.com) and a detailed methods manual. More generally, we emphasize the value of linking data-rich pattern-oriented approaches in ecology with an understanding of the basic biology and mechanisms that generate those patterns.

Resource distribution, habitat structure, and predators greatly influence spatial and temporal landscape use by prey species. The “risky places” hypothesis establishes prey will proactively respond to predators' presence based on habitat cues, whereas the “risky times” hypothesis predicts prey will reactively respond by increasing vigilance in the presence of predators regardless of habitat cues. We fit a multiscale, Bayesian species interaction occupancy model with detection/non-detection data to evaluate black-tailed jackrabbit (Lepus californicus) and eastern cottontail rabbit (Sylvilagus floridanus) habitat use in the presence and absence of coyotes (Canis latrans), American badgers (Taxidea taxus), and swift foxes (Vulpes velox). We also evaluated how species-specific predator presence modified temporal activity patterns of prey. Jackrabbits decreased habitat use in areas with greater forage and opted to use areas with greater visibility when coyotes or swift foxes were present. However, cottontails used habitat in open areas with greater visibility when American badgers were present and all other predators absent, suggesting dissimilar habitat-use patterns dictated by predator-specific risks. Both lagomorph species are nocturnal with segregated peaks of activity compared with predators, suggesting fine-scale temporal use partitioning. Our results provide insights into predator–prey dynamics across heterogenous landscapes in a multi-predator system.

The two most common ecomorphs of giant kelp, Macrocystis pyrifera and Macrocystis integrifolia, exhibit almost no geographic overlap across their range in the temperate waters of North and South America, with few exceptions such as Stillwater Cove, CA, USA. However, in laboratory settings they are able to interbreed. The mechanism for the morphological variation is unknown, and whether these features are genetically fixed or malleable under different environmental conditions is unclear. Our study, for the first time, directly compared the growth, development, and morphological transformations of the two Macrocystis ecomorphs in a common garden experiment. We experimentally tested the influence of local environment on giant kelp morphology by rearing lab-cultured embryonic sporophytes from spores released by M. pyrifera and M. integrifolia sporophylls collected from multiple individuals at Stillwater Cove, CA. The spores were cultured in three treatments: “pyrifera-morph” only, “integrifolia-morph” only, and mixed (50:50 “pyrifera-morph”:“integrifolia-morph” spores). We outplanted the resultant embryonic sporophytes to concrete blocks installed at 7.5–9 m depth in the ocean and monitored the development of the sporophytes over 5 months. Our findings of distinct differences in morphology between the pyrifera-treatment and integrifolia-treatment individuals at multiple stages of development including reproductive adults indicates that the morphological differences between the two ecomorphs are genetically determined rather than environmentally induced. We found that primary stipe length and number of branches can be used as diagnostic traits for distinguishing the ecomorphs prior to the stage when adult sporophyte morphology can be definitively characterized. Additionally, no morphological hybrids were observed in the mixed-treatment, and ultimately the mixed-treatment individuals were more often categorized as “integrifolia-morph”-like than “pyrifera-morph”-like.

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.