Ecosphere最新文献

Urban expansion and anthropogenic development result in wildlife-habitat loss and fragmentation, increased human–wildlife conflicts, and biodiversity loss across the globe. However, some animal species are well adapted to anthropogenic land use and find novel foraging opportunities or refuge from predation in urban and suburban areas. White-tailed deer (Odocoileus virginianus) are abundant in suburban landscapes throughout much of North America and persist at high densities, which causes harmful effects on surrounding plant communities. Using a large camera-trapping dataset (n = 207 camera traps over a 365-day sampling period), we quantified white-tailed deer detection rates in various anthropogenic and natural habitat types in the Cleveland Metroparks, an expansive metropolitan park system. We examined whether deer detection rates varied among habitat types during the summer forage, pre-rut/rut, winter forage, and fawning periods. We also investigated how deer detection rates varied in response to enhanced vegetation index (EVI) values and coyote detection rates during each of these periods. Throughout the year, we found that deer detection rates were greater at camera stations with an abundance of herbaceous and shrubby wetlands, low-to-moderate amounts of anthropogenically developed land use (such as residential housing areas), and herbaceous and woody developed areas (e.g., lawns, picnic areas, or sports fields). During the pre-rut/rut period, deer detection rates were greater in areas with higher EVI values, which suggests that deer may have been searching out areas with green forage as plants senesced during autumn. Deer detection rates were positively associated with coyote activity during the fawning period, which indicates that coyotes and deer were using the same areas at this time of year, or that deer were more active in an attempt to evade coyotes. We suggest that metropolitan parks will experience high deer densities that lead to degraded forest ecosystems due to foraging subsidies that are provided by adjacent residential land use and an abundance of anthropogenically modified green spaces within and around metropolitan parks.

Microbes play central roles in soil nutrient cycling; yet, a limited range of microbial community characteristics have been used to explain ecosystem nutrient cycling rates, and their importance relative to plant and abiotic factors remains unclear. In this study, we assessed which of 126 commonly measured soil fungal and bacterial community characteristics best explained net soil ammonium, nitrate, and phosphate mineralization rates in temperate forests in the Northeastern United States, as well as the relative contributions of microbial, plant, and abiotic factors. Using boosted regression tree modeling, we identified the microbial variables with the highest contributions to models explaining nutrient cycling rates: the relative abundances of ectomycorrhizal fungi and nitrogen (N)-decomposition genes from oligotrophic bacteria were the most important for net ammonification, the relative abundances of indicator taxa in bacterial networks, nitrifying bacteria, and copiotrophic bacteria were the most important for net nitrification, and the relative abundance of fungal phosphorus (P)-cycling oxidoreductase genes was the most important for net soil phosphate change. Microbial variables explained more variation than plant and abiotic variables in multivariate linear models of net nitrification and net phosphate release rates, but not net ammonification rates, which were largely explained by soil edaphic factors. Leaf litter traits were also important in explaining variation in net nitrification rates, and soil temperature was important in explaining rates of net phosphate release in soil. Collectively, our findings suggest that the N-cycling capacity of microbial functional guilds and P-cycling capacity of fungi should be incorporated into ecosystem biogeochemical models to improve our predictions and understanding of nutrient cycling and related ecological processes.

Dietary plasticity is an important trait in an increasingly dynamic world and can reveal how species respond to changes in resource availability, intra- or interspecific interactions, and landscape structure. Small-bodied carnivores occupy a unique trophic position as both consumers and prey while also filling critical roles in species interactions and provisioning of ecological services. Nonetheless, dietary patterns and factors that influence small carnivore foraging are often poorly understood, despite the ecological importance of carnivoran taxa. Here, we examined the diet and foraging of North American martens (Martes spp.), small-bodied mustelids often described as dietary generalists whose foraging patterns are assumed to be influenced by intrinsic and extrinsic factors (e.g., habitat and geography). We used complementary analyses to consider marten diet and foraging at two spatial scales: (1) regionally, using new empirical data collected in the coastal and montane forests of western Oregon and northern California; and (2) continentally, by reviewing and synthesizing previous studies of American (Martes americana) and Pacific martens (Martes caurina) across their North American distributions. Regionally, taxonomic richness and focal prey species varied among sampling sites, while forest cover and edge density had strong, contrasting effects on marten foraging patterns. Continentally, marten diet differed among coastal and interior ecoregions, but foraging did not vary substantially among studies when considering study characteristics. Martens exhibited high dietary plasticity and consumed a remarkable diversity of food items across new and synthesized data, although small mammals and birds were omnipresent prey. A diverse diet and flexible foraging, resulting in facultative variation among and within populations rather than obligate dependence on certain prey taxa, may be an important mechanism by which martens segregate niches with other carnivores or adjust to changing biotic or abiotic conditions. Our findings highlight the need to increase information on sensitive carnivore species, with particular regard to ecological and energetic requirements, to support their continued persistence.

Phytoplankton are commonly used as an ecological tool in assessing water quality and indicating ecosystem health. The purpose of this study was to explore the effects of geospatial and physicochemical variables on variation in phytoplankton community composition and biodiversity in lakes across the State of Oklahoma. We hypothesized that variation in phytoplankton communities is primarily driven by both geospatial and physicochemical variables, specifically precipitation, longitude, nitrogen, and phosphorus. To test this hypothesis, we acquired 438 surface water samples collected during a 3-year period from 109 lakes in Oklahoma through a statewide water quality monitoring program. All phytoplankton samples were counted using compound light microscopy and identified to genus level. Community data analyses were performed to assess spatial variation in community composition and whether the variation can be explained by the physicochemical and geospatial variables. We identified 106 unique phytoplankton taxa, with cyanobacteria comprising an average of 68% of the total biovolume across lakes. We also found significant relationships between phytoplankton biodiversity and urban land, chlorophyll a, electrical conductivity, water temperature, biovolume, and turbidity. The analyses identified one geospatial variable and six physicochemical variables as significantly correlated with phytoplankton community composition, suggesting that physicochemical variables are more predictive of variation in community composition than geospatial variables. Overall, we concluded that although geospatial variables were not strongly predictive of overall phytoplankton community structure, rare phytoplankton taxa (i.e., Haptophyta and Charophyta) do respond to geospatial variation while phytoplankton community composition driven by common taxa (i.e., Cyanobacteria, Chlorophyta, and Bacillariophyta) is structured by physicochemical variables. Our findings emphasize the continued need to focus on in-lake characteristics for maintaining water quality standards and preserving diverse lake ecosystems.

Ecological indicators may provide information about multi-stressor impacts, but they are often applied under hidden and untested assumptions, such as the number of stressors the indicator is sensitive to, the identity of those stressors, and the sensitivity of the indicator to individual stressors. Indicators used under false assumptions lead to perverse outcomes like failure to identify and regulate polluters. We analyzed the sensitivity of New Zealand macroinvertebrate community indicators (macroinvertebrate community index and its quantitative variant and average score per metric, hereafter, collectively, NZMCIs) to multiple stressors. We tested three assumptions: (1) NZMCIs exhibit a negative relationship with dissolved nutrients and suspended fine sediment (SFS). (2) Taxon-specific “tolerance values” (TVs), upon which NZMCIs are based, accurately characterize invertebrates' tolerances of nutrients and SFS. NZMCI TVs have been derived using professional opinion and studies with narrow spatial and temporal domains. We determined whether these TVs are positively correlated with alternative measures of tolerance—“critical tolerances” (TT_crits)—developed using national, long-term datasets and rigorous statistical models. (3) Macroinvertebrate taxa are positively co-tolerant to nutrients and SFS, such that the order of taxon-specific TT_crits for nutrients is positively correlated with that of SFS. We found little support for these assumptions. Although NZMCIs declined with increasing nutrients and SFS, the magnitude of decline was negligible, spanning only 7% of the NZMCI range observed in the data. NZMCI TVs were poorly correlated with TT_crits, so a factor contributing to the low sensitivity of NZMCIs to nutrients and SFS may be TVs that poorly reflect taxon-specific tolerances. Taxa tolerant of nutrients were not necessarily tolerant of SFS; hence, the assumption of positive co-tolerance was unsupported. Given our data and models, NZMCIs appear to be poor indicators of nutrient and SFS effects. Decision-makers concerned with nutrients and SFS impacts should interpret NZMCI data cautiously. Macroinvertebrate communities can tell us a lot about ecosystem health, but how we use them for that purpose should be more critically assessed and matched to the specific water resource problems we are trying to solve. We present suggestions for improving the means by which we use macroinvertebrate communities as ecological indicators.

A growing body of evidence links zoonotic disease risk, including pandemic threats, to biodiversity loss and other upstream anthropogenic impacts on ecosystem health. However, there is little current research assessing viral diversity in endangered species. Here, combining International Union for Conservation of Nature (IUCN) Red List data on 5876 mammal species with data on host–virus associations for a subset of 1273 extant species, we examine the relationship between endangered species status and viral diversity, including the subset of viruses that can infect humans (zoonotic viruses). We show that fewer total viruses and fewer zoonotic viruses are known to infect more threatened species. After correcting for sampling effort, zoonotic virus diversity is mostly independent of threat status, but endangered species—despite a higher apparent research effort—have a significantly lower diversity of viruses, a property that is not explained by collinearity with host phylogeography or life history variation. Although this pattern could be generated by real biological processes, we suspect instead that endangered species may be subject to additional sampling biases not captured by the total volume of scientific literature (e.g., lower rates of invasive sampling may decrease viral discovery). Overall, our findings suggest that endangered species are no more or less likely to host viruses that pose a threat to humans, but future zoonotic threats might remain undiscovered in these species. This may be concerning, given that drivers of endangered species' vulnerability such as habitat disturbance, wildlife trade, or climate vulnerability may increase virus prevalence in reservoirs and risk of spillover into humans.

Chytridiomycosis is caused by Batrachochytrium dendrobatidis (Bd) and contributes significantly to amphibian declines globally. It has affected more than 500 amphibian species on five continents. In South Asia, the Western Ghats is an amphibian biodiversity hotspot; however, the population status of anurans and their burden of chytridiomycosis are not well understood. Our aim was to understand pathogen prevalence, load, and its persistence in a stream anuran community in the Western Ghats. We carried out a capture–mark–recapture (CMR) program in five ephemeral streams of the Tillari Conservation Reserve (TCR), Western Ghats, India, from 2018 to 2020 during the early (wet) and late (dry) recovery periods. We used quantitative polymerase chain reaction (qPCR) to assign disease states: no (N), low (L), and high (H) level to every anuran, based on the Bd loads detected. We constructed population models using CMR data from skittering frogs, with Program MARK and estimated transition probability, apparent survival probability, and capture probability in each disease state. We found that the overall Bd prevalence was 74.6% in the community with an average infection load of 49–700 zoospores/swab. Many anurans cleared infections between early (wet) and late (dry) recovery periods, while some maintained high infection loads. In skittering frogs, the infection states did not influence capture probabilities and apparent survival probabilities. The transition probability between infection states was random and transitions from any disease state to low were more probable than transitions from any disease state to high or no disease states. The maintenance of a substantial burden of Bd in the anuran community with no apparent impact on their survival or capture probabilities suggests an effective pathogen transmission mechanism. As anurans continue to show a declining trend in the Asian tropics, investigation of the impacts of sub-clinical Bd infections in anurans needs impetus.

In systems where low temperatures limit plant productivity, facilitative effects of surrounding vegetation on juvenile plants may outweigh effects of competition for resources. This facilitation could occur through temperature buffering but also via increased availability of root mutualists such as mycorrhizal fungi. Climate warming could cause this balance between facilitation and competition to shift. We investigated how first-year plant performance, biomass allocation, and mycorrhizal colonization were affected by neighboring vegetation, both under ambient temperatures and under experimental warming. We planted juveniles of the grass species Festuca ovina L. (Poaceae) into an alpine tundra ecosystem in central Norway, into one of four microsite types: a moss and lichen layer, other graminoids, both groups, or neither (bare soil). Half of the microsites experienced ambient conditions and half were located within open-top warming chambers. Warming increased shoot biomass of F. ovina, but only when neighbors were not present (i.e., when planted in bare soil). Our results suggest that when abiotic stress was reduced by warming, the importance of competition among F. ovina juveniles and neighboring vegetation increased, in line with the stress gradient hypothesis. These results indicate that climate warming may shift the balance from facilitation to competition among plants in cold ecosystems, although the resource(s) competed for is (are) yet to be identified. We also found that when moss and lichen were present, planted F. ovina were more likely to form mycorrhizae, yet had a significantly lower root biomass, both absolute and relative to their total biomass. Thus, at the juvenile stage, belowground competition and/or increased mycorrhization may decrease plant root production yet without detectable benefits to aboveground growth.

Effects of large-scale flooding on forest composition and structure are a function of flood duration, depth, timing, and frequency. Throughout the Upper Mississippi River System (UMRS), floods in 1993 and 2019 were record-setting events followed by high rates of tree mortality. These events generated interest in species adaptations to flood event characteristics and how forest communities have changed in response to large-scale floods. We investigated associated tree mortality, how the floods differed spatially, and how floodplain forest communities have changed since 1993. Eight UMRS reaches were surveyed in a 1995 study, documenting vegetation species composition, size, and abundance. In 2021, a selection of plots (63%) were revisited and surveyed to quantify 2019 flood effects. For each site, we extracted daily inundation data for flood years and preceding decades from a surface water inundation model. We found post-flood mortality varied spatially and generally reflected inundation duration patterns. Lower latitude reaches experienced longer inundation durations and greater tree mortality in 1993 than in 2019, while higher latitude reaches experienced similar inundation duration and depth and similar mortality between events. Decadal inundation attributes also differed. During 2009–2018, inundation duration was greater and events occurred later than during 1983–1992 in all reaches. Most forest trajectories were Acer saccharinum-dominated and changed relatively little in species composition and structure. The greatest change in composition occurred at plots with high mortality from the 1993 flood, particularly in more flood-prone locations or where there were many small-diameter individuals. In plots dominated by either Quercus spp. or Populus deltoides, species importance shifted toward more shade and flood-tolerant species after 1995 surveys. Self-replacement of these species may be limited by a change in regeneration conditions resulting from an ongoing inundation regime shift in the case of Quercus spp., or succession to more shade-tolerant species in the case of Populus communities. Overall, effects on floodplain forests from the two flood events were heterogeneous. In some cases, forest change was likely just as influenced by shifts in flood regime as it was from singular flood events.

Lepidoptera have long been known to feed on the tears of vertebrates as a presumed source of minerals or nutrients. While this unusual behavior has been observed in a variety of species, only a single previous record has been documented outside of the tropics. Here, we present the first documentation of moths visiting the eyes of a bull moose (Alces americanus americanus), captured via trail camera in Green Mountain National Forest, Vermont, United States. We discuss the biogeography of this behavior, how it may differ between tropical and temperate climates, and its potential impact on moose health.