Acta Oecologica-International Journal of Ecology最新文献

The endangered plant clay phacelia (Phacelia argillacea) is endemic to Spanish Fork Canyon, Utah, USA. In addition to habitat loss and abiotic stressors, herbivory is one of clay phacelia's major threats, but negative effects of herbivory have not been quantified. To examine the effects of simulated herbivory by small mammals, we grew 300 clay phacelia plants in a greenhouse (20 replicates of 15 half-sibling families). After six months of growth, half of the plants were randomly assigned to a defoliation treatment that mimicked herbivory from ground squirrels. After providing additional time for growth and natural pollination, we collected seeds and harvested shoots and roots from a subset of the plants. Among the 15 half-sibling families, we found significant genetic variation in shoot mass and a significant correlation between total mass when defoliated and undefoliated, suggesting a strong genetic component to growth. Defoliation significantly reduced seed production, shoot production and root production by 29%, 32%, and 35%, respectively. For these traits, interactions between family (F) and defoliation (D) were not statistically significant, suggesting fixation for tolerance to herbivory. In contrast, for root-to-shoot ratio, there was a statistically significant F × D interaction, revealing genetic variation for tolerance to herbivory. Depending on the type, intensity, and timing of herbivory, clay phacelia may benefit from either increased allocation to shoots or to roots. In fact, tolerance in terms of reproduction was correlated with shoot mass when defoliated, while tolerance in terms of growth was correlated with root mass when defoliated.

Striped skunks (Mephitis mephitis) are widespread generalist mesocarnivores that occur in a variety of habitats and are often associated with anthropogenic environments. They are also highly persecuted by humans, however, due to their noxious smell and propensity to carry disease. Consequently, the species is relatively understudied and there is still much unknown about the factors that affect their occurrences. To determine the probability of use patterns of striped skunks at the local (within 100 m) and landscape (within 1 km) scales, we deployed 46 and 54 motion-activated cameras between Dec 2021–Jun 2022 and Nov 2022–May 2023, respectively, across sites throughout the state of Illinois. We used an a priori, hypothesis-based approach to model striped skunk occupancy. The best local-scale probability of use model included road density and urban edge (w = 0.79), suggesting an avoidance of roads and selection for the interfaces of urban environments by skunks. The best model at the landscape scale included the interaction of housing density and coyote (Canis latrans) relative abundance (w = 0.31), describing a spatial niche differentiation among coyotes and skunks in urban settings compared to rural environments. Overall, our results suggest the primary drivers of striped skunk use in Illinois are anthropogenic features, but there exists a nuanced relationship, confirming the species’ designation as synanthropic misanthrope. Meanwhile, humans may mediate shifts in space-use patterns among sympatric mesocarnivores due to an expansion and divergence of ecological niches, resulting in reduced spatial overlap and competitive pressures among species.

Ant-attendance of aphids is one of the subjects of interest in ecological studies as a reciprocal service providing benefits to both groups involved. The behavioural patterns in this relation depend on many factors, e.g. biology of the species involved, aphid host plants, activity of natural enemies and abiotic factors. In this respect, the circadian pattern of ant-attendance was almost unknown. The paper presents the results of the pattern of such circadian activity of ants Lasius niger and L. emarginatus attending six aphid species (Panaphis juglandis, Aphis grossulariae, A. urticata, A. umbrella, Myzus persicae and Aphis fabae) feeding on various types of plants and having various dependence of trophobiosis. The highest number of ant workers in aphid colonies was observed at night and dawn, while the lowest was just after solar noon. The circadian pattern of ant activity strongly depends on the weather, especially temperature and relative humidity, with the highest abundance of ants during humid and cool weather. The possible interconnection between the temperature-dependent activity of ants and the water-dependent physiological condition of certain plants is discussed and indicated as an explanation. The issue of possible work division among ant workers attending aphids as an explanation of the observed pattern of activity remains open.

The increase of size and connectivity of forest fragments positively affect bird species number. Here we investigated if variations in the topography, which create valley bottoms and upland areas within the forest fragment, could be also a driving factor. We argue that topography has implications for conservation because forest fragments with higher proportion of valley bottoms could harbor higher bird species number, independently of fragment size. We estimated the number of bird species in 25 forest fragments of Atlantic Forest in southern Brazil. We also mapped the area of valley bottoms in each forest fragment to calculate the percentage of the valley bottom area in relation to the total area of each forest fragment. The results indicate: (1) the percentage of valley bottom area is not correlated with the total area of the forest fragments; and (2) the number of bird species increase with increasing the proportion of bottom valley area and did not respond to total area. These findings suggest the proportion of valley bottoms in a forest fragment is relevant and important for higher species number. Also, high humidity levels in valley bottoms may contribute to enhancing the resilience of forest fragments against the mounting challenges posed by the increasing incidence of forest fires and prolonged dry seasons, a trend intensified by the ongoing effects of climate change. Conservation actions in the studied region should focus on the expansion of the current network of protected areas by combining the inclusion of forest remnants with high proportion of valley bottoms and the restoration of valley bottoms in existing protected areas. Indeed, creating of corridors to connect valley bottoms of forest fragments via riparian forest can improve overall habitat quality.

There is limited information available regarding metabolic rates (MR) in many species or life stages of turtles. I measured MR (as O₂ consumption) in fasted hatchling snapping turtles (Chelydra serpentina) at 5–25 °C. The relationships between temperature and MR (per capita and per gram wet body mass) were exponential and linearized by Log₁₀ transformations. The relative change in MR over a 10 °C range (Q₁₀) varied with the ranges of temperatures compared and ranged from Q_{10, 15 to 5} = 3.6 to Q_{10, 25 to 15} = 9.6 to 9.9, for per capita and per gram values, respectively. The high Q₁₀ values observed here demonstrate reductions in metabolic activity with declining temperatures that typically exceeded predicted values. Such a strong thermal dependence of MR suggests a rapid response to seasonal changes, facilitating energy conservation during cooling periods and growth during warmer periods in this temperate reptile.

Context

During European settlement, Illinois grasslands were converted for agricultural purposes. Remaining natural areas in southern Illinois include natural xeric forest openings, with communities representative of remnant grasslands and adjacent hardwood forests. Previous research in these openings shows plant communities are driven by edaphic conditions.

Objectives

The first objective aimed to characterize spatial scale and autocorrelation structure of these openings based on climatic, environmental, and diversity variables. The second objective was to predict taxonomic, phylogenetic, and functional turnover between 1988 and 2019, using climatic and environmental variables.

Methods

Surveys were conducted to calculate taxonomic, phylogenetics and functional trait metrics and analyses of these dimensions of diversity. Randomization tests were used to assess phylogenetic and functional clustering and over-dispersion at each site. Spatially-explicit climatic and environmental variables were included from earlier surveys and data repositories. Global Moran's I and spatial autocorrelograms were used to assess spatial structure of climatic, environmental, and diversity variables and generalized dissimilarity modeling was used to characterize taxonomic, phylogenetic, and functional turnover based on environmental variables.

Results

Soil depth was the only environmental variable which exhibited significant global spatial autocorrelation. Overall, sandstone sites were phylogenetically over-dispersed while loess sites were phylogenetically clustered. Climate variables and diversity metrics exhibited significant spatial structure during surveys. Generalized dissimilarity models showed that geographic distance between openings was the most influential driver of turnover across surveys.

Conclusions

Previous glacial events explained the spatial structure of soil depth across sites, due to Quaternary loess deposition in loess sites. High diversity values were clustered in the southeastern portions of the study area. Functional generalized dissimilarity models best predicted turnover in these openings compared to taxonomic and phylogenetic models.

The Seasonally Dry Tropical Forests (SDTF), distributed from Mexico to northern Argentina, are habitat to a unique biodiversity. Among these forests, the Caatinga stands out, occupying a large part of the Brazilian Northeast and is subject to cycles of anthropic disturbance and abandonment of exploited areas. Understanding how microbial communities respond to environmental changes is crucial, especially considering the various ecosystem services provided by microorganisms. Among soil microorganisms, arbuscular mycorrhizal fungi (AMF) play a significant role in the maintenance of terrestrial ecosystems. In this study, we aimed to evaluate the structure, composition, and distribution of AMF assemblages, as well as their main drivers, in regeneration areas of the Caatinga. Soil samples were collected in the Catimbau National Park (Pernambuco State), including an old-growth forest representing undisturbed areas, and in early, intermediate, and late regeneration areas. The composition of AMF assemblages differed among regenerating areas and old-growth forest, but their distribution is not related and conditioned to plant assemblages. Instead, soil properties and rainfall are the main factors structuring these assemblages in SDTF. A total of 83 taxa of AMF were identified. Glomus and Acaulospora, which exhibit respectively ruderal and stress-tolerant life strategies were the most abundant genera. The highest number of unique AMF species was recorded in the old-growth forest, contrasting with the late regeneration areas which had the lowest number. The results showed that deterministic processes (soil and rainfall) are structuring the AMF assemblages in areas under regeneration process in SDTF. Plants and AMF do not recover simultaneously over the evaluated regeneration times.

The breeding performance of predators is influenced by the differential consequences of prey density, prey biomass and effective consumption rates. Using camera traps at nests, we investigated whether changes in prey abundances caused functional and/or numerical responses of the common buzzard (Buteo) in a Mediterranean woodland region. After determining 1150 prey delivered to the nests by adults, we found that the biomass of prey caught was not a good indicator of its influence on individual life history traits such as productivity. Indeed, the consumption of small mammal prey, despite representing only 11% of the biomass delivered, had a much greater influence on buzzards' productivity than the consumption of snakes, which made up 47% of the biomass delivered. Live trapping evidenced that small mammals were roughly preyed according to its availability in the field, and their abundance in spring was directly related to buzzards' productivity and inversely related to hatching dates. Small mammals – mostly mice – can be considered as very suitable prey, owing quick handling times, profitability, and high energy intake. Our results pointed out the relevance of mice on buzzards' breeding performance, and altogether with the outstanding role of open-land small mammals on buzzards' demography during autumn-winter, suggested a key role of small mammals on buzzards’ ecology throughout the year cycle in the Mediterranean area studied. These findings have important implications for our understanding of the foraging strategies of generalist species and the role that habitat and environmental factors play in shaping them.

Perennials has been proposed as new crops because their root syndrome offers more ecosystem services and a better use of resources than the annual one. Objective: To compare the ontogenetic trajectory of root syndromes of annual (P. gracilis and P. angustifolia) and perennial (P. pinetorum and P. mendocina) species of Physaria (Brassicaceae) and their root trait relationships.

Results and Conclusion

Roots became conservative as plants grew, independently of the life cycle of the species. However, perennials invested initially more resources in increasing storage capacity (bigger and thicker roots) while annuals favored increasing the exploration capacity (higher SRL). During first anthesis we found tradeoffs between acquisitive and conservative traits, as expected according to the Root Economic Spectrum (RES), but after the first year, those tradeoffs disappeared and perennials were able to combine a thick and deep taproot and high investment in C reserves with some well-developed acquisitive traits such as higher SRL and total length. This suggest that root traits should be selected during the second year, when no tradeoff exist. Differences between annuals and perennials in most structural taproot traits remained constant along the ontogenetic trajectory, thus the relative position of species in the RES did not change over time. We found a gradient of root strategies supported by the RES theory: from acquisitive in the annual P. gracilis (high SRL, STD and total length) to conservative in the perennial P. mendocina (high root biomass, root diameter, tissue density and storage) with intermediate strategies in P. angustifolia and P. pinetorum.

The capability of plants to modify phenotypic characteristics through interactions with the environment can contribute to functional stability, particularly when this plasticity influences traits associated with survival, rendering it a pivotal mechanism for adaptation. Grime's CSR theory is employed to classify plants based on functional traits dictating competitive, stress, and ruderal tolerance strategies, as these traits serve as indicators of plant responses to environmental stimuli. This study examines the variation in plant functional traits (morphophysiological and phytochemical) within herbaceous communities across a chronosequence of natural regeneration after land-use alteration and abandonment. We investigate whether a correlation exists between regeneration duration and community-weighted mean values through principal component analysis and canonical correspondence analysis. Intraspecific variability of traits is assessed using one-way ANOVA and Tukey's post-hoc test at a significance level of 5% for mean comparisons. Generally, with progressing regeneration, intraspecific differences emerge, including elevated carbon:nitrogen ratio, phenolic compounds, and carbon assimilation, alongside reductions in leaf area, plant height, leaf succulence, individual biomass, and leaf nitrogen content. Consequently, pasture and initial regeneration communities harbor species with functional traits akin to ruderal species, whereas species inhabiting later stages exhibit traits associated with competitors. Analysis of intraspecific variation demonstrates that species occupying sites at different regeneration stages exhibit phenotypic plasticity. The findings underscore how alterations in environmental conditions during natural regeneration influence functional trait values, and underscore the utility of CSR theory for quantifying, comparing, and predicting community structure based on adaptive plant strategies.