Community Ecology最新文献

Understanding the complexity of food webs is crucial for assessing ecosystem dynamics. However, the high number of trophic interactions in typical food webs complicates the identification of clear top-down or bottom-up regulatory effects. In this study, we applied interaction asymmetry analysis to examine causality within food webs, allowing for the identification of critical interactions based on topological importance (TI) metrics, which incorporate indirect interactions. We evaluated this method using 34 food web models from the Ecobase database and compared its performance with widely used network metrics. By constructing asymmetry graphs, we transformed original, undirected binary food webs into directed networks highlighting strong causal interactions. Pairwise correlation analyses revealed that ecosystems with higher total biomass indicated stronger bottom-up causal links and greater consumer diversity. Our findings suggest that asymmetry-based metrics provide robust quantitative indicators of causality, offering a straightforward yet powerful tool for assessing ecosystem functioning and health.

Supplementary information: The online version contains supplementary material available at 10.1007/s42974-025-00267-0.

Shrub encroachment into grassland ecosystems has been increasingly observed and documented worldwide in recent years. A grass–shrub transition can affect the diversity, abundance and functional integrity of grassland plant communities and understanding the drivers behind these processes is therefore crucial. While potential environmental drivers are often investigated, the role of spatial patterns of neighbouring shrub density in local shrub encroachment has been less well studied. The aim of this study is to investigate the relative role of neighbouring shrub density and topography as potential key drivers of shrub encroachment in a typical montane grassland ecosystem in New Zealand. We used the SPOT (Satellite Pour l’Observation) 6/7 multispectral imagery captured on one day in 2013 and in 2017 to calculate recent changes in shrub/grass cover during this period. Using the Normalised Difference Vegetation Index (NDVI), we classified the study area into grassland and shrubland and quantified the extent and change in these two land-cover types over the study period. We then investigated the relationships between changes in land cover and neighbourhood shrub density, elevation and aspect. Between 2013 and 2017, there was an overall shrubland increase of + 0.35% of the study area per year, and grassland decrease of −0.43% per year. Locations at which any change in vegetation type occurred were more likely to be at mid-elevation (c. 600–1,000 m a.s.l.) and on west-facing slopes. Highest shrub expansion rates were observed on areas that were on warmer, north-facing slopes and at elevations below 900 m a.s.l.; this is consistent with areas below the pre-human, natural treeline which is estimated to be at very similar elevations. We found a marked threshold in the degree to which neighbourhood shrub density correlated with local shrub encroachment: local shrub encroachment only occurred when shrub cover in the neighbourhood exceeded 40% and peaked at c. 60% indicating the potential for a sudden grass–shrub regime shift once shrub cover reaches a certain level. Our study provides new evidence from the Southern Hemisphere of a measurable and interacting effect of topography and neighbourhood shrub density on recent shrub encroachment rates in montane grasslands even over short time periods.

The ecoregion of the Nebraska Sandhills is the largest intact temperate grassland in the world and is impacted by climate change, specifically drought. Despite the well-established role microorganisms play in ecosystem functioning, little is known about microbial community diversity and assembly processes in the Sandhills. To address this gap of knowledge, we examined microbial communities in three habitats (prairie soils, lake sediments, and lake water) across four lake basins ranging in alkalinity (pH 7–11) over two years (October 2020 and 2021). Replicate soil, sediment, and water samples were characterized for bacterial and microbial eukaryotic communities with 16S and 18S rRNA metabarcoding. Analyses for alpha diversity, community composition, and assembly processes were examined with general linear models, β-NTI (nearest taxon indices) analyses, Mantel tests, and modified Hubbell’s neutral models. Overall, diversity and composition varied by habitat type and lake basin regardless of organismal identity or year. Community assembly processes varied by habitat type as well as by organismal identity, but not by year. However, the role of deterministic selection and stochastic dispersal of individual taxa (i.e., OTUs) was interannually variable. Finally, the prairie soil communities were identified as a reservoir for bacterial diversity and the lake sediment communities as a target group for potential monitoring of the effects of climate change in the western Nebraska Sandhills.

Understanding the determinants of beta diversity patterns is important in ecology and conservation. However, few vertebrate studies have been conducted in landscapes with relict vegetation formed by historical natural processes. For birds, only similarities between relicts and surrounding habitats or other relicts were assessed. Here, we evaluated the determinants of bird beta diversity patterns in a landscape with relict vegetation in the Guasayán mountain range, Dry Chaco ecoregion, northern Argentina. In this landscape, a relict of humid forest develops on the humid slope, whereas dry forests typical of the Dry Chaco develop on the dry slopes and piedmont. These habitats, which harbor three bird communities, differ in their representativeness of the region. We evaluated if the environmental differences among habitats determine bird beta diversity at the local scale (species replacement hypothesis). We found a significant correlation between habitat characteristics and bird communities, a lower bird beta diversity between the most similar habitats, a dominance of species turnover over nestedness, and a species turnover dominated by birds closely associated with the Dry Chaco and humid forests. These findings support the species replacement hypothesis. As other forest relicts, this relict evidences that, in the long-term, an isolated habitat fragment can undergo the loss of species closely associated with that habitat, while maintaining a distinctive bird community in the region. Thus, at the local scale, relicts are important for conservation management, and at the biogeographic scale, they indicate the risk of the extinction of species closely associated with particular habitats.

The current trend of biodiversity deterioration in rural systems is a complex issue that operates across multiple spatial scales. Agroforestry practices have the potential to positively contribute towards addressing these trends by shaping the structure of agricultural landscapes and their underlying ecological functions. This study aims to test a multi-scale analytical approach to understand and account for these processes. Specifically, the study seeks to assess the contributions that agroforestry practices at the farm scale can make towards supporting biodiversity, in response to the wider-scale landscape eco-mosaic structural and functional challenges and requirements (both at the local and extra-local landscape systems). To achieve this, a series of landscape ecology analyses are conducted on an agroforestry-based rice farm located in the western Po Plain region of Northern Italy. These analyses examine various landscape structural traits (such as matrix composition, patch size, shape complexity, and diversity indices) and functional traits (including connectivity and bionomic indices), with different levels of detail for each scale of analysis. This allows for the evaluation of the current ecological status of both the extra-local and local scale landscape systems (including drivers of vulnerability and resilience) and the assessment of the farm's current contributions to biodiversity support. Based on these findings, strategic agroforestry interventions are identified at the farm scale to enhance its capacity to address the wider-scale ecological gaps. Two design scenarios are assessed, wherein functional ecological traits such as landscape diversity, connectivity, and ecological stability are improved. The results confirm the role of farm scale agroforestry management as a buffering tool, demonstrating how it contributes to the restoration of broader-scale landscape vulnerabilities. The applied approach provides cost-effective assessments of biodiversity-related ecological processes, with the accuracy of the findings dependent on the comprehensive multi-scale analysis conducted.

Aim

The study of islands biotas is fundamental to understand biodiversity patterns and process, both on evolutionary and ecological time scales. This study explores the influence of biogeographic and climatic factors on island species–area relationships (ISARs) in volcanic and continental islands, aiming to detect differences in slopes and intercepts between these island origins.

Methods

Data from 5049 vegetation plots on 58 Central Mediterranean Sea islands were collected from various sources. Islands were categorized as volcanic or continental based on their geological origin. area, isolation, maximum elevation, eccentricity, mean annual temperature and annual precipitation were calculated for each island. By using a moving window, we created groups of islands, and ISARs were fitted to each group using the Arrhenius power functions. Linear models and a permutation test were employed to examine how ISAR model parameters varied with the above-mentioned variables.

Results

While ISAR intercept values did not differ between island origins, volcanic islands showed higher ISAR slopes than continental islands. Whereas increasing island isolation and mean annual temperature increased ISAR intercepts on continental islands groups, it decreased on volcanic ones. Increasing annual precipitation decreased ISAR intercept on continental islands groups and increased on volcanic islands groups. Increasing island isolation, eccentricity and mean annual temperature increased the ISAR slope on volcanic islands groups while increasing annual precipitation decreased it. Increasing maximum elevation increased ISAR slope on continental islands groups.

Main conclusions

Our study provides evidence about the importance of island geological origin in determining the observed ISAR patterns. Biogeographic and climatic factors are pivotal in shaping species richness patterns on islands, exerting varying influences on both volcanic and continental islands.

Crinoids of the Order Comatulida are renowned for harboring a remarkable diversity of symbiotic organisms within echinoderms, including polychaetes, myzostomids, gastropods, crustaceans, brittle stars, or fish. Crinoids provide essential services to their symbionts, such as shelter, access to food resources, mating areas, nesting grounds, and nurseries. Symbionts within crinoids developed a variety of strategies, including foraging in the arm ambulacral grooves, preying upon other symbionts, living within galls, or accessing suspended food particles from the water column. In this work, we focused on the Great Reef of Toliara, where we collected specimens from seven crinoid species. Among the 84 crinoids examined, a total of 285 symbiotic organisms were retrieved. These symbionts were either moving freely on their host or found within cysts. Stable isotope analyses of carbon and nitrogen for both hosts and symbionts have shown that (a) all crinoids shared a common trophic niche; (b) a community-based approach indicated that crinoids initiated trophic networks primarily based on suspended particulate organic matter; (c) non-specific symbionts exhibited consistent dietary preferences regardless of their host; (d) myzostomids inhabiting cysts were found to feed on their host tissues; and (e) free-moving symbionts displayed divergent trophic niches linked to their predatory, kleptoparasitic, or filter-feeding behaviors. This research underscores the role of crinoids, particularly comatulid species, as key components of tropical ecosystems in the Western Indian Ocean, inhabited by a hidden biodiversity with complex trophic networks. Their intricate morphology accommodates a range of feeding strategies, supporting a diverse associated fauna.

This study aimed to assess the ecological health of a RAMSAR site lake by leveraging diatoms as ecological indicators. Utilizing six trophic and four saprobic indices, we evaluate the lake's ecological status. Monthly samples were collected from five sites between June 2014 and May 2015. Our findings revealed that the lake exhibited hypereutrophic characteristics according to TN and TP concentrations, as well as trophic state indices, except TIDL. Notably, the TI_VD index showed a significant correlation with TN and TP, while SI_Sla correlated significantly with TN. Despite the substantial organic matter load, our analysis positioned the lake at a beta mesosaprobic level with moderate ecological status across three saprobic indices. Interestingly, the annual average dissolved oxygen (DO) concentration classified the lake water as Class I in terms of water quality. The moderate saprobic index values suggest efficient organic matter oxidation, potentially influenced by high DO concentrations in the lake littoral. Our study underscores the importance of integrating trophic and saprobic indices to comprehensively evaluate ecosystem health and ecological status in shallow eutrophic lakes, offering insights into nutrient enrichment and organic pollution load, respectively.

Palo Laziale Wood is a relatively small biotope (129 ha) situated along the coast of the Metropolitan Area of Rome, Lazio region, Italy. Despite being one of the region's remaining patches of an ancient oak floodplain broad-leaved forest, it conserves numerous priority habitats and species of high conservation interest. The vegetation consists mainly of Turkey oak stands with small temporary ponds and flooded meadows. The forest underwent a dieback in 2003, triggered by a significantly hot and dry summer. In 2018, an ecological restoration project (LIFE PRIMED LIFE17 NAT/GR/000511) was initiated to restore Palo Laziale’s ecosystems. This paper presents the methodological approach employed to assess the vegetation ecology of a degraded forest ecosystem. Such an investigation was a key component of the Adaptative Restoration Plan of the Project. It provided the baseline necessary for designing and calibrating the planned direct conservation actions on the target habitat types (91M0: Pannonian-Balkanic turkey oak-sessile oak forests, 3170*: Mediterranean temporary ponds, 5230*: Arborescent matorral with Laurus nobilis, etc.) and establishing reference values to enable long-term monitoring. Plant taxa comparison from 1 ha square-grid sampling and multivariate analyses were carried out to group species and identify environmental and Ellenberg-based drivers. Six ecologically distinct units were found, eventually confirming the distinctive ecological heterogeneity of Mediterranean ecosystems. Amongst these, the hygrophilous vegetation has resulted to be the one mainly affected by the dieback outbreak. Due to the high heterogeneity, introduced by the massive tree mortality, the method of regular 1 ha squares turned out to be a reliable alternative to random vegetation sampling plots (e.g., phytosociological relevés) to disentangle ecological patterns of fragmented and disturbed habitats.

Tropical coastal environments, notably the southern Gulf of Mexico, are recognized for their rich biodiversity and productive habitats, with key areas being the Terminos Lagoon Flora and Fauna Protected Area (TLFFPA) and the Los Petenes Biosphere Reserve (LPBR). This study, spanning 1985–2011, presents an environmental overview and fish abundance analysis across five zones. Variation has widened, especially in salinity: zone I = 23.4–34.5 to 19.1–36.2; zone II = Palizada-Del Este 0.4–7 to 0.2–2.6, Chumpam-Balchacah 2.6–26.6 to 8.2–34.3, Pom-Atasta, 2.2–19.8 to 0.3–1.6, and Candelaria-Panlau 2.4–18.2 to 1.8–21.9; zone III = 17.4–33.7 to 11.9–25.5; zone IV = 33.5–39.4 to 29.8–41.3. Species richness reached 194, and density (ind/m²) declined in most zones over the years: zone I = 47.8%; zone II = Candelaria-Panlau 74.4%, Chumpam-Balcahcah 22%, Palizada-Del Este 31%, and Pom-Atasta 9.5%; zone III = 61.5%; and zone IV = 32.5%. Coastal ecosystems, dynamic and shaped by diverse forces, face ongoing changes due to human activities, notably in the western region (zones I–III). Temperature and salinity changes lead to reduced density, biomass, and a shift in the composition of dominant species. Evidence supports the notion that introducing invasive species into rivers displaces or diminishes native species. Despite being a Natural Protected Area, the Terminos Lagoon faces intense human activity tied to the fishing and oil industries. In contrast, the LPBR maintains a low impact and a positive conservation status. The study stresses the need for continuous monitoring, especially for TLFFPA, deemed critical for additional information and effective management. Simultaneously, the LPBR should be monitored with adherence to the environmental development plan.