Search Results (81)

Introduction: The global ornamental fish trade is a rapidly expanding sector and a major pathway for the introduction of non-native species, particularly in freshwater ecosystems in developed countries. The introduction of non-native species can result in a range of ecological impacts, including predation, competition, hybridization, and disease transmission, often leading to ecosystem degradation and biotic homogenization. Therefore, it represents a clear ecological risk, especially serious in freshwater systems with a high endemism rate, such as the Iberian Peninsula. The occurrence of ornamental non-native species in the Iberian Peninsula has been common, yet little has been done to describe the overall ornamental fish trade as a first step to evaluate invasion risk. Objective: This study characterizes the import dynamics of ornamental freshwater fish in Portugal between 2020 and 2024 and evaluates its potential role as a pathway for species introductions. Methodology: Data were obtained from the Institute for Nature Conservation and Forests database, including information on species composition, quantities, sizes, prices, and countries of origin. A total of 431 records were analyzed, resulting in 27,689 validated entries of imported freshwater fish, which were taxonomically verified and filtered to retain only freshwater species. Results: A total of 666 species from 88 families were identified, with an average of 380 species imported annually, reflecting high taxonomic diversity. Import volumes increased from approximately 1.25 million individuals in 2020 to 1.75 million in 2024, while total import value nearly doubled from €300,000 to €600,000. Imports were predominantly from five Southeast Asian countries, particularly Indonesia and Vietnam, and largely supported by aquaculture production (88%). A stable core of highly traded species, including Carassius auratus, Poecilia reticulata, and Paracheirodon innesi, suggests a sustained and very high propagule pressure, while some species variability was observed on yearly basis, suggesting the importance of monitoring programs on actual imports. Conclusions: Overall, the ornamental fish trade represents a significant and growing pathway for biological invasions in Portugal. The combination of increasing trade volume, high species diversity, and persistent dominance of key taxa highlights the need for improved monitoring, regulatory frameworks, and public awareness to mitigate ecological risks. Full article

Understory community diversity in urban forests is crucial for maintaining urban ecosystem functions and enhancing urban resilience, but it is threatened by rapid urbanization. Currently, there remains a knowledge gap regarding the multi-scale responses and driving mechanisms of understory community diversity along urbanization gradients, which hinders its scientific conservation and management. This study was conducted in Shanghai, a highly urbanized metropolis in China, at both plot and site scales. A total of 75 plots and 380 quadrats were established across 16 urban forest sites. Five key environmental factors were selected, including distance from the city center, visitor intensity, non-native species richness, overstory coverage, and forest area. Using taxonomic and phylogenetic diversity, regression models and null models were employed to analyze the multi-scale patterns and underlying assembly processes of understory plant communities. The results showed that the effects of environmental factors were scale-dependent, with environmental filtering as the core assembly mechanism. At the plot scale, the distance from the city center exhibited a U-shaped relationship with species richness (p = 0.005), while visitor intensity displayed a unimodal pattern with both species richness (p < 0.001) and Faith’s phylogenetic diversity (PD, p = 0.029). Increased non-native species richness intensified phylogenetic clustering (p < 0.05), and environmental filtering was the dominant process of community assembly. At the site scale, the β-diversity of non-native species drove the increase in phylogenetic the β-diversity of understory communities (p < 0.001); geographical distance had a significant positive effect on βMNTD (p = 0.002); and differences in non-native species could weaken biotic homogenization (p < 0.05). This study clarifies the multi-scale response patterns and driving mechanisms of understory community diversity and structure, providing a scientific basis for optimizing the conservation and management of understory vegetation in urban forests and enhancing urban ecosystem stability. Future work calls for long-term monitoring and broader environmental indicators. Full article

Wetlands are ecosystems with critical functions. However, the accelerated progression of global urbanization and human activities, including agricultural encroachment, has resulted in a notable decline in wetland areas and the degradation of wetland quality worldwide. Consequently, wetland restoration has become a central focus of wetland research. Plant community characteristics are among the simplest and most frequently used indicators for evaluating wetland restoration progress and are a crucial factor in maintaining the health and stability of wetland ecosystems. Therefore, this study aimed to investigate the plant community characteristics of restored wetlands with different durations of abandonment in the lower Tumen River Basin, which is expected to provide guidance for promoting the restoration of abandoned farmlands in this region. We hypothesize that species diversity decreases with increasing abandonment age, plant community composition converges toward that of natural wetlands over time, and beta diversity declines due to increasing biotic homogenization during succession. We established a chronosequence of abandoned wetlands in the lower Tumen River Basin, with sites abandoned for approximately 5, 15, and 30 years. And we use natural wetlands and paddy fields as references. With natural succession, the dominant plant species in the restored wetlands transitioned from annuals/biennials to perennials. The aboveground biomass initially increased and subsequently decreased. A gradual decline in species diversity was observed along with a further reduction in beta diversity, and the species turnover component consistently exceeded the richness difference component. The pronounced biotic homogenization among communities indicates that achieving a stable state comparable to that of natural wetlands may require considerably more time or may not be attainable solely through natural succession. Full article

This study provides an updated overview of Anthophila (wild bees and honey bees) diversity and conservation status in Algeria, explicitly distinguishing between the managed honey bee (Apis mellifera) and native wild Anthophila species. Using a systematic PRISMA-based literature analysis, more than 179 bee species have been documented across Mediterranean and semi-arid ecosystems, confirming their irreplaceable contribution to ecosystem resilience and crop pollination and beekeeping systems. The majority of Algeria’s Anthophila diversity is represented by endemic and native wild bees that sustain natural ecosystems. However, they are under growing human-caused (anthropogenic) pressures in the Anthropocene, including pressure from habitat loss and fragmentation, agricultural intensification, widespread pesticide use, and climate change. In addition, pathogenic threats such as Varroa destructor, Nosema, and associated viruses are well documented in honey bees, while evidence for their presence and impact in wild bees in Algeria remains very limited. These stressors not only weaken specialist species but also accelerate biotic homogenization dominated by A. mellifera. Recent genomic research on native honey bee populations has revealed adaptive signatures linked to immunity and social behavior, offering new opportunities for innovative conservation strategies based on molecular and genetic tools. Such insights highlight the value of preserving local strains, which may hold key traits for resilience under changing environmental conditions. To safeguard Anthophila biodiversity, this study underscores the urgent need for Algeria to implement proven conservation strategies, including habitat restoration initiatives and Anthophila-friendly farming approaches, which are common internationally but remain largely unaddressed at the national scale. By integrating cutting-edge genetic research, ecological restoration, and sustainable innovation, Algeria, with its diverse habitats and largely unexplored Anthophila fauna, holds considerable potential for advancing biodiversity conservation strategies that also support food security. However, this potential can only be realized through further in-depth research and comprehensive species inventories. Full article

Anthropogenic stressors increasingly threaten freshwater biodiversity, with fish communities particularly sensitive to habitat modification. This study evaluates how river morphological alterations influence fish assemblage structure in 114 mountain rivers of the Southern Carpathians, assessing whether such changes cause species loss or drive shifts toward disturbance-tolerant communities. Using a multi-scale analytical framework integrating non-metric multidimensional scaling, redundancy analysis, and variance partitioning, we quantified the contributions of spatial, catchment, and local habitat variables to community patterns. Spatial- and catchment-scale factors explained the largest variance in fish assemblages (12% in adults and 17% in small-bodied fish). However, morphological pressures proved significant in shaping community structure with clear ecological consequences. Weirs and embankments reduced abundances of rheophilic species (flow-dependent) by 27–38%, potamodromous by 23–42%, invertivorous by 26–49%, benthic by 40–46% and lithophilic taxa by 27–41%, indicating the loss of habitat specialists. In contrast, limnophilic taxa (preferring slow or still water) increased 25 times, phytophilic spawners by 17–41%, and tolerant species by 10%, reflecting biotic homogenization. By integrating a trait-based approach, this study highlights functional shifts that may be overlooked in species-level assessments. It underscores the need to couple local habitat restoration with catchment-scale management to conserve fish biodiversity and maintain natural ecological gradients in mountain river systems. Full article

Urban ecosystems are structurally and functionally distinct from their natural counterparts, with anthropogenic management potentially altering fundamental ecological processes such as seasonal community dynamics and impairing their sustainability. However, the mechanisms through which management filters plant diversity across seasons remain poorly understood. This study tested the hypothesis that management acts as an abiotic filter, dampening seasonal community variations and increasing biotic homogenization in urban green spaces. In this respect, through an intensive, multi-seasonal case study comparing two Mediterranean urban green spaces under contrasting management regimes, we analysed plant communities across 120 plots over four seasons. Results reveal a contingency cascade under management: while the species composition remains relatively stable (+26% variability, p < 0.001), the demographic success becomes more contingent (+41%, p < 0.001), and the ecological dominance becomes highly stochastic (+90%, p < 0.001). This hierarchy demonstrates that management primarily randomizes which species achieve dominance, in terms of biomass and cover, from a pool of disturbance-tolerant generalists. A 260% increase in alien and cosmopolitan species and persistent niche pre-emption dominance–diversity patterns also indicate biotic homogenization driven by management filters (mowing, trampling, irrigation, and fertilization) that favors species resistant to mechanical stresses and induces a breakdown of deterministic community assembly. These processes create spatially and temporally variable assemblages of functionally similar species, explaining both high structural variability and persistent functional redundancy. Conversely, seasonally structured, niche-based assemblies with clear dominance–diversity progressions are observed in the unmanaged area. Overall, findings demonstrate that an intensive management homogenizes urban plant communities by overriding natural seasonal filters and increasing stochasticity. The study provides a mechanistic basis for sustainable urban green space management, indicating that reduced intervention can help preserve the seasonal dynamics crucial for sustaining biodiversity and ecosystem functioning. Full article

Human-driven land use change and intensification is a major threat to global biodiversity. High levels of land management intensity may reduce species diversity, change the composition and structure of plant and animal communities and disrupt ecological processes. However, there is still scarce information on the impacts of land management intensity on island pollinator communities and their interactions with plants. Here, we aim to assess how different land use types (natural vegetation, semi-natural pastures, and intensive pastures), representing a gradient of grazing intensification, influence pollinator diversity and plant–pollinator interactions on Terceira Island (Azores). We surveyed 30 sites (10 per land use) and recorded 1453 visits by 41 pollinator species. Alpha diversity did not differ among land uses, but grazing intensification reduced the abundance of several native species while favoring some exotics, such as the honeybee. Network analyses showed changes in structural properties and declines in interactions between native species with increasing grazing disturbance. Introduced species, particularly the honeybee, dominated interactions in intensively managed habitats, replacing native species from key ecological roles. Our findings highlight the vulnerability of island ecosystems to grazing intensification and emphasize the need for conservation measures in the Azores, namely the reduction in grazing intensity, restoration of habitat connectivity, and implementation of pollinator-friendly agri-environmental schemes to enhance native biodiversity and sustain ecosystem services. Full article

Our study addresses how large-scale hydrological alterations shape zooplankton biodiversity in floodplain ecosystems, which are highly sensitive to changes in river connectivity. Following the operation of the Gabčíkovo hydroelectric power plant in the Danube inland delta, we examined the long-term responses of crustacean zooplankton communities, as these organisms are key indicators of hydromorphological disturbance. Based on previous evidence that river regulation often reduces habitat heterogeneity, we hypothesized that hydrological alterations in the Danube riverscape would promote increasing taxonomic and functional homogenization within sites, while simultaneously enhancing differentiation between sites over the past three decades. A total of 121 planktonic crustacean species were recorded across six monitored sites between 1991 and 2020, comprising 49 copepods and 72 cladocerans. Communities showed rising species richness, especially during the first decade of the hydropower plant’s operation. While overall richness increased, dam-induced hydromorphological changes triggered habitat-specific community shifts. In the main channel and adjacent parapotamal arm, taxonomic and functional homogenization occurred, dominated by resilient tychoplanktonic species with a gathering or secondary filter-feeding strategy. In contrast, isolated side arms experienced gradual eutrophication, favoring euplanktonic and primary filter-feeding taxa. The observed taxonomic and functional convergence within both habitat groups reflects the loss of connectivity and the cessation of artificial flooding. Full article

Studying the effects of environmental factors on microbial community assemblies is crucial for understanding microbial biodiversity and ecosystem processes. Although numerous studies have explored the spatial patterns of microbial communities in surface soils, bacterial community distributions in subsurface layers remain poorly understood. We investigated multiple community metrics of soil bacteria in arid and semi-arid grasslands in China, and the V4 region of 16S rDNA was analyzed using soil property measurements, fluorescent PCR, and high-throughput sequencing techniques. Specifically, copiotrophic taxa dominate the topsoil, whereas oligotrophic taxa are prevalent in nutrient-limited subsoil. Bacterial diversity decreases from the topsoil to subsoil, and bacterial distribution and ecological community composition exhibit a strong dependence on environmental factors. Moreover, microbial interaction networks demonstrated a progressive simplification with increasing soil depth: topsoil communities displayed higher modularity and a greater prevalence of positive interactions, whereas subsoil networks were significantly less complex. Null model analyses evidenced assembly mechanisms: deterministic processes (particularly homogeneous selection) dominated the bacterial community assembly, but their influence weakened with depth, whereas stochastic processes (e.g., dispersal limitation) increased progressively from the topsoil to subsoil. The PLS-PM analysis demonstrated that the relative influence of abiotic factors (e.g., climatic conditions and nutrient availability), biotic factors (interspecific interactions), along with drift and dispersal limitations on fungal community assembly exhibited depth-dependent patterns. This study provides novel insights into the vertical stratification of bacterial community in arid and semi-arid grasslands, and advances our understanding of pedogenic process under climate change and microbial adaptive strategies in heterogeneous soil environments. Full article

Amid declining fish diversity and human pressures in freshwater ecosystems, robust basin-scale assessments are vital for effective fisheries management. This study collated nearly four decades of fishery yields from the Pearl and Yangtze Rivers to identify conservation priorities in the Pearl River Basin. It introduced a novel cumulative effect indicator based on zeta diversity—a biodiversity pattern metric—integrated with cumulative effects analysis for management decision-making. The research employed a multi-site generalized dissimilarity model to examine the non-linear relationships between fish species composition (ζ_n) and human pressures, environmental factors, and geospatial variations across elevation gradients. The cumulative effect indicator, reflecting responses to anthropogenic stress when assessing ζ₂ (related to β diversity), helped evaluate basins for conservation or restoration needs based on their unique or homogenized biotic communities. The results suggest that ζ diversity in low-elevation sub-basins has a stronger filtering effect on ζ by human pressures than in mid- to high-elevation sub-basins, where community aggregation is more random. The impact varied with diversity aspects (nestedness vs. turnover) and zeta order. A negative correlation between cumulative effects and community uniqueness validated the novel cumulative effect indicator’s effectiveness for guiding restoration in the Pearl River Delta, potential fishing bans, and karst conservation. This approach offers a theoretical basis for prioritizing areas for freshwater fish diversity conservation and fishing restrictions in the Pearl River Basin. Full article

Urban forests are remnants of forest habitats within urban areas. Their structural alterations create stressful microclimatic conditions that can influence the morphology of sensitive plants, such as ferns. This study analyzed variations in the morphological traits of ferns in four urban forest sites in central Veracruz, Mexico, considering the microclimatic differences arising from vegetation structure. Temperature, humidity, canopy openness, and radiation were measured, along with eight foliar traits, while assessing the impact of site and habit (terrestrial or epiphytic) on the response. Sites with greater alterations in vegetation structure exhibited increased canopy openness, solar radiation, temperature, and a higher number of days with lower relative humidity. In these sites, leaves showed an increase in dry matter content and vein density, indicating a greater investment in resource storage and structural resistance. In the less-disturbed sites, terrestrial ferns demonstrated larger leaf area and specific leaf area, suggesting greater growth potential. Conversely, epiphytes generally had smaller leaves, which could represent an adaptive advantage for these species. The results also suggest a process of biotic homogenization within this plant group, reflecting a similar morphological response, except for indicator species restricted to less disturbed sites. Thus, this study reveals that microclimatic variations induced by urbanization significantly affect plant morphology and, ultimately, species diversity. Full article

Postlarval shrimp frequently face threats from acute hepatopancreatic necrosis disease (AHPND). Although AHPND affects both postlarval and adult shrimp, abiotic and biotic factors are distinct between life stages, such as rearing water nutrient levels and host life stage-dependent microbiota. The response of postlarvae-associated microbiota to AHPND, however, remains largely unexplored compared with its effects on juvenile and adult shrimp. To address this knowledge gap, a comparative analysis of postlarvae-associated microbiota and the ecological processes underlying AHPND progression was performed by sequencing the bacterial V3–V4 hypervariable region of the 16S rRNA gene. AHPND infection was validated by high copies of pirAB genes (Toxin 1) in diseased shrimp hepatopancreas. Advanced AHPND significantly altered the structure of the postlarvae-associated microbiota, with significant enrichment of Bacilli and Bdellovibrionia species in healthy larvae compared with matched AHPND-infected cohorts, although gut microbiota recovery was observed at the late disease stage, corresponding with the cessation of postlarval mortality. AHPND infection explained 11.0% (p < 0.001) of the variance in community structures, whereas postlarvae days post hatching also significantly influenced bacterial communities (7.1% variance, p < 0.001). AHPND-infected shrimp exhibited reduced homogeneous selection and increased dispersal limitation and drift governing their microbiota. These changes were primarily driven by specific microbial lineages, including enriched Bin36 Rhodobacteraceae and Bin11 Flavobacteriaceae, and suppressed Bin63 Vibrio and Bin9 Bacillus in AHPND-infected shrimp. After excluding shrimp age effect, 13 AHPND-discriminatory taxa were identified, accurately distinguishing infected shrimp from healthy individuals with 100% precision. Furthermore, AHPND outbreak weakened the network complexity and stability, which was driven by the suppressed keystone taxa that were positively associated with network robustness. Collectively, our findings deepen the understanding of the inextricable interplay between postlarval shrimp health, microbiota dynamics, and survival, as well as the underlying ecological mechanisms over AHPND progression. Full article

Species respond to environmental changes at different rates, resulting in no change, increased, or decreased resemblance among species assemblages. We explored the patterns of rate of change in bird diversity in five ecoregions of the United States across 30 years. We characterized the rate of change in breeding avian biodiversity using measures of species richness and assemblage dissimilarity, detecting changes in the same for 50% and 70% of the assemblages, respectively. Fast richness declines and species replacement were associated with rapid biotic differentiation within ecoregions, while rapid increases in richness and slowed species replacement were tied to high within-ecoregion biotic homogenization rates. Further, it was exceedingly rare for any biodiversity measured to change slowly over time; most changes were rapid. For the species assemblages studied here, changes in assemblage dissimilarity patterns were more common than changes in species richness, even though species richness has received more research attention. These results underscore the need to combine measures capturing different aspects of biodiversity (e.g., species richness and assemblage differentiation) to provide greater insight into the underlying mechanisms and pathways driving changes in biodiversity patterns. Full article

Abundant and diverse urban bird communities promote ecosystem and human health in cities. However, the estimation of bird community structure requires large amounts of resources. On the other hand, calculating remotely sensed spectral indices is cheap and easy. Such indices are directly related to vegetation cover, built-up cover, and temperature, factors that also affect the presence and abundance of bird species in urban areas. Therefore, spectral indices can be used as proxies of the structure of urban bird communities. We estimated the abundance, taxonomic, functional, and phylogenetic diversity of the bird community at each of 18 50 m radius survey stations in the urban core area of Kavala, Greece. We also calculated eight spectral indices (means and standard deviations, SDs) around survey stations at 50 m, 200 m, and 500 m spatial scales. The land surface temperature SD (LST) was the most important proxy, positively related to bird abundance at the 50 m and 200 m spatial scales. At the same time, the mean green normalized difference vegetation index (GNDVI) was the most important proxy, negatively related to abundance at the 500 m spatial scale. Means and SDs of vegetation indices, such as the normalized difference vegetation index (NDVI), enhanced vegetation index (EVI2), soil-adjusted vegetation index (SAVI), and atmospherically resistant vegetation index (ARVI), were the most important proxies, positively related to taxonomic and functional diversity at all the spatial scales. The mean and SDs of LST, normalized difference moisture index (NDMI), and normalized difference built-up index (NDBI) variously affected taxonomic and functional diversity. The mean and SDs of LST were the best proxies of phylogenetic diversity at the 50 m and 500 m spatial scales, while the SDs of NDBI and NDMI were the best proxies at the 200 m spatial scale. The results suggest that several spectral indices can be used as reliable proxies of various facets of urban bird diversity. Using such proxies is an easy and efficient way of informing successful urban planning and management. Full article

Human-driven changes in land cover and use can significantly impact species ants community structures, often leading to a decline in taxonomic diversity or species homogenization. Ant morphology, used as a proxy for ecological function, offers a valuable framework for understanding the effects of anthropogenic disturbances on ant diversity. This study explored the morphological diversity of ant assemblages in agricultural ecosystems and secondary forests in Italy and the Brazilian Amazon, analyzing how these communities are structured and adapted to different environments. The research aims to understand the ecological interactions and the role of ants in maintaining biodiversity in these contexts. The study was conducted in the Ticino River Natural Park, Italy, and the Paragominas mosaic in Pará, Brazil. The ants were sampled using epigean pitfall traps at 15 agricultural and 13 forest sites. In the secondary forests, the species richness was significantly higher in both countries compared to agricultural areas. In general, the Community Weighted Mean (CWM) of the selected traits (head length, head width, interocular distance, mandible length, eye width, Weber’s length, and tibia length) of Brazilian ants was higher than those of Italian. However, the CWM of agricultural areas of the two countries was more similar. We noticed the convex hull (i.e., the volume of an assemblage in the morphological space) of Brazilian secondary forests was still larger than Italian secondary forests when both assemblages have the same number of species. Morphological homogenization was more pronounced in agricultural settings, whereas secondary forests showed more variability, highlighting the role of environmental filtering in shaping ant communities across land use types. Full article