Loss Of Diversity Research Articles

Evaluation of the conservation value and conservation difficulty of local populations of the rare plant Viola raddeana based on genetic diversity and gene expression information using next‐generation sequencers

AbstractRare plant species identified in project areas where land is to be developed or altered may need to be extracted for ex situ conservation under human control. During ex situ conservation, it is important to minimize the impact of adverse factors including the potentially limited environmental adaptability of rare plants under cultivation and possible losses of genetic diversity due to inbreeding if the number of conserved individuals is low. Here we evaluate the conservation difficulty and genetic diversity of populations of the rare plant Violα raddeana at five sites based on harmful gene accumulation and gene duplication data gathered using RNA‐seq. Additionally, we evaluate the genetic diversity and structure of these populations using single‐nucleotide polymorphism (SNP) data acquired by multiplexed inter‐simple sequence repeat genotyping by sequencing (MIG‐seq). The results obtained indicate that the V. raddeana populations have declined but remain robust toward environmental changes and can undergo voluntary mating at all sites. Moreover, we observed clear genetic differentiation between two populations in close geographic proximity. We considered that if the majority of the remaining individuals of V. raddeana in each genetically related population were transplanted and cultivated, it would be possible to maintain their genetic diversity through ex situ conservation. It is important that V. raddeana be kept under ex situ conservation management. In order to achieve this, we should work with public organizations such as local government agencies and botanical gardens.

Genomic exploration of Thuja plicata indicates no loss of diversity from adults to offspring in UK Woodlands

Thuja plicata is a conifer tree that is valued for its cultural, ecological and wood quality features in its natural range in western North America and is used in Europe as an exotic timber species. It is increasingly used in mixed species forests in the UK that are managed using natural regeneration, raising questions about genetic diversity of both the adult trees and offspring of the species in these stands. We studied population structure and genetic diversity in four UK woodlands of both adults and naturally regenerated offspring of T. plicata. We discovered 194,154 Single Nucleotide Polymorphisms (SNPs) using Genotyping-by-Sequencing (GBS) and retained 655 SNPs across 598 genome sequence scaffolds for analysis. The majority of these scaffolds included only one SNP, suggesting that; the selected SNPs were widely distributed within the genome. We found many monomorphic sites, most of which were restricted to adults in a single woodland, indicative of a genetic differentiation among woodlands. We found three ancestral populations (K = 3) and low levels of admixture across the four sites, indicating that the starting materials were largely from single populations. Estimates of genetic diversity using heterozygosity (Ho) and nucleotide diversity (π) were low (overall Ho = 0.174, π = 0.00226) across all sites but slightly higher in juveniles at two sites. Our genotyping methods and results on standing genetic diversity in this important conifer provide insight into the ability of planted woodlands in the UK to face environmental shifts and disease threats.

Local- and Regional-Scale Climate Variability Drives Complex Patterns of Growth Synchrony and Asynchrony in Deep-Sea Snappers Across the Indo-Pacific.

Climatic variation can play a critical role in driving synchronous and asynchronous patterns in the expression of life history characteristics across vast spatiotemporal scales. The synchronisation of traits, such as an individual's growth rate, under environmental stress may indicate a loss of phenotypic diversity and thus increased population vulnerability to stochastic deleterious events. In contrast, synchronous growth under favourable ecological conditions and asynchrony during unfavourable conditions may help population resilience and buffer against the negative implications of future environmental variability. Despite the significant implications of growth synchrony and asynchrony to population productivity and persistence, little is known about its causes and consequences either within or among fish populations. This is especially true for long-lived deep-sea species that inhabit environments characterised by large-scale interannual and decadal changes, which could propagate growth synchrony across vast distances. We developed otolith growth chronologies for three deep-sea fishes (Etelis spp.) over 65° of longitude and 20° of latitude across the Indo-Pacific region. Using reconstructed time series of interannual growth from six distinct Exclusive Economic Zones (EEZs), we assessed the level of spatial synchrony at the individual-, population- and species-scale. Across five decades of data, complex patterns of synchronous and asynchronous growth were apparent for adult populations within and among EEZs of the Pacific Ocean, mediated by shifts in oceanographic phenomena such as the Pacific Decadal Oscillation. Overall, our results indicate that the degree of synchrony in biological traits at depth depends on life history stage, spatiotemporal scales of environmental variability and the influence of ecological factors such as competition and dispersal. By determining the magnitude and timing of spatially synchronous growth at depth and its links to environmental variability, we can better understand fluctuations in deep-sea productivity and its vulnerability to future environmental stressors, which are key considerations for sustainability.

Comparative efficacy of essential oils against Cutibacterium acnes: effect upon strains from phylotypes with different virulence patterns

Despite being a commensal of human skin, Cutibacterium acnes plays an important role in the pathogenesis of Acne vulgaris, with the loss of bacterial phylotype diversity being related to disease progression. This study evaluated differences in the virulence profile of C. acnes strains from different phylotypes and investigated the possible phylotype-selective efficacy of essential oils (EOs) from Thymus x citriodorus (TC), Thymus mastichina, and Cistus ladanifer compared to Melaleuca alternifolia (tea tree), focusing on both planktonic and biofilm growth forms, the latter being related with pathogenesis and treatment resistance. One collection strain and seven clinical isolates were classified into phylotypes using multiplex-touchdown PCR. Virulence trait differences across phylotypes were evaluated by studying antibiotic resistance, biofilm formation, porphyrin production, and lipase activity. EOs were tested for minimum inhibitory/bactericidal concentrations (MIC/MBC) and effects on biofilm biomass and metabolic activity. Strains from phylotype IA1 were higher biofilm and lipase producers than phylotype II strains. Regarding EO's efficacy, TC EO presented lower planktonic MIC values for all strains compared to the other EOs, presenting a smaller difference in MIC values across phylotypes. TC EO was able to similarly reduce biofilm biomass and metabolic activity in phylotype IA1 clinical strains, being effective at lower concentrations compared with the remaining EOs. Not all virulence traits were phylotype-related, highlighting the multifactorial nature of the disease. TC EO showed a relevant anti-acne potential, outperforming tea tree EO (a species with a commercial claim for Acne vulgaris) against both planktonic and biofilm growth forms of C. acnes.

Plant diversity loss has limited effects on below‐ground biomass and traits but alters community short‐term root production in a species‐rich grassland

Abstract Many biodiversity–ecosystem functioning (BEF) experiments have shown enhanced productivity with biodiversity, often explained by niche differentiation and complementarity effects. Yet, most of these results are based on artificial plant assemblages, with a major focus on above‐ground productivity. Consequently, our comprehension of the BEF relationship in natural ecosystem and for below‐ground functions remains largely unknown. In this study, we simulated a long‐term non‐random species loss in a naturally diverse temperate meadow. We created a richness gradient spanning from 1 to more than 20 species per plot, removing the rare and sub‐ordinate species from the vegetation. After 3 and 6 years of experimental manipulation, soil cores were collected to investigate the effects of species removal on below‐ground biomass, vertical distribution of roots and root traits. We also used ingrowth cores to quantify the short‐term root production of plant communities. We investigated the consistency of below‐ and above‐ground responses to species removal. Consistent with above‐ground responses, species removal had little effect on root biomass and community root traits, except for a decrease in biomass in the uppermost soil layer (0–5 cm) found only after 6 years. Similarly, the vertical distribution of root biomass and traits was largely unaffected by diversity loss, suggesting little evidence for vertical niche differentiation. Nevertheless, species loss decreased the root production in spring (3 months), albeit this lower short‐term root production was diluted after a year, when monocultures of dominants almost matched the annual root production of controls. Synthesis. Our results from a non‐random species removal experiment revealed minimal impact of a realistic diversity loss on root biomass and traits, but a decrease in short‐term fine root production. These results challenge traditional BEF theory and the niche differentiation hypothesis, suggesting that dominant species primarily determine below‐ground biomass structure and characteristics. High diversity may only temporarily increase short‐term root production.

Guideless Artificial Life Model for Reproduction, Development, and Interactions.

Reproduction, development, and individual interactions are vital yet complex natural processes. Tierra (an ALife model proposed by Thomas Ray) and cellular automata, which can manage these aspects in a complex manner, are significantly limited in their ability to express morphology and behavior. In contrast, the virtual creatures proposed by Karl Sims have a considerably higher degree of freedom in terms of morphology and behavior. However, they also exhibit a limited capacity for processes like reproduction, development, and individual interactions. In addition, they employ genetic algorithms, which can result in a loss of biological diversity, as their implementation necessitates predefining a fitness function. Contrarily, the evolution of natural life is determined by mutation and natural selection, rather than by a human-defined fitness function. This study carefully extracts the characteristics of these models to propose a new Artificial Life model that can simulate reproduction, development, and individual interactions while exhibiting a high expressive power for morphology and behavior. The model is based on the concept of incorporating Tierra and cellular automata mechanisms into a cell that moves freely in 3-D space. In this model, no predefined fitness function or form that qualifies as a living creature exists. In other words, this approach can be rephrased as searching for persistent patterns, which is similar to the approach of Conway's Game of Life. The primary objective of this study was to conduct a proof-of-concept demonstration to showcase the capabilities of this model. Guideless simulation by the proposed model using mutation and natural selection resulted in the formation of two types of creatures-dumbbell shaped and reticulated. These creatures exhibit intriguing features, exploiting the degrees of freedom inherent to the proposed model. Particularly noteworthy is their unique method of reproduction, which bears a striking resemblance to that of real organisms. These results reinforce the potential of this approach in modeling intricate processes observed in actual organisms and its ability to generate virtual creatures with intriguing ecologies.

434. Reduced Gut Microbiome Diversity and Compositional Characteristics are Associated with Postoperative Infection in Heart Transplant Recipients

Abstract Background The human microbiome has been linked to important clinical outcomes, including postoperative infection. Loss of diversity has been associated with drug resistant organism colonization, infection, immune defenses, epithelial barrier integrity, and death. The microbiome’s role in postoperative infection among heart transplant (HT) recipients remains poorly understood.Table 1Clinical CharacteristicsTable 1 Clinical Characteristics: Characteristics noted by number and percent or mean and Standard Deviation where appropriate. Abbreviations: ICM – Ischemic Cardiomyopathy; NICM – Non-ischemic cardiomyopathy; CKD – Chronic Kidney Disease; COPD – Chronic Obstructive Pulmonary Disease. Methods Stool microbiomes for 121 HT recipients were determined by metagenomic sequencing. Infections occurring in the first 100 days following transplant were aggregated. Infection was defined as the presence of a compatible clinical syndrome and a positive test result via culture, PCR, serology, or imaging. To determine if infection risk was related to stool microbiome composition, samples at the time of transplant were shotgun sequenced and taxonomy was determined using MetaPhLan 4. Alpha diversity was measured by inverse Simpson, beta diversity was measure by Bray-Curtis dissimilarity.Table 2:Infection Microbiology and Diagnoses Results Average age at HT was 53.6 years and 73% were male, and the cause of heart failure in 71% was nonischemic cardiomyopathy. 194 infections occurred among 72 (60%) patients (Table 2). The most common infections were pneumonia, bloodstream, surgical site, and urinary. Most infections were caused by bacteria, specifically Enterobacerales and Enterococci. (Table 2) Stool microbial Alpha diversity was lower in patients who developed infection; p=0.0026. (Figure 1) Stool microbiome composition also differed significantly between groups. Patients with postoperative infection experienced more single species expansions, most notably Enterococcus and Enterobacterales, which were common etiologies of infection. (Figure 2) Uninfected patients had more abundant obligate anaerobic taxa including Bacteroidetes, Lachnospiraceae, and Ruminococcaceae.Figure 1Alpha and Beta Diversity of Stool Microbiota: A. Stool microbiome alpha-diversity by inverse Simpson p= 0.0026 Wilcoxon. B. Stool microbiome beta-diversity by PcoA Bray-Curtis Dissimilarity p=0.026 PERMANOVA. Conclusion The stool microbiome of HT patients with postoperative infection is marked by lower alpha diversity and notable compositional differences including Enterococci and Enterobacterales expansion coupled with reduced Bacteroidetes, Lachnospiraceae, and Ruminococcaceae. Further study into the interaction between these organisms and the host are needed to better understand their role in infection. Disclosures All Authors: No reported disclosures

Global meta-analysis shows action is needed to halt genetic diversity loss.

Mitigating loss of genetic diversity is a major global biodiversity challenge1-4. To meet recent international commitments to maintain genetic diversity within species5,6, we need to understand relationships between threats, conservation management and genetic diversity change. Here we conduct a global analysis of genetic diversity change via meta-analysis of all available temporal measures of genetic diversity from more than three decades of research. We show that within-population genetic diversity is being lost over timescales likely to have been impacted by human activities, and that some conservation actions may mitigate this loss. Our dataset includes 628 species (animals, plants, fungi and chromists) across all terrestrial and most marine realms on Earth. Threats impacted two-thirds of the populations that we analysed, and less than halfof the populations analysed received conservation management. Genetic diversity loss occurs globally and is a realistic prediction for many species, especially birds and mammals, in the face of threats such as land use change, disease, abiotic natural phenomena and harvesting or harassment. Conservation strategies designed to improve environmental conditions, increase population growth rates and introduce new individuals (for example, restoring connectivity or performing translocations) may maintain or even increase genetic diversity. Our findings underscore the urgent need for active, genetically informed conservation interventions to halt genetic diversity loss.

High-fat diet promotes gestational diabetes mellitus through modulating gut microbiota and bile acid metabolism

IntroductionGestational diabetes mellitus (GDM) is a condition characterized by glucose intolerance during pregnancy, estimated to affect approximately 20% of the whole pregnancies and is increasing in prevalence globally. However, there is still a big gap in knowledge about the association between gut microbiota associated metabolism alterations and GDM development.MethodsAll the participants accomplished the validated internet-based dietary questionnaire for Chinese and serum, fecal samples were collected. HFD, control diet or colesevelam intervention was fed to GDM mice models or Fxr-/- mice models, with or without antibiotics cocktail treatment. Fecal microbiota transplantation were used for further validation. Gut microbiota and metabolites were detected by metagenomic sequencing and high-performance liquid chromatography-mass spectrometry, respectively. Bile acids of serum, fecal samples from human and mice were analysised. Body weight, average feed intake, blood glucose, insulin levels and oral glucose tolerance test was performed among each groups. Expression levels of Fxr, Shp and Fgf15 mRNA and protein were detected by quantitative reverse transcription polymerase chain reaction and western blot, respectively.ResultsOur data indicated that high fat diet (HFD) was linked with higher prevalence of GDM, and HFD was positively associated with poor prognosis in GDM patients. Moreover, compared with normal diet (ND) group, GDM patients from HFD group performed a loss of gut microbiota diversity and enrichment of Alistipes onderdonkii, Lachnospiraceae bacterium 1_7_58FAA, and Clostridium aspaaragiforme while ruduction of Akkermansiaceae, Paraprevotell xylaniphila, and Prevotella copri. Additionally, HFD aggravated GDM in mice and gut microbiota depletion by antibiotics crippled the effect of excess fat intake. BAs profile altered in HFD GDM patients and mice models. Fecal microbiota transplantation (FMT) further confirmed that gut microbiota contributed to bile acids (BAs) metabolic dysfunction during HFD-associated GDM development. Mechanically, HFD-FMT administration activated Fxr, Shp, and Fgf15 activity, disturbed the glucose metabolism and aggravated insulin resistance but not in HFD-FMT Fxr−/− mice and ND-FMT Fxr−/− mice. Furthermore, colesevelam intervention alleviated HFD-associated GDM development, improved BAs metabolism, suppressed Fxr, Shp, and Fgf15 activity only in WT mice but not in the Fxr−/− HFD + Colesevelam group and Fxr−/− HFD group. HFD induced GDM and contributed to poor prognosis in GDM parturients through inducing gut microbial dysbiosis and metabolic alteration, especially appeared in BAs profile. Moreover, Fxr pathway participated in regulating HFD-associated gut microbiota disordered BAs metabolites and aggravating GDM in mice.DiscussionModulating gut microbiota and BAs metabolites could be a potential therapeutic strategy in the prevention and treatment of HFD-associated GDM.

Multiple mechanisms associated with loss of seed bank diversity under nitrogen enrichment

Abstract The soil seed bank is a hidden community below‐ground and a crucial component of plant biodiversity. Nitrogen (N) enrichment can reduce plant species diversity both in above‐ground plant communities and seed banks. However, the mechanisms by which N enrichment affects soil seed banks are not clear. We investigated the direct and indirect mechanisms of N enrichment in soil seed banks in an N addition experiment in an alpine meadow on the eastern Tibetan Plateau. We combined above‐ground plant community and litter data, fungal diversity, seed bank surveys and seed rain monitoring, and conducted a seed burial experiment to explore seed viability. We found that the rate of loss of species diversity was slower in seed banks than in above‐ground plant communities. N enrichment directly affected seed banks by decreasing seed viability and enhancing seed germination. Furthermore, small seeds were more prone to loss of viability and increased seed germination under N enrichment than large seeds. At the same time, N enrichment also indirectly decreased seed bank species richness and number of seeds by altering the composition of the plant community and by increasing the amount of litter and fungal diversity. N enrichment also indirectly decreased number of seeds in seed banks through decreasing number of seeds of seed rain, with increasing negative effects due to higher levels of N enrichment. Synthesis. Our results provide novel insights into multiple direct and indirect mechanisms that can lead to loss of plant diversity in seed banks under N enrichment, with important ramifications on the maintenance of plant biodiversity, ecosystem resilience and restoration in N‐enriched systems.

New Data Indicate Larger Decline in Morphological Diversity in Split-Footed Lacewing Larvae than Previously Estimated

Modern insect decline sparks interest in similar declines of the past. Neuroptera, the group of lacewings, has been suggested to have undergone decline after the Cretaceous, and quantitative studies of larval morphology have supported this view. One of the groups within Neuroptera seeing a major decline is that of split-footed lacewings, Nymphidae. We here report 13 new larval specimens of split-footed lacewings from about 100-million-year-old Kachin amber, Myanmar. We explore how enlarging the data set to 60 specimens and expanding the investigated morphological structures affect the recognition of decline. The expanded data set has an increased morphospace, indicating a lack of saturation. The decline is, therefore, likely even larger than so far anticipated for Nymphidae. The study of head and mouthparts provides the strongest signal for a loss of diversity, which is feasible due to the direct coupling to feeding ecology. Analysis of the trunk region cannot recover a signal for loss of diversity. Sampling issues play a role here: the trunk of the larvae is less often well preserved, and the fossil larvae are more likely in early developmental stages due to the constraints of preservation.

Lived heritage and local cultures: depopulation in Slovakia

ABSTRACT Although there has been a steady increase in population growth in the last two centuries, scholarly and public discussions express concerns about the decline of population vitality and the loss of cultural diversity in many areas of the world. These demographic processes are associated with various forms of development stagnation well observed in several areas of Europe. The age structure of the population in certain areas is distorted, the opportunities for revitalisation are limited, existing social, well-being and education infrastructure are weakened. In some peripheral regions of Slovakia, we witness a kind of vicious circle, when the area is trapped in a cycle of cumulative causation. Two case studies (Stará Halič, Ľuboreč) and effects of depopulations are shown on the local processes of declining reproductive behaviour, disintegration of kinship relationships, limitations of cooperation and reciprocity, changes and reduction of the cultural transfer of knowledge, stability and innovation. From the perspective of anthropology and historical demography, depopulation has a considerable impact on the sustainability of local cultural diversity in Central Europe. We focused on the vitality of cultural heritage to transmit rural housing lifestyle and ecosystem services that make landscape and local culture sustainable.

The Root of All Evil: Money as the Common Driver of Climate Change and Loss of Diversity

The Root of All Evil: Money as the Common Driver of Climate Change and Loss of Diversity

Domestication During Restoration: Unintentional Selection During Eight Generations of Wild Seed Propagation Reduces Herkogamy, Dichogamy and Heterozygosity in Clarkia pulchella.

Seed production on native seed farms has increased to meet the rising demand for plant material for restoration. Although these propagation efforts are necessary for restoration, cultivating wild populations may also result in unintentional selection and elicit evolutionary changes that mimic crop domestication, essentially turning these efforts into artificial domestication experiments. Here, we investigated whether phenotypic and genomic changes associated with domestication occurred in the wildflower Clarkia pulchella Pursh (Onagraceae) by comparing the wild source populations to the farmed population after eight generations of cultivation. At the phenotypic level, the farmed population shifted towards a floral morphology associated with self-pollination, with a significant decrease in both dichogamy and herkogamy. At the genomic level, > 6500 SNPs revealed that mean expected heterozygosity of the farmed population was significantly lower than the wild populations, despite the fact that the farmed population originated from a pool of multiple wild populations. Both the shift towards a selfing phenotype and the loss of diversity are expected consequences of domestication, although the phenotypic shifts in particular occurred much more rapidly than has been observed for other domestication traits. We discuss these results in the context of plant domestication and the implications for retaining the genetic integrity of wild populations during the process of seed production for restoration.

Consanguine Marriage Leads to Hierarchical Imbalance of ABO and STR Frequency and Affects the Genetic Diversity

Consanguinity marriages pose a serious social issue for civil society, leading to genetic syndromes, depression, and imbalanced ABO blood types and STR frequencies. Analyzing dermatoglyphics in regions with prevalent consanguineous marriages can establish a correlation with ABO frequency. Consanguineous marriages complicate forensic DNA analysis due to re-duced genetic diversity. Inbreeding within a closed, small population tends to accelerate the loss of genetic diversity and decrease the heterozygosity of genes, ultimately leading to complete homozygosity, fixation of rare alleles, and potential misidentification in inbred populations. Fo-rensic investigations require careful consideration of population structure. Short Tandem Repeat (STR) profiling is effective but should be complemented with population-specific databases, ad-ditional genetic markers, and advanced statistical methods to address the effects of inbreeding. Understanding the genetic nuances in inbred populations can enhance the accuracy and reliability of DNA profiling.

Evaluating historical changes in a mussel bed community in northern California

Marine foundation species are increasingly impacted by anthropogenic stressors, driving a loss of diversity within these critical habitats. Prior studies suggest that species diversity within mussel beds has declined precipitously in southern California, USA, but it is unclear whether a similar loss has occurred farther north. Here, we resurvey a mussel bed community in northern California first sampled in 1941 to evaluate changes in diversity after 78 years. More broadly, we explore the value and potential challenges of using imperfect historical data to assess community changes. Our 2019 survey documented 90 species/taxa across 10 phyla. The majority of species (~ 72%) were common to all replicate plots, suggesting that variation in species diversity over small spatial scales was unlikely to mask temporal changes. In contrast to results from southern California, we observed no decline in species diversity between timepoints. However, there were shifts in species composition, with an increase in the abundance of southern species and a decrease in northern species, consistent with warming observed at a nearby shoreline site. Overall, our findings are an encouraging sign for the health of this mussel bed community in northern California and illustrate how non-traditional data can contribute to assessments of long-term ecological change.

A complex interplay between natural and anthropogenic factors shapes plant diversity patterns in Mediterranean coastal dunes

ContextA long history of human colonisation has profoundly altered Mediterranean coastal dunes, as well as their capacity of providing ecosystem services important for human well-being. The provisioning of these services depends on the integrity of the dune system, which is formed and maintained by coastal plant communities. Analysing the drivers of plant diversity is thus crucial for preserving Mediterranean coastal ecosystems.ObjectivesWe investigated the influence of natural factors, anthropogenic activities and shoreline dynamism on different facets of plant diversity, i.e. species richness and the proportion of typical and ruderal species. Moreover, we examined whether natural and anthropogenic factors act as direct or rather indirect drivers of the loss of dune plant diversity.MethodsUsing 20 cm resolution orthophotos, we mapped a wide Mediterranean coastal landscape and obtained a set of variables describing the distribution, abundance and size of natural (coastal dune habitats) and anthropogenic (urban areas and tourism facilities) patches. From the orthophotos, we also quantified the shoreline dynamism (coastal erosion and accretion) occurred in the area over a 10-year period. We then analysed how dune plant species richness, as well as the proportion of typical and ruderal species, related to the landscape variables and shoreline dynamism. Also, using piecewise structural equation modelling, we investigated the complex interplay between landscape variables and shoreline dynamism in shaping coastal plant diversity patterns.ResultsWhen focusing on plant species richness, we found no evidence of a negative effect of anthropogenic activities (urbanisation and tourism) on the diversity of coastal vegetation. However, analysing typical and ruderal plant species revealed that the latter were favoured under human-related disturbance, while typical species of the foredune decreased in areas subject to high anthropogenic pressure. Results of the structural equation models highlighted that shoreline dynamism indirectly affected dune plant diversity through its influence on the landscape configuration.ConclusionsOur results indicate that (i) looking only at plant species richness can lead to underestimating the impact of anthropogenic activities on coastal dune vegetation; and (ii) that human-related activities change the composition of dune vegetation, eventually promoting the establishment of ruderal species. Finally, results show that coastal erosion acts as an indirect driver of plant diversity loss.

Reassembly of Disturbed Forests Portends Climate Resilience but Diversity Loss

Shifting species distributions in response to climate change are leading to community reassembly worldwide. Given the importance of forests to the global carbon cycle, reassembly in forests may have important impacts on ecological functioning. Yet, how climate and disturbance jointly influence reassembly has yet to be reconciled. We combined U.S. Forest Service Forest Inventory and Analysis data with a process-based model to explore how reassembly impacts biodiversity and biomass in Eastern USA forests, which constitute > 59% of the USA forest carbon sink. Because regenerating communities provide a window into future assemblages, we first examined changes in seedling and sapling density from 2003 to 2021. We then investigated reassembly by quantifying changes in community climate associations and species richness along gradients of disturbance. Finally, we integrated empirical results with SORTIE-ND simulation models to estimate future forest biomass and quantify the lag time between current regeneration and future biomass along disturbance gradients. Though seedling densities declined between 2003 and 2021, disturbed forests had higher seedling regeneration rates and accelerated community reassembly. Species with warmer climate associations responded favorably to disturbance, resulting in a higher proportion of warm-adapted species. Yet, declining sapling densities in disturbed forests were not sufficient to keep pace with overstory mortality, ultimately leading to reduced future biomass with increasing disturbance severity. Reassembly coincided with higher seedling richness and lower adult richness. These findings highlight that disturbance contributes to forest climate resilience by creating recruitment opportunities for warm-adapted trees, but at a cost for biodiversity and productivity.

The Dead Internet Theory: A Survey on Artificial Interactions and the Future of Social Media

The Dead Internet Theory (DIT) suggests that much of today’s internet, particularly social media, is dominated by non-human activity, AI-generated content, and corporate agendas, leading to a decline in authentic human interaction. This study explores the origins, core claims, and implications of DIT, emphasizing its relevance in the context of social media platforms. The theory emerged as a response to the perceived homogenization of online spaces, highlighting issues like the proliferation of bots, algorithmically generated content, and the prioritization of engagement metrics over genuine user interaction. AI technologies play a central role in this phenomenon, as social media platforms increasingly use algorithms and machine learning to curate content, drive engagement, and maximize advertising revenue. While these tools enhance scalability and personalization, they also prioritize virality and consumption over authentic communication, contributing to the erosion of trust, the loss of content diversity, and a dehumanized internet experience. This study redefines DIT in the context of social media, proposing that the commodification of content consumption for revenue has taken precedence over meaningful human connectivity. By focusing on engagement metrics, platforms foster a sense of artificiality and disconnection, underscoring the need for human-centric approaches to revive authentic online interaction and community building.

Contrasting ecological mechanisms mediate the impact of land conversion on ecosystem multifunctionality

Abstract Land use/cover (LULC) changes have unequivocally affected biodiversity and ecosystem functioning, with enormous repercussions for human well‐being. However, the mechanistic ecological mechanisms underlying the impact of land conversion on ecosystem multifunctionality (EMF) remain insufficiently examined from the perspective of multiple biodiversity attributes in dryland regions with increasing deforestation rates. We investigated how the conversion of natural forests and savannas to agroforestry parklands alters the relationships between multiple biodiversity attributes (taxonomic, functional, phylogenetic and structural) and EMF, while accounting for the effects of environmental factors in the dryland landscapes in Benin. We used forest inventory data from 145 plots spanning forests, savannas and agroforestry parklands and assessed the implications of three land conversion scenarios. We quantified EMF using eight functions that are central to primary productivity and nutrient cycling. We found that EMF was positively related solely to structural diversity in forests. The conversion of forests and savannas to agroforestry parklands decreased EMF both directly and indirectly. The indirect effects were mediated by two contrasting biodiversity effects. When forests were converted to agroforestry parklands through savannas, indirect effects were driven by shifts in functional composition towards the dominance of species with acquisitive traits. In contrast, species diversity reduction explained the indirect effects when savannas were converted to agroforestry parklands. The aridity index and soil texture influenced biodiversity attributes, but not EMF. The present study provides evidence that the biodiversity–EMF relationship is dependent on the LULC type and was evident only in the natural ecosystem through the effects of structural diversity, thereby emphasizing the importance of enhancing structural diversity for promoting EMF in forests. Our findings also demonstrate that land conversion weakened natural EMF through biotic homogenization resulting from two contrasting biodiversity‐related mechanisms, including loss of species diversity and dominance of species with acquisitive resource‐use strategy. Read the free Plain Language Summary for this article on the Journal blog.