We herein constructed a phylogeny of Lepidoptera synthesizing multiple information types, a phylogenomics backbone, a multigene supermatrix with species-comprehensive DNA barcodes, and topological information from a compiled database of standardized machine-readable trees from over 100 previous studies. We then applied the new phylogenetic synthesis as a profiling framework for a large DNA barcode dataset of caterpillars from a tree diversity experiment. The synthesis phylogeny comprised 11,001 species. Phylogenetic information content was taxonomically skewed towards butterflies (i.e., Nymphalidae, Papilionidae and Pieridae), and parts of Macroheterocera (Geometridae, Sphingidae, Saturniidae and Bombycidae), while undersampling of Lepidoptera species diversity was present in Erebidae, Noctuidae, Gelechioidea and Pyraloidea. Caterpillar Phylogenetic Diversity (PD) increased with tree richness in the diversity experiment regardless of processing choices in calculating caterpillar PD, including whether calculated on plot OTU alone, plot OTU placed onto a simple reference phylogeny or plot OTU placed to the comprehensive reference phylogeny. Stronger correlations between tree diversity and uncorrected Faith's PD of caterpillars were observed where OTU were placed onto the full reference tree, and where long branch OTU were removed prior to PD calculation, though no significant differences in the strength of the tree diversity effect across context and processing choice were observed for standardized PD. In calculation of plot-level PD, focus should remain on community sample size, with the results herein supporting the use of any available reference phylogeny as context, though correspondence of PD indices to environmental gradients might be stronger where plot OTU can be placed to a comprehensive reference phylogeny. The phylogeny presented herein enables inference of varied evolutionary information for Lepidoptera DNA barcode sets.

Deadwood is a crucial component of forest ecosystems. Its decay can be influenced by decomposer insects and their interactions. In turn, these insects and their competitive behaviour can respond to tree diversity effects on forest structure and microclimate. However, such responses are still understudied, especially in early forest successional stages when insect communities are beginning to develop. Working in the largest forest biodiversity-ecosystem functioning experiment worldwide in South-East China, we studied how tree diversity influences deadwood-associated insects in their deadwood colonisation, species richness and community structure. Working on 300 plots covering a tree diversity gradient from 1 to 24 species, we searched for ants, termites and beetles in coarse woody debris pieces (CWD, diameter > 7 cm) during two summer seasons (2023 and 2024). We found insects in 383 out of 1355 CWD pieces across 196 plots, including 25 species of ants, 14 species of termites and only nine of beetles. Tree diversity increased the diversity of saproxylic insects, but these effects were mediated by differences in the biomass of fine woody debris (FWD, diameter < 7 cm) across plots. The colonisation of CWD was primarily related to the volume and diversity of CWD itself. The diversity of ants was associated with the biomass of fine woody debris (FWD, diameter < 7 cm), while the diversity of termites related to CWD diversity. However, the strongest driver of richness in both ants and termites was a negative association between each other. This was reflected in consistent negative co-occurrences between dominant ants and termites, as well as among termites. In young forests, tree diversity can already indirectly influence deadwood-associated insects through the accumulation of FWD. Environmental filtering sets the conditions for colonisation and overall richness through deadwood availability and diversity, while biotic competition further structures communities within these constraints.

Abstract Saproxylic insect community assembly is structured by deadwood and forest habitat gradients, as well as biotic interactions such as competition, predation, and parasitism. However, co-variation between abiotic and biotic conditions limits our ability to disentangle their contributions. Furthermore, a focus on beetles in temperate and boreal forests has left important taxonomic and geographic knowledge gaps. Here, we tested how experimentally manipulated tree diversity, deadwood position (lying vs. standing), and biotic interactions with a dominant antagonist (ant exclusion) structure communities of deadwood-cavity-nesting bees, wasps, and their parasitoids in a subtropical forest. Lying deadwood supported less diverse and abundant communities than standing deadwood while retaining approximately twice as much moisture. Moreover, host emergence declined along moisture gradients within each deadwood type. Together, these patterns identify substrate moisture as an important factor limiting bee and wasp communities nesting in deadwood – reflecting reduced brood production, survival, or both – and as a candidate driver for their positive association with standing deadwood in forests. By contrast, neither ant exclusion nor observed ant occurrence was associated with host or parasitoid responses. Because standing deadwood is typically scarce in managed forests, our findings support retaining or creating standing deadwood structures alongside lying deadwood and, more broadly, promoting dry and elevated nesting substrates for cavity-nesting bees and wasps in conservation and restoration measures. Graphical abstract

Biodiversity loss can destabilize ecosystem functioning. How biodiversity–stability relationships are interlinked across trophic levels remains poorly investigated, however, limiting our ability to predict ecosystem-level consequences of declining biodiversity. Here, we analyze the drivers of multi-year herbivore community stability—as a key connector between primary producers and higher trophic levels—and its coupling with host tree diversity and growth stability along a subtropical tree diversity gradient. Phylogenetic diversity, abundance asynchrony and population stability of herbivores emerge as key intra-community regulators of herbivore temporal stability. These regulators, in turn, are strongly affected by changes in tree species richness through tree functional diversity, tree growth asynchrony, and tree growth population stability. Importantly, accounting for herbivore dietary specialization unveils clear stabilizing effects of tree species richness on the community stability of specialists but not of generalists. For the overall herbivore community, higher tree richness results in less stable abundance dynamics. Our findings suggest that biodiversity loss will propagate bottom-up to affect the stability of communities at higher trophic levels, and particularly destabilize communities of more vulnerable specialists. Global change and plantation management may thus also compromise biodiversity conservation by reducing abundance and species richness stability of higher trophic levels. The stability of interactions across trophic levels is crucial for ecosystem resilience but remains poorly understood. This study shows that loss of tree diversity destabilizes specialist herbivores, offering new insights into the mechanisms of pest outbreaks.

Wild bees are widely distributed and effective pollinators, yet they face significant threats such as degradation of forests. Forest restoration has been advocated as a strategy to mitigate these threats and stabilize biodiversity. However, there is a lack of understanding of the ecological consequences of forest restoration on bee diversity, particularly regarding interactions with tree diversity and microenvironment. Using data from the world's largest tree diversity experiment (BEF-China), this study examines how tree species richness, canopy cover, understorey vegetation, and microclimatic conditions affect bee diversity in the context of forest restoration. Our analysis of bee diversity data (8341 individuals from 79 species) revealed that these biotic factors had distinct effects on three dimensions of bee diversity. Specifically, canopy cover had a negative effect on bee taxonomic diversity but a positive effect on phylogenetic and functional diversity. However, these patterns were reversed when the cover of understorey vegetation was accounted for. Moreover, tree species richness exerted an indirect influence on bee diversity through understorey microenvironment. Our findings provide nuance into how tree species richness shapes bee communities via vegetation cover and microclimate, which is informative on habitat characteristics in forest restoration and conservation that better enable the safeguarding of pollinators.

Ecological stability is essential for maintaining ecosystem functioning, but may be imperiled by biodiversity loss. Although the scaling of diversity-stability relationships from populations to communities and metacommunities has been studied within single trophic levels, it remains poorly understood when considering interactions between trophic levels. Here, we utilize data collected from a large-scale forest biodiversity experiment to investigate the scaling of temporal stability from populations, to communities, and meta-communities in a plant-herbivore system, allowing us to disentangle the relative role of top-down and bottom-up regulation. We observe that biodiversity has generally stabilizing effects within and between trophic levels. Specifically, species diversity of herbivores shows strong stabilizing top-down effects by enhancing species stability and asynchrony of plants that cascade to higher levels of organization. In contrast, bottom-up effects play a much smaller role. Our study therefore highlights the importance of top-down processes in safeguarding plant stability across levels of organization, while simultaneously providing a framework that allows the investigation of the multi-layered nature of stability mechanisms that needs to be considered for a successful and sustainable ecosystem management.

Biodiversity loss threatens the multifunctionality of ecosystems on which human well-being ultimately depends. Multitrophic species interactions may be key to explaining the ecological consequences of biodiversity loss, but research explicitly linking species interactions and ecosystem multifunctionality remains rare. To fill this gap, we synthesize data from a large-scale biodiversity experiment established in 2009 in subtropical China that manipulates tree species richness (1-24 species). We integrate 11 types of antagonistic and mutualistic species interaction networks, and 34 ecosystem functions associated with a diverse set of species and trophic levels. Our analysis highlights that characterizing the structure of species interaction networks is invaluable for assessing interaction-mediated biodiversity effects and underlying mechanisms. Positive effects of network size align with expected benefits of multitrophic diversity for ecosystem multifunctionality. Positive effects of niche overlap among interacting species and negative effects of highly connected species (i.e. high linkage density) reveal additional, interaction-mediated drivers. The effects of niche overlap suggest benefits of functionally similar species, and the effects of linkage density underscore the importance of specialized interactions in promoting ecosystem multifunctionality. These findings emphasize that ecosystem service provisioning does not only rely on biodiversity across trophic levels, but to a similar degree on how species interact.

Abstract Interactions between plants and pollinators are crucial for maintaining biodiversity and ecosystem stability. Bees, especially wild and solitary bees, play a vital role in this process. However, the mechanisms underlying the relationship between multiple components of plant diversity and cavity-nesting bee diversity remain unclear, particularly in understudied subtropical forests. This study investigated how plant phylogenetic diversity (PD), functional diversity (FD), and specific leaf morphological-chemical traits influenced solitary bee diversity in a large-scale biodiversity experiment in subtropical China. We sampled solitary bees using trap nests across a tree diversity gradient. Results showed that plant leaf area (LA) and leaf dry matter content (LDMC) positively influenced bee species richness, while plant PD and FD had no significant effects. Our findings highlight the importance of specific plant traits over broad diversity metrics in supporting bee diversity and abundance, suggesting that conservation efforts should prioritize functionally diverse plant assemblages rather than maximizing species counts.

Biodiversity-ecosystem functioning (BEF) research has shown that ecosystem functioning and stability are closely linked to biodiversity. A cornerstone of this field is the BEF-China research platform, i.e. the world’s largest forest biodiversity experiment in subtropical China. It has demonstrated that tree diversity enhances productivity, carbon sequestration and ecosystem stability. However, the strength of these positive tree diversity effects varies widely across forests, possibly because higher trophic levels (such as herbivores and predators) mediate how biodiversity influences ecosystem functioning.To better understand how tree diversity influences higher trophic levels and their contributions to forest functioning, the German Research Foundation (DFG) is funding the project MultiTroph. MultiTroph quantifies species interactions and integrates them into food webs to understand when and why ecosystem functions change or destabilise with species loss. We expect that trophic interaction networks reveal how species share or separate their ecological roles, with more niche overlap in species-rich forests and more niche specialisation in species-poor forests.Here, we outline our conceptual framework and research goals. We are convinced that MultiTroph will expand existing BEF research and provide a more holistic understanding of the role of multi-trophic food webs in forest ecosystems.

Deadwood availability and turnover are fundamental for forest ecosystem functioning, affecting biodiversity and carbon storage. Identifying their drivers already at early forest successional stages is central to restoration and management, yet the effects of tree diversity on deadwood dynamics remain unclear, especially in the subtropics. We evaluated how tree species richness and identity influence accumulation and decay of deadwood in an early successional stage forest working in a large-scale tree diversity experimental platform in subtropical South-East China covering a tree species richness gradient spanning from monocultures to 24-species mixtures. Naturally occurring deadwood was assessed as volume of coarse woody debris (CWD, diameter > 7 cm) and mass of fine woody debris (FWD, diameter < 7 cm). Plots with higher tree species richness produced more FWD and showed reduced inter-plot variability in deadwood accumulation, suggesting that tree species richness is already shaping dead wood dynamics in early successional stages. Stand productivity, however, predicted deadwood accumulation more strongly than richness per se. Instead, decomposition was mainly associated with canopy closure rather than with plot-level tree species diversity or identity. These results indicate that in early successional stages tree diversity and productivity may already set the foundation for future forest structure and carbon cycling, with implications for ecosystem resilience and predictability of deadwood pools in later successional stages. From a management perspective, combining species-rich planting with targeted inclusion of productive species can accelerate the recovery of deadwood habitats for saproxylic organisms, thus yielding carbon and biodiversity co-benefits.

Predator-prey interactions are key to regulating lower trophic levels and stabilizing ecosystem processes. Therefore, understanding prey selection and prey composition of predators is essential, yet especially the small size and diverse diets of predatory arthropods present a significant challenge to conventional field methods. Here, we employed DNA metabarcoding on gut contents of over 1500 arboreal spiders in a subtropical forest in China to construct a high-resolution spider-prey interaction network. Subsequently, we compared prey diversity, composition, starvation rates, and network metrics (predator niche overlap, generality, and prey vulnerability) across different spider hunting guilds and families. Our results revealed an exceptionally broad diet for these spiders, with spiders themselves constituting a significant proportion of prey (i.e. spider on spider predation), besides a wide range of insects, particularly flies and moths. Although, prey composition was broadly similar at high taxonomic levels and functional groups, distinct dietary partitioning was evident at lower (MOTU) taxonomic level. Interaction networks revealed a broader and more generalized diet spectrum of active-hunters compared to web-builders, which resulted in higher diet overlap within the hunting guild (high prey vulnerability and niche overlap). However, network metrics for active hunters were lower than null expectations, suggesting a structuring role of intraspecific competition, while web-builders displayed greater random associations, possibly reflective of the passive mode of prey capture. Collectively, our study offers a high-resolution overview of the dietary niches of subtropical arboreal spiders, revealing how hunting mode shapes their ecological impact and providing significant implications for leveraging these predators in biological control strategies.

Abstract Wild bees face declines, and forests may serve as critical habitats for pollinators. However, how forest composition and the associated floral environment shape pollen provisioning and resource partitioning among cavity-nesting bees remains poorly understood. Here, we leveraged BEF–China, a large-scale subtropical forest biodiversity experiment with experimentally controlled plant (tree and shrub) communities, to investigate how forest composition and spatial context shape pollen provisioning, resource partitioning, and reproductive success of cavity-nesting bees. We used DNA metabarcoding to analyze floral composition of pollen provisioned by five cavity-nesting bee species, with samples collected from BEF–China across three years (2022– 2024). By comparing pollen taxonomic composition from whole-nest pooled samples and individual brood-cell samples with the experimentally planted species pool, we characterized dietary patterns and temporal dynamics of five bee species. Bees primarily relied on floral resources from the surrounding landscape, with planted trees providing essential but temporally restricted pollen supplements during specific phenological stages. Co-occurring bee species exhibited staggered nesting phenology and distinct dietary preferences for different plant families, with fine-scale resource differentiation even during periods of phenological overlap. Our results suggest that managed forests support cavity-nesting bees by providing critical woody floral resources during specific phenological gaps and offering stable nesting environments. To mitigate pollinator declines, forest management should prioritize maintaining diverse, phenologically complementary flowering vegetation within and surrounding forest stands. This ensures temporal continuity of pollen availability throughout the nesting season, which is particularly crucial for restoring pollinator services in simplified forest landscapes.

Positive effects of plant diversity on productivity increase over time through stronger complementarity among species 1 . However, whether these temporal dynamics propagate across trophic levels towards higher-order ecosystem functions remains largely unexplored. Here we tested how tree diversity drives attack rates and trophic interactions of host-parasitoid communities over the course of a decade in a young large-scale forest experiment. We found that the effect of tree species richness on parasitism increased over time, driven both by accelerating stand productivity and changes in food web structure. Parasitism increasingly reflected an attenuation of consumer responses to accumulating resources and a shift towards tree and parasitoid diversity-dependent regulation. The influence of parasitoid species richness on parasitism rose over time as generalist parasitoids concentrated interactions on shared hosts, increasing overall resource use and network robustness to species extinctions. Our results reveal that the functional benefits of biodiversity strengthen over time through shifts in the mechanisms linking trophic levels, underscoring the long-term value of diversity-focused restoration.

Ourapteryx is widely distributed in the Palearctic and Oriental regions, with the highest species diversity found in China. As of 2024, 95 described species have been recorded globally; however, no comprehensive revision of this genus has been published. Identifying Ourapteryx species based solely on wing patterns is challenging due to their extreme similarity, often leading to frequent misidentifications and the oversight of cryptic species. In this study, we utilized 68 morphological species, along with 1050 COI sequences, to develop an integrative taxonomy for Ourapteryx . This taxonomy integrates morphological, molecular, distributional, and ecological evidences. Our findings identified nine candidate species (labeled as sp1–sp7, O. horishana and O. brachycerca ), increasing the total number of recognized species from 68 to 77. Using this updated checklist, we compared four molecular delimitation methods against the outcomes of morphological taxonomy. The analysis indicated that a 2% threshold produced the highest efficiency. Additionally, we explored the reasons behind morpho‐molecular discordance and the presence of hidden species. Our study underscores the importance and reliability of integrative taxonomy, which relies on multiple lines of evidence for accurate species identification and classification.

The bottom-up effect of producers and the top-down effect of predators are well-known factors shaping community assembly and ecosystem functioning through trophic interactions. Communities differing in their functional composition may induce ecological effects with varying directions and intensities, but previous studies in highly diverse ecosystems have struggled with reliably quantifying these interactions at the community level. We used spider gut-content metabarcoding in a subtropical tree diversity experiment to examine the impact of multiple diversity components of both trees and spiders on prey diversity and the network structure of predator-prey interactions. Our findings reveal that prey richness and spider-prey network structure are simultaneously driven by the bottom-up effects of tree communities and the top-down effects of the spider communities. When categorized by hunting modes, the drivers of prey richness and network structure differed between spider guilds. Large phylogenetic and functional differences within web-building spider communities promoted coexistence, leading to increases in the utilized prey richness, generality, niche overlap and prey vulnerability. For hunting spiders, the effects of vertical tree structure complexity indicated restricted mobility but facilitated coexistence through increased shelter availability, and a concomitant reduction of prey richness and dietary breadth. Our study underscores the significance of integrating multiple diversity components and considering functional trait composition across trophic levels when analysing the ecological effects of generalist predators. Our findings enable a better understanding of how predator-prey interaction patterns may be altered under current environmental changes that result in biodiversity loss.

Wild bees are crucial to the pollination of many crops and fruits. However, they face a variety of environmental stressors in agroecosystems, one of which is heavy metal pollution. While studies have assessed heavy metal exposure levels of bee in fields, studies on the effect of agricultural intensification and dietary diversity on bees' exposure to heavy metals is lacking. Across 18 study locations on smallholder farms in Quzhou, China, we measured the concentrations of heavy metals (Cr, Co, Ni, Zn, Cd, and Pb) in mason bee (Osmia excavata) brood provisions. Specifically, we investigated the effects of floral plant diversity (DNA metabarcoding on mason bee brood provisions) and agricultural intensification on mason bee exposure to heavy metals. We found that a greater percentage of farmland within a 200- and 600-meter radius led to significantly increased Pb concentration in the brood provisions for mason bees, but had no effects on the other heavy metals. The concentrations of all tested heavy metals were unaffected by the ratio of non-Brassica to Brassica plants, a genus known to accumulate heavy metals. In addition, Cr and Pb exposure by mason bee larvae was reduced where brood provisions were comprised of a greater diversity of floral plants. Thus, diversifying flower species in agricultural landscapes appears to be an approach to lower heavy metal exposure.

Tree species richness promotes the diversity of higher trophic levels and ecosystem functioning. Tree species richness may thus also affect communities of insect decomposers, and through this, accelerate the decomposition of animal carrion. However, these effects might be masked by other factors driving decomposition, such as forest structure, topography, and competition between different decomposer groups. We placed 1728 dead mice and observed their decomposition for up to seven days, and captured carrion decomposers with mouse-baited traps across 96 plots in the worldwide largest forest biodiversity experiment (BEF-China) in subtropical China in May 2023 and July 2024. We sampled 30,975 decomposer invertebrates from at least 65 species of nine orders. The abundance, species richness, and composition of decomposer groups (flies, ants, other arthropods) was related to sampling year, canopy cover and slope steepness, but not to tree species richness. Flies (Calliphoridae, Sarcophagidae and Muscidae) were nine times more abundant and were more often the primary decomposer of carrion in 2023 than in 2024, especially in closed forests. In contrast, when flies were rare in 2024, ants primarily decomposed carrion, especially in areas with more ants or fewer flies, independently of environmental factors or tree species richness. Carrion decomposition was accelerated in 2023 compared to 2024, in closed forests and partially on steeper slopes, but was not influenced by tree species richness. Carrion decomposition was faster when flies instead of ants were the primary decomposers. When both insect groups co-occurred on carrion, ants typically outcompeted flies, resulting in slower decomposition. This study shows that carrion decomposers were largely unaffected by tree species richness, and consequently, carrion decomposition also appeared to be insensitive to bottom-up effects of tree species richness. Instead, our results highlight the interactive effects of temporal and environmental factors on decomposer communities of small vertebrate carrion, the competitive interactions between decomposer groups, and decomposition rates. Our findings thus challenge the general expectation that tree diversity promotes higher-trophic diversity and ecosystem functioning.

Xylocopinae, a diverse bee subfamily comprising over 1,000 bee species, and also a major model system for studying the pollination and evolution of sociality. The lack of chromosome-level genome assembly resources for the Xylocopinae limits our research of their biology and evolution. Here, we provided the first pseudo-chromosomes genome assembly of the Xylocopa dejeanii combined PacBio CLR long reads, Illumina sequences, and Hi-C data. The final genome is 194.44 Mb located in 16 chromosomes. Our assembly includes 141 scaffolds, with a scaffold N50 length of 13.15 Mb. BUSCO analysis revealed 99.00% completeness. Genome annotation identified 28.27 Mb of repetitive elements, 10,970 protein-coding genes, and 432 ncRNAs. This high-quality X. dejeanii assembly advances our understanding of Xylocopinae genomics and provides new insights into bee evolution.