Insect Conservation and Diversity

O_LICavity-nesting bees and wasps provide essential ecosystem services such as pollination and pest control. Within urban environments, it is likely that cavity-nesting insects are using greenspaces to forage for food and nesting resources, and thus may benefit from urban greenspace management interventions, such as the addition of flower patches and "bee hotels" (trap nests). C_LIO_LIIn contrast to the relatively large body of work demonstrating the effects of wildflower provisioning on bees in an agricultural context, there have been few studies testing the benefits of floral provisioning, or the relative importance of nest site and food constraints on urban cavity-nesting bees and wasps. Consequently, we lack an empirical evidence base for optimising and informing conservation interventions for these taxa. C_LIO_LITo understand how the addition of floral resources influences cavity-nesting insect communities, we conducted a 2-year study in urban greenspaces used for horticulture (allotments). We manipulated floral and nesting resources by adding nectar-rich flower patches and artificial trap nests, and compared nest colonisation by cavity-nesting bees and wasps in sites with floral additions and where no additions were made. Our sites were configured along an urbanisation gradient, allowing us to examine how surrounding urbanisation influenced these patterns. C_LIO_LIContrary to our predictions, we found no significant difference in trap nest uptake in sites where floral resources were added, compared to control sites. However, cavity-nesting insect abundance showed a 6-fold decrease over our urbanisation gradient. The addition of floral resources did not mitigate the negative effects of urbanisation on cavity-nesting insects. C_LI Synthesis and Applications: Although enhancing floral resources in urban systems is a recognised strategy for conserving key pollinators such as social bees, our findings suggest that this approach alone does not address the challenges faced by cavity-nesting bees or wasps in urban landscapes. Our results suggest that accounting for the diversity of resource requirements and incorporating landscape-scale analysis is essential to ensure local conservation interventions will benefit a diversity of insect communities.

Insect populations are declining globally. A major driver of this decline is land use change, including urbanisation. However, urban environments can also offer a wide range of floral resources to pollinators, through ornamental plantings, but these can vary widely in their attractiveness to insects. Often, the largest single planter of ornamental plants in an urban area is the municipality. Here we evaluated the decorative plantings carried out by the city municipality of Regensburg, Germany, by systematically surveying insect visitations on different plant types in late summer, when forage is often limited for pollinators. We found a 130-fold increase from the least to the most attractive plants, and high variation in which insect groups were attracted to which plants. While honey bees, which are not conservation concern, were the most common insect visitors, some decorative plants attracted a very large proportion of wild bees, flies, and wasps. Our results demonstrate that there is great scope for increasing the supply of urban forage to pollinators in general, and specific groups in particular, without requiring new decorative plant types to be sourced or planted. We argue that providing local evidence-based guidance to municipalities offers a quick and potentially cost-neutral method for supporting urban insect populations.

O_LIThe addition of nectar-rich flower patches in human-modified ecosystems is a common practice to mitigate pollinator declines and boost pollination. However, the benefits of these additions for pollinator communities and pollination services are rarely tested, especially in urban environments. C_LIO_LIIn a city-scale experiment we added floral resources to urban allotments and monitored the effects on bees, hoverflies and moths, and tested for improved seed set in a model crop (tomato, Solanum lycopersicum). C_LIO_LIThe addition of wildflowers did not benefit all insect communities. Only social bee abundance (Bombus and Apis) benefitted from increasing floral resource area whereas other insect taxa showed no changes in abundance potentially due to the divergence in foraging patterns of moths, hoverflies, social bees and solitary bees. The addition of wildflower patches enhanced pollination by supporting a 25.3% increase in tomato seed set, providing evidence that wildflower interventions can improve urban pollination. Seed set was higher in more urban sites, suggesting an "oasis effect" where pollinating insects are concentrated into limited greenspaces. This highlights the precarity of pollination services in highly urban areas. C_LIO_LIOur results suggest that the practice of planting wildflower patches can positively affect pollination services in urban areas. The continued promotion of flower patch addition is likely to benefit some key insect taxa, however, the common wildflower species in seed mixes may not benefit hoverflies and moths compared to bees. The taxon-specific foraging patterns we observed should inform the design and development of pollinator-friendly wildflower seed mixes. C_LI Societal impact statementEnhancing urban greenspaces for pollinator communities by planting wildflower patches is increasingly common, but their efficacy for different groups of insects (bees, hoverflies and moths) is unclear. Our city-scale experiment demonstrated that wildflower patches benefitted the abundance of social bees, but did not increase other groups. Wildflower addition increased pollination services, with an increase in seed-set in our model crop, particularly in more urban areas. Wildflower patches do benefit pollinator communities and in turn humans, through the pollination services, but the species mix may not benefit some insect groups. This suggests there is potential to improve the benefit provided by wildflower patches by redesigning pollinator-friendly seed mixes.

Despite the high bee species richness found in the Iberian Peninsula, the lack of distributional data often hampers effective conservation. This gap is particularly critical within protected areas such as the Donana Natural Area, where biodiversity is expected to be increasingly vulnerable to environmental pressures. Here, we present the first checklist of the wild bees of Donana. A total of 385 species belonging to 47 genera were recorded, including recently described species and a newly recorded species for continental Europe, Andrena purpurascens. The exceptional diversity of the areas bee fauna accounts for approximately one-third of the known Iberian apifauna. We provide information on habitat and floral use, offering key ecological insights for conservation planning. This knowledge is essential to support habitat management decisions, particularly in the face of intensifying climate change and water scarcity across the protected area. In addition, to evaluate long-term ecological changes, we compared recent field data (2020-2021) with historical surveys conducted at the same site between 1984 and 1985. While a similar number of species were recorded in both periods (49 vs 43 species), only 15 species were shared between the two periods. This large-scale species turnover indicates the dynamic nature of a region undergoing significant environmental shifts. These findings underscore the importance of baseline biodiversity assessments and long-term monitoring for understanding and mitigating pollinator loss in protected ecosystems, which are increasingly shaped by climate instability and anthropogenic pressures.

We analyzed the wild bee community from 1921 to 2018 at a nature preserve in southern Michigan, USA using museum records and found significant shifts in the bee community. Across the near century of records, species richness peaked in the 1970s and 1980s. There was an intensive bee survey completed by F.C. Evans in 1972 and 1973. We attempted to replicate his effort in 2017 and 2018, and again found a significant decline in species richness and evenness. There was also evidence of declining abundance in many of the more common species. We also conducted traits analyses using neural networks, revealing that oligolectic ground-nesting bees and cleptoparasitic bees were more likely to be extirpated whereas polylectic cavity-nesting bees were more likely to have persisted. Additionally, larger body size was associated with increased probability of local extirpation for polylectic cavity-nesting species. Larger phenological range was associated with increased chances of persistence for polylectic species, while it was associated with extirpation for oligolectic ground-nesting species. Species in the contemporary samples also had a more southerly overall distribution compared to the historic one. Open Research StatementData used for analyses in this manuscript, including Evans original dataset from 1972/1973 with updated species nomenclature, will be permanently archived at the USDA Ag Data Commons after the acceptance of this manuscript and will be citable and accessible here: https://data.nal.usda.gov/dataset/century-sampling-ecological-preserve-reveals-declining-diversity-wild-bees. Complete instructions on how to access all data referenced in this manuscript can be found in Appendix S1.

Urbanisation is reshaping landscapes worldwide, posing challenges to biodiversity and ecosystem function. Cavity-nesting Hymenoptera, including bees and wasps, deliver vital ecological services but are increasingly vulnerable to urbanisation. In this citizen science-based study, we deployed 286 trap nests across Leipzig and Hamburg (Germany) to investigate how urbanisation and landscape-scale environmental features influence the diversity, community composition, reproductive success, offspring survival and demographic status of these insects. Using Bayesian hierarchical and phylogenetically informed modelling, we found that urbanisation significantly reduced species richness, reproductive output and offspring survival in both guilds, despite stable nesting activity, suggesting potential ecological trap effects. For bees, urbanisation also reduced the probability of nests functioning as demographic sources. Environmental drivers shaped responses in taxon-specific ways: bee richness and survival increased with landscape diversity but declined with fragmentation, while wasp richness and nesting declined with higher temperatures, though survival increased with more green cover. Bee nests were more likely to serve as demographic sources in higher temperatures. Community composition responses also diverged; bee communities shifted via increased species turnover, while wasp assemblages remained relatively stable. Temperature was a major driver of compositional dissimilarity in both groups, whereas landscape diversity was associated with homogenisation in bees and diversification in wasps. Our findings demonstrate that cities filter cavity-nesting Hymenoptera through multiple ecological pathways, highlighting the need for differentiated conservation strategies that consider both habitat structure and taxon-specific responses.

Cities have been acclaimed as hotspots for bee biodiversity and potential conservation targets, leading to continued investment in urban pollinator plantings. However, newly created habitats are rarely assessed for their efficacy in supporting bee fitness or the extent to which bees use seeded wildflowers. We compared urban bee nesting in targeted "pocket prairie" pollinator plantings versus urban farms that were intended to support multiple ecosystem services in Cleveland, Ohio, USA. We used trap nests to evaluate nesting success of cavity nesting bees and pollen metabarcoding to determine whether bees collected pollen from seeded plantings during nest provisioning. Pollen DNA revealed most bee-collected pollen was from urban spontaneous vegetation (or "weeds") in Fabaceae, especially Trifolium spp. We also found that urban farms harbored more native bee larvae than targeted pollinator plantings. Finally, when bee nests were situated in a landscape with greater greenspace connectivity, we observed more native bee larvae and greater plant diversity in bees nesting provisions. Collectively, these findings suggest that multi-service greenspaces like urban farms can provide important urban pollinator habitat, and greenspace value for bees is driven by resident weeds and greenspace configuration. Open Research StatementData are not yet provided. Upon acceptance data will be archived in Dryad Digital Repository. Each applicable R package is cited in the text; no novel code is presented. Larval DNA sequences will be available through BOLD, Barcode of Life Data Systems; Pollen DNA reads will be available through Dryad; Raw ecological data (larvae abundance, bloom characteristics, landscape structure) will be available through Dryad. HighlightsO_LIExotic weeds are cavity nesting bees dominant pollen source in cities C_LIO_LIPollen DNA improves foraging observations across a diverse urban matrix C_LIO_LINative bee reproduction was greater in urban farms than pollinator plantings C_LIO_LIMulti-service urban farms can promote win-win conservation scenarios C_LIO_LIGreenspace connectivity modulates bee foraging and nesting success C_LI

Foraging behavior frequently plays a major role in driving the geographic distribution of animals. Buzzing to extract protein-rich pollen from flowers is a key foraging behavior used by bee species across at least 83 genera (these genera comprise [~]58% of all bee species). Although buzzing is widely recognized to affect the ecology and evolution of bees and flowering plants (e.g., buzz-pollinated flowers), global patterns and drivers of buzzing bee biogeography remain unexplored. Here, we investigate the global species distribution patterns within each bee family and how patterns and drivers differ with respect to buzzing bee species. We found that both distributional patterns and drivers of richness typically differed for buzzing species compared to hotspots for all bee species and when grouped by family. A major predictor of the distribution, but not species richness overall for buzzing members of four of the five major bee families included in analyses (Andrenidae, Halictidae, Colletidae and to a lesser extent, Apidae) was the richness of poricidal flowering plant species, which depend on buzzing bees for pollination. As poricidal plant richness was highest in areas with low wind and high aridity, we discuss how global hotspots of buzzing bee biodiversity are likely driven by both biogeographic factors and plant host availability. Whilst we explored global patterns with State-level data, higher resolution work is needed to explore local level drivers of patterns, but from a global perspective, buzz-pollinated plants clearly play a greater role in the ecology and evolution of buzzing bees than previously predicted.

Wild bee communities persist in cities despite major disruption of nesting and food resources by urban development. Bee diversity and abundance is key for urban agriculture and maintenance of plant diversity, and assessing what aspects of cities enhance bee populations will promote our capacity to retain and provision bee habitat. Here, we assessed how variation in land cover and neighborhood development history affected bee communities in the midwestern US urban landscape of Madison, Wisconsin. We sampled bee communities across 38 sites with relatively high (> 55%) or low (< 30%) levels of impervious surface, and assessed effects of land use and neighborhood development history on bee abundance and species richness. We show abundance and richness of bees was lower in recently developed neighborhoods, with particularly strong negative effects on soil nesting bees. Soil nesting bees and bee community richness decreased as cover of impervious surface increased, but above ground nesting bees were minimally impacted. Bee community similarity varied spatially and based on dissimilar local land cover, only for soil nesting bees, and the overall bee community. Impervious surface limited bee abundance and diversity, but new neighborhoods were associated with greater negative effects. We suggest that enhancing the structural diversity of new neighborhoods in urban ecosystems may imitate the structural benefits of older neighborhoods for bee populations.

Pollinator conservation schemes are typically focused on conserving existing-, restoring degraded- or establishing new wild bee habitats. The effectiveness of such conservation schemes depends on the presence of dispersal corridors that allow habitat colonization by bees. Nonetheless, we lack an understanding of the role of semi-natural habitats edges on the connectivity of pollinator communities across intensively managed landscapes. Here, we use data from wild bee communities comprising 953 occurrences from 79 species of non-parasitic bees, sampled at 68 locations distributed across a Norwegian and a Danish landscape to show that the proportion of semi-natural habitat edges is positively correlated to bee species richness and habitat connectivity. Specifically, we found that wild bee species richness sampled along roadsides increased with the proportion of semi-natural habitat edges within1.5 km of the study sites and with local plant species richness. We combined maps showing the proportion of seminatural habitat edges with least cost path analysis to find the most likely dispersal route between our bee communities. We find that these least cost path lengths provide better models of bee species compositional similarity than geographic distance (|{Delta}AICc| > 2), suggesting that seminatural habitat edges act as dispersal corridors in intensively managed landscapes. However, we also find that compositional similarity between communities depend on site-specific plant species richness stressing the importance of improving the habitat quality of edge habitats if they are to function as dispersal corridors. We discuss potential management options for improving wild bee habitat conditions along seminatural habitat edges and illustrate how maps of least cost paths can be used to identify dispersal corridors between pollinator habitats of conservation priority. Maps of dispersal corridors can be used to direct wild bee habitat management actions along seminatural habitat edges to facilitate the dispersal of bees between larger grassland habitats.

O_LIAs evidence of pollinator declines mounts, effective conservation strategies are urgently needed. Current methods focus on planting flowers and frequently overlook nesting habitats, especially for ground nesting bees, which comprise most species. Despite their prevalence, ground-nesting bee habitats remain poorly understood. The lack of evidence-based methods to enhance nesting habitat presents a significant challenge, particularly in environments with limited natural nesting sites, such as urban landscapes. C_LIO_LITo determine whether soil manipulations enhance bee colonization rates, we constructed experimental nesting plots at 21 sites along an urban gradient and implemented five soil surface treatments: bare ground, leaf litter, mounded soil, pebbles, and unmanipulated controls. We collected nesting individuals from experimental plots through observation and emergence traps to investigate preferences for soil surface substrates, and the impact of plot-level and site-level conditions on colonization. C_LIO_LIManipulated treatments significantly increased colonization compared to controls and revealed genus-specific preferences. Treatments also resulted in differences in environmental conditions including temperature, moisture, and soil compaction. C_LIO_LISite-level conditions including slope and urbanization increased colonization while hard soil compaction and bare ground decreased colonization success. Urban and highly vegetated sites were more frequently colonized by ground nesting bees, indicating that our manipulations successfully attracted nest-searching females and may have alleviated limited nesting opportunities. C_LIO_LIPolicy Implications: Simple soil surface manipulations, or soil sanctuaries, represent a practical tool to enhance an essential component of bee habitat and provide a safe nesting location that can improve conservation outcomes for ground-nesting bees across diverse environments. Incorporating ground-nesting bee habitat enhancements into urban planning and land management policies could address habitat limitations for many species. Conservation strategies should prioritize the inclusion of nesting features alongside floral resources to create comprehensive pollinator-supportive landscapes, benefiting both biodiversity and critical ecosystem services. C_LI

Biotic homogenization has been documented following extensive anthropogenic landscape change such as urbanization and agriculture, but diverse native communities also have been reported in these ecosystems. Understanding the influence of landscape-level characteristics on processes of community assembly can inform how human-dominated landscapes shape the structure and composition of local communities, including important pollinators such as bumble bees (Bombus spp.). The objective of this study was to investigate multi-scale patterns of taxonomic, phylogenetic, and functional beta- diversity of bumble bees in greenspaces along an urban-agricultural gradient to understand landscape- scale constraints on processes of community assembly. Bumble bees were collected in greenspaces along an urban-agricultural gradient in Madison, WI, USA. Patterns of biotic homogenization were investigated using measures of beta-diversity and null models relative to a regional bumble bee species pool in a 100 km area surrounding the city. Nine of the expected 13 species from the regional pool were collected in greenspaces in urban and agricultural landscapes. At the regional scale, we found evidence of taxonomic, phylogenetic, and functional homogenization among bumble bee communities in urban and agricultural landscapes, with species that were smaller in size, had shorter wings, were less hairy, but had larger eyes and longer setae on the corbicula (pollen-carrying hind legs) being more common than expected based on null models. When we evaluated filtering from the anthropogenic species pools (i.e., urban and agricultural) to local greenspaces, we found nuanced differences among land cover types, wherein agricultural landscapes supported higher beta-diversity of bumble bee communities than expected while urban landscapes continued to show signals of homogenization. Overall, anthropogenic landscapes acted as a strong filter for bumble bees, broadly selecting for a subset of functionally similar and phylogenetically related species that resulted in homogenization of communities within the region. Our findings support a landscape-level approach to biodiversity conservation that promotes diversifying landscapes to support diverse pollinator populations. OPEN RESEARCH STATEMENTData and novel code associated with this submission are provided in an external repository to be evaluated during the peer review process and are available at https://github.com/kiperry/WI_Bumble_Bees. If this paper is accepted for publication, data and code will be permanently archived within a linked Zenodo repository.

Urban greening actions across the world are being carried out to support resident, rare and locally extinct insect pollinators. In parallel, an array of best-practise resources have been designed to support build-environment practitioners and professionals seeking to or tasked with implementing greening actions for pollinators. Three main themes permeate these resources: (1) small greenspaces can provide large ecological benefits; (2) high-quality pollinator habitat should include a large share of indigenous plant species; and (3) considering stakeholders aspirations, motivations, experience, and concerns is critical for designing effective actions. Despite high interest in implementing these actions, few projects have evaluated their ecological benefits or demonstrated achievement of specific objectives. Even fewer have been specifically co-designed by practitioners and researchers to bridge the science-practice gap. Here, we demonstrate the success of a co-designed greening action in attracting indigenous pollinators to an urban greenspace. We compiled a plant-pollinator interactions dataset in a public park, within a densely urbanised municipality, that was purposefully greened with indigenous plant species to support existing and attract new indigenous pollinators. We then assessed: (1) how pollinator species richness and species-specific occupancy varied amongst plant species, and how these metrics compared between the existing greenspace plant species and the new added indigenous ones; (2) the effect of flower cover of the added indigenous plant species on the probabilities of occurrence of indigenous and introduced pollinators; and (3) the effect of the added indigenous plant species on the structure of the greenspace plant-pollinator ecological network. An addition of only six indigenous plant species resulted in a 2.5-fold increase in the number of indigenous pollinator species and other flower-visiting insects observed in the park. The added indigenous plants established interactions with all the indigenous pollinators and remarkably almost half of these were found interacting exclusively with the added indigenous plants. Additionally, the number of indigenous pollinators associated with a given plant species was on average 3.5 times higher for the added indigenous plants than for the baseline ones and the probabilities of occurrence of indigenous pollinators were on average invariable higher in the added indigenous than in the baseline plant species. The plant and insect community changes sparked by the greening action resulted in concomitant changes to the structure of the sites plant-pollinator network. We found an average 4.2-fold increase in the number of interactions linking the greened compared to the baseline network, with almost half of these interactions comprising those between the added indigenous plants and indigenous pollinators. By showing that replacing lawn with indigenous plants leads to positive ecological outcomes for indigenous pollinators and other flower-visiting insects - including increasing the overall greenspace biodiversity by attracting new indigenous insect species to the site - our findings contribute to the evidence base underpinning best-practise resources and provide encouragement to build-environment practitioners and professionals responsible for or endeavouring to support existing or bringing insect pollinators back into our cities. Our study establishes a pathway and acts as a catalyst for researchers and government officials seeking to collaboratively demonstrate that greening is a valuable and sound investment for achieving goals from local, regional and global biodiversity and sustainability plans and policies.

Intensified agriculture increasingly threatens wild and managed bees by promoting landscape uniformity and reducing floral resource availability whereas urban areas can provide continuous floral resources within green spaces and private gardens. Mass-flowering events of crops and trees, such as lime trees (Tilia spp.), can provide ample floral resources but only for short time periods. Using waggle dance decoding, pollen analysis and bee abundance recordings, we investigated the temporal shift in honeybee foraging behaviour in response to lime tree mass-flowering. Honeybees in urban areas extended their foraging range during lime tree flowering. Foraging behaviour of honeybees in rural areas did not change to such an extent and honeybees foraged in sown flower strips. Our results suggest that honeybees optimize their foraging behaviour to exploit highly rewarding resources instead of extending foraging ranges in times of floral resource scarcity.

Green roofs can provide suitable habitats for pollinating insects in urban areas. Pollinators are a large and diverse group with high economic and ecological relevance to society. Yet their populations are in decline, highlighting the need for new habitats such as green roofs. An understanding of how local and landscape factors of green roofs shape pollinator communities is crucial to optimize the design and development of green roofs. This study aimed to identify how the surrounding landscape and green roof characteristics influence pollinator diversity and abundance. Pollinators - such as bees, wasps, hoverflies and butterflies - were sampled using pan traps and hand netting on 25 green roofs that were categorized into three types based on functionality and vegetation structure: sedum roofs, nature roofs, and roof gardens. To assess pollinator communities, we examined species richness, abundance, and functional diversity--defined here as the range of ecological roles or traits. Roof characteristics (e.g., flower diversity, microrelief, vegetation cover, roof height, size, and age) and landscape factors (e.g. percentage of surrounding green, distance to surrounding green) were analysed in relation to these diversity metrics. We show that a continuous supply of flowers throughout the year, flower abundance and the type of green roof significantly influence pollinator diversity and abundance. Sedum roofs supported lower pollinator diversity compared to the other roof types. Furthermore, our models indicated a decrease in pollinator diversity on higher green roofs, and when honeybee hives are present, while the presence of bee hotels increased pollinator abundance. The study highlights the value of nature roofs and roof gardens, compared to sedum roofs for supporting pollinator diversity. This is linked to the importance of constant forage availability, especially in early spring, which is absent on most sedum roofs. The results from this study offer guidelines to green roof designers on how to design pollinator friendly roofs in urban areas. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=171 SRC="FIGDIR/small/676189v1_ufig1.gif" ALT="Figure 1"> View larger version (34K): org.highwire.dtl.DTLVardef@dfb4caorg.highwire.dtl.DTLVardef@d6478eorg.highwire.dtl.DTLVardef@1f3e725org.highwire.dtl.DTLVardef@1cc4ef0_HPS_FORMAT_FIGEXP M_FIG C_FIG Pollinator species: Macropis europea (Hymenoptera: Melittidae), Helophilus pendulus (Diptera: Syrhidae) and Polyommatus icarus (Lepidoptera: Lycaenidae). All three species were observed on green roofs during the authors fieldwork. Image created using biorender.com and personal drawings. HighlightsO_LIBiodiverse roofs and roof gardens support higher pollinator diversity compared to sedum roofs. C_LIO_LIA continuous supply of flowers throughout the year, along with a higher abundance of flowers, are key factors influencing pollinator diversity and abundance on green roofs. C_LIO_LIRoof height affects the diversity and abundance of different pollinator groups in distinct ways, a novel finding that needs further investigation. C_LIO_LIWe provide guidelines for green roof designers, emphasizing the importance of selecting roof types and designs that ensure constant flower availability. C_LI

Interactions between flowers and flower-visiting insects play central roles in ecosystem functioning. In addition to ensuring pollination, flower-visiting insects are also crucial for numerous other biotic interactions, using floral resources as fuel in their search for prey, hosts, breeding sites, and other resources. Studying insect-flower interactions may thus be strategic to conserve and restore biotic interactions in ecosystems heavily degraded by intensive land use and climate change, such as the arid savannas of the northern Sahel. We aimed to document for the first time the diversity of flower-visiting insects in this region and to examine whether restoration efforts of the Great Green Wall initiative have affected insect abundance and diversity. Using two capture methods, hand netting and pan traps, we inventoried insects visiting flowers of Balanites aegyptiaca. This is the most abundant tree species in the region and is also of economic importance. We sampled three sites in a single locality: a "Restored" site from which livestock are excluded, an "Unrestored" site in intensively grazed rangeland, and a topographical "Depression" site in a grazed area but with high tree density. Each site was sampled at three different periods to examine variation in this extremely harsh and seasonal environment. The open-access flowers of Balanites aegyptiaca are produced in multiple flowering events each year. We found a surprisingly high diversity of insects visiting its flowers, comprising 371 morphospecies from 10 insect orders, with a predominance of Hymenoptera and Diptera. Insect abundance, diversity and species composition differed markedly between seasons. Bees appear to be important pollinators, particularly solitary bees of the family Halictidae, which were abundant in all seasons. Diptera, in particular several families of small flies, were also frequent visitors and were especially abundant and diverse in the wet season. Ants were especially abundant at flowers in the dry season, when few resources other than flowers and flower-visiting insects were likely available to them. Insect abundance and observed diversity differed only little between sites, but estimated total diversity (Chao1 richness) was highest in the Depression site. Insects visiting flowers of B. aegyptiaca included herbivores, decomposers, and parasitoids and predators of diverse arthropods, underlining the role of these floral resources in numerous facets of ecosystem functioning. The floral resources of B. aegyptiaca and other trees, which can flower throughout the year, are likely critical to assure the persistence of numerous insect species. Integrating biotic interactions into ecosystem management is crucial for conservation and restoration in Sahelian ecosystems.

The writings of naturalists from two centuries past are brimming with accounts of the stark differences in the kinds and numbers of organisms encountered during the day and night and between the tropical and temperate zones. However, only recently have ecologists begun to systematically describe and explain the geographic variation in the diel activities of species on Earth. Examining data from 60 insect communities globally, I find that the partitioning of total species richness across three diel activity periods tracks the latitudinal gradient. In general, the proportions of diurnal and nocturnal species are highest among tropical communities and decline poleward, while cathemeral activity characterises over half of all species in communities at high latitudes. These latitudinal trends in diel partitioning at the community level broadly reflect recently documented patterns in the global distributions of vertebrate species using different activity periods. I outline six hypotheses that may account for a latitudinal gradient in the diel partitioning of species richness.

Knowledge on long-distance migration of insects is especially important for food security, public health, and conservation-issues that are especially significant in Africa. During the wet season, the Sahel nourishes diverse life forms which are soon purged by the long dry season. Windborne migration is a key strategy enabling exploitation of such ephemeral havens. However, our knowledge of these large-scale movements remains sparse due to the virtual invisibility of insects flying at altitude. In this first cross-season investigation (3 years) of the aerial insect fauna over Africa, we sampled crepuscular and nocturnal insects flying 40-290 m above ground in four Sahelian villages in Mali, using sticky nets mounted on tethered helium-filled balloons. Nearly half a million insects were caught, representing at least thirteen insect orders following preliminary sorting of the collections. At least 100 insect families were determined to have been captured at altitude in samples collected on 222 nets, obtained in 125 collections over 96 nights. Control nets (raised momentarily to >40 m during system launch and retrieval) confirmed that the insects were captured at altitude, not near the ground. Thirteen ecologically and phylogenetically diverse species were studied in detail. The flight activity of all species peaked during the wet season every year across localities up to ~100 km apart, and occurred over multiple nights, suggesting regular migrations. Species differed in flight altitude, seasonality, and correlations with aerial temperatures, humidity, and wind speed. All taxa exhibited frequent migrations on southerly winds, accounting for the recolonization of the Sahel from southern source populations. "Return" southward movement at the end of the wet season occurred in most taxa but no selectivity for such winds was detected. Extrapolation of aerial density to estimate the seasonal number of migrants crossing Mali at latitude 14{degrees}N suggested numbers in the trillions, even for the modestly abundant taxa. Assuming 2-10 hours of flight, the nightly distances traversed exceed tens and even hundreds of kilometers. Two migration strategies were proposed: "residential Sahelian migration" and "round trip migration". The unprecedented magnitude and diversity of long-range windborne insect migrations highlight the importance of this life strategy in their impact on Sahelian and neighboring ecosystems.

Environmental changes such as urbanisation and habitat fragmentation profoundly impact ecological communities by altering habitats, resources, and microclimate. Ants, with diverse life histories and strong ecological effects, are ideal models to study these pressures. We investigated the response of ant communities, including taxonomic and functional diversity, to urbanisation and habitat fragmentation in the Paris region, comparing 24 urban parks vs 25 rural forests outside the city. We found a clear difference in species composition between urban and rural environments, with a higher prevalence of monogynous and thermophilic species in the city. Forest communities are homogeneous across the three fragmentation levels we studied, while park communities differ noticeably depending on park size, with larger parks harbouring more species. Our findings suggest that urbanisation selects specific ant traits and favours more thermophilic species, thereby increasing the mean thermal preference of urban communities. These selective effects influence which species can colonise and survive in different patches, shaping metacommunity structure and potentially affecting the resilience of ant communities under climate change.

Widespread declines in wild bee populations necessitate urgent action, but there remains insufficient data to guide conservation efforts. Addressing this data deficit, we investigated the relative performance of environmental and/or taxon-based indicators to predict wild bee richness in the eastern and central U.S. Our methodology leveraged publicly available data on bees (SCAN and GBIF data repository), birds (eBird participatory science project) and land cover data (USGS Cropland Data Layer). We used a Bayesian variable selection algorithm to select variables that best predicted bee richness using two datasets: a semi-structured dataset covering a wide geographical and temporal range and a structured dataset covering a focused extent with a standardized protocol. We demonstrate that an indicator based on the combination of bird and land cover data was better at predicting wild bee richness across broad geographies than indicators based on land cover or birds alone, particularly for the semi-structured dataset. In the case of wild bees specifically, we suggest that bird and land cover data serve as useful indicators to guide monitoring and conservation priorities until the quality and quantity of bee data improve.