Butterfly abundance declines over 20 years of systematic monitoring in Ohio, USA

Local climate change velocities and evolutionary history explain multidirectional range shifts in a North American butterfly assemblage

Species are often expected to shift their distributions either poleward or upslope to evade warming climates and colonise new suitable climatic niches. However, from 18-years of fixed transect monitoring data on 88 species of butterfly in the midwestern United States, we show that butterflies are shifting their centroids in all directions, except towards regions that are warming the fastest (southeast). Butterflies shifted their centroids at a mean rate of 4.87 km year-1. The rate of centroid shift was significantly associated with local climate change velocity (temperature by precipitation interaction), but not with mean climate change velocity throughout the species' ranges. Species tended to shift their centroids at a faster rate towards regions that are warming at slower velocities but increasing in precipitation velocity. Surprisingly, species' thermal niche breadth (range of climates butterflies experience throughout their distribution) and wingspan (often used as metric for dispersal capability) were not correlated with the rate at which species shifted their ranges. We observed high phylogenetic signal in the direction species shifted their centroids. However, we found no phylogenetic signal in the rate species shifted their centroids, suggesting less conserved processes determine the rate of range shift than the direction species shift their ranges. This research shows important signatures of multidirectional range shifts (latitudinal and longitudinal) and uniquely shows that local climate change velocities are more important in driving range shifts than the mean climate change velocity throughout a species' entire range.

Insecticides, more than herbicides, land use, and climate, are associated with declines in butterfly species richness and abundance in the American Midwest

Mounting evidence shows overall insect abundances are in decline globally. Habitat loss, climate change, and pesticides have all been implicated, but their relative effects have never been evaluated in a comprehensive large-scale study. We harmonized 17 years of land use, climate, multiple classes of pesticides, and butterfly survey data across 81 counties in five states in the US Midwest. We find community-wide declines in total butterfly abundance and species richness to be most strongly associated with insecticides in general, and for butterfly species richness the use of neonicotinoid-treated seeds in particular. This included the abundance of the migratory monarch (Danaus plexippus), whose decline is the focus of intensive debate and public concern. Insect declines cannot be understood without comprehensive data on all putative drivers, and the 2015 cessation of neonicotinoid data releases in the US will impede future research.

Illuminating patterns of firefly abundance using citizen science data and machine learning models

As insect populations decline in many regions, conservation biologists are increasingly tasked with identifying factors that threaten insect species and developing effective strategies for their conservation. One insect group of global conservation concern are fireflies (Coleoptera: Lampyridae). Although quantitative data on firefly populations are lacking for most species, anecdotal reports suggest that some firefly populations have declined in recent decades. Researchers have hypothesized that North American firefly populations are most threatened by habitat loss, pesticide use, and light pollution, but the importance of these factors in shaping firefly populations has not been rigorously examined at broad spatial scales. Using data from >24,000 surveys (spanning 2008-16) from the citizen science program Firefly Watch, we trained machine learning models to evaluate the relative importance of a variety of factors on bioluminescent firefly populations: pesticides, artificial lights at night, land cover, soil/topography, short-term weather, and long-term climate. Our analyses revealed that firefly abundance was driven by complex interactions among soil conditions (e.g., percent sand composition), climate/weather (e.g., growing degree days), and land cover characteristics (e.g., percent agriculture and impervious cover). Given the significant impact that climactic and weather conditions have on firefly abundance, there is a strong likelihood that firefly populations will be influenced by climate change, with some regions becoming higher quality and supporting larger firefly populations, and others potentially losing populations altogether. Collectively, our results support hypotheses related to factors threatening firefly populations, especially habitat loss, and suggest that climate change may pose a greater threat than appreciated in previous assessments. Thus, future conservation of North American firefly populations will depend upon 1) consistent and continued monitoring of populations via programs like Firefly Watch, 2) efforts to mitigate the impacts of climate change, and 3) insect-friendly conservation practices.

Disproportionate declines of formerly abundant species underlie insect loss

Studies have reported widespread declines in terrestrial insect abundances in recent years1-4, but trends in other biodiversity metrics are less clear-cut5-7. Here we examined long-term trends in 923 terrestrial insect assemblages monitored in 106 studies, and found concomitant declines in abundance and species richness. For studies that were resolved to species level (551 sites in 57 studies), we observed a decline in the number of initially abundant species through time, but not in the number of very rare species. At the population level, we found that species that were most abundant at the start of the time series showed the strongest average declines (corrected for regression-to-the-mean effects). Rarer species were, on average, also declining, but these were offset by increases of other species. Our results suggest that the observed decreases in total insect abundance2 can mostly be explained by widespread declines of formerly abundant species. This counters the common narrative that biodiversity loss is mostly characterized by declines of rare species8,9. Although our results suggest that fundamental changes are occurring in insect assemblages, it is important to recognize that they represent only trends from those locations for which sufficient long-term data are available. Nevertheless, given the importance of abundant species in ecosystems10, their general declines are likely to have broad repercussions for food webs and ecosystem functioning.

Integrated community models: A framework combining multispecies data sources to estimate the status, trends and dynamics of biodiversity

Data deficiencies among rare or cryptic species preclude assessment of community-level processes using many existing approaches, limiting our understanding of the trends and stressors for large numbers of species. Yet evaluating the dynamics of whole communities, not just common or charismatic species, is critical to understanding and the responses of biodiversity to ongoing environmental pressures. A recent surge in both public science and government-funded data collection efforts has led to a wealth of biodiversity data. However, these data collection programmes use a wide range of sampling protocols (from unstructured, opportunistic observations of wildlife to well-structured, design-based programmes) and record information at a variety of spatiotemporal scales. As a result, available biodiversity data vary substantially in quantity and information content, which must be carefully reconciled for meaningful ecological analysis. Hierarchical modelling, including single-species integrated models and hierarchical community models, has improved our ability to assess and predict biodiversity trends and processes. Here, we highlight the emerging 'integrated community modelling' framework that combines both data integration and community modelling to improve inferences on species- and community-level dynamics. We illustrate the framework with a series of worked examples. Our three case studies demonstrate how integrated community models can be used to extend the geographic scope when evaluating species distributions and community-level richness patterns; discern population and community trends over time; and estimate demographic rates and population growth for communities of sympatric species. We implemented these worked examples using multiple software methods through the R platform via packages with formula-based interfaces and through development of custom code in JAGS, NIMBLE and Stan. Integrated community models provide an exciting approach to model biological and observational processes for multiple species using multiple data types and sources simultaneously, thus accounting for uncertainty and sampling error within a unified framework. By leveraging the combined benefits of both data integration and community modelling, integrated community models can produce valuable information about both common and rare species as well as community-level dynamics, allowing for holistic evaluation of the effects of global change on biodiversity.

Population dynamics and drivers of the eastern monarch (Danaus plexippus) across its full annual cycle: a cross-scale synthesis of a model migratory species

The monarch butterfly is arguably the best-known butterfly species throughout its global range. Declines in the size of the overwintering colonies in Mexico have sparked controversy regarding the conservation of the species and this controversy has been heightened since the United States Fish and Wildlife Service and International Union for the Conservation of Nature concluded that the eastern monarch populations were threatened (or in the case of United States Fish and Wildlife Service, warranted listing). Drivers of decline vary through space and time. Here, we present a synthesis of longitudinal monarch abundance studies that aim to disentangle the putative drivers of decline from one another. We find remarkable consistency that suggests monarch populations are indeed declining and that potential drivers of such decline shift over time. We strongly encourage future work on the species paired with mechanistic, experimental designs to address some long-standing knowledge gaps.

Conserved grasslands support similar pollinator diversity as pollinator-specific practice regardless of proximal cropland and pesticide exposure

Pollinator diversity and abundance are declining globally. Cropland agriculture and the corresponding use of agricultural pesticides may contribute to these declines, while increased pollinator habitat (flowering plants) can help mitigate them. Here we tested whether the relative effect of wildflower plantings on pollinator diversity and counts were modified by proportion of nearby agricultural land cover and pesticide exposure in 24 conserved grasslands in Iowa, USA. Compared with general grassland conservation practices, wildflower plantings led to only a 5% increase in pollinator diversity and no change in counts regardless of the proportion of cropland agriculture within a 1 km radius. Pollinator diversity increased earlier in the growing season and with per cent flower cover. Unexpectedly, neither insecticide nor total pesticide concentrations on above-ground passive samplers were related to pollinator diversity. However, pollinator community composition was most strongly related to date of sampling, total pesticide concentration, and forb or flower cover. Our results indicate very little difference in pollinator diversity between grassland conservation practices with and without wildflower plantings. Given the relatively high economic costs of wildflower plantings, our research provides initial evidence that investment in general grassland conservation may efficiently conserve pollinator diversity in temperate regions of intensive cropland agriculture.

Perfluorooctanoic acid induces behavioral impairment and oxidative injury in Nauphoeta cinerea nymphs

Perfluorooctanoic acid (PFOA) is a persistent organic contaminant with potential health threats to both animals and humans. However, the impact of PFOA on insects, which play significant roles in ecosystems, is understudied. We evaluated the toxicological impact of ecologically relevant concentrations of PFOA (0, 25, 50, 100, and 200 µg L-1) on Nauphoeta cinerea nymphs following exposure for 42 consecutive days. We analyzed the behavior of the insects with automated video-tracking software and processed the head, midgut, and fat body for biochemical assays. PFOA-exposed insects exhibited significant reductions in locomotory abilities and an increase in freezing time. Furthermore, PFOA exposure reduced acetylcholinesterase activity in the insect head. PFOA exposure increased the activities of superoxide dismutase, glutathione peroxidase, and catalase in the head and midgut, but decreased them in the fat body. PFOA also significantly increased glutathione-S transferase activity, while decreasing glutathione levels in the head, midgut, and fat body. Additionally, PFOA exposure increased reactive oxygen and nitrogen species, nitric oxide, lipid peroxidation, and protein carbonyl contents in the head, midgut, and fat body of the insects. In conclusion, our findings indicate that PFOA exposure poses an ecological risk to Nauphoeta cinerea.

Looking back on biodiversity change: lessons for the road ahead

Estimating biodiversity change across the planet in the context of widespread human modification is a critical challenge. Here, we review how biodiversity has changed in recent decades across scales and taxonomic groups, focusing on four diversity metrics: species richness, temporal turnover, spatial beta-diversity and abundance. At local scales, change across all metrics includes many examples of both increases and declines and tends to be centred around zero, but with higher prevalence of declining trends in beta-diversity (increasing similarity in composition across space or biotic homogenization) and abundance. The exception to this pattern is temporal turnover, with changes in species composition through time observed in most local assemblages. Less is known about change at regional scales, although several studies suggest that increases in richness are more prevalent than declines. Change at the global scale is the hardest to estimate accurately, but most studies suggest extinction rates are probably outpacing speciation rates, although both are elevated. Recognizing this variability is essential to accurately portray how biodiversity change is unfolding, and highlights how much remains unknown about the magnitude and direction of multiple biodiversity metrics at different scales. Reducing these blind spots is essential to allow appropriate management actions to be deployed. This article is part of the theme issue 'Detecting and attributing the causes of biodiversity change: needs, gaps and solutions'.

Additive and interactive effects of anthropogenic stressors on an insect herbivore

The pressures of global change acting on wild plants and animals include exposure to environmental toxins, the introduction of non-native species, and climate change. Relatively few studies have been reported in which these three main classes of stressors have been examined simultaneously, allowing for the possibility of synergistic effects in an experimental context. In this study, we exposed caterpillars of the Melissa blue butterfly (Lycaeides melissa) to three concentrations of chlorantraniliprole, under three experimental climates, on a diet of a native or a non-native host plant throughout larval development in a fully factorial experiment. We find that high pesticide exposure and a non-native diet exhibit strong negative effects on caterpillars, resulting in 62% and 42% reduction in survival, respectively, while interactive effects tend to be weaker, ranging from 15% to 22% reduction in survival. Interactive effects have been shown to be strong in other contexts, but do not appear to be universal; however, our study shows that the cumulative effects of stressors acting in isolation (additively) are sufficiently strong to severely reduce survival and by extension population persistence in the wild.

Declines of bees and butterflies over 15 years in a forested landscape

Despite growing concerns about pollinator declines,^1,2,3,4 evidence that this is a widespread problem affecting entire communities remains limited.⁵ There is a particular shortage of pollinator time series from relatively undisturbed natural habitats, such as forests, which are generally thought to provide refuge to biodiversity from anthropogenic stressors.⁶ Here, we present the results from standardized pollinator sampling over 15 years (2007-2022) at three relatively undisturbed forested locations in the southeastern United States. We observed significant declines in the richness (39%) and abundance (62.5%) of bees as well as the abundance of butterflies (57.6%) over this time period. Unexpectedly, we detected much stronger declines in the richness and abundance of above-ground-nesting bees (81.1% and 85.3%, respectively) compared with below-ground-nesting bees. Even after dropping the first or last year of sampling, which happened to yield the greatest and lowest numbers of pollinators, respectively, we still detected many of the same negative trends. Our results suggest that sharp declines in pollinators may not be limited to areas experiencing direct anthropogenic disturbances. Possible drivers in our system include increasing mean annual minimum temperatures near our study sites as well as an invasive wood-nesting ant that has become increasingly widespread and abundant in the region over the course of this study.

Challenges and opportunities for using natural history collections to estimate insect population trends

Natural history collections (NHC) provide a wealth of information that can be used to understand the impacts of global change on biodiversity. As such, there is growing interest in using NHC data to estimate changes in species' distributions and abundance trends over historic time horizons when contemporary survey data are limited or unavailable. However, museum specimens were not collected with the purpose of estimating population trends and thus can exhibit spatiotemporal and collector-specific biases that can impose severe limitations to using NHC data for evaluating population trajectories. Here we review the challenges associated with using museum records to track long-term insect population trends, including spatiotemporal biases in sampling effort and sparse temporal coverage within and across years. We highlight recent methodological advancements that aim to overcome these challenges and discuss emerging research opportunities. Specifically, we examine the potential of integrating museum records and other contemporary data sources (e.g. collected via structured, designed surveys and opportunistic citizen science programs) in a unified analytical framework that accounts for the sampling biases associated with each data source. The emerging field of integrated modelling provides a promising framework for leveraging the wealth of collections data to accurately estimate long-term trends of insect populations and identify cases where that is not possible using existing data sources.

Diversity but Not Overall Abundance of Moths and Butterflies (Insecta: Lepidoptera) Decreases around Two Arctic Polluters

Alarming reports on the rapid decline of insects during the past decades call for the exploration of potential drivers of this process. Here, we test the hypothesis that the overall abundance and diversity of moths and butterflies (Lepidoptera) decrease under the impact of industrial pollution in the fragile arctic environment. For this purpose, experienced collectors netted adult Lepidoptera at five tundra sites located 0.5 to 45.3 km from the ore-roasting plant in Zapolyarnyy and at five forest sites located 1.4 to 37.8 km from the copper-nickel smelter at Nikel, in the Murmansk region of Russia. The analysis of the 100 samples collected from 2003 to 2008 and containing 2312 individuals of 122 species revealed that the diversity of Lepidoptera declined significantly near both of these polluters due to both decreases in species richness and changes in the abundance of individual species, whereas the overall abundance of moths and butterflies was independent of the pollution load. These patterns did not differ between Nikel and Zapolyarnyy, and they were consistent with patterns previously found near the copper-nickel smelter at Monchegorsk. The abundances of Lepidoptera species showed variable changes along pollution gradients, from significantly negative to significantly positive, but individual species showed similar density changes around these three polluters. Disproportional increases in the abundance of a few pollution-tolerant species change the community structure and explain why the overall abundance of moths and butterflies does not decline even in localities experiencing extreme loads of sulphur dioxide and heavy metals.

Putting pesticides on the map for pollinator research and conservation

Wild and managed pollinators are essential to food production and the function of natural ecosystems; however, their populations are threatened by multiple stressors including pesticide use. Because pollinator species can travel hundreds to thousands of meters to forage, recent research has stressed the importance of evaluating pollinator decline at the landscape scale. However, scientists’ and conservationists’ ability to do this has been limited by a lack of accessible data on pesticide use at relevant spatial scales and in toxicological units meaningful to pollinators. Here, we synthesize information from several large, publicly available datasets on pesticide use patterns, land use, and toxicity to generate novel datasets describing pesticide use by active ingredient (kg, 1997–2017) and aggregate insecticide load (kg and honey bee lethal doses, 1997–2014) for state-crop combinations in the contiguous U.S. Furthermore, by linking pesticide datasets with land-use data, we describe a method to map pesticide indicators at spatial scales relevant to pollinator research and conservation.

Measurement(s)	LD50 • Pesticide • area of cropland • land cover
Technology Type(s)	dose response design • Survey • remote sensing
Factor Type(s)	pesticide active ingredient • contact vs. oral • state • year • crop group
Sample Characteristic - Organism	Apis mellifera
Sample Characteristic - Environment	cropland ecosystem
Sample Characteristic - Location	contiguous United States of America

Climate and vegetation and their impact on stable C and N isotope ratios in bat guano

Cave guano deposits represent a relatively untapped paleoecological archive that can provide information about past vegetation, climate, and bat diet over several millennia. Recent research suggests that carbon isotope values (δ13C) measured in guano accumulations from insectivorous bats reflect the relative abundance of C3 and C4 plants on the landscape while nitrogen isotope values (δ15N) may reflect precipitation amount. Together, these proxies can provide useful information for restoration practitioners seeking to understand how plant species composition has changed over time in relation to climate and land use. To better calibrate these proxies for use in restoration, we compared instrumental records of precipitation and satellite imagery of vegetation with isotope values measured in modern bat guano from Mary Lawson Cave, a large limestone cavern located in central Missouri. Mary Lawson Cave hosts a maternity colony of insectivorous gray bats (Myotis grisescens), and as such, contains significant guano accumulations. In the fall of 2018, we collected a 60 cm long guano core that dates to 1999 cal AD at its base. Guano core δ13C values decrease from the base toward the surface (from ~-26 to -27‰) whereas δ15N values increase toward the surface even after accounting for ammonia volatilization (from ~3 to 5‰). Presently, the landscape around Mary Lawson Cave is dominated by a deciduous forest and pasture. Given that the land cover has changed very little over this period, the decline in δ13C values toward the present likely reflects a shift in land management on farms and/or increases in invasive C3 species. Rainfall amounts from nearby Lebanon, Missouri, are significantly positively correlated with guano δ15N values, a relationship that is notably opposite that observed previously in soil and plants. We argue that heavy fertilizer application and significant grazing intensity could lead to the accumulation of large pools of excess labile nitrogen which would be vulnerable to leaching during precipitation events. The relationship between guano δ15N values and precipitation may differ for materials from less agriculturally impacted locations or periods and should be extended into the past with caution.

Recovery of moth and butterfly (Lepidoptera) communities in a polluted region following emission decline

Environmental pollution is one of the major drivers of the present-day decline in global biodiversity. However, the links between the effects of industrial pollution on insect communities and the underlying species-specific responses remain poorly understood. We explored the spatial pattern in insect communities by analysing 581 samples of moths and butterflies (containing 25,628 individuals of 345 species) collected along a strong pollution gradient in subarctic Russia, and we recorded temporal changes in these communities during the pollution decline that occurred from 1992 to 2006. In the 1990s, the diversity of the Lepidoptera community was positively correlated with the distance from the copper-nickel smelter at Monchegorsk. The overall abundance of Lepidoptera did not change along the pollution gradient, although the abundance of many species decreased with increasing pollution. The responses of each individual species to pollution were associated with its life history traits. The abundances of monophagous species that fed inside live plant tissues and hibernated as imagoes or pupae were not affected by pollution, whereas the abundances of oligophagous and polyphagous species that fed externally on plants and hibernated as larvae generally declined near the smelter. Substantial decreases in aerial emissions from the smelter between 1992 and 2006 resulted in an increase in the diversity of moths and butterflies in severely polluted habitats, whereas their overall abundance did not change. This recovery of the Lepidoptera community occurred due to the reappearance of rare species that had been previously extirpated by pollution and was observed despite the lack of any signs of recovery of the vegetation in the heavily polluted sites. We conclude that the recovery trajectories of insect communities following emission control can be predicted from studies of their changes along spatial pollution gradients by using space-for-time substitution.

Drastic decline of extensive grassland species in Central Europe since 1950: Forester moths of the genus Jordanita (Lepidoptera, Zygaenidae) as a type example

The decline of biodiversity in general and of insect diversity in particular has been recognized as a major environmental problem in recent years. In this study, we analyze the distribution and the decline of populations of forester moths of the genus Jordanita in Central Europe since 1950 as a type example of the loss of grassland biodiversity, and discuss potential drivers causing this decline. Based on the extensive work in museums and private collections, a literature review and own observations, and including data as far back as 1834, this genus helps to understand the deeper reasons of insect population and biodiversity decline, as the well investigated six Central European species cover a broad range of extensive grassland habitats (fens to low-production grassland and xerothermic steppes) from low altitudes to high alpine meadows. Therefore, they monitor processes relevant also to other, less investigated grassland species. Although there are differences in research intensity over time and in different natural areas, we show that in the whole of Central Europe, the populations of all six investigated Jordanita species broke down massively in the past decades, both in terms of number of populated habitats (about 400 recorded localities after the year 2000 compared with a total number of about 1600 at all times, cumulated for all six species) and in terms of number of individuals. On the other hand, some natural areas on a regional scale have more or less maintained their Jordanita populations, due to conservative land use and due to the early implementation of conservation and protection management plans. The reasons of decline are manifold and monitored in detail by the different species with their different habitat requirements. They comprise (1) loss of habitats due to land use changes (both intensification and abandonment), (2) loss of habitats due to urbanization and construction work, (3) loss of habitat networks to cope with small-scale extinction events, (4) more intensive growth of grass at the expense of other plants in otherwise undisturbed habitats due to fertilization through the air (increased nitrogen levels due to human activities) and (5) use of pesticides.

Multi‐surveyor capture‐mark‐recapture as a powerful tool for butterfly population monitoring in the pre‐imaginal stage

For many elusive insect species, which are difficult to cover by standard monitoring schemes, innovative survey methods are needed to gain robust data on abundance and population trends. We suggest a monitoring of overwintering larvae for the endangered nymphalid butterfly Limenitis reducta. We tested different removal and capture‐mark‐recapture (CMR) approaches in a field study in the “Alb‐Donau” region, Germany. Classical removal and CMR studies require movement of the organisms under study, but in our approach, we replaced movement of the study organisms by random movement of multiple different surveyors. We tested the validity of the approach by comparing detection frequencies from our field data with simulated detections. Our results indicate that multi‐surveyor removal/CMR techniques are suitable for estimating abundance of overwintering L. reducta larvae. Depending on surveyor experience, the average detection probability ranged between 16% for novices and 35% for experts. The uncertainty of population estimates increased with a decrease in personnel expenditure. Estimated larval densities on a spruce clear‐cut varied between one and three individuals per 100 m², probably related to habitat conditions. We suggest a CMR approach with three to four trained surveyors for the monitoring of L. reducta populations in the overwintering stage. Compared with previous sampling methods, our approach is a powerful tool with clear advantages: long survey period, estimates of the absolute population size accompanied by uncertainty measures, and estimates of overwinter mortality. The proposed method can be adapted and used for several different butterfly species, other insect taxa with specific immobile life stages, and some sessile organisms, for example, elusive plants, fungi, or corals.

Climate-driven divergent long-term trends of forest beetles in Japan

Concerning declines in insect populations have been reported from Europe and the United States, yet there are gaps in our knowledge of the drivers of insect trends and their distribution across the world. We report on our analysis of a spatially extensive, 14-year study of ground-dwelling beetles in four natural forest biomes spanning Japan's entire latitudinal range (3000 km). Beetle species richness, abundance and biomass declined in evergreen coniferous forests but increased in broadleaf-coniferous mixed forests. Further, beetles in evergreen coniferous forests responded negatively to increased temperature and precipitation anomalies, which have both risen over the study's timespan. These significant changes parallel reports of climate-driven changes in forest tree species, providing further evidence that climate change is altering forest ecosystems fundamentally. Given the enormous biodiversity and ecosystem services that forests support globally, the implications for biodiversity change resulting from climate change could be profound.

Past and recent farming degrades aquatic insect genetic diversity

Recent declines in once-common species are triggering concern that an environmental crisis point has been reached. Yet, the lack of long abundance time series data for most species can make it difficult to attribute these changes to anthropogenic causes, and to separate them from normal cycles. Genetic diversity, on the other hand, is sensitive to past and recent environmental changes, and reflects a measure of a populations' potential to adapt to future stressors. Here, we consider whether patterns of genetic diversity among aquatic insects can be linked to historical and recent patterns of land use change. We collated mitochondrial cytochrome c oxidase subunit I (COI) variation for >700 aquatic insect species across the United States, where patterns of agricultural expansion and intensification have been documented since the 1800s. We found that genetic diversity was lowest in regions where cropland was historically (pre-1950) most extensive, suggesting a legacy of past environmental harm. Genetic diversity further declined where cropland has since expanded, even after accounting for climate and sampling effects. Notably though, genetic diversity also appeared to rebound where cropland has diminished. Our study suggests that genetic diversity at the community level can be a powerful tool to infer potential population declines and rebounds over longer time spans than is typically possible with ecological data. For the aquatic insects that we considered, patterns of land use many decades ago appear to have left long-lasting damage to genetic diversity that could threaten evolutionary responses to rapid global change.

Prairie Strips and Lower Land Use Intensity Increase Biodiversity and Ecosystem Services

Agricultural landscapes can be managed to protect biodiversity and maintain ecosystem services. One approach to achieve this is to restore native perennial vegetation within croplands. Where rowcrops have displaced prairie, as in the US Midwest, restoration of native perennial vegetation can align with crops in so called “prairie strips.” We tested the effect of prairie strips in addition to other management practices on a variety of taxa and on a suite of ecosystem services. To do so, we worked within a 33-year-old experiment that included treatments that varied methods of agricultural management across a gradient of land use intensity. In the two lowest intensity crop management treatments, we introduced prairie strips that occupied 5% of crop area. We addressed three questions: (1) What are the effects of newly established prairie strips on the spillover of biodiversity and ecosystem services into cropland? (2) How does time since prairie strip establishment affect biodiversity and ecosystem services? (3) What are the tradeoffs and synergies among biodiversity conservation, non-provisioning ecosystem services, and provisioning ecosystem services (crop yield) across a land use intensity gradient (which includes prairie strips)? Within prairie strip treatments, where sampling effort occurred within and at increasing distance from strips, dung beetle abundance, spider abundance and richness, active carbon, decomposition, and pollination decreased with distance from prairie strips, and this effect increased between the first and second year. Across the entire land use intensity gradient, treatments with prairie strips and reduced chemical inputs had higher butterfly abundance, spider abundance, and pollination services. In addition, soil organic carbon, butterfly richness, and spider richness increased with a decrease in land use intensity. Crop yield in one treatment with prairie strips was equal to that of the highest intensity management, even while including the area taken out of production. We found no effects of strips on ant biodiversity and greenhouse gas emissions (N2O and CH4). Our results show that, even in early establishment, prairie strips and lower land use intensity can contribute to the conservation of biodiversity and ecosystem services without a disproportionate loss of crop yield.

Phenological sensitivity and seasonal variability explain climate-driven trends in Mediterranean butterflies

Although climate-driven phenological shifts have been documented for many taxa across the globe, we still lack knowledge of the consequences they have on populations. Here, we used a comprehensive database comprising 553 populations of 51 species of north-western Mediterranean butterflies to investigate the relationship between phenology and population trends in a 26-year period. Phenological trends and sensitivity to climate, along with various species traits, were used to predict abundance trends. Key ecological traits accounted for a general decline of more than half of the species, most of which, surprisingly, did not change their phenology under a climate warming scenario. However, this was related to the regional cooling in a short temporal window that includes late winter and early spring, during which most species concentrate their development. Finally, we demonstrate that phenological sensitivity—but not phenological trends—predicted population trends, and argue that species that best adjust their phenology to inter-annual climate variability are more likely to maintain a synchronization with trophic resources, thereby mitigating possible negative effects of climate change. Our results reflect the importance of assessing not only species' trends over time but also species’ abilities to respond to a changing climate based on their sensitivity to temperature.

Using DNA Metabarcoding to Identify Floral Visitation by Pollinators

The identification of floral visitation by pollinators provides an opportunity to improve our understanding of the fine-scale ecological interactions between plants and pollinators, contributing to biodiversity conservation and promoting ecosystem health. In this review, we outline the various methods which can be used to identify floral visitation, including plant-focused and insect-focused methods. We reviewed the literature covering the ways in which DNA metabarcoding has been used to answer ecological questions relating to plant use by pollinators and discuss the findings of this research. We present detailed methodological considerations for each step of the metabarcoding workflow, from sampling through to amplification, and finally bioinformatic analysis. Detailed guidance is provided to researchers for utilisation of these techniques, emphasising the importance of standardisation of methods and improving the reliability of results. Future opportunities and directions of using molecular methods to analyse plant–pollinator interactions are then discussed.

Decadal Patterns of Forest and Pollinator Recovery Following the Eradication of an Invasive Shrub

Invasive non-native woody shrubs pose a major threat to forested ecosystems in many parts of the world and there is an urgent need for research on the restoration and recovery of these areas. We studied patterns of tree growth and regeneration 13 years after the experimental eradication (by chainsaw or mulching machine followed by herbicide treatments) of Ligustrum sinense Lour. (Chinese privet) from riparian forests in Georgia, United States. We also followed the recovery of bee and butterfly populations using sites with no history of privet invasion as a reference. By the end of the study, the basal area of restored plots was 24% greater, on average, than still-invaded control plots. Because tree growth rates did not differ among treatments, this increase is attributable to the 60% increase in the number of regenerating native stems (dominated by Acer negundo L.) following privet removal. The benefits of privet removal on pollinators were immediate and long-lasting with the richness and abundance of bees and butterflies being consistently higher in restored plots than in control plots. The diversity, abundance, and composition of bees in restored and reference (i.e., never invaded) plots were comparable by the end of the study. This was less true for butterflies, however, possibly due to the legacy effects of privet invasion on plant communities. Our results demonstrate the long-term benefits of removing privet on forest regeneration and pollinator communities. Indeed, without such efforts, it is probable that forest cover will gradually thin and ultimately disappear from privet-invaded areas as overstory trees die without replacement.

How and why grasshopper community maturation rates are slowing on a North American tall grass prairie

Invertebrate growth rates have been changing in the Anthropocene. We examine rates of seasonal maturation in a grasshopper community that has been declining annually greater than 2% a year over 34 years. As this grassland has experienced a 1°C increase in temperature, higher plant biomass and lower nutrient densities, the community is maturing more slowly. Community maturation had a nutritional component: declining in years/watersheds with lower plant nitrogen. The effects of fire frequency were consistent with effects of plant nitrogen. Principal components analysis also suggests associated changes in species composition-declines in the densities of grass feeders were associated with declines in community maturation rates. We conclude that slowed maturation rates-a trend counteracted by frequent burning-likely contribute to long-term decline of this dominant herbivore.

The Invisible Hand of the Periodic Table: How Micronutrients Shape Ecology

Beyond the better-studied carbohydrates and the macronutrients nitrogen and phosphorus, a remaining 20 or so elements are essential for life and have distinct geographical distributions, making them of keen interest to ecologists. Here, I provide a framework for understanding how shortfalls in micronutrients like iodine, copper, and zinc can regulate individual fitness, abundance, and ecosystem function. With a special focus on sodium, I show how simple experiments manipulating biogeochemistry can reveal why many of the variables that ecologists study vary so dramatically from place to place. I conclude with a discussion of how the Anthropocene's changing temperature, precipitation, and atmospheric CO2 levels are contributing to nutrient dilution (decreases in the nutrient quality at the base of food webs).

Butterfly declines in protected areas of Illinois: Assessing the influence of two decades of climate and landscape change

Despite increasing concern regarding broad-scale declines in insects, there are few published long-term, systematic butterfly surveys in North America, and fewer still that have incorporated the influence of changing climate and landscape variables. In this study, we analyzed 20 years of citizen science data at seven consistently monitored protected areas in Illinois, U.S.A. We used mixed models and PERMANOVA to evaluate trends in butterfly abundance, richness, and composition while also evaluating the effects of temperature and land use. Overall butterfly richness, but not abundance, increased in warmer years. Surprisingly, richness also was positively related to percent impervious surface (at the 2 km radius scale), highlighting the conservation value of protected areas in urban landscapes (or alternately, the potential negative aspects of agriculture). Precipitation had a significant and variable influence through time on overall butterfly abundance and abundance of resident species, larval host plant specialists, and univoltine species. Importantly, models incorporating the influence of changing temperature, precipitation, and impervious surface indicated a significant overall decline in both butterfly abundance and species richness, with an estimated abundance decrease of 3.8%/year and richness decrease of 1.6%/year (52.5% and 27.1% cumulatively from 1999 to 2018). Abundance and richness declines were also noted across all investigated functional groups except non-resident (migratory) species. Butterfly community composition changed through time, but we did not find evidence of systematic biotic homogenization, perhaps because declines were occurring in nearly all functional groups. Finally, at the site-level, declines in either richness or abundance occurred at five of seven locations, with only the two largest locations (>300 Ha) not exhibiting declines. Our results mirror those of other long-term butterfly studies predominantly in Europe and North America that have found associations of butterflies with climate variables and general declines in butterfly richness and abundance.

Changes in climate drive recent monarch butterfly dynamics

Declines in the abundance and diversity of insects pose a substantial threat to terrestrial ecosystems worldwide. Yet, identifying the causes of these declines has proved difficult, even for well-studied species like monarch butterflies, whose eastern North American population has decreased markedly over the last three decades. Three hypotheses have been proposed to explain the changes observed in the eastern monarch population: loss of milkweed host plants from increased herbicide use, mortality during autumn migration and/or early-winter resettlement and changes in breeding-season climate. Here, we use a hierarchical modelling approach, combining data from >18,000 systematic surveys to evaluate support for each of these hypotheses over a 25-yr period. Between 2004 and 2018, breeding-season weather was nearly seven times more important than other factors in explaining variation in summer population size, which was positively associated with the size of the subsequent overwintering population. Although data limitations prevent definitive evaluation of the factors governing population size between 1994 and 2003 (the period of the steepest monarch decline coinciding with a widespread increase in herbicide use), breeding-season weather was similarly identified as an important driver of monarch population size. If observed changes in spring and summer climate continue, portions of the current breeding range may become inhospitable for monarchs. Our results highlight the increasingly important contribution of a changing climate to insect declines.

Climate change effects on animal ecology: butterflies and moths as a case study

Butterflies and moths (Lepidoptera) are one of the most studied, diverse, and widespread animal groups, making them an ideal model for climate change research. They are a particularly informative model for studying the effects of climate change on species ecology because they are ectotherms that thermoregulate with a suite of physiological, behavioural, and phenotypic traits. While some species have been negatively impacted by climatic disturbances, others have prospered, largely in accordance with their diversity in life-history traits. Here we take advantage of a large repertoire of studies on butterflies and moths to provide a review of the many ways in which climate change is impacting insects, animals, and ecosystems. By studying these climate-based impacts on ecological processes of Lepidoptera, we propose appropriate strategies for species conservation and habitat management broadly across animals.

Cross-Ecosystem Fluxes of Pesticides from Prairie Wetlands Mediated by Aquatic Insect Emergence: Implications for Terrestrial Insectivores

Contaminants alter the quantity and quality of insect prey available to terrestrial insectivores. In agricultural regions, the quantity of aquatic insects emerging from freshwaters can be impacted by insecticides originating from surrounding croplands. We hypothesized that, in such regions, adult aquatic insects could also act as vectors of pesticide transfer to terrestrial food webs. To estimate insect-mediated pesticide flux from wetlands embedded in an important agricultural landscape, semipermanetly and temporarily ponded wetlands were surveyed in cropland and grassland landscapes across a natural salinity gradient in the Prairie Pothole Region of North Dakota (USA) during the bird breeding season in 2015 and 2016 (n = 14 and 15 wetlands, respectively). Current-use pesticides, including the herbicide atrazine and the insecticides bifenthrin and imidacloprid, were detected in newly emerged insects. Pesticide detections were similar in insects emerging from agricultural and grassland wetlands. Biomass of emerging aquatic insects decreased 43%, and insect-mediated pesticide flux increased 50% along the observed gradient in concentrations of insecticides in emerging aquatic insects (from 3 to 577 ng total insecticide g^-1 insect). Overall, adult aquatic insects were estimated to transfer between 2 and 180 µg total pesticide wetland^-1  d^-1 to the terrestrial ecosystem. In one of the 2 study years, biomass of emerging adult aquatic insects was also 73% lower from agricultural than grassland wetlands and was dependent on salinity. Our results suggest that accumulated insecticides reduce the availability of adult aquatic insect prey for insectivores and potentially increase insectivore exposure to insect-borne pesticides. Adult aquatic insects retain pesticides across metamorphosis and may expose insectivores living near both agricultural and grassland wetlands to dietary sources of toxic chemicals. Environ Toxicol Chem 2021;40:2282-2296. Published 2021. This article is a U.S. Government work and is in the public domain in the USA.

Thermal flexibility and a generalist life history promote urban affinity in butterflies

Urban expansion poses a serious threat to biodiversity. Given that the expected area of urban land cover is predicted to increase by 2-3 million km² by 2050, urban environments are one of the most widespread human-dominated land-uses affecting biodiversity. Responses to urbanization differ greatly among species. Some species are unable to tolerate urban environments (i.e., urban avoiders), others are able to adapt and use areas with moderate levels of urbanization (i.e., urban adapters), and yet others are able to colonize and even thrive in urban environments (i.e., urban exploiters). Quantifying species-specific responses to urbanization remains an important goal, but our current understanding of urban tolerance is heavily biased toward traditionally well-studied taxa (e.g., mammals and birds). We integrated a continuous measure of urbanization-night-time lights-with over 900,000 species' observations from the Global Biodiversity Information Facility to derive a comprehensive analysis of species-specific (N = 158 species) responses of butterflies to urbanization across Europe. The majority of butterfly species included in our analysis avoided urban areas, regardless of whether species' urban affinities were quantified as a mean score of urban affinity across all occurrences (79%) or as a species' response curve to the whole urbanization gradient (55%). We then used species-specific responses to urbanization to assess which life history strategies promote urban affinity in butterflies. These trait-based analyses found strong evidence that the average number of flight months, likely associated with thermal niche breath, and number of adult food types were positively associated with urban affinity, while hostplant specialism was negatively associated with urban affinity. Overall, our results demonstrate that specialist butterflies, both in terms of thermal and diet preferences, are most at risk from increasing urbanization, and should thus be considered in urban planning and prioritized for conservation.

The role of climate change in pollinator decline across the Northern Hemisphere is underestimated

Pollinator biodiversity loss occurs at unprecedented rates globally, with particularly sharp declines documented in the North Temperate Zone. There is currently no consensus on the main drivers of the decline. Although climate change is expected to drive biodiversity loss in the future, current warming is often suggested to have positive impacts on pollinator assemblages in higher latitudes. Consequently, pollinator conservation initiatives in Europe and the USA tend to lack climate adaptation initiatives, an omission of which may be risky if climate change has significant negative impacts on pollinators. To gain an understanding of the impacts of climate change on pollinator biodiversity in the Northern Hemisphere, we conducted a literature review on genetic, species and community level diversity. Our findings suggest that global heating most likely causes homogenization of pollinator assemblages at all levels of pollinator biodiversity, making them less resilient to future stochasticity. Aspects of biodiversity that are rarely measured (e.g. genetic diversity, β-diversity, species evenness) tend to be most affected, while some dimensions of climate change, such as fluctuations in winter weather conditions, changes in the length of the vegetational season and increased frequency of extreme weather events, that seldom receive attention in empirical studies, tend to be particularly detrimental to pollinators. Negative effects of global heating on pollinator biodiversity are most likely exacerbated by homogenous and fragmented landscapes, widespread across Europe and the US, which limit opportunities for range-shifts and reduce micro-climatic buffering. This suggests the need for conservation initiatives to focus on increasing landscape connectivity and heterogeneity at multiple spatial scales.

Phenological sensitivity to temperature mediates herbivory

Species interactions drive ecosystem processes and are a major focus of global change research. Among the most consequential interactions expected to shift with climate change are those between insect herbivores and plants, both of which are highly sensitive to temperature. Insect herbivores and their host plants display varying levels of synchrony that could be disrupted or enhanced by climate change, yet empirical data on changes in synchrony are lacking. Using evidence of herbivory on herbarium specimens collected from the northeastern United States and France from 1900 to 2015, we provide evidence that plant species with temperature-sensitive phenologies experience higher levels of insect damage in warmer years, while less temperature-sensitive, co-occurring species do not. While herbivory might be mediated by interactions between warming and phenology through multiple pathways, we suggest that warming might lengthen growing seasons for phenologically sensitive plant species, exposing their leaves to herbivores for longer periods of time in warm years. We propose that elevated herbivory in warm years may represent a previously underappreciated cost to phenological tracking of climate change over longer timescales.

Recent climate change is creating hotspots of butterfly increase and decline across North America

Some insect populations are experiencing dramatic declines, endangering the crucial ecosystem services they provide. Yet, other populations appear robust, highlighting the need to better define patterns and underlying drivers of recent change in insect numbers. We examined abundance and biodiversity trends for North American butterflies using a unique citizen-science dataset that has recorded observations of over 8 million butterflies across 456 species, 503 sites, nine ecoregions, and 26 years. Butterflies are a biodiverse group of pollinators, herbivores, and prey, making them useful bellwethers of environmental change. We found great heterogeneity in butterfly species' abundance trends, aggregating near zero, but with a tendency toward decline. There was strong spatial clustering, however, into regions of increase, decrease, or relative stasis. Recent precipitation and temperature appeared to largely drive these patterns, with butterflies generally declining at increasingly dry and hot sites but increasing at relatively wet or cool sites. In contrast, landscape and butterfly trait predictors had little influence, though abundance trends were slightly more positive around urban areas. Consistent with varying responses by different species, no overall directional change in butterfly species richness or evenness was detected. Overall, a mosaic of butterfly decay and rebound hotspots appeared to largely reflect geographic variability in climate drivers. Ongoing controversy about insect declines might dissipate with a shift in focus to the causes of heterogeneous responses among taxa and sites, with climate change emerging as a key suspect when pollinator communities are broadly impacted.

Mining the Species Diversity of Lacewings: New Species of the Pleasing Lacewing Genus Dilar Rambur, 1838 (Neuroptera, Dilaridae) from the Oriental Region

Simple Summary

The pleasing lacewing (Dilaridae) is a little known family of the holometabolous order Neuroptera, and our understanding of their species diversity has long remained poor. Here, we present descriptions of 12 new species of the pleasing lacewing genus Dilar Rambur, which is widely distributed in the Palaearctic and Oriental regions. We found disparate wing marking patterns as well as several unique characters of the male genitalia of the new species, which highlight the diverse morphologies of Dilar. Based on a faunal analysis, eight areas of endemism of Dilar were distinguished, and the state of their species diversity and endemism were summarized. The Oriental part of China was revealed as the region with the highest species diversity of this genus, and Yunnan within this region stood out as the most species-rich subregion.

Abstract

The species diversity of insects is extraordinarily rich, but still has been insufficiently explored or underestimated particularly for uncommon groups. The pleasing lacewings (Dilaridae) are a little known family of Neuroptera with distinct sexually dimorphic antennae. The species diversity of pleasing lacewings was recently found to be severely underestimated and requires a comprehensive investigation, as well as systematic reviews. Here, we report on 12 new species of the pleasing lacewing genus Dilar Rambur, 1838, from the Oriental region, namely D. forcipatus sp. nov. and D. laoticus sp. nov. from Laos (new country record of Dilar); D. malickyi sp. nov., D. phraenus sp. nov. and D. rauschorum sp. nov. from northern Thailand; D. striatus sp. nov. from northern Vietnam; D. cangyuanensis sp. nov., D. daweishanensis sp. nov., D. nujianganus sp. nov., D. weibaoshanensis sp. nov., D. yucheni sp. nov., and D. zhangweiae sp. nov. from Yunnan and Tibet, both in southwestern China. The new species of Dilar display several types of wing marking patterns, and the morphology of the male genitalia is highly diverse. A comprehensive examination of the species diversity and distribution of Dilar concluded that Yunnan (southwestern China) represents a biogeographic region with high endemism and the richest species diversity. The potential correlation between vertical distribution and geographical latitude in Dilar was also analyzed.

Agricultural intensification and climate change are rapidly decreasing insect biodiversity

Major declines in insect biomass and diversity, reviewed here, have become obvious and well documented since the end of World War II. Here, we conclude that the spread and intensification of agriculture during the past half century is directly related to these losses. In addition, many areas, including tropical mountains, are suffering serious losses because of climate change as well. Crops currently occupy about 11% of the world's land surface, with active grazing taking place over an additional 30%. The industrialization of agriculture during the second half of the 20th century involved farming on greatly expanded scales, monoculturing, the application of increasing amounts of pesticides and fertilizers, and the elimination of interspersed hedgerows and other wildlife habitat fragments, all practices that are destructive to insect and other biodiversity in and near the fields. Some of the insects that we are destroying, including pollinators and predators of crop pests, are directly beneficial to the crops. In the tropics generally, natural vegetation is being destroyed rapidly and often replaced with export crops such as oil palm and soybeans. To mitigate the effects of the Sixth Mass Extinction event that we have caused and are experiencing now, the following will be necessary: a stable (and almost certainly lower) human population, sustainable levels of consumption, and social justice that empowers the less wealthy people and nations of the world, where the vast majority of us live, will be necessary.

The decline of butterflies in Europe: Problems, significance, and possible solutions

We review changes in the status of butterflies in Europe, focusing on long-running population data available for the United Kingdom, the Netherlands, and Belgium, based on standardized monitoring transects. In the United Kingdom, 8% of resident species have become extinct, and since 1976 overall numbers declined by around 50%. In the Netherlands, 20% of species have become extinct, and since 1990 overall numbers in the country declined by 50%. Distribution trends showed that butterfly distributions began decreasing long ago, and between 1890 and 1940, distributions declined by 80%. In Flanders (Belgium), 20 butterflies have become extinct (29%), and between 1992 and 2007 overall numbers declined by around 30%. A European Grassland Butterfly Indicator from 16 European countries shows there has been a 39% decline of grassland butterflies since 1990. The 2010 Red List of European butterflies listed 38 of the 482 European species (8%) as threatened and 44 species (10%) as near threatened (note that 47 species were not assessed). A country level analysis indicates that the average Red List rating is highest in central and mid-Western Europe and lowest in the far north of Europe and around the Mediterranean. The causes of the decline of butterflies are thought to be similar in most countries, mainly habitat loss and degradation and chemical pollution. Climate change is allowing many species to spread northward while bringing new threats to susceptible species. We describe examples of possible conservation solutions and a summary of policy changes needed to conserve butterflies and other insects.

Insects and recent climate change

Insects have diversified through more than 450 million y of Earth's changeable climate, yet rapidly shifting patterns of temperature and precipitation now pose novel challenges as they combine with decades of other anthropogenic stressors including the conversion and degradation of land. Here, we consider how insects are responding to recent climate change while summarizing the literature on long-term monitoring of insect populations in the context of climatic fluctuations. Results to date suggest that climate change impacts on insects have the potential to be considerable, even when compared with changes in land use. The importance of climate is illustrated with a case study from the butterflies of Northern California, where we find that population declines have been severe in high-elevation areas removed from the most immediate effects of habitat loss. These results shed light on the complexity of montane-adapted insects responding to changing abiotic conditions. We also consider methodological issues that would improve syntheses of results across long-term insect datasets and highlight directions for future empirical work.

Glyphosate inhibits melanization and increases susceptibility to infection in insects

Melanin, a black-brown pigment found throughout all kingdoms of life, has diverse biological functions including UV protection, thermoregulation, oxidant scavenging, arthropod immunity, and microbial virulence. Given melanin's broad roles in the biosphere, particularly in insect immune defenses, it is important to understand how exposure to ubiquitous environmental contaminants affects melanization. Glyphosate-the most widely used herbicide globally-inhibits melanin production, which could have wide-ranging implications in the health of many organisms, including insects. Here, we demonstrate that glyphosate has deleterious effects on insect health in 2 evolutionary distant species, Galleria mellonella (Lepidoptera: Pyralidae) and Anopheles gambiae (Diptera: Culicidae), suggesting a broad effect in insects. Glyphosate reduced survival of G. mellonella caterpillars following infection with the fungus Cryptococcus neoformans and decreased the size of melanized nodules formed in hemolymph, which normally help eliminate infection. Glyphosate also increased the burden of the malaria-causing parasite Plasmodium falciparum in A. gambiae mosquitoes, altered uninfected mosquito survival, and perturbed the microbial composition of adult mosquito midguts. Our results show that glyphosate's mechanism of melanin inhibition involves antioxidant synergy and disruption of the reaction oxidation-reduction balance. Overall, these findings suggest that glyphosate's environmental accumulation could render insects more susceptible to microbial pathogens due to melanin inhibition, immune impairment, and perturbations in microbiota composition, potentially contributing to declines in insect populations.

Spatial phylogenetics of butterflies in relation to environmental drivers and angiosperm diversity across North America

Broad-scale, quantitative assessments of insect biodiversity and the factors shaping it remain particularly poorly explored. Here we undertook a spatial phylogenetic analysis of North American butterflies to test whether climate stability and temperature gradients have shaped their diversity and endemism. We also performed the first quantitative comparisons of spatial phylogenetic patterns between butterflies and flowering plants. We expected concordance between the two groups based on shared historical environmental drivers and presumed strong butterfly-host plant specializations. We instead found that biodiversity patterns in butterflies are strikingly different from flowering plants, especially warm deserts. In particular, butterflies show different patterns of phylogenetic clustering compared with flowering plants, suggesting differences in habitat conservation between the two groups. These results suggest that shared biogeographic histories and trophic associations do not necessarily assure similar diversity outcomes. The work has applied value in conservation planning, documenting warm deserts as a North American butterfly biodiversity hotspot.

Fewer butterflies seen by community scientists across the warming and drying landscapes of the American West

Uncertainty remains regarding the role of anthropogenic climate change in declining insect populations, partly because our understanding of biotic response to climate is often complicated by habitat loss and degradation among other compounding stressors. We addressed this challenge by integrating expert and community scientist datasets that include decades of monitoring across more than 70 locations spanning the western United States. We found a 1.6% annual reduction in the number of individual butterflies observed over the past four decades, associated in particular with warming during fall months. The pervasive declines that we report advance our understanding of climate change impacts and suggest that a new approach is needed for butterfly conservation in the region, focused on suites of species with shared habitat or host associations.