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The amount of semi‐natural habitat surrounding farm fields is a common but inconsistent predictor of natural enemy populations and predation services. Standard land cover metrics may not accurately capture the actual availability of limiting resources for natural enemies and can miss important dynamics across space and time. Theory from animal movement and landscape ecology predicts that regions with more, spatio‐temporally continuous resources (i.e. food and shelter) should have larger predator populations and enhanced biological control. To test these predictions empirically, we designed a study measuring aphids, lady beetles and predation services in agricultural landscapes in Wisconsin, USA. In two study years, we sampled lady beetles and aphids in 336 crop fields (corn, soybean, alfalfa and small grains) and adjacent semi‐natural habitat patches (grasslands and woodlands) across 24 1.5 km buffer landscapes at four to seven time points each, and in 1 year, we assessed predation rates with sentinel egg cards. We used aphid counts to model habitat‐specific aphid phenologies, from which we calculated landscape indices of prey amount and continuity. These indices, along with semi‐natural habitat area, were used to predict lady beetle abundance. While there were strong differences in the abundance and timing of aphids by habitat, semi‐natural habitat amount was still a better predictor of lady beetle counts and sentinel egg predation than either aphid amount or continuity indices in these landscapes. Synthesis and applications. Our findings confirm the robust relationship between lady beetles and semi‐natural habitat in agricultural landscapes, and highlight the complexities of measuring fine‐scale resource heterogeneity in real landscapes. Retaining or adding woodland and grassland patches in agricultural landscapes is likely to support larger lady beetle populations and enhance predation in crop fields. Our results suggest that these habitats may be more important for shelter than prey continuity, though this mechanism warrants further investigation. Future work should continue to refine experimental methods for the successful integration of landscape ecology and animal behaviour to support conservation goals. [ABSTRACT FROM AUTHOR]

One of the most challenging aspects of bee ecology and conservation is species-level identification, which is costly, time consuming, and requires taxonomic expertise. Recent advances in the application of deep learning and computer vision have shown promise for identifying large bumble bee (Bombus) species. However, most bees, such as sweat bees in the genus Lasioglossum, are much smaller and can be difficult, even for trained taxonomists, to identify. For this reason, the great majority of bees are poorly represented in the crowdsourced image datasets often used to train computer vision models. But even larger bees, such as bumble bees from the B. vagans complex, can be difficult to separate morphologically. Using images of specimens from our research collections, we assessed how deep learning classification models perform on these more challenging taxa, qualitatively comparing models trained on images of whole pinned specimens or on images of bee forewings. The pinned specimen and wing image datasets represent 20 and 18 species from 6 and 4 genera, respectively, and were used to train the EfficientNetV2L convolutional neural network. Mean test precision was 94.9% and 98.1% for pinned and wing images respectively. Results show that computer vision holds great promise for classifying smaller, more difficult to identify bees that are poorly represented in crowdsourced datasets. Images from research and museum collections will be valuable for expanding classification models to include additional species, which will be essential for large scale conservation monitoring efforts. [ABSTRACT FROM AUTHOR]

The extent to which persisting species may fill the functional role of extirpated or declining species has profound implications for the structure of biological communities and ecosystem functioning. In North America, arthropodivorous bats are threatened on a continent‐wide scale by the spread of white‐nose syndrome (WNS), a disease caused by the fungus Pseudogymnoascus destructans. We tested whether bat species that display lower mortality from this disease can partially fill the functional role of other bat species experiencing population declines. Specifically, we performed high‐throughput amplicon sequencing of guano from two generalist predators: the little brown bat (Myotis lucifugus) and big brown bat (Eptesicus fuscus). We then compared changes in prey consumption before versus after population declines related to WNS. Dietary niches contracted for both species after large and abrupt declines in little brown bats and smaller declines in big brown bats, but interspecific dietary overlap did not change. Furthermore, the incidence and taxonomic richness of agricultural pest taxa detected in diet samples decreased following bat population declines. Our results suggest that persisting generalist predators do not necessarily expand their dietary niches following population declines in other predators, providing further evidence that the functional roles of different generalist predators are ecologically distinct. [ABSTRACT FROM AUTHOR]

Pollinators are undergoing a global decline. Although vital to pollinator conservation and ecological research, species-level identification is expensive, time consuming, and requires specialized taxonomic training. However, deep learning and computer vision are providing ways to open this methodological bottleneck through automated identification from images. Focusing on bumble bees, we compare four convolutional neural network classification models to evaluate prediction speed, accuracy, and the potential of this technology for automated bee identification. We gathered over 89,000 images of bumble bees, representing 36 species in North America, to train the ResNet, Wide ResNet, InceptionV3, and MnasNet models. Among these models, InceptionV3 presented a good balance of accuracy (91.6%) and average speed (3.34 ms). Species-level error rates were generally smaller for species represented by more training images. However, error rates also depended on the level of morphological variability among individuals within a species and similarity to other species. Continued development of this technology for automatic species identification and monitoring has the potential to be transformative for the fields of ecology and conservation. To this end, we present BeeMachine, a web application that allows anyone to use our classification model to identify bumble bees in their own images. [ABSTRACT FROM AUTHOR]

1. Resource pulses, narrow periods of high resource availability, can elicit strong behavioural responses across diverse taxa. Mass‐flowering agricultural crops are an example of a resource pulse that insect pollinators exploit. However, the underlying mechanism behind changes in pollinator behaviour associated with mass‐flowering crops is still relatively unexplored. 2. The present study quantified the behavioural response of bumble bees, an important wild pollinator, to commercial cranberry bloom, an important mass‐flowering crop in Wisconsin, U.S.A. Over a 2‐year period, foraging trip duration was measured using radio frequency identification at 14 farms situated across landscape contexts, ranging from high to low natural area (woodland amount). Using transect surveys, floral resource abundance at a landscape scale was estimated. 3. It was found that bumble bees were highly sensitive to temporal changes in landscape‐level resource abundance associated with the onset of cranberry bloom, during which they decreased foraging trip duration by 22% and increased the number of foraging trips during bloom by 24% on average relative to the period before and after bloom. This phenomenon was consistent across colonies, individual bees, and landscape contexts, despite a higher abundance of flowers in low woodland landscapes. Bumble bee colonies growing in low‐ and high‐woodland landscapes exhibited a similar performance. 4. As mass‐flowering crops are probably a factor influencing bumble bee foraging behaviour in agricultural regions, investigations should continue into how variable resource landscapes, particularly those offering resource pulses, affect wild pollinators and the pollination services they provide. [ABSTRACT FROM AUTHOR]

Restoration of grassland ecosystems is essential for mitigating global losses of biodiversity and is typically initiated to foster persistent, long‐term increases in biodiversity. Yet, evaluating long‐term impacts of restoration on biodiversity is rare, especially across sites restored using consistent methods. Evaluation of restoration outcomes is particularly important for increasing predictive capacity in restoration ecology to determine the level of restoration effort that is required to achieve both short‐ and long‐term restoration goals. We conducted a multisite study that explicitly compared the impacts of no intervention ("passive" or "natural" recovery), low intervention (seeding native plants), and moderate intervention (seeding native plants and using fire management) at 32 restored prairies differing in the age of restoration (3–23 years). Grasslands with natural recovery have equivalent native plant species richness compared to sites with low and moderate restoration intervention, however, they have significantly lower‐quality vegetation, as measured by Floristic Quality (mean C). We found that managing restored prairies with fire maintains native plant richness over time and is correlated with higher vegetation quality and presence of seeded species. Seed mixes with a high mean C score are positively correlated with plant community quality. However, seed mixes with more species are negatively correlated with the proportion of seeded species present. We found that while the degree of restoration intervention has no effect on the number of native plant species, greater levels of assisted recovery are required to produce restored prairies that resemble high‐quality remnant vegetation and, especially, to maintain these successes over the long term. [ABSTRACT FROM AUTHOR]

Allochthonous resource movement across ecosystem boundaries creates episodic linkages between ecosystems. The sensitivity of the community to external resources of varying duration can alter the baseline upon which future pulses of allochthony can act. We explored the terrestrial ecosystem response to pulsed inputs of lake-derived resources with a manipulative experiment in a subarctic heathland where we assessed plant community and nutrient availability responses to additions of midge carcasses (Diptera: Chironomidae). Insect carcasses were added as either a one-time pulse or a 4-yr press to simulate differing durations of allochthony, which is common in the area. We found that midge pulses significantly elevated soil inorganic [N] in the first year (7× over background levels) but were significantly diminished (1.5×) by the second year after the initial pulse. The press treatment continued to elevate total soil inorganic [N] to 13× over background levels by the fourth year of midge additions, but then declined to 3.6× background in year 5 when experimental midge additions had ceased. In contrast to the soil inorganic N response, plant biomass was similar in pulse-addition and control plots over the course of the experiment. However, by the second year of the study plant biomass in press-addition plots were significantly higher than controls (>50%), and continued to increase over the 4 yr of the press treatment. Midge addition stimulated dominance of graminoids and thatch litter in plots that had previously been primarily heathland vegetation, a response that persisted 4 yr post-midge addition. Our findings suggest that soil and plant community responses to persistent insect carcass deposition (e.g., press) into heathland vegetation has the potential to carry forward in a way that modifies the baseline ecosystem conditions upon which additional allochthony may act. [ABSTRACT FROM AUTHOR]

The expansion of modern agriculture has led to the loss and fragmentation of natural habitat, resulting in a global decline in biodiversity, including bees. In many countries, farmers can participate in cost-share programs to create natural habitat on their farms for the conservation of beneficial insects, such as bees. Despite their dependence on bee pollinators and the demonstrated commitment to environmental stewardship, participation in such programs by Wisconsin cranberry growers has been low. The objective of this study was to understand the barriers that prevent participation by Wisconsin cranberry growers in cost-share programs for on-farm conservation of native bees. We conducted a survey of cranberry growers (n = 250) regarding farming practices, pollinators, and conservation. Although only 10% of growers were aware of federal pollinator cost-share programs, one third of them were managing habitat for pollinators without federal aid. Once informed of the programs, 50% of growers expressed interest in participating. Fifty-seven percent of growers manage habitat for other wildlife, although none receive cost-share funding to do so. Participation in cost-share programs could benefit from outreach activities that promote the programs, a reduction of bureaucratic hurdles to participate, and technical support for growers on how to manage habitat for wild bees. [ABSTRACT FROM AUTHOR]

Ecoinformatics, as defined in this review, is the use of preexisting data sets to address questions in ecology. We provide the first review of ecoinformatics methods in agricultural entomology. Ecoinformatics methods have been used to address the full range of questions studied by agricultural entomologists, enabled by the special opportunities associated with data sets, nearly all of which have been observational, that are larger and more diverse and that embrace larger spatial and temporal scales than most experimental studies do. We argue that ecoinformatics research methods and traditional, experimental research methods have strengths and weaknesses that are largely complementary. We address the important interpretational challenges associated with observational data sets, highlight common pitfalls, and propose some best practices for researchers using these methods. Ecoinformatics methods hold great promise as a vehicle for capitalizing on the explosion of data emanating from farmers, researchers, and the public, as novel sampling and sensing techniques are developed and digital data sharing becomes more widespread. [ABSTRACT FROM AUTHOR]

Simplification of agricultural landscapes is expected to have positive effects on many crop pests and negative effects on their natural enemies, potentially leading to increased pest pressure, decreased crop yield, and increased insecticide use. While many intermediate links in this causal chain have empirical support, there is mixed evidence for ultimate relationships between landscape simplification, crop yield, and insecticide use, especially at large spatial and temporal scales. We explored relationships between landscape simplification (proportion of a county in harvested cropland) and insecticide use (proportion of harvested cropland treated with insecticides), using county-level data from the US Census of Agriculture and a variety of standard and spatiotemporal regression techniques. The best model indicated that insecticide use across the US has increased between 1997 and 2012, was strongly dependent on the crops grown in a county, increased with average farm income and size, and increased with annual growing degree days. After accounting for those variables, and other unidentified spatial and temporal structure in the data, there remained a statistically significant, moderate, positive relationship between insecticide use and landscape simplification. These results lend general support to the causal chain outlined above, and to the notion that a landscape perspective is useful for managing ecosystem services that are provided by mobile organisms and valuable to agriculture. [ABSTRACT FROM AUTHOR]

Natural habitats can affect the population dynamics of mobile insects, and the spatial and temporal effects on agricultural pest species may be especially relevant for tailoring management strategies to the farm context. Drosophila suzukii Matsumura (Diptera: Drosophilidae) is suspected to utilize woodland habitat for wild hosts and overwintering with possible adverse effects of woods on adjacent fruit crops. A two-year study in the Upper Midwest, USA examined if the amount of woodland in the landscape affects early season activity and relative abundance of D. suzukii in raspberry fields. Thirty-five farms were selected to span a gradient of low-to-high woodland area at the 1.5 km scale. The first capture of D. suzukii occurred earlier at farms in high woodland landscapes. However, woodland area was not correlated with metrics of D. suzukii abundance in raspberry (growth rate, peak, fall, or total fly catch) suggesting similar crop infestation risk across landscapes. However, woodland area was negatively correlated with fall fly catch in the adjacent woods and significantly more flies were captured in the woods than raspberry. This study suggests woodland landscapes affect early season crop risk and the high numbers of D. suzukii in the woods have implications for understanding overwintering. [ABSTRACT FROM AUTHOR]

In plant-pollinator networks, foraging choices by pollinators help form the connecting links between species. Flexible foraging should therefore play an important role in defining network topology. Factors such as morphological trait complementarity limit a pollinator's pool of potential floral resources, but which potential resource species are actually utilized at a location depends on local environmental and ecological context. Pollinators can be highly flexible foragers, but the effect of this flexibility on network topology remains unclear. To understand how flexible foraging affects network topology, we examined differences between sets of locally realized interactions and corresponding sets of potential interactions within 25 weighted plant-pollinator networks in two different regions of the United States. We examined two possible mechanisms for flexible foraging effects on realized networks: (1) preferential targeting of higher-density plant resources, which should increase network nestedness, and (2) context-dependent resource partitioning driven by interspecific competition, which should increase modularity and complementary specialization. We found that flexible foraging has strong effects on realized network topology. Realized connectance was much lower than connectance based on potential interactions, indicating a local narrowing of diet breadth. Moreover, the foraging choices pollinators made, which particular plant species to visit and at what rates, resulted in networks that were significantly less nested and significantly more modular and specialized than their corresponding networks of potential interactions. Preferentially foraging on locally abundant resources was not a strong driver of the realization of potential interactions. However, the degree of modularity and complementary specialization both increased with the number of competing pollinator species and with niche availability. We therefore conclude that flexible foraging affects realized network topology more strongly through resource partitioning than through focusing on high-density resources. [ABSTRACT FROM AUTHOR]

Honey bees are the most important managed pollinator worldwide and are vital to the success of modern agriculture. Native, wild bees are also important pollinators in both natural and agricultural systems, and are highly sensitive to habitat in the surrounding landscape. Few studies, however, have considered how managed honey bees, and their effectiveness as crop pollinators, may be influenced by variation in the surrounding landscape. If honey bees are influenced by areas outside of the crop fields in which they are placed, their effectiveness as crop pollinators could be diminished. The goal of this study was to determine whether the relationship between honey bee hive density and crop yield varies with the composition of the surrounding landscape. We collected historical (2000–2011) data on yield and honey bee hive stocking density from 38 commercial cranberry growers in central Wisconsin. Using mixed-model regression analyses we found that cranberry yield was strongly, positively correlated with hive density but this effect diminished as the proportion of the surrounding landscape in woodland increased. Thus, at cranberry marshes in low-woodland landscapes (e.g., <42% woodland within 1 km), increasing the density of honey bees increased yields by about1000 kg/hive, while cranberry marshes in high woodland landscapes saw no effect of adding honey bees. These results suggest that honey bees, like wild bees, are influenced by non-crop areas in the surrounding landscape and that landscape context should be considered when making management recommendations for the use of honey bees for crop pollination. [ABSTRACT FROM AUTHOR]

Native, wild bees are important pollinators for both crop and wild plants. With concerns over the availability and cost of managed honeybees, attention has turned to native, wild bees as crop pollinators. However, the ability of native, wild bees to provide sufficient pollination may depend on their populations at local scales., Therefore, at the farm scale, we examined the pollination contribution of both native, wild bees and managed honeybees to apples and assessed the relative importance of bee abundance vs. species richness. Over three growing seasons, apple fruit set, bee abundance and bee species richness were measured at orchards in Wisconsin, half of which used managed honeybees, thus allowing us to independently examine the contribution of native, wild bees to fruit set. We additionally conducted observations of honeybees and wild bees foraging on apple blossoms in order to examine functional complementarity., We found that apples are highly dependent on animal pollinators. However, fruit set was not significantly higher at orchards with managed honeybees, nor did it increase with the number of honeybees per orchard. Instead, fruit set significantly increased with the species richness of native, wild bees during bloom., Honeybees and wild bees showed different foraging preferences: honeybees more frequently visited apple flowers on densely blooming trees, while wild bees showed no preference for floral density, thereby evenly visiting trees throughout the orchard., Synthesis and applications. Our results show that native, wild bees play a significant and unique role in apple pollination within our region and cannot therefore be replaced by managed bees. Moreover, our findings suggest that bee conservation efforts should focus specifically on maintaining or increasing bee species richness in order to improve pollination and crop yields. [ABSTRACT FROM AUTHOR]

Highlights: [•] Aquatic–terrestrial and crop–noncrop linkages are conceptually similar. [•] Exchanges in agroecosystems are governed by natural enemy production and dispersal. [•] Donor habitats on the landscape determine the coverage of dispersal. [•] Land-cover/use and climate change will impact habitats, natural enemy exchange. [Copyright &y& Elsevier]

1. Dispersal plays a key role in structuring the local population densities of many insect species, yet the movement patterns across the landscape of most species are poorly understood. By measuring the stable isotope of carbon ( δC) from multiple tissues, a novel approach applied to field-collected insects, we were able to infer differences in movement patterns of two species of mobile generalist insect predators. 2. Coccinella septempunctata L (7-spot ladybeetle) and Harmonia axyridis Pallas (multicoloured Asian ladybeetle) were collected in agricultural habitats in 2003 and 2004, and were assayed for δC in the elytra (slow turnover) and fat/reproductive tissues (fast turnover). δC values were used to infer diet use of C3 versus C4 crops. 3. Coccinella septempunctata was relatively more faithful to a particular habitat and tended to stay in alfalfa and soybean (C3-based photosynthetic crops) over long periods during the summer. This contrasts with H. axyridis which showed isotopic evidence consistent with frequent late-season movement between C3 and C4 crops such as corn in the landscape. 4. These differing patterns suggest that in the late summer season H. axyridis individuals traverse the environment more extensively and utilise broadly dispersed aphid resources, whereas C. septempunctata adults are more specialised on alfalfa and soybean crops. [ABSTRACT FROM AUTHOR]

Ecologists are increasingly interested in how disjunct habitats are connected through the cross-habitat movement of matter, prey, nutrients, and detritus and the implications for recipient systems. The study of lake ecosystems has been dominated by the study of pelagic (open-water) production and processes, though there is growing awareness of the role of terrestrial inputs and benthic trophic pathways. Here, we review the phenomena of airborne fluxes to and from lakes. We assemble published data on terrestrial particulate organic carbon (TPOC) deposition to lakes, insect production, and insect emergence and use these data to simulate how airborne lake-to-land and land-to-lake carbon flux is expected to scale with ecosystem size, while taking into account among-lake variability in emergence and TPOC deposition. Emergent insect flux to land increases as a function of lake size, while TPOC deposition to lakes decreases as a function of lake size. TPOC deposition exceeds insect emergence in small lakes, while in large lakes, insect emergence exceeds TPOC deposition. We present a general framework for considering directional fluxes across habitat boundaries. Furthermore, our results highlight the overarching role of ecosystem geometry in determining insect emergence, airborne carbon deposition, and net carbon flux between adjacent ecosystems. Les écologistes sont de plus en plus intéressés à savoir comment les habitats séparés sont reliés par des mouvements croisés de la matière, des proies, des nutriments et du détritus entre les habitats et aussi à en connaître les conséquences sur les systèmes récipiendaires. L'étude des écosystèmes lacustres a été dominée par la détermination de la production et des processus pélagiques (en eau libre), bien qu'il y ait une perception croissante du rôle des apports terrestres et des voies trophiques benthiques. Nous faisons une rétrospective du phénomène des flux atmosphériques provenant des lacs et y aboutissant. Nous rassemblons les données publiées sur les précipitations de carbone organique particulaire terrestre (TPOC) dans les lacs, sur la production des insectes et sur l'émergence des insectes et nous utilisons ces données pour simuler comment les flux atmosphériques de carbone du lac vers le milieu terrestre et du milieu terrestre vers le lac sont fonction de la taille de l'écosystème, tout en tenant compte de la variabilité de l'émergence et des précipitations de TPOC entre les lacs. Le flux d'insectes émergés vers le milieu terrestre augmente en fonction de la taille du lac, alors que les précipitations de TPOC dans les lacs diminuent en fonction de la taille du lac. Les précipitations de TPOC sont supérieures à l'émergence des insectes dans les petits lacs, alors que, dans les grands lacs, l'émergence des insectes dépasse les précipitations de TPOC. Nous présentons un cadre général pour l'étude des flux directionnels à travers les frontières des habitats. De plus, nos résultats soulignent le rôle prédominant de la géométrie de l'écosystème dans la détermination de l'émergence des insectes, des précipitations atmosphériques de carbone et du flux net de carbone entre les écosystèmes adjacents. [ABSTRACT FROM AUTHOR]

Abstract: Agri-environmental schemes (AES) are hypothesized to enhance biodiversity and ecosystem services in agroecosystems. We investigated how non-crop habitats in one AES influence seed-eating ground beetles (Coleoptera: Carabidae) and post-dispersal weed seed predation, an ecosystem service provided by these beetles. We found that the abundance of beetles was higher in the non-crop habitats than within the crop fields. Species diversity (measured by Simpson''s D), however, was greater in crop fields than in non-crop habitats. In addition, beetle assemblages were distinct between the crop and non-crop habitats possibly due to differences in the frequency and intensity of disturbance between crop and non-crop habitats. Seed predation by small predators (mainly ground beetles) was greater in the non-crop habitat than within the potato field. Moreover, we found a positive association between seed predation and beetle diversity both within the crop and in the non-crop habitat which provides evidence of a relationship between biodiversity and ecosystem services. Yet, differences in species assemblages suggest that species identity also affects rates of seed predation. [Copyright &y& Elsevier]

Recently, food web studies have started exploring how resources from one habitat or ecosystem influence trophic interactions in a recipient ecosystem. Benthic production in lakes and streams can be exported to terrestrial habitats via emerging aquatic insects and can therefore link aquatic and terrestrial ecosystems. In this study, we develop a general conceptual model that highlights zoobenthic production, insect emergence, and ecosystem geometry (driven principally by area-to-edge ratio) as important factors modulating the flux of aquatic production across the ecosystem boundary. Emerging insect flux, defined as total insect production emerging per meter of shoreline (g C·m-1·yr-1) is then distributed inland using decay functions and is used to estimate insect deposition rate to terrestrial habitats (g C·m-2yr-1). Using empirical data from the literature, we simulate insect fluxes across the water-land ecosystem boundary to estimate the distribution of fluxes and insect deposition inland for lakes and streams. In general, zoobenthos in streams are more productive than in lakes (6.67 vs. 1.46 g C·m-2yr-1) but have lower insect emergence to aquatic production ratios (0.19 vs. 0.30). However, as stream width is on average smaller than lake radius, this results in flux (F) estimates 2 Y2 times greater for lakes than for streams. Ultimately, insect deposition onto land (within 100 m of shore) adjacent to average-sized lakes (10-ha lakes, 0.021 g C·m-2yr-1) is greaterthan for average-sized streams (4 m width, 0.002 g C·m-2yr-1) used in our comparisons. For the average lake (both in size and productivity), insect deposition rate approaches estimates of terrestrial secondary production in low-productivity ecosystems (e.g., deserts and tundra, ≈0.07 g C·m-2yr-1). However, larger lakes (1300 ha) and streams (16 m) can have average insect deposition rates ,(≈0.01-2.4 g C·m-2yr-1) comparable to estimates of secondary production of more productive ecosystems such as grasslands. Because of the potentially large inputs of emerging aquatic insects intoterrestrial habitats, ecosystem processes and terrestrial consumers can be influenced by insect inputs. The relative contribution of lakes and streams to this flux will vary among landscapes depending on the number and size of these ecosystems types on the landscape. [ABSTRACT FROM AUTHOR]

The influence of natural areas on ground beetle (Coleoptera: Carabidae) diversity and community composition in Wisconsin potatoes was assessed at local and large spatial scales. To accomplish this, ground beetle communities were sampled in potatoes and grassy field-margin habitats set in landscapes composed of varying amounts of natural area. At a local scale, field-margin habitats supported more, and different, carabid species than potatoes. Large carabids, brachypterous species, species typical of dry habitats and species that feed on seeds were all underrepresented in potatoes compared to field margins. However, the amount of field-margin habitat surrounding potatoes did not affect carabid community structure in the crop. At a larger scale, beetle diversity in potatoes increased and community composition changed with increases in the amount of natural area within 1.5km of the crop. However, this effect was not evident in adjacent field-margin habitats. These results suggest that the amount of natural area surrounding potatoes affects the composition of potential crop colonizers at a large spatial scale but that disturbances currently limit the types of species that colonize potatoes. [Copyright &y& Elsevier]

Despite a recent emphasis on understanding cross-habitat interactions, few studies have examined the ecological linkages between lakes and surrounding terrestrial habitats. The current paradigm of land–lake interactions is typically unidirectional: the view is that nutrients and matter are transported downslope from the surrounding watershed to their ultimate lacustrine destination. Emergent aquatic insects, which spend their larval stages in lake sediments and emerge as adults to mate over land, can act as vectors of material, energy and nutrients from aquatic to terrestrial habitats. In this study, we document a gradient of midge (Diptera: Chironomidae) infall rates into terrestrial habitats (measured as g dw midges m−2 d−1) surrounding eight lakes in Northern Iceland (≈66°N latitude). Lakes ranged from having virtually no midge infall (for example, Helluvaðstjörn, 0.03 g m−2 d−1) to extreme levels (for example, Mývatn, 19 g m−2 d−1) with abundances of midges decreasing logarithmically with distance from shore. Annual midge input rates are estimated as high as 1200–2500 kg midges ha−1 y−1. As midges are approximately 9.2% total N, this can result in a significant fertilization effect of terrestrial habitats with consequences for plant quality and community structure. In addition, we used naturally-occurring δ13C and δ15N isotopes to examine food web structure and diet sources of terrestrial arthropod consumers surrounding lakes with differing amounts of midge input. Terrestrial arthropods showed increased utilization of aquatic-derived (that is, midge) C relative to terrestrial sources as midge infall increased. This pattern was particularly pronounced for predators, such as spiders and opiliones, and some detritivores (Collembola). These findings suggest that, despite being largely ignored, aquatic-to-terrestrial linkages can be large and midges can fuel terrestrial communities by directly serving as resources for predators and decomposers. [ABSTRACT FROM AUTHOR]

Invasive plants are generally thought to have negative impacts on native communities. Rarely, however, are the impacts of invasive plants on native insects examined, limiting our understanding of the broader effects of invasive plants on native habitats. In this study, I document the use of purple loosestrife, Lythrum salicaria L. (Lythraceae), an aggressive wetland invasive, by Hemileuca sp. (Saturniidae), a native silkmoth. This buckmoth is a unique ecological variant of the more widespread buck moth, Hemileuca maia (Drury), and is of conservation concern in some areas. Hemileuca sp. was regularly observed feeding on L. salicaria in 2003 and 2004 at two sites in southern Wisconsin. Densities of late instars were as high as 12 individuals/m² and caused significant defoliation of L. salicaria with an average 34% loss of foliage relative to undamaged plants. Experimental manipulations of Hemileuca sp. caterpillars showed that herbivory could decrease seed production as much as 66%. In a laboratory assay, Hemileuca sp. feeding on L. salicaria had significantly lower pupal mass and lower survivorship to pupation (24%) relative to larvae feeding on Salix foliage (90%). Moreover, in two-choice preference assays, larvae preferred Salix over Lythrum foliage. Populations of Hemileuca sp. were subject to intense parasitism (up to 93%) by a tachinid parasitoid, Leschenaultia flavipes (Bigot). This combination of factors suggests there may be significant negative selection on Hemileuca sp. feeding on L. salicaria and that invaded habitats may be ecological sinks for the native herbivores. [ABSTRACT FROM AUTHOR]

Traditionally, researchers have used measurements of carbon stable isotopes to infer the composition of consumers’ diets. However, since consumer’s tissues may process carbon isotopes differently, particularly following a diet shift, it is possible to use measurements of carbon isotopes in multiple tissues to determine not only the composition of an individual’s diet, but also the temporal dynamics thereof. This study examined how stable isotopes of carbon (13C/12C, expressed as δ 13C) changed in different adult tissues of two predacious beetles, Harmonia axyridis and Coccinella septempunctata (Coleoptera: Coccinellidae). In the laboratory, we switched ladybeetles from a C3-based diet (soybean aphids, Aphis glycines) to a C4-based one (corn leaf aphids, Rhopalosiphum maidis). The δ 13C of metabolically active tissues such as the body fat and reproductive organs changed rapidly (≤5 days) following the diet shift. Tissues expected to be more metabolically inert, such as wings, changed more slowly over the same period. Although these general patterns were largely similar between males and females, females had more rapid changes in δ 13C in fat and reproductive tissues. However, females showed a significant depletion in δ 13C after 10 days, while males’ δ 13C continued to increase. Given the results of this experiment, it is now possible to distinguish between ladybeetles eating a mixed diet (beetles with multiple tissues at similar, intermediate, equilibrial δ 13C signatures) from those that have shifted diets (beetles with different tissues at distinctly different δ 13C values). Thus, this approach can be used broadly to infer not only what constitutes the diet of a consumer, but also the temporal history of dietary intake. [ABSTRACT FROM AUTHOR]

Invasive plants are one of the most serious threats to native species assemblages and have been responsible for the degradation of natural habitats worldwide. As a result, removal of invasive species and reestablishment of natural vegetation have been attempted in order to restore biodiversity and ecosystem function. This study examined how native arthropod assemblages, an abundant and functionally important group of organisms in many ecosystems, are affected by the incursion of the invasive wetland plantPhragmites australisand if the restoration of the native vegetation in brackishSpartina alternifloramarshes results in the reestablishment of the arthropod community. The invasion ofPhragmitesinto a coastalSpartinamarsh in southern New Jersey seriously altered arthropod assemblages and trophic structure by changing the abundance of trophic groups (detritivores, herbivores, carnivores) and their taxonomic composition. Herbivore assemblages shifted from the dominance of external free-living specialists (e.g., planthoppers) inSpartinato concealed feeders inPhragmites(stem-feeding cecidomyiids). Moreover, free-living arthropods inPhragmitesbecame dominated by detritivores such as Collembola and chironomids. The dominant marsh spiders, web-building linyphiids, were significantly reduced inPhragmiteshabitats, likely caused by differences in the physical environment of the invaded habitats (e.g., lower stem densities). Thus, trophic structure of arthropod assemblages inPhragmites, as seen in the large shifts in feeding guilds, was significantly different from that inSpartina. Removal ofPhragmiteswith the herbicide glyphosate resulted in the rapid return ofSpartina(≤5 yrs). Moreover, return of the dominant vegetation was accompanied by the recovery of most original habitat characteristics (e.g., live and dead plant biomass, water flow rate). The arthropod assemblage associated withSpartinaalso quickly returned to its preinvasion state and was not distinguishable from that in uninvadedSpartinareference sites. This study provides evidence that the reestablishment of native vegetation in areas previously altered by an invasive plant can result in the rapid recovery of the native arthropod assemblage associated with the restored habitat. [ABSTRACT FROM AUTHOR]

Pulsed resources, such as natural and anthropogenic inputs of nutrients into natural communities, can have important consequences for primary productivity, as well as for consumers and their predators. Little, however, is known of how a resource pulse influences community assemblages for periods longer than one growing season. This study, repeated twice and in two different habitats on a mid-Atlantic Spartina alterniflora salt marsh, showed that a one-time nitrogen (N) subsidy can have not only significant within-year effects on plant primary production and herbivore and natural enemy abundance, but can also have long-term effects on plants and arthropod food web structure. Spartina plants exhibited significantly greater biomass for 2-3 yr and elevated percentage of N for up to two years following the nutrient pulse, an effect that had direct positive effects on herbivores that were sensitive to variation in plant N content. Populations of Prokelisia planthoppers (Hemiptera: Delphacidae) were elevated in fertilized plots for up to three years following the nutrient addition. However, Trigonolylus uhieri, an herbivorous mind (Hemiptera: Miridae), was more abundant on previously fertilized plants only for a brief time, either within the same season as the nutrient addition, or for only one year after the pulse. The carryover effect of the nutrient pulse on plants and herbivores also propagated to the third trophic level. Both non-lycosid spiders (mostly linyphiids) and a specialist egg predator of Spartina planthoppers (Tytthus vagus) were more abundant in previously fertilized plots for up to two years following the nutrient pulse. In contrast, wolf spider (Lycosidae) densities were elevated in fertilized plots only within the same season as the initial fertilization pulse. Food web structure, as indexed by herbivore:predator ratio, was altered in plots that received a one-time N subsidy, with the arthropod food web in fertilized Spartina taking three years to resemble that of unperturbed Spartina. The response of particular herbivores and predators to the nutrient pulse was in part habitat dependent (contiguous Spartina meadows vs. isolated islets), suggesting that habitat heterogeneity combined with the differential dispersal ability of arthropods can influence the long-term response of a food web to a nutrient pulse. [ABSTRACT FROM AUTHOR]

Elucidating the relative strength of top-down and bottom-up forces in communities of phytophagus insects has been a major historical focus. Current consensus is that both forces play a role, but it is poorly known if these forces act differently on herbivores in the same assemblage and what factors underlie this variation. Using manipulative experiments with an assemblage of sap-feeding phytophagous insects (six species of planthoppers, leafhoppers, and heteropteran bugs) inhabiting intertidal Spartina marshes, we examined the association between herbivore behavior, risk of predation, and ultimately the relative impact of top-down (wolf spider predation) and bottom-up (host-plant nutrition) factors on the population density of each sap-feeding herbivore. A factorial experiment on open Spartina islets in the field (two levels of plant nutrition crossed with two levels of spider predation) showed that bottom-up and top-down manipulations differentially affected the various sap-feeders. Overall, bottom-up effects dominated in this sap-feeder community, whereby the density of all six sap-feeders increased when the nitrogen content of Spartina was elevated. By contrast, wolf-spider addition significantly suppressed populations of only the Prokelisia species and had little impact on the other four sap-feeder species in the community. Functional-response experiments and behavioral studies revealed that certain species (Prokelisia planthoppers) were at much higher risk of attack by wolf spiders than other sap-feeders in the assemblage and that risk of predation was associated with a species' particular "escape/defensive behavior." Moreover, risk of spider predation was roughly linked to the strength of top-down impacts in the field, because species with ineffective escape behaviors and a high risk of spider attack (Prokelisia planthoppers) were the only sap-feeders whose populations were suppressed by spider predation in the field. Thus, specific behavioral... [ABSTRACT FROM AUTHOR]

Investigates the association of population growth of Prokelisia dolus planthoppers with plant resources and spider predation. Characteristics of high-marsh meadow habitats; Enhancement of host-plant biomass and nutrition; Relationship between biomass of Spartina and planthopper.

Centuries of landscape changes associated with agriculture have dramatically reduced the amount and increased the temporal variability of the floral resources that support key pollinating insects such as bumble bees. Adapting to these novel resource conditions is important to ensure the persistence of bumble bee species. While several species appear to be in decline in modern agricultural landscapes, others have thrived, suggesting adaptation to exploit highly variable floral resources. Bombus impatiens, the common eastern bumble bee, is a prime example of such a species.We designed an experiment to compare how free‐foraging colonies of B. impatiens performed adjacent to areas with either temporally continuous or variable (pulsed) patches of purple tansy (Phacelia tanacetifolia) plantings.We found that colonies in Phacelia landscapes grew faster, had gained more mass, and produced more gynes than did colonies in reference landscapes with no Phacelia.Comparing colony responses between pulsed and continuous flowering resources showed that total mass gain at the end of the experiment was greater with continuous flowering resources. In contrast, colony growth rate and total gyne production were comparable for colonies adjacent to Phacelia plantings that were continuous versus pulsed.While low in statistical replication, given the scale of the experimental manipulation, our experiment shows that although B. impatiens colonies can exploit periods of resource discontinuity and gain mass, these continuously available floral resources appear important for colony growth and benefit gyne production. [ABSTRACT FROM AUTHOR]

In North America, white‐nose syndrome (WNS) has caused precipitous declines in hibernating bat populations, raising the question of whether the rapid loss of arthropodivorous bats may affect the abundance of their prey. During the summers of 2015–2018 (1 year after the arrival of WNS in Wisconsin, USA), we performed intensive arthropod black‐light trapping, ultrasonic acoustic monitoring, and emergence counts at 10 little brown (Myotis lucifugus) and big brown (Eptesicus fuscus) bat maternity roosts with paired control sites. For little brown bats, which are severely affected by WNS, roost counts declined by 95% over the four‐year period, compared to a 38% decline in big brown bat roost counts. Total arthropod abundance decreased by 49%, although decreases among common little brown bat prey were less severe. Our natural predator exclusion experiment supports existing evidence that bats can have measurable trophic impacts on arthropod communities, primarily via top‐down effects on common prey. [ABSTRACT FROM AUTHOR]

Presents a study which experimentally created a host plant shift for a specialized leafmining fly, Liriomyza helianthi. Natural enemies as agents of natural selection on herbivorous insects; Enemy-free space; Larval transfers; Parasitoids.

Balancing agricultural production with other ecosystem services is a vexing challenge. The Yahara River watershed in southern Wisconsin is a place where tensions among farmers, policymakers, and citizens at-large run high because nutrient loss from the agricultural practices of a few drive the impairment of surface waters for many. Reducing manure and fertilizer application, as well as increasing perennial grass cover have been proposed as potential solutions. Using the Agro-IBIS agroecosystem model, we examined 48 scenarios of future land management and climate for the Yahara River watershed to the year 2070. Scenarios included combinations of reduced livestock and increased perennial grassland under alternative climate trajectories. Results suggested that business as usual will lead to further environmental degradation with phosphorus-loading to waterways increasing 13, 7, and 23% under baseline, warmer and drier, and warmer and wetter climates, respectively. Watershed-wide phosphorous yield and nitrate leaching could be reduced by 50%, but only when nutrient application was reduced 50% and grassland cover was increased 50%. Furthermore, water quality improvements only materialized 50 years after modified land management practices were implemented under the most likely future climate. Our findings highlight that improving water quality under a changing climate will require long-term investment and transformative changes to current agricultural land use and land cover. Agricultural management solutions exist but are unlikely to be implemented without policies that incentivize transformative agricultural change. [ABSTRACT FROM AUTHOR]

To mitigate the effects of habitat loss on bee conservation and crop pollination, farmers are encouraged to plant flowers along the edges of crop fields. However, it is unclear where and to what degree these flower plantings are effective. Recent studies suggest that flower plantings may be less effective if they are established in landscapes with either very low or very high amounts of non-crop habitat. Moreover, while field edge flower plantings often increase the abundance and richness of bees in field edges, it is unclear whether this improves crop pollination or bee nesting success, which could increase bee populations over time. In this study we examined how field edge flower plantings and the landscape context in which they are established affect wild bee conservation and crop pollination. Across two years we established flower plantings of 0.1–0.5 ha along the edges of 17 of 34 commercial cucumber fields arranged across a gradient of landscape complexity. We then measured wild bee abundance, richness, and crop pollination in and around cucumber fields with and without plantings and assessed the nesting success of stem-nesting bees. We found that both field edge flowers and landscape-scale non-crop habitat had independent, positive effects on bee abundance, richness, nesting, or crop pollination in one of the two years of the study, and that the effects of field edge flowers on bees and crop pollination were not influenced by the surrounding landscape. We also found that managing field edges in a way that maintains naturally-occurring flowers may matter as much or more than flower plantings for short-term increases in bee abundance and richness. However, certain species of planted flowers might be associated with improved bee nesting success, an outcome important for both bee conservation and sustained crop pollination. • Examined how flower plantings and landscape affect wild bees and crop pollination. • Local flowers and surrounding landscape had positive effects in 1 of 2 study years. • Effects of field edge flowers were not influenced by the surrounding landscape. • Managing field edges to maintain naturally occurring flowers is important. • Local flowers may improve success of stem-nesting bees. [ABSTRACT FROM AUTHOR]

Warming temperatures are allowing native insect herbivores to expand into regions that previously exceeded their thermal tolerance, encounter new host species, and pose significant threats to native communities. However, the dynamics of these expansions remain poorly understood, particularly in the extent to which outbreaks remain reliant on emigration from historical hosts or are driven by local reproduction within novel hosts in the expanded range. We tested these non‐mutually exclusive hypotheses using spatially explicit data on mountain pine beetle (Dendroctonus ponderosae), which historically undergoes intermittent outbreaks in low‐elevation lodgepole pine (Pinus contorta), but is now causing severe mortality in a high‐elevation endangered species, whitebark pine (Pinus albicaulis). We compiled data from 2000 to 2019 across British Columbia, Canada, at 1‐km2 resolution, and analyzed spatiotemporal patterns of beetle infestations, lodgepole pine distributions, expansion into habitats dominated by whitebark pine, and the likelihood of future outbreaks in all pine communities under simulated conditions. Overall, we found strong support for the hypothesis of emigration from the historical host species continuing to be a major driver of outbreaks in the more recently accessed host. First, beetle population pressure was consistently the best predictor of infestation severity in both lodgepole and whitebark pine, and appeared to be mostly unidirectional from lodgepole to whitebark pine. Second, infestations in lodgepole pine were of a longer duration than those in whitebark pine, which appeared too brief to sustain transitions from endemic to eruptive dynamics. Furthermore, resource depletion appears to drive emigration from lodgepole pine, whereas in whitebark pine drought appears to favor establishment of immigrants although bioclimatic factors and stand structure preclude self‐sustaining outbreaks. Finally, we project that most pine in British Columbia will be at risk in the event of a new major outbreak. We describe implications for conserving and protecting whitebark pine and to other climate‐driven range expansions. [ABSTRACT FROM AUTHOR]

Loss of natural habitat due to increases in agricultural extent raises the question of whether human‐dominated landscape types can support biodiversity, particularly for declining insect pollinators. Compared to more rural agricultural landscapes, urban areas may confer benefits for bumble bee populations by providing stable and diverse floral resources. However, disentangling the effects of local‐ and landscape‐scale characteristics on bumble bee populations in human‐modified landscapes is challenging.Here, we assessed bumble bee occupancy using a repeated transect sampling design conducted during the summers of 2019 and 2020 within the metropolitan area of Madison, WI, and the surrounding agricultural landscape. We fit hierarchical occupancy models to estimate the detection (p) and occupancy (ψ) probabilities relative to local habitat quality (floral abundance and floral richness) and landscape (agricultural‐urban gradient) features for eight bumble bee species. We hypothesised that bumble bees were more likely to occupy urban areas, serving as refugia, relative to agricultural sites.We found that the detection probability of all bumble bee species was seasonal and influenced by maximum floral abundance at survey sites, independent of the surrounding land cover type. After accounting for species‐specific detection probabilities, the effect of urbanisation on bee occupancy was weak, and no species were less likely to occupy urban than rural agricultural areas.Our findings suggest that bumble bee occupancy is associated with a 'honeypot effect' where local resource availability, in the form of higher floral abundance, is most important in limiting the occupancy of bumble bees across urban and agricultural landscapes. [ABSTRACT FROM AUTHOR]

Agricultural intensification is a key suspect among putative drivers of recent insect declines, but an explicit link between historical change in agricultural land cover and insect occurrence is lacking. Determining whether agriculture impacts beneficial insects (e.g. pollinators), is crucial to enhancing agricultural sustainability. Here, we combine large spatiotemporal sets of historical bumble bee and agricultural records to show that increasing cropland extent and decreasing crop richness were associated with declines in over 50% of bumble bee species in the agriculturally intensive Midwest, USA. Critically, we found that high crop diversity was associated with a higher occurrence of many species pre‐1950 even in agriculturally dominated areas, but that current agricultural landscapes are devoid of high crop diversity. Our findings suggest that insect conservation and agricultural production may be compatible, with increasing on‐farm and landscape‐level crop diversity predicted to have positive effects on bumble bees. [ABSTRACT FROM AUTHOR]

Agricultural landscapes in North America have developed through complex interactions of biophysical, socioeconomic and technological forces. While they can be highly productive, these landscapes are increasingly simplified, causing biodiversity loss. As a result, ecosystem services associated with biodiversity are being dismantled. Agricultural landscape structure arises from collective decisions of farmers over long time periods, which are usually not intentionally coordinated beyond the farm scale. Regaining ecosystem services will require active efforts to intentionally redesign landscapes, in part based on ecological evidence about relationships between landscape structure and ecosystem services. Here we focus on services provided by arthropods and how to foster them at landscape scales. We first provide a brief history of how agricultural landscape structure in temperate North America developed and review the landscape-scale ecological drivers underpinning arthropod-based ecosystem services. We then propose ecological and social principles for designing agricultural landscapes, based on the ecological evidence we reviewed and on previous efforts in agricultural landscape design. Finally, we look ahead to discern prospects for putting agricultural landscape design into practice, including ecological, technological and policy opportunities. To reap benefits from arthropod-based services, future agricultural landscapes will need to increase in structural heterogeneity and diversity across multiple dimensions including crop, farmer and consumer diversity. A number of knowledge gaps persist, including how to design landscapes at spatial scales that are relevant to service providers, identifying areas of overlap or conflict between design for ecosystem services and for biodiversity conservation more broadly and navigating the social and political processes needed to implement landscape design. [ABSTRACT FROM AUTHOR]

Plants resist herbivores using both constitutive and induced defenses. Limited resources and biosynthesis costs of anti‐herbivore compounds may impose tradeoffs between these modalities, but the evidence is conflicting. We postulated that biological and ecological scale may influence potential tradeoffs and analyzed constitutive‐induced relationships from genotypic to interspecific levels. We focused on one system, conifer phloem monoterpenes that resist bark beetle attack, to minimize variation from feeding guild or phylogeny. We examined 45 half‐siblings in common gardens (n = 763), seven populations of five species with tree‐level data (n = 436) and 29 studies of nine species with population‐mean data in forests. All studies evaluated mature trees to correspond with beetle behavior in nature and employed common methods of induction and analysis. Rather than a global tradeoff between constitutive and induced defenses, relationships varied with level of biological organization. In common gardens, constitutive concentrations and inducibility (I–C) were inversely related across families and individuals. These relationships did not extend to forest populations, however, where constitutive concentrations and inducibility were positively related. Across populations and species, constitutive concentrations and inducibility were likewise positively related. There was no evidence for inducibility tradeoffs between monoterpene quantity and composition: trees showed no or positive relationships between constitutive concentrations and induced compositional changes. These results suggest environmental variability can supersede underlying physiological tradeoffs in some systems, allowing plants with greater resource pools to excel in multiple defense components. This is further supported by microsite effects on inducibility exceeding family effects in the common gardens, and by relationships between constitutive and absolute induced concentrations being positive at all levels. We present a general model for understanding how underlying physiological tradeoffs are variably manifested across scales. These results can contribute to the protection and resilience of agronomic and native ecosystems and help contextualize organismal‐level allocations to ecosystem‐level patterns across heterogeneous landscapes. [ABSTRACT FROM AUTHOR]

Disturbances have long been recognized as important forces for structuring natural communities but their effects on trophic structure are not well understood, particularly in terrestrial systems. This is in part because quantifying trophic linkages is a challenge, especially for small organisms with cryptic feeding behaviors such as insects, and often relies on conducting labor‐intensive feeding trials or extensive observations in the field. In this study, we used stable isotopes of carbon and nitrogen to examine how disturbance (annual biomass harvesting) in tallgrass prairies affected the trophic position, trophic range, and niche space of ants, a widespread grassland consumer. We hypothesized that biomass harvest would remove important food and nesting resources of insects thus affecting ant feeding relationships and trophic structure. We found shifts in the feeding relationships inferred by isotopic signatures with harvest. In particular, these shifts suggest that ants within harvest sites utilized resources at lower trophic levels (possibly plant‐based resources or herbivores), expanded trophic breadth, and occupied different niche spaces. Shifts in resource use following harvest could be due to harvest‐mediated changes in both the plant and arthropod communities that might affect the strength of competition or alter plant nitrogen availability. Because shifts in resource use alter the flow of nutrients across the food web, disturbance effects on ants could have ecosystem‐level consequences through nutrient cycling. [ABSTRACT FROM AUTHOR]

We develop a transdisciplinary deliberative model that moves beyond traditional scientific collaborations to include nonscientists in designing complexity-oriented research. We use the case of declining honey bee health as an exemplar of complex real-world problems requiring cross-disciplinary intervention. Honey bees are important pollinators of the fruits and vegetables we eat. In recent years, these insects have been dying at alarming rates. To prompt the reorientation of research toward the complex reality in which bees face multiple challenges, we came together as a group, including beekeepers, farmers, and scientists. Over a 2-year period, we deliberated about how to study the problem of honey bee deaths and conducted field experiments with bee colonies. We show trust and authority to be crucial factors shaping such collaborative research, and we offer a model for structuring collaboration that brings scientists and nonscientists together with the key objects and places of their shared concerns across time. [ABSTRACT FROM AUTHOR]

Managed bees are critical for crop pollination worldwide. As the demand for pollinator-dependent crops increases, so does the use of managed bees. Concern has arisen that managed bees may have unintended negative impacts on native wild bees, which are important pollinators in both agricultural and natural ecosystems. The goal of this study was to synthesize the literature documenting the effects of managed honey bees and bumble bees on wild bees in three areas: (1) competition for floral and nesting resources, (2) indirect effects via changes in plant communities, including the spread of exotic plants and decline of native plants, and (3) transmission of pathogens. The majority of reviewed studies reported negative effects of managed bees, but trends differed across topical areas. Of studies examining competition, results were highly variable with 53% reporting negative effects on wild bees, while 28% reported no effects and 19% reported mixed effects (varying with the bee species or variables examined). Equal numbers of studies examining plant communities reported positive (36%) and negative (36%) effects, with the remainder reporting no or mixed effects. Finally, the majority of studies on pathogen transmission (70%) reported potential negative effects of managed bees on wild bees. However, most studies across all topical areas documented the potential for impact (e.g. reporting the occurrence of competition or pathogens), but did not measure direct effects on wild bee fitness, abundance, or diversity. Furthermore, we found that results varied depending on whether managed bees were in their native or non-native range; managed bees within their native range had lesser competitive effects, but potentially greater effects on wild bees via pathogen transmission. We conclude that while this field has expanded considerably in recent decades, additional research measuring direct, long-term, and population-level effects of managed bees is needed to understand their potential impact on wild bees. [ABSTRACT FROM AUTHOR]

Integration of energy crops into agricultural landscapes could promote sustainability if they are placed in ways that foster multiple ecosystem services and mitigate ecosystem disservices from existing crops. We conducted a modeling study to investigate how replacing annual energy crops with perennial energy crops along Wisconsin waterways could affect a variety of provisioning and regulating ecosystem services. We found that a switch from continuous corn production to perennial-grass production decreased annual income provisioning by 75%, although it increased annual energy provisioning by 33%, decreased annual phosphorous loading to surface water by 29%, increased below-ground carbon sequestration by 30%, decreased annual nitrous oxide emissions by 84%, increased an index of pollinator abundance by an average of 11%, and increased an index of biocontrol potential by an average of 6%. We expressed the tradeoffs between income provisioning and other ecosystem services as benefit-cost ratios. Benefit-cost ratios averaged 12.06 GJ of additional net energy, 0.84 kg of avoided phosphorus pollution, 18.97 Mg of sequestered carbon, and 1.99 kg of avoided nitrous oxide emissions for every $1,000 reduction in income. These ratios varied spatially, from 2- to 70-fold depending on the ecosystem service. Benefit-cost ratios for different ecosystem services were generally correlated within watersheds, suggesting the presence of hotspots – watersheds where increases in multiple ecosystem services would come at lower-than-average opportunity costs. When assessing the monetary value of ecosystem services relative to existing conservation programs and environmental markets, the overall value of enhanced services associated with adoption of perennial energy crops was far lower than the opportunity cost. However, when we monitized services using estimates for the social costs of pollution, the value of enhanced services far exceeded the opportunity cost. This disparity between recoverable costs and social value represents a fundamental challenge to expansion of perennial energy crops and sustainable agricultural landscapes. [ABSTRACT FROM AUTHOR]

1. Changes in one prey species' density can indirectly affect the abundance of another prey species if a shared predator eats both species. Sometimes, indirect effects occur when prey straddle habitats, including when riparian predator populations grow in response to emergent aquatic insects and increase predation on terrestrial prey. However, predators may largely switch to aquatic insects or become satiated, reducing predation on terrestrial prey. 2. To determine the net indirect effect of aquatic insects on terrestrial arthropods via generalist spider predators, a field experiment was conducted mimicking midge influx and a wolf spider numerical response inside enclosures near an Icelandic lake. Lab mesocosms were also used to assess per capita rates of spider predation under differing levels of midge abundance. 3. Midges always decreased sentinel prey predation, but this effect increased with predator density. When midges were absent, predation increased 30% at a high spider density, but predation was equal between spider treatments when midges were present. In situ arthropods showed no effect of midge or spider treatments, although non-significant abundance patterns were observed congruent with sentinel prey results. 4. In lab mesocosms, prey survivorship increased ≥50% where midges were present and rapidly saturated; the addition of 5, 20, 50, and 100 midges equivalently reduced spider predation, supporting predator distraction rather than satiation as the root cause. 5. The present results demonstrate a strong positive indirect effect of midges and broadly support the concept that predator responses to alternative prey are a major influence on the magnitude and direction of predator-mediated indirect effects. [ABSTRACT FROM AUTHOR]

In the United States, policy initiatives aimed at increasing sources of renewable energy are advancing bioenergy production, especially in the Midwest region, where agricultural landscapes dominate. While policy directives are focused on renewable fuel production, biodiversity and ecosystem services will be impacted by the land-use changes required to meet production targets. Using data from field observations, we developed empirical models for predicting abundance, diversity, and community composition of flower-visiting bees based on land cover. We used these models to explore how bees might respond under two contrasting bioenergy scenarios: annual bioenergy crop production and perennial grassland bioenergy production. In the two scenarios, 600,000 ha of marginal annual crop land or marginal grassland were converted to perennial grassland or annual row crop bioenergy production, respectively. Model projections indicate that expansion of annual bioenergy crop production at this scale will reduce bee abundance by 0 to 71%, and bee diversity by 0 to 28%, depending on location. In contrast, converting annual crops on marginal soil to perennial grasslands could increase bee abundance from 0 to 600% and increase bee diversity between 0 and 53%. Our analysis of bee community composition suggested a similar pattern, with bee communities becoming less diverse under annual bioenergy crop production, whereas bee composition transitioned towards a more diverse community dominated by wild bees under perennial bioenergy crop production. Models, like those employed here, suggest that bioenergy policies have important consequences for pollinator conservation. [ABSTRACT FROM AUTHOR]

Irruptive forest insects such as bark beetles undergo intermittent outbreaks that cause landscape-scale tree mortality. Despite their enormous economic and ecological impacts, we still have only limited understanding of the dynamics by which populations transition from normally stable endemic to irruptive densities. We investigated density-dependent changes in mountain pine beetle reliance on stressed hosts, host selection, spatial configuration of attacks, and the interaction of host selection and spatial configuration by performing a complete census of lodgepole pine across six stands and 6 years. In addition, we compared the dynamics of mountain pine beetle with those of other bark beetles. We found that as population size increased, reliance on stressed trees decreased and new attacks shifted to larger trees with thicker phloem and higher growth rates that can support higher offspring production. Moreover, the spatial configuration of beetle-attacked trees shifted from random to spatially aggregated. Further, we found evidence that beetle utilization of larger trees was related to aggregation behavior as the size of tree attacked was positively correlated at 10–25 m, within the effective distance of pheromone-mediated signaling. In contrast, non-irruptive bark beetle species did not exhibit such density-dependent spatial aggregation at the stand scale or switches in host selection behavior. These results identify how density-dependent linkages between spatial configuration and host utilization can converge to drive population transitions from endemic to irruptive phases. Specifically, a combination of stand-level spatial aggregation, behavioral shifts, and higher quality of attainable hosts defines a critical threshold beyond which continual population growth becomes self-driving. [ABSTRACT FROM AUTHOR]

Not all agriculture based on perennial plants is ecologically sound or socially just. But an agroecological concept of perennial agriculture must be. We suggest three key elements of an agroecological vision for perennial agriculture. First, perennial agriculture must be managed with regard for the future as much as the present. Second, perennial agriculture must be situated in an ecological and social context, meeting the material, social, and ecological needs of the individuals and communities that engage in producing agricultural goods – making it what we term an "agroecological endeavor." Third, perennial agriculture must include a diversity of plants, including – but not limited to – perennial plants. Thus, we propose envisioning perennial agriculture as the perennial management of an agroecological endeavor that includes perennial plants. [ABSTRACT FROM AUTHOR]

Cross-ecosystem movement of nutrients and biomass can have important effects on recipient systems. Emerging aquatic insects are subsidies to terrestrial ecosystems and can influence foodweb interactions in riparian systems. In a 2-year field experiment, we simulated aquatic insect deposition by adding adult midge carcasses (150 g dry mass m year) to 1-m heathland plots at a site with low natural midge deposition. We established four levels of midge-addition treatments and measured stable isotopes (δC and δN) in plants and arthropods within each treatment. We used a multiple-source isotope Bayesian mixing model to estimate the terrestrial versus aquatic contribution to the diets of arthropods. Aquatic resources were incorporated into plant, detritivore, and predator biomass. Detritivorous Collembola showed the greatest difference in isotope values (+3 ‰ δN and +4 ‰ δC) between midge-addition and reference treatments. Isotope values of small spiders followed the same trend of enrichment as Collembola while other arthropods (mites and large spiders) were only enriched after 2 years of midge addition. Although predator diets did not change, they became isotopically enriched via their likely prey (Collembola). Plants also had elevated δN (+1 ‰) in midge-addition treatments. The time required and amount of midge-derived C and N detected varied and depended on trophic position. Midge-derived nutrients were no longer present in arthropod biomass in the year following midge addition. Aquatic insect carcasses can be rapidly incorporated into terrestrial food webs in nearshore habitats, and repeated inputs can be detected at multiple trophic levels, thus highlighting the importance of the detrital pathway for aquatic to terrestrial cross-ecosystem subsidies. [ABSTRACT FROM AUTHOR]

Aquatic insects link adjacent ecosystems by transporting nutrients, energy, and material as they move from bodies of water into terrestrial habitats. Insects emerging from streams and rivers are known to benefit arthropod predators such as spiders, but their influence may extend to other arthropod feeding groups as well. We conducted a terrestrial arthropod survey at a series of lakes spanning a strong gradient of midge (Chironomidae, Diptera) emergence. These small, short-lived insects reach high densities in some areas such that their carcasses litter the ground, and serve as a potential resource for non-predatory arthropods. Our study revealed that arthropod assemblages in areas of high midge density were significantly different from those with few midges, the result of an increase of all taxa rather than changes in taxonomic composition. Eight of nine terrestrial arthropod taxa sampled showed a strong positive response to the presence of midges including detritivores and herbivores in addition to predators. Taxa that could consume living or dead midges directly responded especially strongly to midge gradients. Our results strongly suggest that midges enter the terrestrial arthropod food web through multiple pathways, increasing numbers of a wide range of arthropods. Furthermore, they emphasize the importance of lakes as sources of aquatic insects that significantly alter processes in the neighboring terrestrial environment. [ABSTRACT FROM AUTHOR]

Abstract: The federally endangered Karner blue butterfly (Lycaeides samuelis) is the focal species for a conservation plan designed to create and maintain barrens habitats. We investigated whether habitat management for Karner blue butterflies influences avian community structure at Fort McCoy Military Installation in Wisconsin, USA. From 2007 through 2009 breeding bird point count and habitat characteristic data were collected at 186 sample points in five habitat types including two remnant barrens types, barrens habitat restored from woodland and managed specifically for the Karner blue butterfly, and two woodland habitat types. Although the bird community of managed barrens was not identical to the communities of remnant barrens, the Field Sparrow (Spizella pusilla), a species of conservation concern, and sparse canopy associated bird species, such as the Baltimore Oriole (Icterus galbula) and Eastern Bluebird (Sialia sialis) were predicted to occupy managed barrens and remnant barrens in similar proportions. Adjacent habitat was the most influential factor in determining the community of bird species using the managed barrens. In Wisconsin, and likely throughout the range of the Karner blue butterfly, management for the butterfly creates habitat that attracts a bird community similar to that of remnant barrens, and benefits several avian species of conservation concern. Additionally, the landscape context surrounding the managed habitat influences avian community composition. Managed barrens that are adjacent to remnant barrens, rather than adjacent to woodland habitats, have the highest potential for conserving barrens breeding birds. [Copyright &y& Elsevier]

Abstract: Cultivation of biofuel crops could change agricultural landscapes, affecting natural enemies at multiple scales. We sampled five natural enemy families with sticky cards in three model biofuel habitats (corn, switchgrass and prairie; n =60) across southern Michigan and Wisconsin, comparing captures between habitats and relating them to the area of forest, annual crop and herbaceous perennial habitat in the landscape within 2km of sites. In a first analysis, we compared Coccinellidae assemblages between habitats and examined the impact of habitat type and landscape composition on species richness and abundance. Results showed that, at the habitat scale, perennial grasslands supported a greater abundance of uncommon, native coccinellids and hosted distinct species assemblages compared to corn. At a broader scale, abundances of exotic and uncommon native ladybeetles responded differently to landscape composition, decreasing with the area of herbaceous perennials and annual crops, respectively. In a second analysis, we related family-level abundances of Anthocoridae, Syrphidae, Dolichopodidae and Chrysopidae to habitat type and landscape composition. Dolichopodids were more abundant in grasslands, while anthocorid and syrphid abundance increased over fivefold with the area of herbaceous, perennial habitat in the landscape surrounding corn, but not grassland, sites. These findings suggest that perennial grasslands used for bioenergy production could conserve natural enemies which are less abundant in corn, the dominant biofuel in existing landscapes. Moreover, cultivating annual cropland with herbaceous, perennial habitats could affect the abundance of natural enemies in existing crops and alter the suitability of entire landscapes for these beneficial taxa. [Copyright &y& Elsevier]

Management-intensive rotational grazing is used by many farmers seeking to balance profitability, environmental stewardship, and quality of life. Productivity of pastures in much of the upper Midwest is limited to April through October, so promoting high quality forage production during the grazing season and for winter storage is critical to dairy and beef farm profitability. We conducted an experiment on pastures dominated by Kentucky bluegrass (Poa pratens/s L.), orchardgrass (Dactyl/s glomerata L.), meadow fescue [Schedonorus pratensis (Huds.) P. Beauv.], perennial ryegrass (Lolium perenne L.), and white clover (Trifolium repens L.) to compare forage production, forage quality, and root production under management-intensive rotational grazing, continuous grazing, haymaking, and land with no agronomic management. Rotational paddocks were grazed by cow-calf pairs monthly for -2 d and then allowed to rest for -28 d. Plots designated for haymaking were harvested two times per growing season. Potential utilizable forage, quantified by incorporating the estimates of refused and nonutilized biomass, and relative forage quality were significantly greater under management-intensive rotational grazing when compared to the other treatments. Root production in the surface 15 cm was significantly lower under both grazing treatments compared to the undefoliated control site. The perception of improved production has been used to advocate for rotationally grazed over continuously grazed systems in subhumid pasture, but experimental results have been equivocal. Our results point to managed grazing as a viable alternative to continuous grazing and haymaking in terms of both forage production and quality but not root production. [ABSTRACT FROM AUTHOR]