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Although urban gardens are often celebrated for supporting bee abundance and diversity within cities, little is known about how garden management and urbanization levels influence bee foraging behavior and ability to utilize resources within these landscapes. Specifically, the preferences and diet breadth of bees may depend critically on local and landscape conditions in human-managed, urban environments. To understand how foraging patterns and pollen preferences are influenced by urban landscape composition, we first examined if bees visit plants grown within urban gardens and second assessed the relationships between local floral resources, urban land cover, and pollen collection patterns, focusing on 20 community gardens across 125 km of the California central coast. We targeted a well-studied, essential native pollinator in this ecoregion, Bombus vosnesenskii, and analyzed pollen on the bodies of individuals collected in our study gardens to compare their contents to local and landscape garden composition factors. We found that greater landscape-level urban cover and greater plant species richness in the garden both drove higher within-garden pollen collection. We also found that B. vosnesenskii preferred ornamental plant species over highly available crop species in the gardens. Our study indicates that landscapes that support plant diversity, including both ornamental plants and sustenance-oriented food crops, promote greater within-garden pollen collection patterns, with likely benefits for urban garden food production.

It is often argued that biodiversity and ecosystem functioning are linked by both habitat and species composition, and that this relationship is particularly critical for mobile ecosystem service providers. This may be especially true for pollinators, which are essential for the reproduction of the majority of flowering plant species, are highly mobile, and can exhibit dramatically different foraging behaviors across ecosystems. Understanding how habitat and community composition impact pollination is especially relevant in urban environments where pollinators can promote food security. We examined the relationships between local resource density, landscape composition, pollinator abundance and richness, and pollination services in an urban agricultural system spanning >125 km of the California central coast. We used a replicated, experimental approach to evaluate the reproductive success of jalapeno peppers across urban gardens and conducted a greenhouse experiment to evaluate the benefits of insect-mediated pollination to pepper reproduction. In the greenhouse, we found that jalapeno fruit weight and seed number was significantly greater with insect-mediated pollination than without. In the field, we found that jalapeno seed number increased significantly with herbaceous (weed, crop, and ornamental) plant richness and the number of perennial trees and shrubs at the site level, but decreased with the amount of natural landscape cover. We also found that higher pollinator richness enhanced seed number in floral-dense gardens, likely due to the greater functional complementarity of a more diverse pollinator community. Furthermore, there was a positive relationship between pollinator abundance and seed number, but it weakened in gardens with more flowers, likely through lower per-plant pollinator visitation in the presence of competing floral resources. As in past studies, we found that mulch had a negative impact on pollinator abundance, highlighting that abiotic factors commonly managed by gardeners can directly impact ecosystem service providers. This study demonstrates that local conditions can significantly influence ecosystem service provision and that urban gardeners need to optimize for both pollinator richness and floral resource availability to achieve optimal pollination.

Author(s): Vandermeer, John; Armbrecht, Inge; De la Mora, Aldo; Ennis, Katherine K; Fitch, Gordon; Gonthier, David J; Hajian-Forooshani, Zachary; Hsieh, Hsun-Yi; Iverson, Aaron; Jackson, Douglas; Jha, Shalene; Jimenez-Soto, Esteli; Lopez-Bautista, Gustavo; Larsen, Ashley; Li, Kevin; Liere, Heidi; Macdonald, Andrew; Marin, Linda; Mathis, Kaitlyn A; Monagan, Ivan; Morris, Jonathan R; Ong, Theresa; Pardee, Gabriella L; Rivera-Salinas, Iris Saraeny; Vaiyda, Chatura; Williams-Guillen, Kimberly; Yitbarek, Senay; Uno, Shinsuke; Zemenick, Ash; Philpott, Stacy M; Perfecto, Ivette | Abstract: AbstractWhether an ecological community is controlled from above or below remains a popular framework that continues generating interesting research questions and takes on especially important meaning in agroecosystems. We describe the regulation from above of three coffee herbivores, a leaf herbivore (the green coffee scale, Coccus viridis), a seed predator (the coffee berry borer, Hypothenemus hampei), and a plant pathogen (the coffee rust disease, caused by Hemelia vastatrix) by various natural enemies, emphasizing the remarkable complexity involved. We emphasize the intersection of this classical question of ecology with the burgeoning field of complex systems, including references to chaos, critical transitions, hysteresis, basin or boundary collision, and spatial self-organization, all aimed at the applied question of pest control in the coffee agroecosystem.

Ecological networks can provide insight into how biodiversity loss and changes in species interactions impact the delivery of ecosystem services. In agroecosystems that vary in management practices, quantifying changes in ecological network structure across gradients of local and landscape composition can inform both the ecology and function of productive agroecosystems. In this study, we examined natural-enemy-herbivore co-occurrence networks associated with Brassica oleracea (cole crops), a common crop in urban agricultural systems. Specifically, we investigated how local management characteristics of urban community gardens and the landscape composition around them affect (1) the abundance of B. oleracea herbivores and their natural enemies, (2) the natural-enemy : herbivore ratio, and (3) natural-enemy-herbivore co-occurrence network metrics. We sampled herbivores and natural enemies in B. oleracea plants in 24 vegetable gardens in the California, USA central coast region. We also collected information on garden characteristics and land-use cover of the surrounding landscape (2km radius). We found that increased floral richness and B. oleracea abundance were associated with increased parasitoid abundance, non-aphid herbivore abundance, and increased network vulnerability; increased vegetation complexity suppressed parasitoid abundance, but still boosted network vulnerability. High agricultural land-use cover in the landscape surrounding urban gardens was associated with lower predator, parasitoid, and non-aphid herbivore abundance, lower natural-enemy : herbivore ratios, lower interaction richness, and higher trophic complementarity. While we did not directly measure pest control, higher interaction richness, higher vulnerability, and lower trophic complementarity are associated with higher pest control services in other agroecosystems. Thus, if gardens function similarly to other agroecosystems, our results indicate that increasing vegetation complexity, including trees, shrubs, and plant richness, especially within gardens located in intensively farmed landscapes, could potentially enhance the biodiversity and abundance of natural enemies, supporting ecological networks associated with higher pest control services.

Community gardens are important urban green spaces with a variety of social and ecological benefits, one of which is access to healthy food. Similar to rural agriculture, the quantity and quality of the food produced can be compromised by pest damage. In fact, many urban gardeners report crop damages caused by vertebrate and invertebrate pests. Yet, because the food produced in community gardens is mostly for self-consumption and thus not under market quality standards, the damage thresholds and the point when gardeners perceive a pest problem and how they decide to manage it, may greatly vary from gardener to gardener. Here, we investigated how socio-demographic factors and experience affect whether gardeners report having a pest problem and which pest management practices they use. We surveyed 187 gardeners from 18 different urban community gardens in three counties in the California central coast, USA. We also collected information about gardener socio-demographic factors (age, gender, ethnicity), as well as education, and years of experience in agriculture. The majority of gardeners reported having pests in their plots but their ethnicity, the amount of time they spend in the gardens, and whether they work in agricultural-related employment or not influenced the likelihood of reporting pests. We found that the majority of gardeners use curative, non-synthetic practices for managing pests, but that some use preventive practices and some don't do anything to control pests. The likelihood of using practices that are curative depended on gardeners' ethnicity, the amount of time they spend in the gardeners, and their gender. Our results suggest that the agricultural knowledge of urban community gardeners and the practices they use varies greatly and that, in order to be successful, extension programs may need to take this diversity into account when promoting the agroecological paradigm in urban agricultural (UA) systems.

Urban agriculture has received considerable attention for its role in supporting biodiversity and ecosystem services, and health and well-being for growing urban populations. Urban gardens managed with agroecological practices and higher plant diversity support more biodiversity and may support higher crop production. Plant selection in gardens is a function of temperature and environmental conditions and also depends on gardener socio-demographic characteristics, motivations for gardening, and gardening experience. In this study, we examined how plant richness and composition vary with gardener socio-demographic factors, gardening experience and garden use, and gardener motivations. We focused on the socio-demographic factors of age, gender, education, and region of national origin, used information on years spent gardening and hours spent in gardens as a proxy for gardening experience, and collected information on motivations, as well as crop and ornamental plants grown by individual gardeners. We found that gender, region of origin, time spent gardening, and gardener motivations all influenced plant richness or composition. Specifically, women plant more plant species than men, especially of ornamental plants, and individual gardeners motivated by nature connection tend to plant strongly different plant compositions in their gardens. We also found that region of national origin strongly influences crop composition. In contrast to previous studies, we did not find that gardeners more motivated by food grow a higher proportion of or more crop species compared with ornamentals. Thus we show that multiple socio-demographic characteristics and motivations influence garden plant communities, and thus assuring access to gardens for all groups may boost plant richness and support ecosystem services in gardens.

Complex landscapes with high resource availability can support more diverse natural enemy communities and better natural pest control by providing resources and facilitating organism dispersal. Moreover, in agricultural landscapes, local agroecosystem management can support biodiversity maintenance and pest control by adding resources in less complex landscapes with fewer resources. However, we lack an understanding of how local and landscape factors interact to affect natural enemy communities and their site fidelity to agroecosystems in urban landscapes (i.e., cityscapes). To better understand how local and landscape factors influence natural enemies in urban agroecosystems, we used urban community gardens as a model system to test if and how local resource manipulation and differences in cityscape quality affect natural enemy (ladybird beetles, parasitoid wasps) communities and their fidelity to urban habitats. We performed two manipulations. First, we added local floral resources in 6 of 12 gardens situated in different cityscapes to measure differences in natural enemy biodiversity. Second, in those 12 gardens, with and without resource additions, we manipulated populations of a common natural enemy, Hippodamia convergens, to assess fidelity to the gardens. Floral resource additions increased parasitoid abundance and changed community composition, but had little effect on ladybeetle abundance, richness or site fidelity. Rather, ladybeetle fidelity to gardens was lower in gardens in low quality cityscapes with high impervious cover. Cityscape quality influences natural enemies in and fidelity to gardens. Landscape-moderated biodiversity patterns observed in rural landscapes likely differ from urban contexts with implications for pest control.

Urban gardens in Central California are highly vulnerable to the effects of climate change, experiencing both extended high heat periods as well as water restrictions because of severe drought conditions. This puts these critical community-based food production systems at risk as California is expected to experience increasing weather extremes. In agricultural systems, increased vegetation complexity, such as greater structure or biodiversity, can increase the resilience of food production systems from climate fluctuations. We test this theory in 15 urban gardens across California's Central Coast. Local- and landscape-scale measures of ground, vegetation, and land cover were collected in and around each garden, while climate loggers recorded temperatures in each garden in 30min increments. Multivariate analyses, using county as a random factor, show that both local- and landscape-scale factors were important. All factors were significant predictors of mean temperature. Tallest vegetation, tree/shrub species richness, grass cover, mulch cover, and landscape level agricultural cover were cooling factors; in contrast, garden size, garden age, rock cover, herbaceous species richness, and landscape level urban cover were warming factors. Results were similar for the maximum temperature analysis except that agriculture land cover and herbaceous species richness were not significant predictors of maximum temperature. Analysis of gardener watering behavior to observed temperatures shows that garden microclimate was significantly related to the number of minutes watered as well as the number of liters of water used per watering event. Thus gardeners seem to respond to garden microclimate in their watering behavior even though this behavior is most probably motivated by a range of other factors such as water regulations and time availability. This research shows that local management of ground cover and vegetation can reduce mean and maximum temperatures in gardens, and the reduced temperatures may influence watering behavior of gardeners.

Urban community gardens provide habitat for biodiversity within urban landscapes. Beneficial insects, those that provide important ecosystem services like pollination and pest control, are among the many inhabitants of these green spaces. Garden management and the composition of the urban matrix in which they are embedded can affect not only the abundance and species richness of beneficial insects but also their community composition and functional traits. During 2014 and 2015 (June to September), we collected ladybird beetles (Coleoptera: Coccinellidae) in 19 community gardens in three counties of the California Central Coast. We examined the effects of garden- and landscape-level characteristics on ladybird community composition and functional traits. Out of the 19 species collected, only 3 were non-native to California (3 were not identified to species). Similarities in ladybird species composition were not driven by geographic distance between gardens, which suggest that beetles in these landscapes are not experiencing dispersal limitation. Instead, three landscape-level environmental variables and seven garden-scale ones correlated with changes in community composition. Even though we perceive cities as highly disturbed low-quality landscapes, our results suggest that highly mobile arthropods such as ladybird beetles, may not perceive the urban matrix as a barrier to movement and that urban gardens can be inhabited by native species with different sizes, diet breadths and diets. Nevertheless, our results also suggest garden specific management practices, such as altering ground cover, can affect the taxonomic and functional composition of ladybird beetles with potential implications to their ecosystem services.

Urban gardens are vital green spaces, providing food for residents and space for engaged citizenry and community development. In California, climate change conditions (heat and drought) are becoming more extreme, threatening the resilience of urban gardens. Water use restrictions limit the timing and amount of water that gardeners can access, exacerbating these climate challenges for urban food production. Together with volunteer gardeners, we examined how ambient temperature, water use, vegetation, ground cover, and soil management affect rates of soil moisture gain and loss in urban gardens for a six-week period in the summer of 2017, during the hottest part of the growing season. We found that plot-level management of soils is essential for creating urban garden plots that maintain stable levels of water within garden soils. Although plots with better soil quality (i.e. water holding capacity) experienced slower rates of soil moisture gain after a watering event, they also experienced slower rates of soil moisture loss after the event, leading to soils with more stable, less fluctuating moisture profiles over time. This may benefit gardeners because under extreme climates (such as heat and drought) and water use restrictions, maintaining more stable soils for their plants means that the soils will retain water over a longer period after each watering event. Overall, such results highlight that better soil management that improves soil quality measures such as water holding capacity are potential solutions for maintaining soil moisture and reducing water use under changing climate conditions.

Urban agroecosystems can provide habitat for biodiversity and can benefit human communities through urban food provisioning. Moreover, urban agroecosystems could be managed so as to optimize ecosystem services like natural pest control provided by trophic interactions between natural enemies and herbivores. As in other ecosystems, predation and parasitism regulate herbivores in urban settings, but less is known about the relative importance of direct and indirect effects at local and landscape scales in highly managed urban agroecosystems. We collected data on herbivore (cabbage aphid) density and parasitism ratios (proportion of parasitized aphid “mummies”) in 25 community gardens in three counties in the California central coast, USA. We used structural equation modeling to examine the effects of direct factors (host plant characteristics and parasitism) and indirect factors (soil, garden, and landscape characteristics) on herbivore density changes at two time points in the growing season (June and August). Aphid density, but not parasitism, varied across counties over the season, and there was a strong negative relationship between aphid density and parasitism. Direct effects were strong drivers of aphid density but not parasitism. In June, aphid density increased with host plant volume but decreased with greater floral density, while parasitism was only influenced by aphid density. In August, host plant volume similarly positively affected aphid density, and soil water holding capacity increased host plant volume. In addition, host plant density had a strong negative effect on parasitism. Urban gardeners may be able to reduce aphid pest densities by increasing floral resource density and strategically spatially distributing host plants throughout garden beds, though these processes depend on the season. The indirect effects of soil water holding capacity on aphid densities further suggest a critical role of human management on pest populations and pest control services through soil amendments and irrigation.

A new species of myrmecophilous lady beetle, Diomus lupusapudoves, sp. nov. (Coleoptera: Coccinellidae: Diomini), is described from a coffee agroecosystem in Chiapas, Mexico. The new species was found preying on the green coffee scale pest, Coccus viridis (Green), tended primarily by Azteca sericeasur Longino and Pheidole synanthropica Longino ants. The larval, pupal, and adult stages of the new species are described and habitus illustrations or photos provided along with anatomical details of the adult male and female genitalia. The species is most similar to Diomus thoracicus Fabricius (=type species of Diomus), another myrmecophile, which inhabits ant nests and feeds on ant brood. The new species has a peculiar onisciform larva that lacks dorsal setae, features that it shares with D. thoracicus. The new species is only the second species in the genus reported as a myrmecophile, although the life histories of most species have been poorly documented.

The idea that noncrop habitat enhances pest control and represents a win–win opportunity to conserve biodiversity and bolster yields has emerged as an agroecological paradigm. However, while noncrop habitat in landscapes surrounding farms sometimes benefits pest predators, natural enemy responses remain heterogeneous across studies and effects on pests are inconclusive. The observed heterogeneity in species responses to noncrop habitat may be biological in origin or could result from variation in how habitat and biocontrol are measured. Here, we use a pest-control database encompassing 132 studies and 6,759 sites worldwide to model natural enemy and pest abundances, predation rates, and crop damage as a function of landscape composition. Our results showed that although landscape composition explained significant variation within studies, pest and enemy abundances, predation rates, crop damage, and yields each exhibited different responses across studies, sometimes increasing and sometimes decreasing in landscapes with more noncrop habitat but overall showing no consistent trend. Thus, models that used landscape-composition variables to predict pest-control dynamics demonstrated little potential to explain variation across studies, though prediction did improve when comparing studies with similar crop and landscape features. Overall, our work shows that surrounding noncrop habitat does not consistently improve pest management, meaning habitat conservation may bolster production in some systems and depress yields in others. Future efforts to develop tools that inform farmers when habitat conservation truly represents a win–win would benefit from increased understanding of how landscape effects are modulated by local farm management and the biology of pests and their enemies., This work was supported through the National Socio-Environmental Synthesis Center (SESYNC) National Science Foundation Award DBI-1052875 for the project “Evidence and Decision-Support Tools for Controlling Agricultural Pests with Conservation Interventions” organized by D.S.K. and R.C.-K

The strength and prevalence of trophic cascades, defined as positive, indirect effects of natural enemies (predatory and parasitic arthropods) on plants, is highly variable in agroecosystems. This variation may in part be due to the spatial or landscape context in which these trophic cascades occur. In 2011 and 2012, we conducted a natural enemy exclusion experiment in soybean fields along a gradient of landscape composition across southern Wisconsin and Michigan, USA. We used structural equation modeling to ask (1) whether natural enemies influence biocontrol of soybean aphids (SBA) and soybean yield and (2) whether landscape effects on natural enemies influence the strength of the trophic cascades. We found that natural enemies (NE) suppressed aphid populations in both years of our study, and, in 2011, the yield of soybean plants exposed to natural enemies was 37% higher than the yield of plants with aphid populations protected from natural enemies. The strength of the trophic cascade was also influenced by landscape context. We found that landscapes with a higher proportion of soybean and higher diversity habitats resulted in more NE, fewer aphids, and, in some cases, a trend toward greater soybean yield. These results indicate that landscape context is important for understanding spatial variability in biocontrol and yield, but other factors, such as environmental variability and compensatory growth, might overwhelm the beneficial effects of biocontrol on crop yield.

Agroecological research has improved our understanding of the drivers and benefits of biodiversity, thus providing the scientific basis needed to achieve agricultural multifunctionality. We review how agroecology has contributed to our understanding of the effects of local and landscape level drivers on beneficial insects, as well as on the ecosystem services they provide. Several syntheses from agroecosystem research indicate that both populations and biodiversity of pollinator and natural enemies decline with increases in local agricultural intensification and that landscape composition and configuration may mediate these local scale effects. Changes in agricultural management may affect predation and pollination services by altering the resource base for natural enemies and pollinators, by altering their species pool, and by modifying their interactions. The effects of these drivers depend on taxonomical or functional groups and landscape context. Studies that directly measure the cascading eff...

Urban agricultural (UA) systems appear in many forms, from community farms and rooftop gardens to edible landscaping and urban orchards. They can be productive features of cities, providing important environmental and social services that benefit and support urban communities. These benefits include the provision of high levels of biodiversity and ecosystem services that contribute to urban nature and environmental processes as well as a range of social benefits, such as food and nutrition, cultural resources and recreational benefits. However, there are a number of challenges that prevent UA from expanding despite various acknowledged benefits. Increasing competition for space and environmental constraints often limits the ability to establish UA systems in many city areas, and negative spillover from UA to urban areas can create hazards to the natural environment and the local community. Further expansion and development of UA as a productive green infrastructure will require win-win strategies that maximize environmental and social benefits while taking advantage of vacant or under-utilized pockets of urban land.

Trait-mediated indirect interactions (TMII) can be as important as density-mediated indirect interactions. Here, we provide evidence for a novel trait-mediated cascade (where one TMII affects another TMII) and demonstrate that the mechanism consists of a predator eavesdropping on chemical signaling. Ants protect scale insects from predation by adult coccinellid beetles – the first TMII. However, parasitic phorid flies reduce ant foraging activity by 50% – the second TMII, providing a window of opportunity for female beetles to oviposit in high-quality microsites. Beetle larvae are protected from ant predation and benefit from living in patches with high scale densities. We demonstrate that female beetles can detect pheromones released by the ant when attacked by phorids, and that only females, and especially gravid females, are attracted to the ant pheromone. As ants reduce their movement when under attack by phorids, we conclude that phorids facilitate beetle oviposition, thus producing the TMII cascade.

Trait-mediated indirect interactions (TMII) are important driving-forces causing trophic cascades in aquatic and terrestrial food webs. Furthermore, since most biological communities are not simple food chains but complex networks of interactions, one TMII within a community might easily be infl uenced by another TMII. In other words, TMII themselves can be cascades with potential implications for community dynamics. Here we report on one of such cascade, where a parasitic fl y induces behavioral changes that disrupt a trait-mediated ant–hemipteran mutualism. We show that during parasiteinduced low-activity periods, the ant Azteca instabilis fails to protect its mutualistic scale-insect partner against predatory ladybeetles. Th us, in the presence of the parasite, ladybeetles ate as many scales in ant-patrolled plants as they did in ant-free plants. Th ese results demonstrate how, through a cascade of trait-mediated interactions, associations between members of a community can be drastically altered.

The entomogenous fungus, Lecanicillium lecanii is hyperparasitic on Hemileia vastatrix , the cause of coffee leaf rust in the laboratory, and has frequently been observed attacking it in the field. The existence of a complex ecological web involving the spatially clustered mutualism of an ant ( Azteca instabilis ) with a scale insect ( Coccus viridis ), where the scale insect was infected by L. lecanii , prompted a search for a spatial correlation between the attack of L. lecanii on the scale insect and the incidence of rust in a commercial coffee crop. A weak but statistically significant effect of hyperparasitic control of coffee rust was observed on two distinct scales: in a 45-ha plot and on a scale of approximately 10 m. It was concluded that this effect was linked to an indirect effect of the ant‐coccid mutualism, where L. lecanii was a parasite of the coccid.

Agriculture is being challenged to provide food, and increasingly fuel, for an expanding global population. Producing bioenergy crops on marginal lands--farmland suboptimal for food crops--could help meet energy goals while minimizing competition with food production. However, the ecological costs and benefits of growing bioenergy feedstocks--primarily annual grain crops--on marginal lands have been questioned. Here we show that perennial bioenergy crops provide an alternative to annual grains that increases biodiversity of multiple taxa and sustain a variety of ecosystem functions, promoting the creation of multifunctional agricultural landscapes. We found that switchgrass and prairie plantings harbored significantly greater plant, methanotrophic bacteria, arthropod, and bird diversity than maize. Although biomass production was greater in maize, all other ecosystem services, including methane consumption, pest suppression, pollination, and conservation of grassland birds, were higher in perennial grasslands. Moreover, we found that the linkage between biodiversity and ecosystem services is dependent not only on the choice of bioenergy crop but also on its location relative to other habitats, with local landscape context as important as crop choice in determining provision of some services. Our study suggests that bioenergy policy that supports coordinated land use can diversify agricultural landscapes and sustain multiple critical ecosystem services.

Interactions among members of biological communities can create spatial patterns that effectively generate habitat heterogeneity for other members in the community, and this heterogeneity might be crucial for their persistence. For example, stage-dependent vulnerability of a predatory lady beetle to aggression of the ant, Azteca instabilis, creates two habitat types that are utilized differently by the immature and adult life stages of the beetle. Due to a mutualistic association between A. instabilis and the hemipteran Coccus viridis – which is A. orbigera main prey in the area – only plants around ant nests have high C. viridis populations. Here, we report on a series of surveys at three different scales aimed at detecting how the presence and clustered distribution of ant nests affect the distribution of the different life stages of this predatory lady beetle in a coffee farm in Chiapas, Mexico. Both beetle adults and larvae were more abundant in areas with ant nests, but adults were restricted to the peripheries of highest ant activity and outside the reach of coffee bushes containing the highest densities of lady beetle larvae. The abundance of adult beetles located around trees with ants increased with the size of the ant nest clusters but the relationship is not significant for larvae. Thus, we suggest that A. orbigera undergoes an ontogenetic niche shift, not through shifting prey species, but through stage-specific vulnerability differences against a competitor that renders areas of abundant prey populations inaccessible for adults but not for larvae. Together with evidence presented elsewhere, this study shows how an important predator is not only dependent on the existence of two qualitatively distinct habitat types, but also on the spatial distribution of these habitats. We suggest that this dependency arises due to the different responses that the predator's life stages have to this emergent spatial pattern.

For both applied and theoretical ecological science, the mutualism between ants and their hemipteran partners is iconic. In this well-studied interaction, ants are assumed to provide hemipterans protection from natural enemies in exchange for nutritive honeydew. Despite decades of research and the potential importance in pest control, the precise mechanism producing this mutualism remains contested. By analyzing maximum likelihood parameter estimates of a hemipteran population model, we show that the mechanism of the mutualism is direct, via improved hemipteran growth rates, as opposed to the frequently assumed indirect mechanism, via harassment of the specialist parasites and predators of the hemipterans. Broadly, this study demonstrates that the management of mutualism-based ecosystem services requires a mechanistic understanding of mutualistic interactions. A consequence of this finding is the counter intuitive demonstration that preserving ant participation in the ant-hemipteran mutualism may be the best way of insuring pest control.

Background Spatial heterogeneity is essential for the persistence of many inherently unstable systems such as predator-prey and parasitoid-host interactions. Since biological interactions themselves can create heterogeneity in space, the heterogeneity necessary for the persistence of an unstable system could be the result of local interactions involving elements of the unstable system itself. Methodology/Principal Findings Here we report on a predatory ladybird beetle whose natural history suggests that the beetle requires the patchy distribution of the mutualism between its prey, the green coffee scale, and the arboreal ant, Azteca instabilis. Based on known ecological interactions and the natural history of the system, we constructed a spatially-explicit model and showed that the clustered spatial pattern of ant nests facilitates the persistence of the beetle populations. Furthermore, we show that the dynamics of the beetle consuming the scale insects can cause the clustered distribution of the mutualistic ants in the first place. Conclusions/Significance From a theoretical point of view, our model represents a novel situation in which a predator indirectly causes a spatial pattern of an organism other than its prey, and in doing so facilitates its own persistence. From a practical point of view, it is noteworthy that one of the elements in the system is a persistent pest of coffee, an important world commodity. This pest, we argue, is kept within limits of control through a complex web of ecological interactions that involves the emergent spatial pattern.

Coccinellids (Coleoptera: Coccinellidae) are generally unable to prey on ant-tended prey. However, particular coccinellid species have morphological, behavioral, or chemical characteristics that render them immune to ant attacks, and some species are even restricted to ant-tending areas. The benefit gained from living in close association with ants can be twofold: (1) gaining access to high-density prey areas and (2) gaining enemy-free space. Here, the myrmecophily of Azya orbigera Mulsant (Coleoptera: Coccinellidae), an important predator of the green coffee scale, Coccus viridis (Green) (Hemiptera: Coccidae), is reported. In this paper, three main questions were studied. (1) Are the waxy filaments of A. orbigera larvae effective as defense against attacks of the mutualistic ant partner of C. viridis, Azteca instabilis F. Smith (Hymenoptera: Formicidae)? (2) Does A. instabilis reduce the rate at which A. orbigera larvae prey on scales? (3) Do A. orbigera larvae gain enemy-free space by living in close association with A. instabilis? Laboratory and field experiments were conducted to answer these questions. We found that, because of the sticky waxy filaments of A. orbigera larvae, A. instabilis is incapable of effectively attacking them and, therefore, the predation rate of A. orbigera on C. viridis does not decrease in the presence of ants. Furthermore, A. instabilis showed aggressive behavior toward A. orbigera's parasitoids, and the presence of ants reduced the parasitism suffered by A. orbigera. This is the first time that this kind of indirect positive effect is reported for an ant and a coccidophagous coccinellid. Furthermore, this indirect positive effect may be key to the persistence of A. orbigera's populations.