Aaron Iverson

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

FIGURES 4–8. Diomus spp. adult habitus illustrations: 4–7, D. lupusapudoves (4, male holotype; 5–6, common variations in male color pattern present in the type series; 7, representative female paratype); 8, D. urban, female from Chiapas, Mexico.

Remote Amazonian communities are often largely self-sufficient, made possible in part by their agricultural skills and deep ecological knowledge of their landscapes. Mastery of their local flora undoubtedly plays a vital role in daily life, yet communities in the Amazon can vary widely in both the diversity of plants that they utilize and in how they manage plants in their agricultural landholdings. The dominant drivers of these differences in ecological knowledge and practices between communities are not clearly understood. We compare the agricultural practices and diversity of utilized plants in an Indigenous Urarina community and a Mestizo community in the Peruvian Amazon. Through field surveys and farmer interviews, we assessed the diversity of utilized plants found in the homegardens (N = 17) and chacras (cropped fields; N = 47), as well as multiple agricultural characteristics of the chacras and fallow fields (N = 32). Households from the Mestizo community cultivated a larger ...

The family Coccinellidae contains many common aphidophagous and coccidophagous natural enemies, providing benefits to agroecosystems through their pest control services. Infrequently, but with great adaptive benefits, predatory coccinellid species form close relationships with ants and are facultatively or obligately myrmecophilous. We studied the behavior and distribution of two myrmecophilous coccinellids, Azya orbigera (Mulsant) and an undescribed species of Diomus to determine potential niche partitioning by the beetles. Both species feed on the green coffee scale pest, Coccus viridis (Green), in a coffee agroecosystem in Chiapas, Mexico. We also asked how the Diomus sp. is capable of avoiding ant aggression, given that its larvae appear to be physically rather vulnerable, unlike A. orbigera larvae, which are covered with long waxy filaments. Through field surveys and lab experiments we detected some degree of resource partitioning and significant spatial segregation among A. or...

Agricultural intensification is implicated as a major driver of global biodiversity loss. Local management and landscape scale factors both influence biodiversity in agricultural systems, but there are relatively few studies to date looking at how local and landscape scales influence biodiversity in tropical agroecosystems. Understanding what drives the diversity of groups of organisms such as spiders is important from a pragmatic point of view because of the important biocontrol services they offer to agriculture. Spiders in coffee are somewhat enigmatic because of their positive or lack of response to agricultural intensification. In this study, we provide the first analysis, to our knowledge, of the arboreal spiders in the shade trees of coffee plantations. In the Soconusco region of Chiapas, Mexico we sampled across 38 sites on 9 coffee plantations. Tree and canopy connectedness were found to positively influence overall arboreal spider richness and abundance. We found that diff...

ABSTRACTHuman land use threatens global biodiversity and compromises multiple ecosystem functions critical to food production. Whether crop yield-related ecosystem services can be maintained by few abundant species or rely on high richness remains unclear. Using a global database from 89 crop systems, we partition the relative importance of abundance and species richness for pollination, biological pest control and final yields in the context of on-going land-use change. Pollinator and enemy richness directly supported ecosystem services independent of abundance. Up to 50% of the negative effects of landscape simplification on ecosystem services was due to richness losses of service-providing organisms, with negative consequences for crop yields. Maintaining the biodiversity of ecosystem service providers is therefore vital to sustain the flow of key agroecosystem benefits to society.

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 so...

We tested chemical and insect feeding-induced insect resistance on soybean plants.The chemical induction effects of jasmonic acid (JA) and salicylic acid (SA) were investigated. We also evaluated the effects of plants stressed with previous insect herbivory. A larval antibiosis screening technique (LAST) and a preference test were performed in petri dishes using Mexican bean beeetles. Epilachna varivestis Mulsant, to monitor the effects of resistance in soybeam. Results from the LAST assessment showed evidence of both chemical and insect feeding induction of resistance. JA applied to the plant resulted in greater insect mortality and less larval damage than did the controls, indicating an increased resistance to herbivorous stress. In contrast, plants treated with SA had slightly less resistance. In the previously insect-damaged study, plants that had portions of lower leaves consumed by the beetle developed a higher level of resistance to subsequent feeding of the upper leaves. Preference studies were inconclusive because of a general lack of insect feeding. Induced resistance could provide a means to enhance the natural resistance of soybeans to pests, benefiting both consumers and producers.

Summary Agriculture comprises the largest global land use, makes it a leading cause of habitat loss. It is therefore critical to identify how to best construct agricultural systems that can simultaneously provide food and other ecosystem services. This challenge requires that we determine how to maximize win‐win relationships and minimize trade‐offs between services. Through meta‐analysis, we tested whether within‐field crop diversification (polyculture) can lead to win‐win relationships between two ecosystem services: yield of a focal crop species and biocontrol of crop pests. We selected only studies that recorded both services (N = 26 studies; 301 observations), allowing us to better determine the underlying mechanisms of our principal findings. We calculated log‐response ratios for both ecosystem services in mono‐ and polycultures. We found win‐win relationships between per‐plant yield of the primary crop and biocontrol in polyculture systems that minimized intraspecific competi...

Agroecological factors at local-management and landscape scales influence organisms residing in agriculture. Management for control of insect pests of agricultural commodities can be facilitated by our knowledge of these factors. We sampled for a minor coffee pest, a leaf-chewing beetle (Rhabdopterus jansoni), across sites that varied in coffee shade management and landscape land use composition. We show that R. jansoni abundance increased with higher local shade tree density, and the percentage of high-shade plantations and habitat diversity in the surrounding landscape. Sites at lower elevations also had more R. jansoni than at higher elevations. This study suggests that this minor pest prefers high-shade plantations, landscapes dominated by high-shade coffee land use, and lower elevations. These results will be useful for understanding this pest’s population dynamics with continuing shade intensification and climate change occurring in the Mexican and Central American coffee growing region.

ABSTRACT Background/Question/Methods Biotic and abiotic contexts can alter the outcome of defense mutualisms between plants and their partners. This conditionality may be specifically true for indirect ant-plant mutualisms mediated by honeydew-producing hemiptera (hereafter hemiptera) because plants may compete for ant attendance with other plants that also host high densities of hemiptera. In this study we tested the hypothesis that ant (Azteca instabilis) limitation of coffee berry borer (seed predator) would be conditional upon the species of tree ants nest in. We predicted coffee below Inga spp. trees (many hemiptera) would have weaker benefits from A. instabilis than coffee below non-Inga spp. (few hemiptera). In six coffee plantations we compared the borer infestation of coffee plants (on 3-5 plants) and the number of coffee plants foraged upon by A. instabilis below Inga spp. and non-Inga spp. trees with active A. instabilis nests as well as paired control trees without A. instabilis. We also estimated the total benefit of A. instabilis nests to coffee (mean proportion infested in control tree – A. instabilis tree × number of coffee plants foraged upon by A. instabilis × mean number of berries per coffee plant). Results/Conclusions There was twice as many hemipterans in the A. instabilis nest trees of Inga spp. relative to non-Inga spp. Azteca instabilis activity was 50% higher and there were 14 times more hemipterans on coffee below non-Inga spp. relative to Inga spp. nest trees. Across all coffee plants there was a 6 times higher proportion of coffee fruits infested with the berry borer below control trees (without A. instabilis) relative to paired A. instabilis trees. The difference between each tree pair (control – A. instabilis) was 66% greater for non-Inga spp. relative to Inga spp. trees, although this differences was not significant (pest control per coffee plant). Azteca instabilis foraged on 86% more coffee plants under non-Inga spp. relative to under Inga spp. trees. Estimation of nest level reduction of berry borer was 6 times greater for non-Inga spp. (254 berries rescued) relative to Inga spp. (40 berries rescued). Results suggest that at nest level scales, A. instabilis suppression of the berry borer and indirect benefits to coffee are limited by abundance of hemiptera in nest trees. Thus, it appears competition for ant attendance between coffee and trees may alter the strength of the ant-hemiptera-coffee association.

ABSTRACT Background/Question/Methods Land-use change is considered the strongest driver of biodiversity loss. An alarming fact considering that approximately 40% of the terrestrial land surface is now used for agriculture. Yet some agriculture practices maintain high levels of biodiversity, and therefore it is essential to understand which components are key for biodiversity conservation within these land-use types. We conducted a meta-analysis of the literature to determine the importance of local and landscape level factors in promoting within farm biodiversity. Based on a literature search in ISI Web of Science, we included data from studies that compared local management factors (organic vs. conventional, intensive vs. extensive, etc.), compared landscape level factors (% natural area, % forest, etc. in surrounding farms within >200m radius; hereafter % non-crop area), and measured richness or abundance within farm (55 studies). Within each study, the log response ratio (less intensive site/ more intensive site) was calculated as an effect size for mean richness and abundance. We also calculated the correlation coefficient (r) from the relationship between the landscape level (non-crop area %) and richness or abundance. We hypothesized that both local and landscape scale factors would have significant beneficial effects on richness within agricultural systems. Results/Conclusions Our results suggest that the mean log response ratio of species richness was significantly greater than zero, indicating that overall richness was higher in less intensively (organic or extensive) compared to more intensively managed farms (conventional) (mean response ratio = 0.34, lower 95% CI = 0.19, upper 95% CI = 0.49). Landscape factors also had a significant effect on richness within farms. The mean correlation coefficient for the relationship between percent non-crop area (landscape variable) and species richness was significantly greater than zero (mean response ratio = 0.21, lower 95% CI = 0.097, upper 95% CI = 0.323). Local and landscape factor effects on abundance paralleled effects on species richness; both local and landscape factors had significant effects on abundance. These results suggest that both local and landscape level factors are important for the conservation of biodiversity within agricultural systems. Thus conservation strategies within agricultural landscapes should take a local and regional approach.

In response to anthropogenic environmental change, the cues that animals use throughout their lifecycle to optimize fitness may become unreliable, resulting in an ecological trap. Here we investigated whether commercial bumble bee Bombus impatiens colonies managed for early spring crop pollination act as ecological traps for wild nest‐searching Bombus queens by subverting their natural nest usurpation behaviour. An average of 10 dead wild queens were recovered from each standard colony during the 2‐week period of the experiment, but colonies with queen excluders were successful in preventing wild queen deaths. The use of queen excluders did not impact colony performance in terms of resident queen survival, colony reproduction, colony weight gain or worker body size. Sites where wild nest‐searching queens were small had higher rates of failed usurpation, suggesting smaller‐sized queens are disproportionately at risk from failed usurpation. Furthermore, sites where commercial colonies...

The mutualism between plants and pollinators is built upon the trophic ecology of flowers and florivores. Yet the ecology of flowers-as-food is left implicit in most studies of plant-pollinator ecology, and it has been largely neglected in mainstream trophic ecology. This deficit is especially evident in an emerging issue of basic and applied significance: competition between pollinators for floral resources. In this synthesis, we start by exploring the notion of floral resource limitation upon which most studies concerning competition between pollinators are tacitly predicated. Both theoretical and empirical lines of evidence indicate that floral resource limitation must be understood as a complex ecological contingency; the question is not whether but when, where, and in what regions of floral trait space resources are limiting. Based on this premise, we propose a framework for understanding floral resource availability in terms of temporal, spatial, and functional structure. Whil...

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. 

<i>Diomus lupusapudoves,</i> sp. nov. (Figs. 1–7, 9, 11–15) <b>Diagnosis.</b> Due to variability in the dorsal color pattern (Figs. 4–7), the new species is best identified by the exact configuration of the adult male genital structures (Figs. 11–12) and by the myrmecophilous, onisciform (=platyform) larva (Figs. 14–15) possessing a finely granulate dorsum devoid of setae, and with the epipleurum of each abdominal segment extended into an oblique lateral plate, forming a protective skirt-like border to shield the underside of the body and appendages. This species closely resembles another myrmecophile, <i>Diomus thoracicus</i> (Fabricius, 1801), recorded from northern South America and the Antilles, to Mexico and southern Florida (Peck 2015), but the adult of our new species is smaller on average (1.7–2.1 mm vs. 2.0– 2.4 mm). <i>Diomus thoracicus</i> male genitalia (illustrated in Gordon 1999) are structurally quite similar as well, but possess at least 1.5× the number of setae along the outer margins of each paramere and have the trabes strongly inflated in apical 2/3. The larva of <i>D. thoracicus</i> is also onisciform (Vantaux <i>et al.</i> 2010; Roux <i>et al.</i> 2017), but has the dorsal surface a uniform light bluish gray except for the contrasting white epipleurum of each abdominal segment. The perimeter of the body is distinctly fimbriate in <i>D. thoracicus</i>, whereas the new species has only a few setae on the head and posterior end of the abdomen. In addition, the head of the <i>D. thoracicus</i> larva projects anteriorly, and is not enclosed laterally by the sides of the pronotum as it is in the new species. Although larvae of both species are myrmecophilous, <i>D. thoracicus</i> larvae are intranidal parasites that feed on ant brood, whereas larvae of the new species are coccidophagous and occur on open vegetation. Another species, <i>D. urban</i> Gordon, 1999 (Fig. 8), was found infrequently alongside the new species among colonies of <i>C. viridis</i> in the coffee agroecosystem that we studied [...]

Diomus Mulsant <i>Scymnus (Diomus)</i> Mulsant 1850: 951. Type species: <i>Coccinella thoracica</i> Fabricius, 1801, by subsequent designation of Korschefsky 1931. <i>Diomus</i>: Weise 1895:144. <i>Nephus (Diomus)</i>: Iablokoff-Khnzorian 1976: 377. <i>Amidellus</i> Weise 1923: 141. Type species: <i>Scymnus ementitor</i> Blackburn, 1895 by original designation. Synonymized by Ślipiński 2007: 87 (see Gordon (1976) and Pang & Gordon (1986) for a more complete bibliography). <i>Diomus</i> is the most speciose genus in the tribe Diomini Gordon, 1999, and possibly the largest genus in the entire family Coccinellidae Latreille, 1807 (Pang & Ślipiński 2009, 2010). <i>Diomus</i> was originally placed as a subgenus of <i>Scymnus</i> Kugellan, 1794, and classified, until recent times, in the tribe Scymnini Mulsant, 1846 along with a miscellaneous assortment o...

Several beetle species in the family Coccinellidae have evolved close associations with ants in order to consume ant-tended hemipteran prey. These myrmecophilous lady beetles employ various strategies for avoiding ant aggression, including physical and chemical protection. We asked how the lady beetle Diomus lupusapudoves Vandenberg, Iverson and Liere (Coccinellidae: Diomini) is capable of avoiding ant aggression in a Mexican coffee agroecosystem, given that its larvae are physically unprotected from the aggressive Azteca sericeasur Longino (Formicidae: Leptomyrmecini) ants. Through a classic scale-ant mutualism, these ants protect the primary food source of D. lupusapudoves , the green coffee scale, Coccus viridis Green (Coccidae: Coccini), an agricultural pest of coffee. Through three quantitative behavioral lab experiments, we found that the ants did not show aggression towards either D. lupusapudoves larvae or towards C. viridis . Similarly, the ants were not antagonistic to crickets (Orthoptera), which normally induce aggression, when they were covered in a coating of D. lupusapudoves larvae residues. Through a survival analysis, we found that D. lupusapudoves larvae are not apparently toxic to the ants, as ants that consumed a sugar solution containing the D. lupusapudoves larvae lived longer than those fed only a control sugar solution. From these series of experiments, we deduce that the D. lupusapudoves larvae likely employ chemical mimicry, allowing them to coexist with the aggressive A. sericeasur ants. The myrmecophilous behavior of the D. lupusapudoves larvae assists them in their role as an important biological control agent of the green coffee scale.

FIGURES 1–3. Photos taken in a coffee agroecosystem, Finca Irlanda, Chiapas, Mexico: 1, closeup of coffee plant infested with green coffee scale, C. viridis—note larva of the lady beetle D. lupusapudoves feeding on a scale near the leaf vein despite the proximity of P. synanthropica ants (center of image). 2, Closeup of D. lupusapudoves larva feeding on scale. 3, pupa of D. lupusapudoves—note glandular hairs on cuticle, and shed larval skin partially visible near caudal end.

Resistance and resilience have become important concepts in the evaluation of disturbance events, providing a framework that is useful in light of the expected increase in frequency and occurrences of hurricanes as a consequence of climate change. Hurricane Maria landed on Puerto Rico as a category 4 storm in September of 2017. Among the affected elements were agricultural systems, including coffee agroecosystems. Historically, coffee has been a major backbone of the island’s agricultural sector. Grown with a range of management styles, the coffee agroecosystem provides an excellent model system to study the resistance/resilience of agroecosystems faced with hurricane disturbance. Sampling 28 farms and comparing pre-hurricane data (2013) with post hurricane data we find that management style had only a small effect on either resistance or resilience, likely due to the especially strong nature of the storm. Rather, the socio-political context of individual farms seems to be a more us...

Background/Question/Methods Biotic factors affect species distribution and abundance therefore the overall impact of organisms on ecosystems. Indeed, some species have a strong effect on the distribution of other species because they act as keystone species that cascade (up or down) their effects to other trophic levels. In addition to their importance for biodiversity conservation in the tropics, coffee agroeocosystems are an excellent model where to study the effect of keystone players on species distribution and abundance. In organic coffee farms the diversity of trees that provide shade to the coffee plants is high whereas in farms tending towards intensification most of the shade trees belong to the Inga genus. In addition, in these agroecosystems the arboreal ant Azteca instabilis is a keystone species regarding biological control. Here we examine the spider diversity that inhabits the trunks of shade trees of coffee agroecosytems in relation to two keystone players: A. instab...

Aside from the Green Revolution, perhaps no other contemporary food or agricultural movement has had as much impact on the way we produce food as the organic agriculture (OA) movement. Global sales of organic produce have increased remarkably, nearly tripling from 2000 to 2009, reaching a value of US$ 55 billion. This increase is driven largely by consumers, who seek alternatives for reasons of personal and ecological health, about which information is largely intuitive or available in media sources widely accessible to the public. However, the rapid rise of OA has also led to a state of confusion for all but the most nuanced devotees. What exactly is OA? Can OA actually meet global food demand? Is organic consumption confined to wealthy individuals in wealthier countries? Additionally, one question in particular often remains unanswered in the literature: have organic family farmers benefitted from this boom in organic foods or have profits gone elsewhere? The book, Organic Agriculture for Sustainable Livelihoods, edited by Niels Halberg and Adrian Muller, provides a much-needed addition to the literature on OA and adeptly addresses the aforementioned questions and much more. The principle aim of the authors, as indicated by the title, is to assess the potential of OA for improving livelihoods, rural development, and ecosystem health. In so doing, this book (through dozens of contributors) provides a very thorough assessment of the multiple dimensions of OA, including the environmental, socioeconomic, policy, equity, and market aspects. Additionally, it addresses the important challenges and shortcomings of OA, and how these might be overcome. The authors primarily address small-scale landholders in developing countries, although developed nations are intricately involved in many of the market chains, as is discussed. The book is highly relevant to agriculture across the globe, as the editors do well in including chapters and/or case studies from most regions of the developing world. What is OA? The actual definition is hard to pin down and varies from one entity to the next. However, several unifying principles are espoused in the book: OA should not simply be the absence of synthetic chemicals, but ‘‘a production system that sustains the health of soils, ecosystems, and people. It relies on ecological processes, biodiversity, and cycles adapted to local conditions...[it] combines tradition, innovation, and science to benefit the shared environment and promote fair relationships and a good quality of life for all involved.’’ The definition thus expands beyond a traditional focus on soil fertility, and shares several similarities with the language used to describe A. Iverson (&) Department of Ecology and Evolutionary Biology, University of Michigan, 2019 Kraus Natural Science Building, 830 N. University St., Ann Arbor, MI 48109-1048, USA e-mail: iverson@umich.edu

Biodiversity loss--one of the most prominent forms of modern environmental change--has been heavily driven by terrestrial habitat loss and, in particular, the spread and intensification of agriculture. Expanding agricultural land-use has led to the search for strong conservation strategies, with some suggesting that biodiversity conservation in agriculture is best maximized by reducing local management intensity, such as fertilizer and pesticide application. Others highlight the importance of landscape-level approaches that incorporate natural or semi-natural areas in landscapes surrounding farms. Here, we show that both of these practices are valuable to the conservation of biodiversity, and that either local or landscape factors can be most crucial to conservation planning depending on which types of organisms one wishes to save. We performed a quantitative review of 266 observations taken from 31 studies that compared the impacts of localized (within farm) management strategies a...

Background/Question/Methods Agricultural lands currently cover ~40% of the earth’s terrestrial surface, and increased agricultural intensification has resulted in the degradation of biodiversity and various ecosystem services associated with agriculture. However, individual agroecosystems have varying impacts on ecosystem services, and attention is turning to methods of agricultural management that are capable of providing not only food, but also multiple services. In determining how to optimize food production and ecosystem service provision, it is crucial to first understand what ecological factors—both at a local- and landscape-level scale—are most influential in providing these services. I addressed the question of how pest predation by vertebrates and biodiversity conservation are influenced by local- and landscape-level heterogeneity in Puerto Rican coffee farms. Central to this question is whether plant diversity or simply vegetation structure has a stronger influence on serv...