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Growing evidence reveals strong overlap between microbiomes of flowers and bees, suggesting that flowers are hubs of microbial transmission. Whether floral transmission is the main driver of bee microbiome assembly, and whether functional importance of florally sourced microbes shapes bee foraging decisions are intriguing questions that remain unanswered. We suggest that interaction network properties, such as nestedness, connectedness, and modularity, as well as specialization patterns can predict potential transmission routes of microbes between hosts. Yet microbial filtering by plant and bee hosts determines realized microbial niches. Functionally, shared floral microbes can provide benefits for bees by enhancing nutritional quality, detoxification, and disintegration of pollen. Flower microbes can also alter the attractiveness of floral resources. Together, these mechanisms may affect the structure of the flower-bee interaction network.

Microbial symbiosis drives physiological processes of higher-order systems, including the acquisition and consumption of nutrients that support symbiotic partner reproduction. Metabolic analytics provide new avenues to examine how chemical ecology, or the conversion of existing biomass to new forms, changes over a symbiotic life cycle. We applied these approaches to the nematode Steinernema carpocapsae, its mutualist bacterium, Xenorhabdus nematophila, and the insects they infect. The nematode-bacterium pair infects, kills, and reproduces in an insect until nutrients are depleted. To understand the conversion of insect biomass over time into either nematode or bacterium biomass, we integrated information from trophic, metabolomic, and gene regulation analyses. Trophic analysis established bacteria as meso-predators and primary insect consumers. Nematodes hold a trophic position of 4.6, indicative of an apex predator, consuming bacteria and likely other nematodes. Metabolic changes associated with Galleria mellonella insect bioconversion were assessed using multivariate statistical analyses of metabolomics data sets derived from sampling over an infection time course. Statistically significant, discrete phases were detected, indicating the insect chemical environment changes reproducibly during bioconversion. A novel hierarchical clustering method was designed to probe molecular abundance fluctuation patterns over time, revealing distinct metabolite clusters that exhibit similar abundance shifts across the time course. Composite data suggest bacterial tryptophan and nematode kynurenine pathways are coordinated for reciprocal exchange of tryptophan and NAD

Developing bees derive significant benefits from the microbes present within their guts and fermenting pollen provisions. External microbial symbionts (exosymbionts) associated with larval diets may be particularly important for solitary bees that suffer reduced fitness when denied microbe-colonized pollen.To investigate whether this phenomenon is generalizable across foraging strategy, we examined the effects of exosymbiont presence/absence across two solitary bee species, a pollen specialist and generalist. Larvae from each species were reared on either microbe-rich natural or microbe-deficient sterilized pollen provisions allocated by a female forager belonging to their own species (conspecific-sourced pollen) or that of another species (heterospecific-sourced pollen). Our results reveal that the presence of pollen-associated microbes was critical for the survival of both the generalist and specialist larvae, regardless of whether the pollen was sourced from a conspecific or heterospecific forager.Given the positive effects of exosymbiotic microbes for larval fitness, we then examined if the magnitude of this benefit varied based on whether the microbes were provisioned by a conspecific forager (the mother bee) or a heterospecific forager. In this second study, generalist larvae were reared only on microbe-rich pollen provisions, but importantly, the sources (conspecific versus heterospecific) of the microbes and pollen were experimentally manipulated.Bee fitness metrics indicated that microbial and pollen sourcing both had significant impacts on larval performance, and the effect sizes of each were similar. Moreover, the effects of conspecific-sourced microbes and conspecific-sourced pollen were strongly positive, while that of heterospecific-sourced microbes and heterospecific-sourced pollen, strongly negative.Our findings imply that not only is the presence of exosymbionts critical for both specialist and generalist solitary bees, but more notably, that the composition of the specific microbial community within larval pollen provisions may be as critical for bee development as the composition of the pollen itself.

As pollen and nectar foragers, bees have long been considered strictly herbivorous. Their pollen provisions, however, are host to abundant microbial communities, which feed on the pollen before and/or while it is consumed by bee larvae. In the process, microbes convert pollen into a complex of plant and microbial components. Since microbes are analogous to metazoan consumers within trophic hierarchies, the pollen-eating microbes are, functionally, herbivores. When bee larvae consume a microbe-rich pollen complex, they ingest proteins from plant and microbial sources and thus should register as omnivores on the trophic "ladder." We tested this hypothesis by examining the isotopic compositions of amino acids extracted from native bees collected in North America over multiple years. We measured bee trophic position across the six major bee families. Our findings indicate that bee trophic identity was consistently and significantly higher than that of strict herbivores, providing the first evidence that omnivory is ubiquitous among bee fauna. Such omnivory suggests that pollen-borne microbes represent an important protein source for larval bees, which introduces new questions as to the link between floral fungicide residues and bee development.

Biological control plays an important role in many integrated pest management programmes, but can be disrupted by other control strategies, including chemical and cultural controls. In commercial cranberry (Vaccinium macrocarpon Aiton; Ericaceae) production, a spring flood can replace an insecticide application, providing an opportunity to study the compatibility of the flood (a cultural control) with biological control. We suspect that chemical controls will tend to reduce the number of natural enemies, while the flood, through removal of detritus and detritivores, may cause generalist predators to prey-switch to consume proportionally more pest individuals. We measured the abundance of herbivores (Lepidoptera), detritivores, Arachnida, and parasitoids (Hymenoptera) every week for six weeks in Wisconsin (United States of America) cranberry beds following either an insecticide spray or a cultural control flood. We found that detritivore populations rapidly declined in both flood and spray treatments; conversely, carnivore populations (spiders and parasitoids) were more abundant in the flooded beds than in sprayed beds. Populations of key cranberry pests were similar between flooded and sprayed beds. Our results showed that early-season flooding preserved more natural enemies than an insecticide application. This increase in natural enemy abundance after the flood may allow for greater continuity in herbivore suppression, potentially providing a basis for long-term cranberry pest management.

Compound-specific nitrogen stable isotope analysis provides an approach for estimating animal trophic position that may overcome key issues associated with stable isotope analysis of bulk tissue. Yet compound-specific trophic discrimination factors have not been estimated for a broad range of habitats, taxa, and diets. We conducted a controlled-feeding experiment to characterize the variation in compound-specific (TDFAA) and bulk (TDFBulk) trophic discrimination factors of four freshwater fish species fed on three distinct diets. We also compared TDFAA of fish muscle and scale to evaluate the viability of scales for making food web inferences. Mean ± 1 SD TDFBulk was 2.2‰ ± 0.9‰, and there were significant effects of species and diet trophic position on TDFBulk. Mean ± 1 SD TDFAA was 6.9‰ ± 0.8‰. Although there was no effect of species on TDFAA, there were significant differences in TDFAA across the three diets. TDFAA from fish scales were not significantly different from those of muscle. Our study illustrates the advantages of estimating trophic position using compound-specific stable isotopes and the need for continued investigation of factors resulting in variation in TDF values.

Detritivory is the dominant trophic paradigm in most terrestrial, aquatic, and marine ecosystems, yet accurate measurement of consumer trophic position within detrital (=“brown”) food webs has remained unresolved. Measurement of detritivore trophic position is complicated by the fact that detritus is suffused with microbes, creating a detrital complex of living and nonliving biomass. Given that microbes and metazoans are trophic analogues of each other, animals feeding on detrital complexes are ingesting other detritivores (microbes), which should elevate metazoan trophic position and should be rampant within brown food webs. We tested these hypotheses using isotopic (15N) analyses of amino acids extracted from wild and laboratory‐cultured consumers. Vertebrate (fish) and invertebrate detritivores (beetles and moths) were reared on detritus, with and without microbial colonization. In the field, detritivorous animal specimens were collected and analyzed to compare trophic identities among laboratory‐reared and free‐roaming detritivores. When colonized by bacteria or fungi, the trophic positions of detrital complexes increased significantly over time. The magnitude of trophic inflation was mediated by the extent of microbial consumption of detrital substrates. When detrital complexes were fed to vertebrate and invertebrate animals, the consumers registered similar degrees of trophic inflation, albeit one trophic level higher than their diets. The wild‐collected detritivore fauna in our study exhibited significantly elevated trophic positions. Our findings suggest that the trophic positions of detrital complexes rise predictably as microbes convert nonliving organic matter into living microbial biomass. Animals consuming such detrital complexes exhibit similar trophic inflation, directly attributable to the assimilation of microbe‐derived amino acids. Our data demonstrate that detritivorous microbes elevate metazoan trophic position, suggesting that detritivory among animals is, functionally, omnivory. By quantifying the impacts of microbivory on the trophic positions of detritivorous animals and then tracking how these effects propagate “up” food chains, we reveal the degree to which microbes influence consumer groups within trophic hierarchies. The trophic inflation observed among our field‐collected fauna further suggests that microbial proteins represent an immense contribution to metazoan biomass. Collectively, these findings provide an empirical basis to interpret detritivore trophic identity, and further illuminate the magnitude of microbial contributions to food webs.

The differential discrimination of nitrogen isotopes (N-15/N-14) within amino acids in consumers and their diets has been routinely used to estimate organismal tropic position (TP). Analogous isotopic discrimination can occur within plants, particularly in organs lacking chloroplasts. Such discrimination likely arises from the catabolic deamination of amino acids, resulting in a numerical elevation of estimated TP, within newly synthesized biomass. To investigate this phenomenon, we examined the 15N/14N of amino acids (delta N-15(AA)) in spring leaves and flowers from eight deciduous and two annual plants. These plants were classified on the basis of their time of bloom, plants that bloomed when their leaves were absent (Type I) versus plants that bloomed while leaves were already present (Type II). Based on the delta N-15(AA) values from leaves, both plant types occupied comparable and ecologically realistic mean TPs (= 1.0 +/- 0.1, mean +/- 1 sigma). However, the estimated TPs of flowers varied significantly Type I: 2.2 +/- 0.2; Type II: 1.0 +/- 0.1). We hypothesize that these results can be interpreted by the following sequence of events: (1) Type I floral biomass is synthesized in absence of active photosynthesis; (2) the catabolic deamination of amino acids in particular, leaves behind N-15 in the residual pool of amino acids; and (3) the incorporation of these N-15-enriched amino acids within the biomass of Type I flowers results in the numerical elevation of the TPs. In contrast, the actively photosynthesizing Type II leaves energetically sustain the synthesis of Type II flower biomass, precluding any reliance on catabolic deamination of amino acids. Amino acids within Type II flowers are therefore isotopically comparable to the Type II leaves. These findings demonstrate the idiosyncratic nature of the delta N-15(AA) values within autotrophic organs and have implications for interpreting trophic hierarchies using primary producers and their consumers.

Quantifying resource partitioning is central to community and food web ecology and of increasing interest in an era of rapid global change disrupting biotic interactions. Multichannel feeding – consuming resources from both green and brown food webs – can be a stabilizing force in communities. While multichannel feeding has been well-documented in invertebrate and aquatic systems, it has been relatively under-studied in terrestrial vertebrate populations. Applied ecologists are seeking approaches to assess niche partitioning and cryptic trophic pathways, like multichannel feeding, which have been difficult to quantify, especially among vertebrates. Using both bulk (δ13C and δ15N) and compound specific stable isotope ratios (δ15N glutamic acid and phenylalanine), we tested how three common and competing tree squirrel partition resources. Our complementary analyses revealed that squirrels partitioned niche space and, because of differences in multichannel foraging, possessed different trophic identities. While all squirrels consumed food items from green and brown food webs, their dependence on each differed, revealing an important, yet cryptic, mechanism behind apparent stable co-occurrence of these competitors. Our work supports multichannel feeding as a potential mechanism promoting coexistence in this guild of terrestrial vertebrates, and provides a framework to quantify resource partitioning in other ecological communities.

Simple sequence repeats (SSRs) in chloroplast and mitochondrial DNA, which have not been previously developed in the Ericaceae or, more specifically, in the genus Vaccinium, can be powerful tools for determining evolutionary relationships among taxa. In this study, 30 chloroplast, 23 mitochondrial, and 1 mitochondrion-like SSRs were identified in cranberry (V. macrocarpon), and primer-pairs were developed and tested for each locus. Although no polymorphisms were detected for any of the 54 SSR loci in nine diverse cranberry genotypes, all primers were cross-transferable to some extent to a panel of 12 additional Vaccinium taxa and four non-Vaccinium Ericaceae species. A Neighbor-Joining tree of the estimated average squared distances resolved the species by genus and by section within Vaccinium. Similar topologies with increased branch support were observed in Bayesian inference trees constructed from the DNA sequences of six plastid and two mitochondrial SSR loci. Two multiplexing/poolplexing panels of M13 fluorescently labeled primers, which amplify 24 of the 54 markers, were developed and can serve as an efficient, cost-effective means for characterizing the basic molecular phylogeny of Vaccinium. Increased understanding of evolutionary relationships among Vaccinium species should facilitate interspecific hybridization and introgression efforts to improve economically important traits of commercial berry crops.

Stable nitrogen isotopic composition of amino acids (δ (15)NAA) has recently been employed as a powerful tool in ecological food web studies, particularly for estimating the trophic position (TP) of animal species in food webs. However, the validity of these estimates depends on the consistency of the trophic discrimination factor (TDF; - Δδ (15)NAA at each shift of trophic level) among a suite of amino acids within the tissues of consumer species. In this study, we determined the TDF values of amino acids in tadpoles (the Japanese toad, Bufo japonicus) reared exclusively on one of three diets that differed in nutritional quality. The diets were commercial fish-food pellets (plant and animal biomass), bloodworms (animal biomass), and boiled white rice (plant carbohydrate), representing a balanced, protein-rich, and protein-poor diet, respectively. The TDF values of two "source amino acids" (Src-AAs), methionine and phenylalanine, were close to zero (0.3-0.5‰) among the three diets, typifying the values reported in the literature (∼0.5‰ and ∼0.4‰, respectively). However, TDF values of "trophic amino acids" (Tr-AAs) including alanine, valine, leucine, isoleucine, and glutamic acid varied by diet: for example, the glutamic acid TDF was similar to the standard value (∼8.0‰) when tadpoles were fed either the commercial pellets (8.0‰) or bloodworms (7.9‰), but when they were fed boiled rice, the TDF was significantly reduced (0.6‰). These results suggest that a profound lack of dietary protein may alter the TDF values of glutamic acid (and other Tr-AAs and glycine) within consumer species, but not the two Src-AAs (i.e., methionine and phenylalanine). Knowledge of how a nutritionally poor diet can influence the TDF of Tr- and Src-AAs will allow amino acid isotopic analyses to better estimate TP among free-roaming animals.

Food webs are known to have myriad trophic links between resource and consumer species. While herbivores have well-understood trophic tendencies, the difficulties associated with characterizing the trophic positions of higher-order consumers have remained a major problem in food web ecology. To better understand trophic linkages in food webs, analysis of the stable nitrogen isotopic composition of amino acids has been introduced as a potential means of providing accurate trophic position estimates. In the present study, we employ this method to estimate the trophic positions of 200 free-roaming organisms, representing 39 species in coastal marine (a stony shore) and 38 species in terrestrial (a fruit farm) environments. Based on the trophic positions from the isotopic composition of amino acids, we are able to resolve the trophic structure of these complex food webs. Our approach reveals a high degree of trophic omnivory (i.e., noninteger trophic positions) among carnivorous species such as marine fish and terrestrial hornets.This information not only clarifies the trophic tendencies of species within their respective communities, but also suggests that trophic omnivory may be common in these webs.

Detritivory represents the dominant trophic mode on Earth, and within this vast consumer group, microbes tend to predominate. Virtually all detritus is replete with microbes, many of which consume the detrital substrate, rendering it a complex of living and non-living components. A detrital mass, therefore, can be considered an ‘undead’ food-web in which the resident microbes busily displace non-living biomass with their own, while carnivorous microbes prey upon other organisms. In this food-chain, bacteria and fungi have been shown to register just as animals do, demonstrating that microbes are analogous to animals within trophic hierarchies. Given that microbial consumers are often suffused throughout detrital substrates, the detritus becomes a complex of multiple trophic groups. It has long been suggested that microbial consumers within soil systems represent distinct trophic groups, and in recent studies, these hypotheses have been tested empirically. The detrital complex, then, can be considered a dynamic microcosm of the broader food-web, and the trophic identities within the complex (as well as the metazoans that consume the complex), can be measured and interpreted. This multi-trophic aspect of ‘undead’ detritus tends to elevate the trophic positions of animals (i.e., trophic inflation), which derives from the assimilation of heterotrophic (microbial) and autotrophic proteins. Importantly, inclusion of microbes in trophic hierarchies provides a more comprehensive framework within which to interpret organismal-, population-, and community-scale trophic identities. However, in recalibrating our trophic ‘lens’ to include microbial consumers, there remain some long-standing concepts, questions, and definitions that will need to be revisited.

Degree-day models link ambient temperature to the development of insects, making such models valuable tools in integrated pest management. These models increase management efficacy by quantifying and predicting pest phenology. In Wisconsin, the top insect pest of cranberry production is the cranberry fruitworm, Acrobasis vaccinii Riley (Lepidoptera: Pyralidae). Control of this species is often complicated by the fact that the larvae feed entirely within the fruit. Timing of control tactics, therefore, is critical and generally targets the adult and egg stages. However, the commencement of oviposition and egg hatch are extremely difficult to track empirically, forcing pest management strategies to rely on proxy events that are more apparent but less informative as indicators of cranberry fruitworm egg presence. This research provides the upper and lower temperature-mediated growth thresholds of this pest, which represents the first steps toward the creation of a degree-day model. Using field-collected A. vaccinii, we reared the larvae within cranberry fruit and monitored larval growth at nine different constant temperatures. We determined the average growth rate at each temperature and modeled growth rates as a function of temperature. We then calculated the precise upper and lower developmental temperature thresholds of this species. Future work will be able to use these thresholds to generate degree-day accumulations that correspond to phenological events in the field, providing a powerful predictive tool for pest management in cranberry production.

Greater resource use by diverse communities might result from species occupying complementary niches. Demonstrating niche complementarity among species is challenging, however, due to the difficulty in relating differences between species in particular traits to their use of complementary resources. Here, we overcame this obstacle by exploiting plastic foraging behavior in a community of predatory insects common on Brassica oleracea plants in Washington, USA. These predators complemented one another by partitioning foraging space, with some species foraging primarily along leaf edges and others at leaf centers. We hypothesized that emergent biodiversity effects would occur when predators partitioned foraging space on leaves, but not when spatial complementarity was dampened. Indeed, on intact leaves, edge- and center-foraging predators combined to kill more prey than any single predator species could by itself. These emergent diversity effects, however, disappeared on plants damaged by the caterpillar Plutella xylostella. Caterpillar chew-holes brought edge habitats to the center of leaves, so that all predator species could attack aphids anywhere on plants. With spatial niche differences diminished, there were no benefits of predator diversity; the most voracious single predator species killed the most aphids. Thus, caterpillar herbivory determined whether multi-predator-species effects reflected complementarity or species' individual impacts. Our study provides direct evidence for a causative relationship between niche differentiation and increased resource consumption by diverse communities, as revealed by ecological engineers that homogenize the foraging environment.

Consumer diversity generally increases resource consumption. Consumers can also impact other species by altering their behavior, but it is unclear how such nonconsumptive effects scale with diversity. We independently manipulated predator species richness and the consumptive and nonconsumptive effects of predator communities to measure the role of each factor in protecting Brassica oleracea plants from caterpillar herbivory. Plant biomass was greatest when diverse predator assemblages induced antipredator behaviors in herbivores, an effect not further strengthened when predators could also kill caterpillars. Predators within diverse communities were more likely to forage on plants and to disrupt herbivore feeding, reflecting greater aversion to foraging among conspecific than heterospecific competitors. Predator diversity, therefore, initiated behavioral changes at the predator and then herbivore trophic levels, both to the benefit of plants. Our results indicate that strong, emergent species-richness effects can be transmitted entirely through behavioral interactions, independent of resource consumption.

American Entomologist • Winter 2009 Undergraduate curricula of many institutions of higher education include General Education Requirements (GERs). Most GER courses provide an overview of a given subject area to students who may have little experience and/or interest in the subject matter, which can present obstacles to achieving standards of proficiency. Generating and sustaining interest is critical, and teaching methods that emphasize interdisciplinary approaches may help students effectively weave course content into their current knowledge base. At Washington State University, Insects, Science, and World Cultures (Entom 150) is a lower-division, GER science course designed for non-science majors and elementary education majors. Students enrolled in the course represent diverse backgrounds, interests, and academic majors. The content and pedagogy of Entom 150 are intended to address the needs and challenges of a heterogeneous student population. Insects, Science, and World Cultures offers an interdisciplinary view of the global impact of insects on the arts, myths & legends, cuisine, medicine, scientific research, and agriculture. It emphasizes the role of insects and their products in various cultures around the world (historical and contemporary) and uses insects as a tool to examine topics of broad interest (e.g., nutrition and undernourishment in developing nations, biological control, pesticides, environmental issues, energy flow, insects as “recyclers,” forensics, water quality, and insects as key Insect Myths: An Interdisciplinary Approach Fostering Active Learning

Larvae of Sparganothis sulfureana Clemens frequently attack cranberries, often resulting in economic damage to the crop. Because temperature dictates insect growth rate, development can be accurately estimated based on daily temperature measurements. To better predict S. sulfureana development across the growing season, we investigated the temperature range within which S. sulfureana larvae can feed and grow. Larvae were reared at 13 constant temperatures ranging from 6.5-38.6 °C. Larval growth rate was determined by the rate of change of larval weight across time. The respective growth rates among these temperatures were modeled using simple linear, cubic, and Lactin nonlinear development functions. These models isolated the lower temperature threshold at which growth became nonzero and the upper temperature at which growth was maximized. All three models were significantly predictive of S. sulfureana growth, but the cubic model best represented the observed growth rates, effectively isolating lower and upper thresholds of 9.97 and 29.89 °C, respectively. We propose that these thresholds be used to create a degree-day model of temperature-mediated S. sulfureana development.

New techniques are presented on the use of 15 N to mark insects. 15 N, a stable isotope of nitrogen, was enriched above natural abundance in plant and insect tissues. Two laboratory studies demonstrated that enriched 15 N-concentrations could be tracked from plant to insect using mass spectrometry. In the first study, adult Cotesia plutellae (Kurdjimov) (Hymenoptera: Braconidae) and Hippodamia convergens Guerin-Meneville (Coleoptera: Coccinellidae) were allowed to feed at the flowers of rapid-cycling Chinese cabbage plants that had been fertilized with 15 N-enriched potassium nitrate (KNO 3 - 15 NO 3 ). Both insect groups were found to have significantly elevated 15 N levels after visiting the flowers of the 15 N-enriched plants for 48 hours. In the second study, 15 N-enriched bean plant (Phaseolus vulgaris L.) tissue was incorporated into an insect diet and fed to navel orangeworms, Amyelois transitella (Walker) (Lepidoptera: Pyralidae). When the navel orangeworm larvae were 4th instars, they were removed from the diet and exposed to the parasitoid, Goniozus legneri Gordh (Hymenoptera: Bethylidae). Results indicated that the enriched 15 N-concentration of the bean plants was transferred to the navel orangeworms and, subsequently, to the parasitoids. This work may provide useful techniques to help establish whether agriculturally important entomophaga visiting 15 N-enriched flowers or parasitizing enriched sentinel larvae in the field can be effectively marked with 15 N.

The application of next-generation sequencing (NGS) technologies for the development of simple sequence repeat (SSR) or microsatellite loci for genetic research in the botanical sciences is described. Microsatellite markers are one of the most informative and versatile DNA-based markers used in plant genetic research, but their development has traditionally been a diffi cult and costly process. NGS technologies allow the effi cient identifi cation of large numbers of microsatellites at a fraction of the cost and effort of traditional approaches. The major advantage of NGS methods is their ability to produce large amounts of sequence data from which to isolate and develop numerous genome-wide and gene-based microsatellite loci. The two major NGS technologies with emergent application in SSR isolation are 454 and Illumina. A review is provided of several recent studies demonstrating the effi cient use of 454 and Illumina technologies for the discovery of microsatellites in plants. Additionally, important aspects during NGS isolation and development of microsatellites are discussed, including the use of computational tools and high-throughput genotyping methods. A data set of microsatellite loci in the plastome and mitochondriome of cranberry ( Vaccinium macrocarpon Ait.) is provided to illustrate a successful application of 454 sequencing for SSR discovery. In the future, NGS technologies will massively increase the number of SSRs and other genetic markers available to conduct genetic research in understudied but economically important crops such as cranberry.