Lepidopteran Larvae Research Articles

Spider mites avoid caterpillar traces to prevent intraguild predation

The phytophagous spider mites Tetranychus kanzawai and Tetranychus urticae (Acari: Tetranychidae) can be as small as < 0.5 mm; thus, they are often incidentally consumed along with food plant leaves by voracious lepidopteran larvae (hereafter, ‘caterpillars’; Shirotsuka and Yano, 2012). Therefore, the ability to avoid such intraguild predation should confer a selective advantage to mites. We experimentally demonstrated that adult females of both mite species avoided settling on food plant leaves with traces of all tested caterpillar species (Bombyx mori, Papilio xuthus, Spodoptera litura, and Theretra oldenlandiae). We examined additional interactions using B. mori and T. kanzawai and found that B. mori trace avoidance by T. kanzawai lasted for more than 48 h. Tetranychus kanzawai also avoided B. mori traces on plant stems, along which mites access leaves. Moreover, T. kanzawai avoided acetone extracts of B. mori traces applied to filter paper, indicating that chemical substances of caterpillar traces are responsible for the avoidance. This study is the first demonstration of a repellent effect of herbivore trace chemicals on heterospecific herbivores. Although spider mites have developed resistance against many synthetic pesticides (Attia et al., 2013; Van Leeuwen et al., 2010), this study showed the potential of using natural compounds simulating caterpillar traces in repelling spider mites from agricultural crops.

The selective advantage of mast flowering in Veratrum album subsp. oxysepalum: Implications of the predator satiation hypothesis.

Synchronous, highly variable flower or seed production among years within a population (i.e., masting) has been reported in numerous perennial plants. Although masting provides ecological advantages such as enhancing pollination efficiency and/or escape from predator attack, little is known about the degree of these advantages and variations in masting behavior among populations of conspecific plants. We determined flowering ramet density and reproductive success (fruit-set success and herbivorous damage) of a perennial herb, Veratrum album subsp. oxysepalum, across six lowland and six alpine populations in northern Japan during 2-3 years. We then analyzed the relationship between floral density and reproductive success to assess the ecological significance of mast flowering. Flowering intervals of individual plants were estimated by counting annual scars on rhizomes. Most populations had mast flowering, but the intervals between flowering for individual plants were shorter in the alpine populations than in the lowland populations. Floral damage by stem borers (dipteran larvae) and seed predation by lepidopteran larvae were intense in the lowland populations. Seed production of individual ramets increased with higher floral density owing to the effective avoidance of floral-stem damage and seed predation. Although stem borers were absent in the alpine habitat, seed predation decreased with higher floral density also in the alpine populations. Pollination success was independent of floral density in both of the alpine and lowland populations. These results strongly support the predator satiation hypothesis for mast flowering by this species.

Maximizing the Role of the Internal Larval Parasitoid, Meteorus gyrator (Thunberg) in the Open Field as a Biological Control Agent Considering the Effects of Climatic Changes

Background: Members of Braconidae, i.e., Meteorus spp. assault certain lepidopterous larvae in Egyptian fields. The recorded species M.rubens (gregarious) and M.gyrator (solitary) were the most species reared from some lepidopterous larvae attacking various host plants in two chosen Governorates in Egypt through two experimental years. This work aims to increase the parasitizing efficiency of M.gyrator in fields by releasing an impressive number of parasitoid adults.
 Methods:
 
 Samples of lepidopteran larvae were picked up from the prevailing plants in fields of El-Ghaebia and El-Sharkia Governorates, for two successive years (2020 to 2021). The prevailing plants are: clover, cabbage, okra, tomato, maize, jew's mallow, bean, soybean, cotton, pea, and lettuce. Collected larvae were reared under optimal conditions until their pupation or in anticipation of the migration of the full-grown endoparasitoid's larvae for pupation.
 Parasitoid’s production: Species of some lepidopterous larvae were reared in the NRC laboratory for large-scale manufacturing of the parasitoid Meteorus gyrator.
 
 Results: Acquired results uncover that Agrotis ipsilon was the primary noctuid host larvae of M. rubens during its abundant periods (February-May). While in case of M.gyrator it was recorded in fewer numbers (at its abundant periods, May-August); which was raised from other lepidopteran larvae.
 The M. rubens parasitism percentage reached 26.50 and 21.79% at El-Gharbia Governorate through the two experimental years, respectively; whereas in the case of M. gyrator it was 2.25% in the 2nd experimental year only. In El-Sharkia, M. rubens parasitism percentage was 18.60 and 28.60%, respectively throughout the two experimental years; while it was 10.00% for M. gyrator in the first year only.
 Conclusion: To boost the productivity of this solitary internal parasitoid as a bio-control agent, it is mandatory to increase its adults population in any field.

Hemocyte response to treatment of susceptible and resistant Asian corn borer (Ostrinia furnacalis) larvae with Cry1F toxin from Bacillus thuringiensis

Midgut receptors have been recognized as the major mechanism of resistance to Cry proteins in lepidopteran larvae, while there is a dearth of data on the role of hemocyte's response to Cry intoxication and resistance development. We aimed at investigating the role of circulating hemocytes in the intoxication of Cry1F toxin in larvae from susceptible (ACB-BtS) and resistant (ACB-FR) strains of the Asian corn borer (ACB), Ostrinia furnacalis. Transcriptome and proteome profiling identified genes and proteins involved in immune-related (tetraspanin and C-type lectins) and detoxification pathways as significantly up-regulated in the hemocytes of Cry1F treated ACB-FR. High-throughput in vitro assays revealed the binding affinity of Cry1F with the tetraspanin and C-type lectin family proteins. We found significant activation of MAPKinase (ERK 1/2, p38α, and JNK 1/2) in the hemocytes of Cry1F treated ACB-FR. In testing plausible crosstalk between a tetraspanin (CD63) and downstream MAPK signaling, we knocked down CD63 expression by RNAi and detected an alteration in JNK 1/2 level but a significant increase in susceptibility of ACB-FR larvae to Cry1F toxin. Information from this study advances a change in knowledge on the cellular immune response to Cry intoxication and its potential role in resistance in a lepidopteran pest.

Morphological and genetic variability of Cotesia tibialis species complex (Hymenoptera: Braconidae: Microgastrinae)

Cotesia tibialis is a gregarious koinobiont parasitoid of lepidopteran larvae. Due to the wide range of variability of some morphological traits, several new species were already described from the C. tibialis complex. Nixon left open the possibility that there are more by recognizing two seasonal forms. To investigate whether there are hidden taxa within C. tibialis, of 14 samples we analysed morphological characters such as the colouration of female hind femora and male antennae, and the colour and structure of the mass cocoons. The results of the analyses of the colouration of female hind femora and cocoons refute the previously defined forms within C. tibialis. Using the method of geometric morphometrics to investigate the shape of the females’ fore wings, we also did not find support of the existence of two seasonal forms of C. tibialis. Finally, applying the mitochondrial barcoding region COI the genetic differences between selected C. tibialis morphotypes were analysed. Based on both morphological and molecular analyses, one morphotype obtained from smoke-white cocoons was completely discriminated against all others, indicating that it is a potentially new species, or one of those already described which Nixon returned to C. tibialis as a synonym. The status of the other 13 morphotypes is still unclear and requires further analyses.

Establishment of Toxicity and Susceptibility Baseline of Broflanilide for Aphis gossypii Glove

The Aphis gossypii is an important pest that can damage cotton plants and can cause a huge economic loss worldwide. Chemical control is a main method to manage this pest, but the cotton aphid resistance to insecticides has become a severe problem in the management of the cotton aphid. It is important to introduce a novel insecticide for rotational application with other insecticides. Broflanilide, as a meta-diamide insecticide with a special mode of action, showed high efficiency against lepidopterous larvae. However, we found that broflanilide possessed high insecticidal activity against the sap-sucking pest A. gossypii. The susceptibility of A. gossypii to broflanilide from 20 field populations in main cotton planting areas of China in 2021 was determined by the leaf-dipping method. LC50 values of broflanilide to A. gossypii ranged from 0.20 μg mL-1 to 1.48 μg mL-1. The susceptible baseline of A. gossypii to broflanilide was established with the LC50 value of 0.41 μg mL-1 and might be used to calculate the resistance ratio (RR) of cotton aphid population in broflanilide resistance monitoring. The RR value of field populations in China was from 0.49 to 3.61 in 2021. It suggested that the broflanilide may be a potential agent in the resistance management of A. gossypii to insecticides. These results are significantly useful for the rational chemical control of cotton aphids.

Enigma moth parasitoid: a new Australian cyclostome genus and species, Ovaustra aurantia Tetley, Glatz & Fagan Jeffries, gen. et sp. nov. (Hymenoptera: Braconidae) from Kangaroo Island

AbstractOvaustra aurantia Tetley, Glatz & Fagan‐Jeffries, gen. et sp. nov. (Mesostoinae) is described from Kangaroo Island. South Australia, Australia, and is a solitary, koinobiont, egg‐larval parasitoid of the enigma moth, Aenigmatinea glatzella Kristensen & Edwards, 2015, in the monotypic family Aenigmatineidae Kristensen & Edwards, 2015 (Lepidoptera). Female parasitoids oviposit into the eggs of A. glatzella soon after female moths place them beneath minute adpressed leaves at the growing foliar tips of the larval host plant Callitris gracilis R.T. Baker (Cupressaceae). Adult parasitoids emerge from A. glatzella larval chambers located directly beneath the bark of small branches, some way from the growing tip. Adults can be seen on or near foliage of C. gracillis primarily during October and coinciding with the presence of adult host moths. Morphological and preliminary molecular evidence place Ovaustra Glatz, Fagan‐Jeffries & Tetley, gen. nov. within Mesostoinae s.l. and indicate that its closest relatives are likely to reside within a group of genera from Australia and New Zealand whose hosts and biology are not well defined but are apparently quite broad, including lepidopteran, coleopteran and dipteran larvae, as well as primary plant gall induction.

Enhancing the oral and topical insecticidal efficacy of a commercialized spider venom peptide biopesticide via fusion to the carrier snowdrop lectin (Galanthus nivalis agglutinin).

Spear®-T sold as a contact foliar spray for the control of glasshouse pests such as aphids, thrips, spider mites and whiteflies, contains the recombinant spider venom peptide GS-ω/κ-HxTx-Hv1h (named as GS-ω/κ-HxTx-Hv1a by Vestaron) as the active ingredient. Here we investigate whether fusion of the peptide to snowdrop lectin, (Galanthus nivalis agglutinin; GNA) enhances the efficacy of this venom peptide towards aphid pests. Recombinant GS-ω/κ-HxTx-Hv1h (HxTx-Hv1h) and an HxTx-Hv1h/GNA fusion protein were produced using the yeast Pichia pastoris. Purified proteins showed comparable toxicity when injected into lepidopteran (Mamestra brassicae) larvae, but significant differences in oral and contact activity towards aphids. HxTx-Hv1h had comparable acute oral toxicity to pea (Acyrthosiphon pisum) and peach potato (Myzus persicae) aphids with respective Day (2) median lethal concentration (LC50 ) values of 111 and 108 μm derived from diet assays. The fusion protein also showed comparable oral toxicity to both species but D2 LC50 values were >3-fold lower (35 and 33 μm for pea and peach potato aphids, respectively) as compared to HxTx-Hv1h. Topically applied toxin and fusion protein, but not GNA, caused significant reductions in pea aphid survival. Contact effects on mortality were significantly greater for aphids exposed to fusion protein as compared to toxin alone. Whole aphid fluorescence microscopy and immunoblotting suggest that improved efficacy is due to enhanced persistence of HxTx-Hv1h when fused to GNA following internalisation of ingested or topically applied proteins. This is the first study to report on the insecticidal activity of HxTx-Hv1h towards aphids and results suggest that a fusion protein-based approach offers opportunities to significantly enhance oral and contact efficacy of naturally derived toxins, such as HxTx-Hv1h, towards crop pests. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Pine caterpillar occurrence modeling using satellite spring phenology and meteorological variables

Outbreaks of leaf-feeding Lepidopteran insects substantially weaken the quality of forest trees and strongly affect the ecosystem functions of plant photosynthesis and carbon uptake. The narrow phenological time window of leaf out about ten days, during which Lepidopteran larvae feed on high nutrient newly flushed leaves, may change the insect community and outbreak dynamics by determining the survival rate of larvae. The Chinese pine Caterpillar (Dendrolimus tabulaeformis Tsai et Liu) infestation of the northern Chinese pine (Pinus tabulaeformis) forest in China is a major concern, and accurately modeling the day of insect occurrence (DIO) in the spring remains challenging. With continuous in-situ observed insect activities of 20 plots and satellite and meteorological observations from 1983 to 2014, we found a strong synchronization (r = 0.54, p = 0.001) between the satellite-based vegetation spring phenology, i.e. the green-up day (GUD), and DIO of the pine caterpillar over time. We used partial least squares regression and ridge regression models, and identified that monthly preseason air temperature, wind speed, specific humidity, and downward radiation were key environmental cues that awakened the overwintering pine caterpillars. After removing the collinearity of multiple variables, we showed that the dimensionality reduction-based regression models substantially improved the accuracy of DIO modeling than commonly used models, such as interval and degree-day models. In particular, including GUD significantly enhanced the predictive strength of the models increasing the coefficient of determination (R 2) by 17.1% and consequently a decrease of 16.5% in the root mean square error. We further showed that evapotranspiration changed the environmental moisture content, which indirectly affected the activities of insects. Our results revealed a useful linkage between spring leaf development and insect occurrence, and therefore are of great importance for the large-scale monitoring of pest outbreaks with future remote sensing observations.

Conservation of Three-Dimensional Structure of Lepidoptera and Trichoptera L-Fibroins for 290 Million Years.

The divergence of sister orders Trichoptera (caddisflies) and Lepidoptera (moths and butterflies) from a silk-spinning ancestor occurred around 290 million years ago. Trichoptera larvae are mainly aquatic, and Lepidoptera larvae are almost entirely terrestrial—distinct habitats that required molecular adaptation of their silk for deployment in water and air, respectively. The major protein components of their silks are heavy chain and light chain fibroins. In an effort to identify molecular changes in L-fibroins that may have contributed to the divergent use of silk in water and air, we used the ColabFold implementation of AlphaFold2 to predict three-dimensional structures of L-fibroins from both orders. A comparison of the structures revealed that despite the ancient divergence, profoundly different habitats, and low sequence conservation, a novel 10-helix core structure was strongly conserved in L-fibroins from both orders. Previously known intra- and intermolecular disulfide linkages were accurately predicted. Structural variations outside of the core may represent molecular changes that contributed to the evolution of insect silks adapted to water or air. The distributions of electrostatic potential, for example, were not conserved and present distinct order-specific surfaces for potential interactions with or modulation by external factors. Additionally, the interactions of L-fibroins with the H-fibroin C-termini are different for these orders; lepidopteran L-fibroins have N-terminal insertions that are not present in trichopteran L-fibroins, which form an unstructured ribbon in isolation but become part of an intermolecular β-sheet when folded with their corresponding H-fibroin C-termini. The results are an example of protein structure prediction from deep sequence data of understudied proteins made possible by AlphaFold2.

Insect Pests and their Direct Damage of Piliostigma reticulatum (D.C.) Hochst Flowers and Pods in North-Soudanian Region of Burkina Faso

Aims: The objective of this work is to gain a better understanding of insect pests of flowers, fresh and ripe pods of P. reticultum in Burkina Faso.
 Study Design: The P. reticultum trees were selected randomly. Also, the collection of flowers and pods from these trees was done in the same way.
 Place and Duration of Study: Flowers, fresh pods and mature pods of P. reticulatum were collected in a village in the province of Bam called Yilou.
 The observations were conducted in the laboratory. The study was carried out between December 2020 and September 2021.
 Methodology: 120 flowers, 200 fresh pods and 2000 ripe pods of P. reticulatum were collected. Fresh flowers and pods were collected randomly from 20 trees and ripe pods from 100 trees. In the laboratory, fresh flowers and pods were dissected and insects were collected. Ripe pods were stored in the laboratory in polyethylene bags at room temperature for up to six months. When the bags were opened, all the insects observed were captured and placed in vials containing 70º alcohol. Insect damage to the pods was assessed using a score from 1 to 5. The pods were then dissected and the insects were collected again. All insects were identified under a binocular "stereomicroscope using identification keys.
 Results: The results showed that Thysanoptera (Thripidae) were the most important insects in the flowers followed by Hymenoptera (Formicidae) and Coleoptera (Curculionidae). The main pests on fresh pods were Lepidoptera larvae (Lepidochrysops quassi Karsch). The extent of damage on mature pods in storage was high with an average score of 4.68. The pests of these pods in stock are Caryedon serratus (Olivier) followed by Tribolium castaneum (Herbst).
 Conclusion: The study revealed that thrips, L. quassi and C. serratus are the main pests of P. reticulatum flowers, fresh pods and socked pods respectively.

Host-Specific larval lepidopteran mortality to pathogenic Serratia mediated by poor diet

Insect guts often harbor an abundance of bacteria. Many of these members are commensal, but some may emerge as opportunistic pathogens when the host is under stress. In this study, we evaluated how dietary nutritional concentration mediates a shift from commensal to pathogenic, and if host species influences those interactions. We used the lepidopterans (Noctuidae) fall armyworm (Spodoptera frugiperda), beet armyworm (Spodoptera exigua), and corn earworm (Helicoverpa zea) as hosts and a Serratia strain initially isolated from healthy fall armyworm. Diet concentration was altered by bulk reduction in nutritional content with dilution using cellulose. Our experiments revealed that low nutrient diet increased mortality from Serratia for beet armyworm and corn earworm. However, for fall armyworm, little mortality was observed in any of the diet combinations. Dietary nutrition and oral inoculation with Serratia did not change the expression of two antimicrobial peptides in fall and beet armyworm, suggesting that other mechanisms that mediate mortality were involved. Our results have implications for how pathogens may persist as commensals in the digestive tract of insects. These findings also suggest that diet plays a very important role in the switch from commensal to pathogen. Finally, our data indicate that the host response to changing conditions is critical in determining if a pathogen may overtake its host and that these three lepidopteran species have different responses to opportunistic enteric pathogens.

Phytochemical screening and effect of Viscum album L. on monoamine oxidase A and B activity and serotonin, dopamine and serotonin receptor 5-HTR1A levels in Galleria mellonealla (Lepidoptera)

Ethnopharmacological relevanceViscum album L. (European mistletoe), a member of the Santalaceae, is a hemiparasitic, evergreen shrub growing on deciduous and coniferous trees. In traditional and folk medicine, mistletoe was used for the treatment of central nervous system disorders such as epilepsy, hysteria, insomnia, nervous excitability, neuralgia, headache, dizziness and fatigue. However, relatively little is known of its neuropharmacological activity. Aim of the studyThe aim of the present study was to evaluate the effect of treatment with aqueous and hydroethanolic extracts from Viscum album L. parasitizing birch, linden and pine, on MAO-A and MAO-B activity as well as serotonin, dopamine and serotonin receptor 5-HTR1A levels in Galleria mellonella (Lepidoptera) larvae. Materials and methodsThe phytochemical composition of the extracts was characterised using UPLC-DAD-ESI-MS/MS. To investigate the neuropharmacological activity of Viscum album L. extracts, Galleria mellonella (Lepidoptera) larvae were used as a model organism. The inhibitory potential of the extracts against MAO-A and MAO-B was determined by fluorometry. The serotonin, dopamine and serotonin receptor 5-HTR1A levels in larvae hemolymph after treatment were quantified by ELISA. ResultsUPLC-DAD-ESI-MS/MS analysis allowed the identification of 88 compounds, either full or in part. Most of the characterised phytochemicals were flavonoids, hydroxycinnamic acids and lignans. Screening found that aqueous and hydroethanolic mistletoe extracts inhibited the enzymatic activity of either MAO-A or MAO-B or both. Additionally, mistletoe extract administration increased the levels of serotonin and serotonin receptor 5-HTR1A. None of the tested extracts had any significant effect on dopamine level. ConclusionsA key novel finding was that the aqueous and hydroethanolic extracts from Viscum album L. inhibited monoamine oxidase activity and increased the levels of serotonin and serotonin receptor 5-HTR1A in Galleria mellonella (Lepidoptera) larvae. These properties may be due to the presence of phenolic constituents, particularly flavonoids. Further research based on bioassay-guided fractionation of mistletoe is needed to identify CNS-active molecules.

Producing fluorescent plants to lure and trap insect pests.

Producing fluorescent plants to lure and trap insect pests.

The first record of Metacordyceps neogunnii (Metacordyceps, Clavicipitaceae) isolated from larva of Lepidoptera in Vietnam: morphological, phylogenetic characterization and chemical constituent analysis

An entomopathogenic fungus, specimen DL0091 parasitized on the larvae of Lepidoptera, was collected from Lang Biang Biosphere Reserve, located in Lam Dong Province, Vietnam. The specimen DL0091 has been analyzed to be contained numerous chemical constituents, especially containing adenosine of 634 mg/Kg and cordycepin of 35.2 mg/Kg. Due to containing many bioactive compounds, DL0091 was promised to be a precious natural source that could be applied in fields of medicine and function food for health care. For classification, based on the morphology analysis, it was identified as Metacordyceps neogunnii (Metacordyceps, Clavicipitaceae) sharing the similar characteristics of M. neogunnii T.C. Wen & K.D. Hyde. Morphology of this species differed from Cordyceps neogunnii (Berk.) Berk., by many characteristics, such as the larger stroma of DL0091 (15–130 mm x 2–6 mm), of asci (550–680 μm × 5–8 μm), etc. Additionally, the combined multi-gene phylogenetic analysis, including ITS, Tef and Rpb1, well supported its systematic position in the clade of M. neogunnii, which was used as traditional herb in China and other Asian countries. In summary, DL0091 was identified as M. neogunnii, containing many bioactive compounds, could be used as the medicinal potential in human healthcare.

Host Cytoskeleton Gene Expression Is Correlated with the Formation of Ascovirus Reproductive Viral Vesicles.

Ascoviruses are large DNA viruses that primarily infect lepidopteran larvae. They differ markedly from other plant or animal viruses by initiating replication in the nucleus, then inducing nuclear lysis followed by extensive cellular hypertrophy and subsequent cleavage of the entire enlarged cell into numerous viral vesicles. Most progeny virions are assembled in these vesicles as they circulate in the hemolymph. Here, we report transcriptome studies of host cytoskeletal genes in larvae infected with ascoviruses from 6 h to 21 days post-infection (dpi). We focused on the cabbage looper, Trichoplusia ni, infected with the Trichoplusia ni ascovirus (TnAV), along with supporting studies on the fall armyworm, Spodoptera frugiperda, infected with the Spodoptera frugiperda ascovirus (SfAV). In T. ni, many cytoskeleton genes were upregulated at 48 hours post-infection (hpi), including 29 tubulins, 21 actins, 21 dyneins, and 13 kinesins. Mitochondrial genes were upregulated as much as two-fold at 48 hpi and were expressed at levels comparable to controls in both T. ni and S. frugiperda, even after 21 dpi, when several cytoskeleton genes remained upregulated. Our studies suggest a temporal correlation between increases in the expression of certain host cytoskeletal genes and viral vesicle formation. However, these results need confirmation through functional genetic studies of proteins encoded by these genes.

Entomopathogenic Fungi Infecting Lepidopteran Larvae: A Case from Central Argentina.

Immature stages of insects are vulnerable to various antagonists, including pathogens. While the abiotic factors affecting pathogen prevalence in insect populations are reasonably well documented, much less is known about relevant ecological interactions. We studied the probability of the larvae of three lepidopteran species to die from fungal infection as a function of insect species and food plants in central Argentina. Local free-growing food plants were used to feed the lepidopteran larvae. The prevalence of entomopathogenic fungi remained low (about 5%), which is a value well consistent with observations on similar systems in other regions. Eight fungal species recorded, primarily belonging to Fusarium and Aspergillus, add evidence to the reconsideration of the nutritional modes in these genera in distinguishing the role of some species (complexes) to cause insect infections. Food plant species were found to have a substantial effect on the prevalence of entomopathogenic fungi. This was especially clear for the most abundant fungal species, a representative of the Fusarium fujikuroi complex. Feeding on a particular plant taxon can thus have a specific fitness cost. Compared to the data collected from Northern Europe, the Argentinian assemblages from the families Aspergillaceae and Nectriaceae overlapped at the genus level but did not share species. It remains to be confirmed if this level of divergence in the composition of assemblages of entomopathogenic fungi among distant regions represents a global pattern.

Opposing Growth Responses of Lepidopteran Larvae to the Establishment of Gut Microbiota.

Gut microbiota can have diverse impacts on hosts, the nature of which often depend on the circumstances. For insect gut microbes, the quality and nature of host diets can be a significant force in swinging the pendulum from inconsequential to functionally important. In our study, we addressed whether beneficial microbes in one species impart similar functions to related species under identical conditions. Using fall armyworm (Spodoptera frugiperda), beet armyworm (Spodoptera exigua), and other noctuid hosts, we implemented an axenic rearing strategy and manipulated gut bacterial populations and dietary conditions. Our results revealed that some gut Enterococcus and Enterobacter isolates can facilitate utilization of a poor diet substrate by fall armyworm, but this was not the case for other more optimized diets. While Enterococcus provided benefits to fall armyworm, it was decidedly antagonistic to beet armyworm (Spodoptera exigua) under identical conditions. Unique isolates and bacterial introductions at early growth stages were critical to how both larval hosts performed. Our results provide robust evidence of the roles in which bacteria support lepidopteran larval growth, but also indicate that the directionality of these relationships can differ among congener hosts. IMPORTANCE Insects have intimate relationships with gut microbiota, where bacteria can contribute important functions to their invertebrate hosts. Lepidopterans are important insect pests, but how they engage with their gut bacteria and how that translates to impacts on the host are lacking. Here we demonstrate the facultative nature of gut microbiota in lepidopteran larvae and the importance of diet in driving mutualistic or antagonistic relationships. Using multiple lepidopteran species, we uncover that the same bacteria that can facilitate exploitation of a challenging diet in one host severely diminishes larval performance of another larval species. Additionally, we demonstrate the beneficial functions of gut microbiota on the hosts are not limited to one lineage, but rather multiple isolates can facilitate the exploitation of a suboptimal diet. Our results illuminate the context-dependent nature of the gut microbiomes in invertebrates, and how host-specific microbial engagement can produce dramatically different interactions.

Increased abundance and productivity of a grassland bird after experimental control of invasive tall fescue

Tall fescue (Schedonorus arundinaceus) is a widespread invasive grass in the United States that degrades habitat quality for biodiversity. Herbicide followed by seeding of native plants reduces tall fescue and is predicted to restore habitat quality over time, but little is known about short‐term (1–2 year) impacts on native species. We conducted a landscape‐scale controlled experiment to assess the short‐term effects of herbicide and seeding on the reproduction of an obligate grassland bird, the dickcissel (Spiza americana). In 2014, four sites in southern Iowa were each subdivided into three patches (mean 7 ha). One patch in each site was treated with glyphosate herbicide (spray‐only), one with herbicide and native seeding (spray‐and‐seed), with the third serving as a control. Two sites were grazed by cattle from April to July and two sites were ungrazed. We monitored dickcissel reproduction in 2016, finding that they were more abundant, built more nests, experienced less cowbird parasitism, had increased nest survival, and produced more fledglings on spray‐only and spray‐and‐seed treatments compared to control patches. Dickcissels nested infrequently on grazed sites—especially grazed control patches. We did not detect any impacts on clutch size, provisioning rates, or nestling mass, but Araneae (spiders) and Lepidoptera larvae (caterpillars) may have been smaller on sprayed patches. Positive responses by dickcissels were likely due to successful reduction of tall fescue and improved access to suitable nest sites through increased vegetation heterogeneity. Our results indicate that using herbicide and seeding to restore tall fescue‐dominated sites improves habitat quality for this grassland bird, shortly after restoration.

Canopy opening increases leaf‐shredding arthropods and nutrient mineralization but not mass loss in wet tropical forest

AbstractHurricanes alter forest habitat by opening the canopy and depositing fresh wood and leaves. The objectives of this study were to evaluate the effects of hurricane and drought‐driven changes to forests on green litter decomposition, invertebrate communities, and nutrient mineralization over a short period (6 months) after disturbance. We used three complete replicated blocks with two canopy treatments: control and trim + detritus. Green leaves were enclosed in litterbags of three different mesh sizes to determine the effect of soil fauna of varying body sizes. Litterbags were retrieved from the field after 21, 35, 84, and 168 days and transported to the laboratory in individually sealed plastic bags. We extracted and identified invertebrates, measured leached and mineralized litter nutrients using ion resin membranes placed for 1 week under the leaves inside the litterbags, and determined litter mass loss. Additional resin membranes were placed in the lowest litter layer above the mineral soil. The number of arthropod taxonomic groups and nutrient mineralization differed significantly between control and trim + detritus. Regardless of mesh size, bags in control plots had consistently higher invertebrate richness than in trim + detritus plots. Nitrogen mineralization and phosphorous mineralization were significantly higher in trim + detritus in large mesh size, and decomposer arthropod abundance was highest in large‐sized mesh bags. These data suggest that within functional categories, variations in feeding behavior among arthropod orders may affect the release of nutrients from organic matter. Percent mass loss did not differ between canopy treatments or litterbag mesh sizes, but instead decreased during drought. Invertebrate composition, but not abundance, differed significantly between canopy treatments with greater dominance by shredders (Lepidoptera and Diptera larvae) in trim + detritus, which corresponded to higher rates of nutrient mineralization from green leaves. These results suggest that regional drought dominated the mesoclimate surpassing any microclimate variation in response to canopy treatments. Since mass loss did not differ between canopy treatments or litterbag mesh sizes, our results suggest that differences in short‐term nutrient fluxes from green litter are mostly related to changes in the litter invertebrate food web rather than rates of decomposition.