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ABSTRACT Interactions between plants and herbivores promote evolutionary change. Studying the evolution of herbivore mechanisms aimed to cope with different host plant species is a critical intersection between evolutionary biology and sustainable pest management. Generalist herbivores are of particular interest, as hybridization between genetically distinct populations can increase the standing genetic variation and therefore the adaptive potential of the species. Tetranychus urticae is a generalist arthropod known for its adaptive potential, evidenced in its immense host range and ability to develop metabolic resistance to xenobiotics. However, the molecular underpinnings associated with the potential of host adaptation and the consequences of host adaptation in this, and many other pests remain elusive. Here, we use two independent, empirical approaches to identify and map the genetic basis of host plant performance and adaptation in genetically distinct populations of T. urticae. In the first approach, we subject a genetically diverse mite population to tomato selection and map genomic regions linked to the phenotypic evolution of increased reproductive performance. In the second approach, we map genomic regions responsible for performance on tomato by comparing the genomes of pooled individuals from an F2 backcross between populations with high and low reproductive performance. Both approaches revealed specific and shared genomic regions associated with host plant performance and adaptation and key candidate genes were identified. Our findings highlight the power of spider mite genetic approaches to identify the complex genetic basis of host adaptation in generalist herbivores. [ABSTRACT FROM AUTHOR]

Climate change has the potential to disrupt phenological synchrony among interacting species that vary in their phenological sensitivity to temperature. The phenological synchrony observed between winter moth Operophtera brumata caterpillars and oak leafing in spring has become an emblematic test case of this phenomenon, with caterpillars seemingly advancing their phenology more than their host-plant. However, work on this trophic interaction—and on phenological mismatch more widely—routinely overlooks the potential for trophic generalism to buffer the negative effects of mismatch. In the largest study of its kind—using over 3500 individuals reared from egg to pupa—I tested the performance of winter moth caterpillars from four UK populations across nine host-plant species, and considered how adaptation to locally abundant host-plants may modulate performance in different populations. I found that caterpillars survive and grow well across a range of host-plant species, with some evidence of a host-plant by population interaction in performance. Contrary to widespread assumptions, oak seems a relatively poor host-plant species. Occupying a broad trophic niche may help consumers like the winter moth exploit a narrow phenological niche, whereby phenological variation among host-plant species buffers them against asynchrony with any one particular host-plant species. Determining the significance of trophic generalism in the ecology of consumers is a crucial first step towards assessing its role as a potential buffering mechanism and, hence, evaluating the true threat posed by mismatch. [ABSTRACT FROM AUTHOR]

Abstract Background The fall armyworm (FAW) Spodoptera frugiperda, a highly invasive, polyphagous pest, poses a global agricultural threat. It has two strains, the C-corn and R-rice strains, each with distinct host preferences. This study compares detoxification enzyme gene families across these strains and related Spodoptera species to explore their adaptation to diverse host plant metabolites. Results A total of 1,995 detoxification-related genes, including cytochrome P450 monooxygenases (CYPs), carboxylesterases (COEs), glutathione S-transferases (GSTs), UDP-glucuronosyltransferases (UGTs), and ATP-binding cassette transporters (ABCs), were identified across the genus Spodoptera, including S. littoralis, S. litura, S. picta, S. exigua, and both FAW strains. A higher abundance of phase I detoxification enzymes (CYPs and COEs) and GSTs was observed in Spodoptera species, while FAW strains exhibited fewer detoxification genes, with notable differences in copy numbers between the C and R strains. Analyses at the subfamily level revealed significant variation in gene distribution and expression, particularly within phase I and II detoxification enzymes. Expansions in CYP6AE were detected in the C strain, while contractions in GST-ε, CYP9A, CYP4M, UGT33B, and UGT33F occurred in both strains. In contrast, no substantial variation was observed in phase III ABC enzymes. Functional predictions and protein interaction networks suggest a broader expansion of metabolism-related genes in the R strain compared to the C strain. Conclusions These findings emphasize the pivotal role of phase I and II detoxification enzymes in host adaptation, providing molecular insights into FAW’s capacity for host range expansion, which are crucial for devising targeted and sustainable pest management strategies. Graphical Abstract The differential expression of detoxification enzyme gene families in different strains of Spodoptera frugiperda.

Hyphantria cunea is a significant invasive pest characterized by its polyphagous nature and robust reproductive capabilities. In the present study, the interaction between Morus alba seedlings and H. cunea larvae was revealed by combining the induced chemical defense of M. alba with the adaptive strategies of H. cunea larvae. Larval feeding damage swiftly triggers both local and systemic chemical defenses in M. alba, involving nutrients (amino acids, proteins, soluble sugars), secondary metabolites (total phenol, total flavone, tannin, lignin), and flavonoid synthesis pathways. Mild damage induced defense responses in M. alba that persisted until day 21, inhibiting the growth of a subsequent batch of H. cunea larvae after 7 days of continuous feeding. Conversely, at moderate damage levels, these induced defenses diminished by day 21, temporarily failing to affect the larval growth. In response to these defenses, H. cunea larvae significantly up-regulated the expression of most detoxification enzyme genes, which remained active throughout. Initially, some trypsin and lipase genes in the larvae were significantly up-regulated, but with prolonged feeding, gene expression shifted towards the α-amylase family. Feeding by H. cunea larvae can stimulate the induced chemical defense of M. alba. The H. cunea larvae can adapt to the M. alba chemical defense by modulating their digestive and metabolic detoxification mechanisms. [ABSTRACT FROM AUTHOR]

Polyphagy is an adaptative strategy allowing species to develop and survive on multiple diets. Phytophagous insects can be exposed to sub-optimal resources, as host plants vary in nutritional quality. Some insects may rely on symbiotic bacteria to better utilize less favorable substrates. The invasive fruit fly Drosophila suzukii is a highly successful pest worldwide. The use of ripening and ripe fruits, a niche neglected by other drosophilids, and its polyphagy may have contributed to its global spread. The role of D. suzukii's Wolbachia strain (wSuz) remains unconfirmed, although a mutualistic role has been hypothesized via virus protection or dealing with abiotic stress. In some insect species, Wolbachia acts as a nutritional mutualist. This study explored the role of wSuz in D. suzukii adaptation to fluctuating diet regimes. To simulate a diet shift, we used Wolbachia-infected and uninfected flies, maintained on a corn-based (low-starch) or a grape-based (high-starch) diet for at least 10 generations. Then, we placed individuals from each line on one or the other diet for 30 days. The effects of Wolbachia and the diet treatments were assessed by quantifying female fecundity, egg-to-adult development time and survival, and offspring mass. The presence of Wolbachia positively affected female fecundity and offspring mass after a diet shift. Wolbachia also increased survival during larval development regardless of the diet, supporting its mutualistic role. Our results underline the role of wSuz on D. suzukii diet tolerance and performance. A better understanding of the role of symbionts in invasive species could help to improve management strategies. [ABSTRACT FROM AUTHOR]

The species of Cryptophlebia occurring in Hawai'i are reviewed, resulting in the discovery of a previously unrecognized native species, described hereas C. alaula , sp. nov. The discovery of C. alaula and its status as the putative sister species of C. illepida (Butler) supports the endemicity of C. illepida , a species whose status in Hawai'i has historically been contested, and is often treated as an invasive pest of unknown origin. Cryptophlebia alaula is hypothesized to be a specialist on fruits and seeds of 'a'ali'i (Dodonaea viscosa). This raises interesting questions regarding the evolution of monophagy and polyphagy in Cryptophlebia and patterns of speciation in Hawaiian Tortricidae more broadly. The conservation status of C. alaula is briefly discussed. All species occurring in Hawai'i are described or redescribed, figured, with a key to species of both sexes provided. [ABSTRACT FROM AUTHOR]

Pyrgonota bifoliata (Insecta: Hemiptera: Membracidae) is a distinct endemic Philippine treehopper species complex distinguished by its extremely elevated and bifurcated pronotal structures. An earlier study suggested that P. bifoliata is a host specialist that feeds on Bridelia (Phyllanthaceae) in northern Luzon and Rubus (Rosaceae) in southern Mindanao. However, the host plant range across the geographical distribution of the P. bifoliata species complex is still poorly understood. In this study, field observations and DNA barcoding were performed to determine the host plant range of P. bifoliata in the Mount Makiling Forest Reserve of Laguna Province on the island of Luzon. The morphology of the last-instar nymph of P. bifoliata was described to facilitate the identification of the species and its host plants. Behavioural interactions between P. bifoliata and its associated ants were also recorded. The results revealed that Piper umbellatum (Piperaceae) and Saurauia latibractea (Actinidiaceae) were the major host plants used by both nymphs and adults of P. bifoliata. The findings indicate that P. bifoliata in the Mount Makiling Forest Reserve of central Luzon is a polyphagous host generalist that primarily utilises two distantly related plant species. The adults of P. bifoliata also occur on Alangium longiflorum (Cornaceae) and Ficus ulmifolia (Moraceae). The nymphs of P. bifoliata are gregarious in small groups and visited by three ant species (Crematogaster sp., Pheidole sp. and Technomyrmex sp.); however, the adults of P. bifoliata are solitary and are never observed with ants. Unlike other treehoppers that are subsocial, the females of P. bifoliata exhibited no maternal care behaviours, such as egg or nymph guarding. [ABSTRACT FROM AUTHOR]

The Diaprepes root weevil (DRW), Diaprepes abbreviatus , is a broadly polyphagous invasive pest of agriculture in the southern United States and the Caribbean. Its genome was sequenced, assembled, and annotated to study genomic correlates of specialized plant-feeding and invasiveness and to facilitate the development of new methods for DRW control. The 1.69 Gb D. abbreviatus genome assembly was distributed across 653 contigs, with an N50 of 7.8 Mb and the largest contig of 62 Mb. Most of the genome was comprised of repetitive sequences, with 66.17% in transposable elements, 5.75% in macrosatellites, and 2.06% in microsatellites. Most expected orthologous genes were present and fully assembled, with 99.5% of BUSCO genes present and 1.5% duplicated. One hundred and nine contigs (27.19 Mb) were identified as putative fragments of the X and Y sex chromosomes, and homology assessment with other beetle X chromosomes indicated a possible sex chromosome turnover event. Genome annotation identified 18,412 genes, including 43 putative horizontally transferred (HT) loci. Notably, 258 genes were identified from gene families known to encode plant cell wall degrading enzymes and invertases, including carbohydrate esterases, polysaccharide lyases, and glycoside hydrolases (GH). GH genes were unusually numerous, with 239 putative genes representing 19 GH families. Interestingly, several other beetle species with large numbers of GH genes are (like D. abbreviatus) successful invasive pests of agriculture or forestry. [ABSTRACT FROM AUTHOR]

Nutrition provides the resources necessary to carry out all the physiological functions organisms require. This has important implications for insect pest management, as polyphagous species can experience considerable nutritional variability, which may impact their response to management tactics.Many studies have shown that dietary protein and carbohydrates play a primary role in insect fitness and that insects regulate their intake of these macronutrients to reach an optimal balance or intake target. Importantly, this intake target can vary across developmental stages, gender, and environmental conditions as physiological requirements change.In this study, we determined the intake target for adult spotted‐wing Drosophila, Drosophila suzukii, an invasive polyphagous fruit pest. We found that adult D. suzukii regulate their intake to meet a 1:4–1:5 protein‐to‐carbohydrate ratio, which is slightly more carbohydrate‐biased than the larval intake target. We also examined the effect of nutritional state on susceptibility to three commonly‐used insecticides by rearing flies on diets with different field‐relevant protein‐to‐carbohydrate ratios and exposing adults to an LC50 dose of zeta‐cypermethrin, spinetoram, or pyrethrin.Overall, female flies had higher survivorship than males, and diet effects varied across insecticides. Diet had no impact in the spinetoram treatments, while the extreme carbohydrate‐ and protein‐biased diets produced the lowest survivorship and reproductive performance in the zeta‐cypermethrin treatments. Survivorship increased with dietary protein in the pyrethrin treatments but reproductive performance did not differ across diets. Our results suggest that tactics, which reduce fly access to dietary protein sources, such as sterilisation, could increase fly susceptibility to insecticides. [ABSTRACT FROM AUTHOR]

Abstract Background The false codling moth (FCM), Thaumatotibia leucotreta (Meyrick, 1913), is a significant pest of various important economic crops and is a EU quarantine pest. In the last decade the pest has been reported on Rosa spp. In this study we determined whether this shift occurred within specific FCM populations across seven eastern sub-Saharan countries or whether the species opportunistically switches to this novel host as it presents itself. To achieve this, we assessed the genetic diversity of complete mitogenomes of T. leucotreta specimens intercepted at import and analysed potential linkages with the geographical origin and host species. Results Genomic, geographical and host information were integrated into a T. leucotreta Nextstrain build which contains 95 complete mitogenomes generated from material intercepted at import between January 2013 and December 2018. Samples represented seven sub-Saharan countries and mitogenomic sequences grouped in six main clades. Discussion If host strains of FCM would exist, specialization from a single haplotype towards the novel host is expected. Instead, we find specimens intercepted on Rosa spp. in all six clades. The absence of linkage between genotype and host suggests opportunistic expansion to the new host plant. This underlines risks of introducing new plant species to an area as the effect of pests already present on the new plant might be unpredictable with current knowledge.

BackgroundHalyomorpha halys (Stål), the brown marmorated stink bug, is a highly invasive insect species due in part to its exceptionally high levels of polyphagy. This species is also a nuisance due to overwintering in human-made structures. It has caused significant agricultural losses in recent years along the Atlantic seaboard of North America and in continental Europe. Genomic resources will assist with determining the molecular basis for this species' feeding and habitat traits, defining potential targets for pest management strategies.ResultsAnalysis of the 1.15-Gb draft genome assembly has identified a wide variety of genetic elements underpinning the biological characteristics of this formidable pest species, encompassing the roles of sensory functions, digestion, immunity, detoxification and development, all of which likely support H. halys' capacity for invasiveness. Many of the genes identified herein have potential for biomolecular pesticide applications.ConclusionsAvailability of the H. halys genome sequence will be useful for the development of environmentally friendly biomolecular pesticides to be applied in concert with more traditional, synthetic chemical-based controls.

Many scolytine beetle species have been expanding in new territories, travelling with wood and plants for planting, sometimes with a high impact on plant health. Here, we attempt to quantify the mobility of these species and to identify the biological drivers of mobility and impact. Mobility was estimated by counting the numbers of landmasses (contiguous pieces of land, surrounded by ocean or sea) colonised by each species. A series of potential drivers (taxonomic tribes; feeding regimes; polyphagy; reproductive strategy; host taxa; aggregation pheromones and long-range primary attractants), as well as impact on host health were recorded. A total of 163 species were identified, out of 5546 counted in the whole subfamily. The cosmopolitan taxa amongst the subfamily showed significant disharmony with regards to invasion frequency. Four tribes (Xyleborini; Ipini; Crypturgini; Hylastini) were significantly over-represented and two others (Corthylini; Hexacolini) were under-represented. Some 53% of the 163 species are inbreeding, a very significant excess as compared to the whole subfamily (29%). The inbreeders colonised more landmasses than the outbreeders. There is a significant relationship between the number of host families attacked by a species and the number of colonised landmasses. Most of the invasive species are recorded to respond to long-range host primary attractants, only one quarter respond to pheromones. All very mobile species respond to long-range primary attractants and none is known to respond to pheromones. Very mobile species are all associated with a substantial or moderate impact. The most mobile species belong to a limited number of subtribes. They are often inbreeding, polyphagous and respond to long-range primary attractants, but do not produce pheromones. However, there are many counter-examples. The outbreeding Scolytus multistriatus attacks only three host families, producing aggregation pheromones and has established in thirteen landmasses, with a high impact. Due to these many exceptions, species-based risk prediction relying on the few traits routinely analysed in literature suffers from important uncertainties. [ABSTRACT FROM AUTHOR]

Simple Summary: The Fuller's rose weevil Naupactus cervinus has become a globally invasive pest of several ornamental plants and fruit trees. This weevil has caused severe economic losses, and eggs laid on fruit are a quarantine barrier for several countries' exports of fruit to markets in East Asia. Previous studies revealed that a genotype with high colonization ability successfully expanded throughout most continents, even in areas of inadequate environmental conditions, where this insect performs unexpectedly well, and that parthenogenesis may have helped to expand its geographic range. Pre-existing variation might have been eroded either by natural selection, leading to fixation of this variant able to cope with different environmental conditions to those in the native range, or by repeated bottlenecks during the process of invasion. To better understand the ecology of this invasive pest, we enlarged the sampling in areas of introduction, such as the southern United States, and surveyed genetic variation through mitochondrial and nuclear sequences in 13 localities across three states. Our results indicate that the invader genotype, already identified, has also colonized the continental United States (US), supporting the hypothesis of a general-purpose genotype capable of coping with adverse conditions and enlarging its geographical range. Parthenogenesis, and its associated lack of recombination, may help in maintaining a general-purpose genotype that facilitates the colonization of distant, unsuitable areas. However, demographic advantages linked to parthenogenesis as the sole mode of reproduction are also possible. Naupactus cervinus is a parthenogenetic weevil native to South America that is currently distributed worldwide. This flightless species is polyphagous and capable of modifying gene expression regimes for responding to stressful situations. Naupactus cervinus was first reported in the continental United States in 1879 and has rapidly colonized most of the world since. Previous studies suggested that an invader genotype successfully established even in areas of unsuitable environmental conditions. In the present work, we analyze mitochondrial and nuclear sequences from 71 individuals collected in 13 localities across three states in the southern US, in order to describe the genetic diversity in this area of introduction that has not yet been previously studied. Our results suggest that 97% of the samples carry the most prevalent invader genotype already reported, while the rest shows a close mitochondrial derivative. This would support the hypothesis of a general purpose genotype, with parthenogenesis and its associated lack of recombination maintaining the linkage of genetic variants capable of coping with adverse conditions and enlarging its geographical range. However, demographic advantages related to parthenogenetic reproduction as the main driver of geographic expansion (such as the foundation of a population with a single virgin female) cannot be ruled out. Given the historical introduction records and the prevalence of the invader genotype, it is possible that the continental US may act as a secondary source of introductions to other areas. We propose that both the parthenogenesis and scarce genetic variation in places of introduction may, in fact, be an asset that allows N. cervinus to thrive across a range of environmental conditions. [ABSTRACT FROM AUTHOR]

Abstract Background The cotton leafworm, Spodoptera littoralis, is a highly polyphagous pest of many cultivated plants and crops in Africa and Europe. The genome of this pest will help us to further understand the molecular mechanisms of polyphagy. Results Herein, the high-quality genome of S. littoralis was obtained by Pacific Bioscience (PacBio) sequencing. The assembled genome size of S. littoralis is 436.55 Mb with a scaffold N50 of 6.09 Mb, consisting of 17,207 annotated protein-coding genes. Phylogenetic analysis shows that S. littoralis and its sibling species S. litura diverged about 5.44 million years ago. Expanded gene families were mainly involved in metabolic detoxification and tolerance to toxic xenobiotics based on GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analysis. Comparative genomics analysis showed that gene families involved in detoxification and chemosensation were significantly expanded in S. littoralis, representing genetic characteristics related to polyphagy and an extensive host range. Conclusions We assembled and annotated the reference genome of S. littoralis, and revealed that this pest has the genetic features of strong detoxification capacity, consistent with it being a significant risk to a wide range of host crops. These data resources will provide support for risk assessment and early warning monitoring of major polyphagous agricultural pests.

When an invasive species first breaches quarantine and establishes in yet another country, it invariably causes consternation for growers, in part because of incomplete understanding of the plants that are at risk. The Fall Armyworm, Spodoptera frugiperda (J.E. Smith) is the most recent example in Australia. The number of plants that this polyphagous noctuid is reported to attack is vast, including many crop species. Consequently, initial reactions from grower industry groups that perceived themselves at risk were to demand emergency use of insecticides. Yet the field evidence suggests that many crops might not be at risk and since S. frugiperda arrived in Australia, maize crops have suffered most damage, followed by sorghum. We question the accuracy of some of the claims of reported host plants of S. frugiperda and report experiments that compared oviposition behavior, neonate silking behavior, and larval performance on five crops: the known hosts maize and sorghum, and the putative hosts cotton, peanut, and pigeon pea. Maize ranked highest in all preference and performance measures, followed by sorghum and peanut, with pigeon pea and cotton ranking lowest. Although S. frugiperda can survive, develop, and pupate on the crop species we examined, cotton and pigeon pea are not preferred by the pest in either the larval or adult stages. We suggest that before a plant is listed as a host for a given insect that the evidence should be fully reported and carefully evaluated. Collecting an immature insect from a plant does not make that plant a host! [ABSTRACT FROM AUTHOR]

Polyphagous insect species develop using multiple host plants. Often considered beneficial, polyphagy can also be costly as host nutritional quality may vary. Drosophila suzukii (Matsumura) is an invasive species that can develop on numerous fruit species over the annual cycle. Here, we assessed the contribution of winter-available fruit to the development of seasonal populations of D. suzukii, under fluctuating late winter/early spring temperature regimes. We infested an artificial diet and three suitable fruit species available in winter/early spring (Aucuba japonica, Elaeagnus ×submacrophylla, Viscum album) with D. suzukii larvae under three temperature regimes: constant 20 °C, fluctuating controlled regime of 8-15 °C (12 h of light at 8 °C and 12 h of dark at 15 °C), and uncontrolled outdoor regime during spring. As expected, fly performance was impaired by early spring-like environmental conditions, whatever the development diet, and the winter fruit were suboptimal diets compared to the artificial diet, whatever the thermal regime. However, under cold fluctuating temperature regimes, the ranking of fruit supporting the best performance changed, highlighting the occurrence of physiological trade-offs. Winter-acclimated females preferentially oviposited in A. japonica and/or E. ×submacrophylla, whatever the thermal regime, which does not support the preference-performance hypothesis. This finding is also discussed in the context of D. suzukii management strategies., (© 2025 The Author(s). Insect Science published by John Wiley & Sons Australia, Ltd on behalf of Institute of Zoology, Chinese Academy of Sciences.)

Polyphagous insects often show specialization in feeding on different host plants in terms of survival and growth and, therefore, can be considered minor or major pests of particular hosts. Whether polyphagous insects employ a common transcriptional response to cope with defenses from diverse host plants is under‐studied. We focused on patterns of transcriptional plasticity in polyphagous moths (Noctuidae), of which many species are notorious pests, in relation to herbivore performance on different host plants. We compared the transcriptional plasticity of five polyphagous moth species feeding and developing on three different host plant species. Using a comparative phylogenetic framework, we evaluated if successful herbivory, as measured by larval performance, is determined by a shared or lineage‐specific transcriptional response. The upregulated transcriptional activity, or gene expression pattern, of larvae feeding on the different host plants and artificial control diet was highly plastic and moth species‐specific. Specialization, defined as high herbivore success for specific host plants, was not generally linked to a lower number of induced genes. Moths that were more distantly related and showing high herbivore success for certain host plants showed shared expression of multiple homologous genes, indicating convergence. We further observed specific transcriptional responses within phylogenetic lineages. These expression patterns for specific host plant species are likely caused by shared evolutionary histories, for example, symplesiomorphic patterns, and could therefore not be associated with herbivore success alone. Multiple gene families, with roles in plant digestion and detoxification, were widely expressed in response to host plant feeding but again showed highly moth species‐specific. Consequently, high herbivore success for specific host plants is also driven by species‐specific transcriptional plasticity. Thus, potential pest moths display a complex and species‐specific transcriptional plasticity. [ABSTRACT FROM AUTHOR]

We propose a higher classification of the lycaenid hairstreak tribe Eumaeini – one of the youngest and most species‐rich butterfly tribes – based on autosome, Lepidopteran Z sex chromosome and mitochondrial protein‐coding genes. The subtribe Neolycaenina Korb is a synonym of Callophryidina Tutt and subtribe Tmolusina Bálint is a synonym of Strephonotina K. Johnson, Austin, Le Crom, & Salazar. Proposed names are Rhammina Prieto & Busby, new subtribe; Timaetina Busby & Prieto, new subtribe; Atlidina Martins & Duarte, new subtribe; Evenina Faynel & Grishin, new subtribe; Jantheclina Robbins & Faynel, new subtribe; Paiwarriina Lamas & Robbins, new subtribe; Cupatheclina Lamas & Grishin, new subtribe; Parrhasiina Busby & Robbins, new subtribe; Ipideclina Martins & Grishin, new subtribe; and Trichonidina Duarte & Faynel, new subtribe. Phylogenetic results from the autosome and Z sex chromosome analyses are similar. Future analyses of datasets with hundreds of terminal taxa may be more practical time‐wise by focussing on the smaller number of sex chromosome sequences (2.6% of nuclear protein‐coding sequences). The phylogenetic classification and biological summaries for each subtribe suggest that a variety of factors affected Eumaeini diversification. About a dozen kinds of male secondary sexual organs with frequent evolutionary gains and losses occur in Atlidina, Evenina and Jantheclina (141 species combined). Females have been shown to use these organs to discriminate between conspecific and nonconspecific males, facilitating sympatry among close relatives. Eumaeina, Rhammina and Timaetina (140 species combined) are overwhelmingly montane with some evidence for a higher incidence of sympatric diversification. Seven Neotropical lineages in five subtribes invaded the temperate parts of the Nearctic Region with a diversification increase in the Callophryidina (262 species). North American Satyrium and Callophrys then invaded the Palearctic at least once each, with a major species‐richness increase in Satyrium. The evolution of litter‐feeding detritivores within Calycopidina (172 species) resulted in an increase in diversification rate compared with its flower‐feeding sister lineage. Atlidina, Strephonotina, Parrhasiina and Strymonina (562 species combined) each contain a mixture of genera that specialize on one or two caterpillar food plant families and genera that are polyphagous. These would be appropriate subtribes to assess how the breadth of caterpillar food plants and the frequency of host shifts affected diversification. [ABSTRACT FROM AUTHOR]

Hypothenemus crudiae (Panzer, 1791) is for the first time recorded in Abkhazia, and H. atomus Hopkins, 1915, in the southern Primorskii Territory in the Russian Far East. A key to Hypothenemus species of the fauna of Russia and adjacent countries is given. [ABSTRACT FROM AUTHOR]

Background: The cotton leafworm, Spodoptera littoralis, is a highly polyphagous pest of many cultivated plants and crops in Africa and Europe. The genome of this pest will help us to further understand the molecular mechanisms of polyphagy. Results: Herein, the high-quality genome of S. littoralis was obtained by Pacific Bioscience (PacBio) sequencing. The assembled genome size of S. littoralis is 436.55 Mb with a scaffold N50 of 6.09 Mb, consisting of 17,207 annotated protein-coding genes. Phylogenetic analysis shows that S. littoralis and its sibling species S. litura diverged about 5.44 million years ago. Expanded gene families were mainly involved in metabolic detoxification and tolerance to toxic xenobiotics based on GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analysis. Comparative genomics analysis showed that gene families involved in detoxification and chemosensation were significantly expanded in S. littoralis, representing genetic characteristics related to polyphagy and an extensive host range. Conclusions: We assembled and annotated the reference genome of S. littoralis, and revealed that this pest has the genetic features of strong detoxification capacity, consistent with it being a significant risk to a wide range of host crops. These data resources will provide support for risk assessment and early warning monitoring of major polyphagous agricultural pests. [ABSTRACT FROM AUTHOR]

Abstract The whitefly Bemisia tabaci is a closely related group of >35 cryptic species that feed on the phloem sap of a broad range of host plants. Species in the complex differ in their host‐range breadth, but the mechanisms involved remain poorly understood. We investigated, therefore, how six different B. tabaci species cope with the environmental unpredictability presented by a set of four common and novel host plants. Behavioral studies indicated large differences in performances on the four hosts and putative specialization of one of the species to cassava plants. Transcriptomic analyses revealed two main insights. First, a large set of genes involved in metabolism (>85%) showed differences in expression between the six species, and each species could be characterized by its own unique expression pattern of metabolic genes. However, within species, these genes were constitutively expressed, with a low level of environmental responsiveness (i.e., to host change). Second, within each species, sets of genes mainly associated with the super‐pathways “environmental information processing” and “organismal systems” responded to the host switching events. These included genes encoding for proteins involved in sugar homeostasis, signal transduction, membrane transport, and immune, endocrine, sensory and digestive responses. Our findings suggested that the six B. tabaci species can be divided into four performance/transcriptomic “Types” and that polyphagy can be achieved in multiple ways. However, polyphagy level is determined by the specific identity of the metabolic genes/pathways that are enriched and overexpressed in each species (the species' individual metabolic “tool kit”).

BackgroundThe whitefly Bemisia tabaci (Hemiptera: Aleyrodidae) is among the 100 worst invasive species in the world. As one of the most important crop pests and virus vectors, B. tabaci causes substantial crop losses and poses a serious threat to global food security.ResultsWe report the 615-Mb high-quality genome sequence of B. tabaci Middle East-Asia Minor 1 (MEAM1), the first genome sequence in the Aleyrodidae family, which contains 15,664 protein-coding genes. The B. tabaci genome is highly divergent from other sequenced hemipteran genomes, sharing no detectable synteny. A number of known detoxification gene families, including cytochrome P450s and UDP-glucuronosyltransferases, are significantly expanded in B. tabaci. Other expanded gene families, including cathepsins, large clusters of tandemly duplicated B. tabaci-specific genes, and phosphatidylethanolamine-binding proteins (PEBPs), were found to be associated with virus acquisition and transmission and/or insecticide resistance, likely contributing to the global invasiveness and efficient virus transmission capacity of B. tabaci. The presence of 142 horizontally transferred genes from bacteria or fungi in the B. tabaci genome, including genes encoding hopanoid/sterol synthesis and xenobiotic detoxification enzymes that are not present in other insects, offers novel insights into the unique biological adaptations of this insect such as polyphagy and insecticide resistance. Interestingly, two adjacent bacterial pantothenate biosynthesis genes, panB and panC, have been co-transferred into B. tabaci and fused into a single gene that has acquired introns during its evolution.ConclusionsThe B. tabaci genome contains numerous genetic novelties, including expansions in gene families associated with insecticide resistance, detoxification and virus transmission, as well as numerous horizontally transferred genes from bacteria and fungi. We believe these novelties likely have shaped B. tabaci as a highly invasive polyphagous crop pest and efficient vector of plant viruses. The genome serves as a reference for resolving the B. tabaci cryptic species complex, understanding fundamental biological novelties, and providing valuable genetic information to assist the development of novel strategies for controlling whiteflies and the viruses they transmit.

Simple Summary: In this study, we produced a genomic resource for the light brown apple moth, Epiphyas postvittana, to understand the biological basis of adaptation to a high number of hosts (polyphagy) and the invasive nature of this and other lepidopteran pests. The light brown apple moth is an invasive pest of horticultural plants, with over 500 recorded plant hosts. With origins in Australia, the pest has subsequently spread to New Zealand, Hawaii, California and Europe, causing significant economic losses for fruit producers. Comparative genomic analyses with other lepidopteran genomes indicate that a high proportion of the genome is made up of repetitive sequences, with the majority of the known elements being DNA transposable elements and retrotransposons. Twenty gene families show significant expansions, including some likely to have a role in its pest status. Finally, population genomics, investigated by a RAD-tag approach, indicated likely patterns of invasion and admixture, with Californian moths most probably being derived from Australia. The light brown apple moth, Epiphyas postvittana is an invasive, polyphagous pest of horticultural systems around the world. With origins in Australia, the pest has subsequently spread to New Zealand, Hawaii, California and Europe, where it has been found on over 500 plants, including many horticultural crops. We have produced a genomic resource, to understand the biological basis of the polyphagous and invasive nature of this and other lepidopteran pests. The assembled genome sequence encompassed 598 Mb and has an N50 of 301.17 kb, with a BUSCO completion rate of 97.9%. Epiphyas postvittana has 34% of its assembled genome represented as repetitive sequences, with the majority of the known elements made up of longer DNA transposable elements (14.07 Mb) and retrotransposons (LINE 17.83 Mb). Of the 31,389 predicted genes, 28,714 (91.5%) were assigned to 11,438 orthogroups across the Lepidoptera, of which 945 were specific to E. postvittana. Twenty gene families showed significant expansions in E. postvittana, including some likely to have a role in its pest status, such as cytochrome p450s, glutathione-S-transferases and UDP-glucuronosyltransferases. Finally, using a RAD-tag approach, we investigated the population genomics of this pest, looking at its likely patterns of invasion. [ABSTRACT FROM AUTHOR]

Herbivore diet breadth has been hypothesised to be driven by plant quality (physiological efficiency hypothesis) or natural enemies (enemy‐free space hypothesis). These hypotheses on their own are now known to be insufficient explanations for the range of herbivore diet breadths and more integrative approaches consider how trade‐offs and ecological contingencies shape host plant use by herbivores. I carried out laboratory experiments to test whether physiological efficiency and defence against natural enemies trade off when larvae of the ornate bella moth, Utetheisa ornatrix (L.) (Lepidoptera: Erebidae), a genus‐specialist pod‐boring herbivore, feeds on leaves and pods of four Crotalaria species (Fabaceae). Different components of U. ornatrix physiological efficiency traded off amongst each other and with defence against adult predation by the spider Lycosa erythrognatha Lucas (Araneae: Lycosidae). Crotalaria micans Link provided the highest survival and fast development but low pupal weight and defence. Crotalaria ochroleuca G. Don provided poor survival, slow development, and low defence, but high pupal weight. Crotalaria pallida Aiton provided slow development and intermediate survival and pupal weight, but the best defence. Crotalaria vitellina Ker Gawl. provided high survival, fast development, and efficient defence, but low pupal weight. Compared to leaves, feeding on green seeds provided greater defence against predation, and developmental benefits, independent of host plant species, but there was a large cost in boring into the pod to reach the seeds. I therefore provide evidence that the trade‐offs among physiological efficiency components and between physiological efficiency and defence could maintain multiple host plant use in specialist herbivores. I also show that feeding on green seeds incurs a cost through pod‐boring but gives the moth benefits in adult defence. Therefore, the evolution of host plant use and pod‐boring in insect herbivores could be driven by defence as much as by physiological efficiency. [ABSTRACT FROM AUTHOR]

Abstract Model organisms such as Drosophila melanogaster have been key tools for advancing our fundamental and applied knowledge in biological and biomedical sciences. However, model organisms have become intertwined with the idea of controlled and stable laboratory environments, and their natural history has been overlooked. In holometabolous insects, lack of natural history information on larval ecology has precluded major advances in the field of developmental ecology, especially in terms of manipulations of population density early in life (i.e., larval density). This is because of relativistic and to some extent, arbitrary methodologies employed to manipulate larval densities in laboratory studies. As a result, these methodologies render comparisons between species impossible, precluding our understanding of macroevolutionary responses to population densities during development that can be derived from comparative studies. We recently proposed a new conceptual framework to address this issue, and here, we provide the first natural history investigation of Drosophila melanogaster larval density under such framework. First, we characterized the distribution of larval densities in a wild population of D. melanogaster using rotting apples as breeding substrate in a suburban area in Sweden. Next, we compiled the commonly used methodologies for manipulating larval densities in laboratory studies from the literature and found that the majority of laboratory studies identified did not manipulate larval densities below or above the densities observed in nature, suggesting that we have yet to study true life history and physiological responses to low and high population densities during D. melanogaster development. This is, to our knowledge, the first direct natural history account of larval density in nature for this model organism. Our study paves the way for a more integrated view of organismal biology which re‐incorporates natural history of model organisms into hypothesis‐driven research in developmental ecology.

Abstract Herbivorous insects such as butterflies and moths are essential to natural and agricultural systems due to pollination and pest outbreaks. However, our knowledge of butterflies' and moths' nutrition is fragmented and limited to few common, charismatic, or problematic species. This gap precludes our complete understanding of herbivorous insects' natural history, physiological and behavioral adaptations that drive how species interact with their environment, the consequences of habitat fragmentation and climate change to invertebrate biodiversity, and pest outbreak dynamics. Here, we first report a population of the Buff‐tip moth Phalera bucephala (Lepidoptera: Notodontidae) feeding on a previously unknown family of host plants, the mountain currant Ribes alpinum (Saxifragales: Grossulariaceae). This is the first report of a Notodontid moth feeding on Grossulariaceae hosts. Using no‐choice and choice assays, we showed that P. bucephala has strong foraging preferences for a previously unknown hosts, the R. alpinum but also, although to a smaller extent, R. uva‐crispa compared with a previously known host (the Norway maple Acer sp.). These findings demonstrate that P. bucephala feed on—and show strong preference for Grossulariaceae host plants, indicating flexible physiological mechanisms to accommodate hosts plants from various families. This makes this species a potential model organism to study the behavioral and physiological mechanisms underpinning insect–plant interactions and diet breadth evolution. We discuss the broad ecological implications of these observations to the biology of the species, the potential negative effects of interspecific competition with endemic specialist moths, and highlight questions for future research.

Abstract Background Halyomorpha halys (Stål), the brown marmorated stink bug, is a highly invasive insect species due in part to its exceptionally high levels of polyphagy. This species is also a nuisance due to overwintering in human-made structures. It has caused significant agricultural losses in recent years along the Atlantic seaboard of North America and in continental Europe. Genomic resources will assist with determining the molecular basis for this species’ feeding and habitat traits, defining potential targets for pest management strategies. Results Analysis of the 1.15-Gb draft genome assembly has identified a wide variety of genetic elements underpinning the biological characteristics of this formidable pest species, encompassing the roles of sensory functions, digestion, immunity, detoxification and development, all of which likely support H. halys’ capacity for invasiveness. Many of the genes identified herein have potential for biomolecular pesticide applications. Conclusions Availability of the H. halys genome sequence will be useful for the development of environmentally friendly biomolecular pesticides to be applied in concert with more traditional, synthetic chemical-based controls.

Defensive metabolites and nutrient restriction of host plants are 2 major obstacles to the colonization of insect herbivores. The green peach aphid (GPA) Myzus persicae (Sulzer) broadly colonizes plants with diverse nutritional and defensive traits. However, how GPA adapts to nutritional and defensive traits within different plants remains largely unknown. To elucidate this, we first investigated the performances and transcriptomes of GPA feeding on cabbage Brassica oleracea and pepper Capsicum annuum. The green peach aphid had lower weight and fecundity when feeding on cabbage than on pepper. The transcriptomic analysis found 824 differentially expressed genes (DEGs), and 13 of the top 20 Kyoto Encyclopedia of Genes and Genomes pathways are related to nutrient metabolism, energy metabolism, and detoxification. Specifically, we found 160 DEGs associated with the metabolism of protein and amino acids, sugar and lipids, and xenobiotic substances, 86 upregulated in cabbage-fed GPA. Fourteen cathepsin B genes were strongly upregulated in cabbage-fed GPA, and were enriched in lysosome pathway and 2 dominated gene ontology terms peptidase activity and proteolysis. In addition, cabbage-fed GPA upregulated sugar and lipid digestion, while downregulated lipid biosynthesis processes. Furthermore, 55 metabolic detoxification enzyme genes were differentially expressed between GPA on 2 hosts, and detoxification enzyme activities of GPA indeed changed accordingly to the host. Then, we found that cabbage has lower amino acids nutrition quality for GPA compared to pepper. Our results suggested that adjustment of nitrogen nutrient metabolism, sugar and lipid metabolism, and metabolic detoxification in a host-specific manner play crucial roles in the adaptations of GPA to different host plants., (© The Author(s) 2024. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Phytophagous insects may be expected to prefer host-plant species on which their larvae perform best, but this has rarely been explored in grass-feeding butterflies. We explored links between oviposition preferences, larval food preferences, and performance (larval survival and development time, pupal mass, and adult longevity) on 18 species of grass in the common evening brown, Melanitis leda L. (Nymphalidae: Melanitini), a tropical butterfly that has been recorded from a large number of species of grass. Melanitis leda oviposited on all of the grass species offered in choice experiments, and larvae were able to develop to the adult stage on almost all of them. Oviposition preferences were for species of plants on which larval survival was higher, but were not correlated with larval development. The mother's choice of host plant appeared to affect performance of the resulting adults as large butterflies had longer life spans. Ovipositing females appeared to adjust clutch size and position of their eggs on a plant depending on plant traits. Larval survival was only marginally correlated with larval growth rate on the different species of plants. Larvae showed host-plant preferences that were not correlated with adult oviposition preferences, larval survival, or larval growth. Overall, while M. leda can utilize a large number of species of grass, it shows marked oviposition preferences. Apparent fine-tuning of clutch size and positioning of eggs on plants with different traits might be another adaptation associated with using a large number of species of plants. We conclude that this grass feeding butterfly selects oviposition sites that maximize the chances of their larvae surviving.

Abstract Background The glasshouse whitefly, Trialeurodes vaporariorum, is a damaging crop pest and an invasive generalist capable of feeding on a broad range of host plants. As such this species has evolved mechanisms to circumvent the wide spectrum of anti-herbivore allelochemicals produced by its host range. T. vaporariorum has also demonstrated a remarkable ability to evolve resistance to many of the synthetic insecticides used for control. Results To gain insight into the molecular mechanisms that underpin the polyphagy of T. vaporariorum and its resistance to natural and synthetic xenobiotics, we sequenced and assembled a reference genome for this species. Curation of genes putatively involved in the detoxification of natural and synthetic xenobiotics revealed a marked reduction in specific gene families between this species and another generalist whitefly, Bemisia tabaci. Transcriptome profiling of T. vaporariorum upon transfer to a range of different host plants revealed profound differences in the transcriptional response to more or less challenging hosts. Large scale changes in gene expression (> 20% of genes) were observed during adaptation to challenging hosts with a range of genes involved in gene regulation, signalling, and detoxification differentially expressed. Remarkably, these changes in gene expression were associated with significant shifts in the tolerance of host-adapted T. vaporariorum lines to natural and synthetic insecticides. Conclusions Our findings provide further insights into the ability of polyphagous insects to extensively reprogram gene expression during host adaptation and illustrate the potential implications of this on their sensitivity to synthetic insecticides.

Abstract The enemy‐free space hypothesis (EFSH) contends that generalist predators select for dietary specialization in insect herbivores. At a community level, the EFSH predicts that dietary specialization reduces predation risk, and this pattern has been found in several studies addressing the impact of individual predator taxa or guilds. However, predation at a community level is also subject to combinatorial effects of multiple‐predator types, raising the question of how so‐called multiple‐predator effects relate to dietary specialization in insect herbivores. Here, we test the EFSH with a field experiment quantifying ant predation risk to insect herbivores (caterpillars) with and without the combined predation effects of birds. Assessing a community of 20 caterpillar species, we use model selection in a phylogenetic comparative framework to identify the caterpillar traits that best predict the risk of ant predation. A caterpillar species' abundance, dietary specialization, and behavioral defenses were important predictors of its ant predation risk. Abundant caterpillar species had increased risk of ant predation irrespective of bird predation. Caterpillar species with broad diet breadth and behavioral responsiveness to attack had reduced ant predation risk, but these ant effects only occurred when birds also had access to the caterpillar community. These findings suggest that ant predation of caterpillar species is density‐ or frequency‐dependent, that ants and birds may impose countervailing selection on dietary specialization within the same herbivore community, and that contingent effects of multiple predators may generate behaviorally mediated life‐history trade‐offs associated with herbivore diet breadth.

Bryophytes represent favourable habitats for many arthropods, but their utilisation as a food source is marginal. While one of the largest monophyletic groups that represent obligatory bryophyte consumers are the Byrrhidae, host ranges for species in this group of beetles remain largely unknown due to their cryptic appearance and rarity. The occasional notes of 'associated' moss species that do exist are related to where Byrrhidae were found and not to diet analysis. Because the majority of Byrrhidae are stenobionts with limited dispersal, the assumption that associated moss species are also used as food is a useful hypothesis.To test this hypothesis, 328 individuals were sampled from the species: Cytilus sericeus, Byrrhus fasciatus, Byrrhus pilula, and Byrrhus glabratus. Mosses from both the stomachs and the immediate microhabitats of beetles were determined with the aim of (i) identifying their host range and (ii) testing whether the moss species from microhabitats in which beetles were collected were also found in their stomachs.Almost 40 bryophyte species were found in beetle stomachs and accumulation curves for all beetle species failed to achieve asymptotes, together showing that all species are highly polyphagous.Although a strong general correlation existed between moss consumption and occupation, discrepancies were present at the individual level with there being considerably higher moss species richness in beetle stomachs than in their immediate microhabitats. Our results question the assumption that bryophyte occupancy and consumption can be used interchangeably when studying host use in these insects. [ABSTRACT FROM AUTHOR]

The whitefly Bemisia tabaci is a closely related group of >35 cryptic species that feed on the phloem sap of a broad range of host plants. Species in the complex differ in their host‐range breadth, but the mechanisms involved remain poorly understood. We investigated, therefore, how six different B. tabaci species cope with the environmental unpredictability presented by a set of four common and novel host plants. Behavioral studies indicated large differences in performances on the four hosts and putative specialization of one of the species to cassava plants. Transcriptomic analyses revealed two main insights. First, a large set of genes involved in metabolism (>85%) showed differences in expression between the six species, and each species could be characterized by its own unique expression pattern of metabolic genes. However, within species, these genes were constitutively expressed, with a low level of environmental responsiveness (i.e., to host change). Second, within each species, sets of genes mainly associated with the super‐pathways "environmental information processing" and "organismal systems" responded to the host switching events. These included genes encoding for proteins involved in sugar homeostasis, signal transduction, membrane transport, and immune, endocrine, sensory and digestive responses. Our findings suggested that the six B. tabaci species can be divided into four performance/transcriptomic "Types" and that polyphagy can be achieved in multiple ways. However, polyphagy level is determined by the specific identity of the metabolic genes/pathways that are enriched and overexpressed in each species (the species' individual metabolic "tool kit"). [ABSTRACT FROM AUTHOR]

Determining the host range of an invasive insect in a new environment is a key step in the development of management strategies. As the brown marmorated stink bug, Halyomorpha halys Stål, expands into agricultural regions of North America, efforts to elucidate its dietary habits on a landscape scale rely on intensive sampling of potential host plants. Although this approach yields useful information, results can be biased toward common and easily sampled plant species; important hosts can be missed if sampling them is impractical or limited in scope. Here we lay the groundwork for the application of gut content analysis to the feeding ecology of H. halys by investigating the persistence of host plant DNA in the digestive tracts of insects with known feeding histories. Adult H. halys were fed bean seedlings (Phaseolus lunatus L.) for 7 d, followed by a forced host switch to carrot (Daucus carota L.). Insect guts were dissected out at 0, 1, 3, 7, and 14 d following the switch, and host plant chloroplast genes (trnF and trnL) were amplified via polymerase chain reaction. Amplicons were identified using high-throughput sequencing and analyzed for Phaseolus DNA. The original host remained detectable at 3 d (trnF) and 14 d (trnL) in substantial quantities. The proportion of total reads identified as Phaseolus rapidly decreased with time; a concomitant increase in Daucus reads was observed. Our results indicate that high-throughput sequencing of gut contents has great potential for exploring the dietary histories of field-caught H. halys and other phytophagous insects. [ABSTRACT FROM AUTHOR]

Herbivorous insects such as butterflies and moths are essential to natural and agricultural systems due to pollination and pest outbreaks. However, our knowledge of butterflies' and moths' nutrition is fragmented and limited to few common, charismatic, or problematic species.This gap precludes our complete understanding of herbivorous insects' natural history, physiological and behavioral adaptations that drive how species interact with their environment, the consequences of habitat fragmentation and climate change to invertebrate biodiversity, and pest outbreak dynamics.Here, we first report a population of the Buff‐tip moth Phalera bucephala (Lepidoptera: Notodontidae) feeding on a previously unknown family of host plants, the mountain currant Ribes alpinum (Saxifragales: Grossulariaceae). This is the first report of a Notodontid moth feeding on Grossulariaceae hosts.Using no‐choice and choice assays, we showed that P. bucephala has strong foraging preferences for a previously unknown hosts, the R. alpinum but also, although to a smaller extent, R. uva‐crispa compared with a previously known host (the Norway maple Acer sp.).These findings demonstrate that P. bucephala feed on—and show strong preference for Grossulariaceae host plants, indicating flexible physiological mechanisms to accommodate hosts plants from various families. This makes this species a potential model organism to study the behavioral and physiological mechanisms underpinning insect–plant interactions and diet breadth evolution.We discuss the broad ecological implications of these observations to the biology of the species, the potential negative effects of interspecific competition with endemic specialist moths, and highlight questions for future research. [ABSTRACT FROM AUTHOR]

Model organisms such as Drosophila melanogaster have been key tools for advancing our fundamental and applied knowledge in biological and biomedical sciences. However, model organisms have become intertwined with the idea of controlled and stable laboratory environments, and their natural history has been overlooked.In holometabolous insects, lack of natural history information on larval ecology has precluded major advances in the field of developmental ecology, especially in terms of manipulations of population density early in life (i.e., larval density). This is because of relativistic and to some extent, arbitrary methodologies employed to manipulate larval densities in laboratory studies. As a result, these methodologies render comparisons between species impossible, precluding our understanding of macroevolutionary responses to population densities during development that can be derived from comparative studies.We recently proposed a new conceptual framework to address this issue, and here, we provide the first natural history investigation of Drosophila melanogaster larval density under such framework. First, we characterized the distribution of larval densities in a wild population of D. melanogaster using rotting apples as breeding substrate in a suburban area in Sweden.Next, we compiled the commonly used methodologies for manipulating larval densities in laboratory studies from the literature and found that the majority of laboratory studies identified did not manipulate larval densities below or above the densities observed in nature, suggesting that we have yet to study true life history and physiological responses to low and high population densities during D. melanogaster development.This is, to our knowledge, the first direct natural history account of larval density in nature for this model organism. Our study paves the way for a more integrated view of organismal biology which re‐incorporates natural history of model organisms into hypothesis‐driven research in developmental ecology. [ABSTRACT FROM AUTHOR]

Background Herbivorous insects represent a major fraction of global biodiversity and the relationships they have established with their food plants range from strict specialists to broad generalists. Our knowledge of these relationships is of primary importance to basic (e.g. the study of insect ecology and evolution) and applied biology (e.g. monitoring of pest or invasive species) and yet remains very fragmentary and understudied. In Lepidoptera, caterpillars of families Saturniidae and Sphingidae are rather well known and considered to have adopted contrasting preferences in their use of food plants. The former are regarded as being rather generalist feeders, whereas the latter are more specialist. New information To assemble and synthesise the vast amount of existing data on food plants of Lepidoptera families Saturniidae and Sphingidae, we combined three major existing databases to produce a dataset collating more than 26,000 records for 1256 species (25% of all species) in 121 (67%) and 167 (81%) genera of Saturniidae and Sphingidae, respectively. This dataset is used here to document the level of polyphagy of each of these genera using summary statistics, as well as the calculation of a polyphagy score derived from the analysis of Phylogenetic Diversity of the food plants used by the species in each genus. [ABSTRACT FROM AUTHOR]

The meadow spittlebug, Philaenus spumarius L. (Hemiptera: Aphrophoridae), is the main vector of the phytopathogenic bacterium Xylella fastidiosa in Europe, where the ST53 strain induces the olive quick decline syndrome, causing severe economic damage in southern Italy. The wide range of plant species infected by X. fastidiosa, and the wide host range of P. spumarius suggest that a large number of wild and cultivated plants may become infected by the pathogen following unintentional introduction events. Therefore, it is necessary to detail the host plant preference of the vector, in order to include preferred plants in the field, in pathogen‐targeted diagnostic efforts. This would allow the identification of main sources of X. fastidiosa acquisition by P. spumarius; such plant species represent an important target for rational disease management. Here, we investigated the host plants of P. spumarius in north‐western Italy, a region where X. fastidiosa is still not present but is regarded as a primary threat. We designed a new molecular diagnostic tool targeting chloroplast DNA, to characterize the gut content of single P. spumarius adults. The newly set up, nested PCR/sequencing‐based identification protocol was proven to be useful for retrieving sequences from the last two different host plants used by P. spumarius, even if limited persistence of intact chloroplast DNA was reported in the spittlebug gut. We propose this protocol as a new tool for supporting research on xylem feeder biology that could be particularly useful for highly polyphagous species such as P. spumarius. Furthermore, the method could help monitor X. fastidiosa invasion, and contribute to the study of vector ecology and pathogen epidemiology. [ABSTRACT FROM AUTHOR]

Most herbivorous insects are diet specialists in spite of the apparent advantages of being a generalist. This conundrum might be explained by fitness trade‐offs on alternative host plants, yet the evidence of such trade‐offs has been elusive. Another hypothesis is that specialization is nonadaptive, evolving through neutral population‐genetic processes and within the bounds of historical constraints. Here, we report on a striking lack of evidence for the adaptiveness of specificity in tropical canopy communities of armored scale insects. We find evidence of pervasive diet specialization, and find that host use is phylogenetically conservative, but also find that more‐specialized species occur on fewer of their potential hosts than do less‐specialized species, and are no more abundant where they do occur. Of course local communities might not reflect regional diversity patterns. But based on our samples, comprising hundreds of species of hosts and armored scale insects at two widely separated sites, more‐specialized species do not appear to outperform more generalist species. [ABSTRACT FROM AUTHOR]

Generalist insect herbivores, those recorded as using numerous hosts (tens or even hundreds of species), are not well understood ecologically. We suggest ways to investigate the ecology of these species beyond the practice of accumulating host records. We present reasons why multiple host use by herbivorous insects needs to be quantified in the field, both locally and geographically, and also through time. Further, the host use patterns generated must be based on certain knowledge that cryptic species are not conflated in the results as one species. Such results reveal a lot about the ecology of the species concerned and about generalist–host relationships more widely. This provides a sound basis for the functional significance of multiple host use to be interpreted and tested further. Structured sampling programs conducted previously in the field indicate that generalist insect herbivores are strongly associated with only a relatively small subset of their recorded host species, their primary host plants. A focus on these particular host plants is fundamental to (i) understanding the ecology of the herbivore species in question and (ii) investigating the sensory and behavioural mechanisms associated with host location. We conclude that the principal influence on patterns of multiple host use in the field is the mechanism by which herbivorous insects recognise cues from potential hosts and use them to localise plants. These mechanisms represent species-specific and species-wide adaptations to the usual environment of the species in question. Working from this perspective should contribute substantially to developing a strong and realistic interpretation of the origins and functional significance of multiple host use in herbivorous arthropods. [ABSTRACT FROM AUTHOR]

Background: The glasshouse whitefly, Trialeurodes vaporariorum, is a damaging crop pest and an invasive generalist capable of feeding on a broad range of host plants. As such this species has evolved mechanisms to circumvent the wide spectrum of anti-herbivore allelochemicals produced by its host range. T. vaporariorum has also demonstrated a remarkable ability to evolve resistance to many of the synthetic insecticides used for control. Results: To gain insight into the molecular mechanisms that underpin the polyphagy of T. vaporariorum and its resistance to natural and synthetic xenobiotics, we sequenced and assembled a reference genome for this species. Curation of genes putatively involved in the detoxification of natural and synthetic xenobiotics revealed a marked reduction in specific gene families between this species and another generalist whitefly, Bemisia tabaci. Transcriptome profiling of T. vaporariorum upon transfer to a range of different host plants revealed profound differences in the transcriptional response to more or less challenging hosts. Large scale changes in gene expression (> 20% of genes) were observed during adaptation to challenging hosts with a range of genes involved in gene regulation, signalling, and detoxification differentially expressed. Remarkably, these changes in gene expression were associated with significant shifts in the tolerance of host-adapted T. vaporariorum lines to natural and synthetic insecticides. Conclusions: Our findings provide further insights into the ability of polyphagous insects to extensively reprogram gene expression during host adaptation and illustrate the potential implications of this on their sensitivity to synthetic insecticides. [ABSTRACT FROM AUTHOR]

1. Although polyphagy is widespread among Drosophila, some specialist species have evolved in response to resource competition and other selection factors favouring niche separation. The small fruit specialist Drosophila suzukii Matsumura has evolved a unique serrated ovipositor that allows it to access ripening fruit, a niche unavailable to most Drosophila. However, it is unclear whether ancestral traits (the use of non‐fruit resources) are maintained in this specialist species. 2. In this study, maternal preferences and offspring fitness in response to novel apple, mushroom, and bird manure‐based diets were investigated by comparing oviposition and offspring survival and development on various diets. The effect of those diets on survival at cool temperatures and the effect of natal environment/previous exposure on adult preferences were evaluated. 3. Female D. suzukii accepted non‐fruit diets such as mushroom and bird manure, and offspring completed their larval development on all diets tested. However, D. suzukii did not perform well on diets that included bird manure. By contrast, combinational apple/mushroom diets were associated with greater oviposition, lower mortality, faster development, and larger offspring than other diets. These diets were also associated with increased resistance to cold stress, and preference for these diets was positively affected by previous feeding experience. 4. These data suggest that D. suzukii may use non‐fruit resources when preferred resources are scarce. Given that this pest is adapted to temperate climates, alternative resources might provide seasonal nutritional support when fruit resources are not temporally available, although field data are needed to support this hypothesis. [ABSTRACT FROM AUTHOR]

The enemy‐free space hypothesis (EFSH) contends that generalist predators select for dietary specialization in insect herbivores. At a community level, the EFSH predicts that dietary specialization reduces predation risk, and this pattern has been found in several studies addressing the impact of individual predator taxa or guilds. However, predation at a community level is also subject to combinatorial effects of multiple‐predator types, raising the question of how so‐called multiple‐predator effects relate to dietary specialization in insect herbivores. Here, we test the EFSH with a field experiment quantifying ant predation risk to insect herbivores (caterpillars) with and without the combined predation effects of birds. Assessing a community of 20 caterpillar species, we use model selection in a phylogenetic comparative framework to identify the caterpillar traits that best predict the risk of ant predation. A caterpillar species' abundance, dietary specialization, and behavioral defenses were important predictors of its ant predation risk. Abundant caterpillar species had increased risk of ant predation irrespective of bird predation. Caterpillar species with broad diet breadth and behavioral responsiveness to attack had reduced ant predation risk, but these ant effects only occurred when birds also had access to the caterpillar community. These findings suggest that ant predation of caterpillar species is density‐ or frequency‐dependent, that ants and birds may impose countervailing selection on dietary specialization within the same herbivore community, and that contingent effects of multiple predators may generate behaviorally mediated life‐history trade‐offs associated with herbivore diet breadth. [ABSTRACT FROM AUTHOR]

Advances in understanding non-genetic inheritance have prompted broader interest in environmental effects. One way in which such effects may influence adaptation is via the transmission of acquired habitat biases. Here I explore how natal experience influences adult host orientation in the oligophagous passion vine butterfly Heliconius charithonia. As an exemplar of the 'pupal mating' system, this species poses novelty among diurnal Lepidoptera for the extent to which male as well as female reproductive behaviours are guided by olfactory host cues. I sampled wild adult females breeding exclusively upon Passiflora incarnata, assigned their offspring to develop either upon this species or its local alternative Passiflora suberosa, and then assessed the behaviour of F1 adults in a large rainforest enclosure. Despite the fact that juvenile performance was superior upon P. incarnata, females oviposited preferentially upon their assigned natal species. Mate-seeking males also indicated a bias for the proximity of their natal host, and there was evidence for assortative mating based upon host treatment, although these data are less robust. This study is, to my knowledge, the first to support Hopkins' hostplant principle in butterflies, and points to inducible host preferences capable of reinforcing ecological segregation and ultimately accelerating evolutionary divergence in sympatry. [ABSTRACT FROM AUTHOR]

The Old World bollworm, Helicoverpa armigera (Hübner), is one of the most destructive agricultural pests worldwide. It was first recorded in Brazil in 2013, yet despite this recent introduction, H. armigera has spread throughout much of Latin America. Where H. armigera has become established, it is displacing or hybridizing with the congeneric New World pest Helicoverpa zea. In addition to the adaptive qualities that make H. armigera a megapest, such as broad range pesticide resistance, the spread of H. armigera in the New World may have been hastened by multiple introductions into South America and/or the Caribbean. The recent expansion of the range of H. armigera into the New World is analyzed herein using mtDNA of samples from South America, the Caribbean Basin, and the Florida Peninsula. Phylogeographic analyses reveal that several haplotypes are nearly ubiquitous throughout the New World and native range of H. armigera , but several haplotypes have limited geographic distribution from which a secondary introduction with Euro-African origins into the New World is inferred. In addition, host–haplotype correlations were analyzed to see whether haplotypes might be restricted to certain crops. No specialization was found; however, some haplotypes had a broader host range than others. These results suggest that the dispersal of H. armigera in the New World is occurring from both natural migration and human-mediated introductions. As such, both means of introduction should be monitored to prevent the spread of H. armigera into areas such as the United States, Mexico, and Canada, where it is not yet established. [ABSTRACT FROM AUTHOR]