Journal of Invertebrate Pathology

Parasites can manipulate host behavior to increase their fitness while decreasing host fitness, a phenomenon known as an extended phenotype. Nucleopolyhedroviruses (NPVs), baculoviruses that infect Lepidopteran larvae, have been found to induce vertical climbing behavior and hyperactivity in exposed larvae. We quantified variation in the horizontal wandering behavior induced by different naturally-occurring pathogen isolates in the NPV that infects Dione (Agraulis) vanillae Linnaeus (Lepidoptera: Nymphalidae). Lab-raised larvae were infected with a constant dose of one of five different field-collected NPV isolates or a water control (n=98 larvae total), and placed in mazes to measure the horizontal distance wandered away from a food source. Virus-exposed larvae exhibited increased maximum distance of horizontal movement compared to the control, but did not significantly differ in the probability of wandering versus no movement. We also found variation in the distance wandered among the five virus isolates. However, grouping the five isolates into two previously-described viral strains or genogroups did not improve predicted differences in movement, perhaps due to the presence of within-strain genetic variation among isolates in the viral genes involved in controlling host behavior. Further work is needed to determine whether the observed between-isolate variation is the result of adaptive evolution. These results suggest that the NPV infecting D. vanillae manipulates larval behavior to increase horizontal wandering, which could lead to higher pathogen fitness by increasing long-distance dispersal of the virus across the landscape.

Invasive ambrosia beetles and fungal pathogens threaten forest ecosystems worldwide, exemplified in Hawaii by the widespread loss of keystone species [o]hia (Metrosideros polymorpha), due to Rapid [O]hia Death (ROD). A unique occurrence of five ambrosia beetle species (one native, four introduced) that vary in their symbiotic relationships with two introduced fungal pathogens provide an opportunity to test hypotheses of how opportunistic symbioses facilitate disease dynamics involving dominant forest trees. ROD is caused by two novel Ceratocystis fungal pathogens whose spores can spread via association with ambrosia beetles as they bore into [o]hia trees. We examined beetle-pathogen interactions of all five ambrosia beetle species in three ROD-affected regions on Hawaii Island, and used quantitative PCR (qPCR) to provide the first molecular confirmation of the two ROD pathogens associated with the exterior, mycangia, and gut of each beetle species. Results from generalized linear models and correlation networks show that pathogen acquisition and transport, including the potential for consumption and the presence of the pathogens, are determined by beetle invasion status and mycangia morphology. A niche construction framework suggests that both varying symbioses and opportunism facilitate disease spread, with the three invasive Xyleborus species emerging as key disease vectors. Identifying the beetle species that are more likely to contribute to disease spread, and understanding their biology as vectors, can inform targeted conservation strategies for [o]hia and for insect-pathogen threats in forests worldwide, and illustrates the potential ecosystem-level impacts of novel and opportunistic symbioses between globally distributed invasive vectors and pathogens.

The honey bee (Apis mellifera) gut microbiome plays a central role in host health, yet its variation across agricultural landscapes remains poorly resolved. This study investigates how major environmental stressors, particularly pesticide exposure and RNA virus loadings, shape the honey bee gut microbiome in a large-scale field study conducted across Canada, spanning diverse agroecosystems from British Columbia to Quebec. We identify consistent associations between specific bacterial taxa and major RNA viruses, including enrichment of Serratia marcescens with SBV and depletion of Bombella intestini with BQCV. Pesticide exposure is likewise linked to reproducible shifts in key microbial taxa. Together, these findings reveal that interacting stressors jointly shape the bee gut microbiome and enable prediction of microbiome responses in agroecosystems. HighlightsDistinct associations identified between gut bacteria and major bee RNA viruses (BQCV, SBV, LSV, IAPV) Pesticide exposure is linked to reproducible shifts in key microbial taxa Combined virus-pesticide effects form coordinated clusters that predict microbiome variation and specific bacterial responses Integrated modeling demonstrates that environmental stressors can jointly explain microbiome structure beyond crop effects Graphical abstractSchematic overview of potential links between pesticide exposure and RNA virus infection and their effects on the bee gut bacterial community. Solid arrows indicate associations supported by the present study, whereas dashed arrows indicate hypothesized or unresolved interactions. Associations between the presence of specific bee RNA viruses (left) or pesticide residues (right) and changes in the relative abundance of particular gut taxa (pink {uparrow}, increased; blue {downarrow}, decreased). The pesticide subtype is indicated by the icon in the cell (leaf - herbicide, hyphae - fungicide and insect - insecticide). Several bacterial taxa showed reproducible associations with specific viral or pesticide variables, including Bombella intestini, Serratia marcescens, Melissococcus plutonius, Paenibacillus alvei, Apibacter sp. wkB309, and Gilliamella sp. A7. Abbreviations: BQCV Black queen cell virus; LSV, Lake Sinai virus; SBV, Sacbrood virus; IAPV, Israeli acute paralysis virus. (p/n/b) indicate the sample matrix in which the pesticide was detected, namely pollen, nectar, and bee tissue, respectively. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=133 SRC="FIGDIR/small/731697v1_ufig1.gif" ALT="Figure 1"> View larger version (40K): org.highwire.dtl.DTLVardef@cb92a4org.highwire.dtl.DTLVardef@1087045org.highwire.dtl.DTLVardef@102cabforg.highwire.dtl.DTLVardef@4ce2f1_HPS_FORMAT_FIGEXP M_FIG C_FIG

The migratory endoparasitic pinewood nematode (PWN), Bursaphelenchus xylophilus, is the causal agent of pine wilt disease, causing significant economic and ecological losses in conifer forest ecosystems in Europe and Asia. Understanding the molecular mechanisms regulating PWN parasitism-related genes may lead to new sustainable solutions for control. Based on previous PWN transcriptomic datasets from the pre-parasitic and parasitic stages and from the pharyngeal gland cells (GC), an in silico analysis was performed to identify transcription factors (TF) highly expressed in the GC. Seven candidates TF genes were selected, and their spatial expression validated by in situ hybridisation. From those, two GC-expressed TFs, BXY_079 and BXY_022, each encoding zinc finger domains, were successfully knocked down by RNA interference. Transcriptomic data from silenced BXY_079 and BXY_022 TFs, analysed with existing life cycle specific transcriptomic data, showed that both TFs control genes expressed at similar times, by repressing male-related genes while activating genes expressed during the J3 and D3 stages, yet each represents the extreme of the others minor function. In addition to these common roles, BXY_079 also activates parasitism-related genes in the J2 stage. These BXY_079-activated parasitism-related genes predominantly encode proteins with lytic functions, including secreted peptidases and glycoside hydrolases. Consistent with their proposed role in parasitism, these genes are highly expressed during the parasitic juvenile stages and are likely involved in nematode feeding, tissue penetration, and migration within the host. In contrast, BXY_022 also represses the expression of several genes related to the reproduction system, such as major sperm proteins and cytosolic motility proteins, particularly in the adult male stage. Taken together, both dual-functional TFs work together, non-redundantly, to regulate gene expression across the life cycle, while each is additionally specialised to regulate diverse and distinct gene sets: ranging from genes implicated in lytic parasitic functions to sexual dimorphism.

Diapause is a critical adaptive strategy that enables temperate mosquito species to survive adverse environmental conditions and maintain population persistence across seasons. In Culex pipiens, diapause plays a key role in overwintering and influences the seasonal dynamics of arbovirus transmission. However, diapause expression is often assessed using single traits, limiting our understanding of its integrated physiological basis and variation among populations. In this study, we investigated the behavioural, morphological, and reproductive signatures of diapause across three laboratory strains of Culex pipiens (Mogden, Pirbright, and Pirbright Hybrid) reared under diapause-inducing (10 {degrees}C), cold (14 {degrees}C), and control (26-27 {degrees}C) conditions. We quantified blood-feeding behaviour, wing size as a proxy for somatic growth, and spermatheca size as an indicator of reproductive development. Diapause-inducing conditions resulted in a coordinated phenotype characterised by strong suppression of blood-feeding, increased somatic size, and marked inhibition of reproductive development. Mosquitoes reared at 10 {degrees}C exhibited near-complete feeding inhibition and significantly reduced spermatheca size, consistent with reproductive arrest, while those reared at 14 {degrees}C showed intermediate phenotypes. In contrast, control mosquitoes displayed active feeding and fully developed reproductive structures. Wing size increased progressively with decreasing temperature, with the largest individuals observed under diapause-inducing conditions. When analysed together, wing size and spermatheca development exhibited opposing responses across temperature treatments, revealing a strong negative association and indicating a trade-off between somatic growth and reproductive investment. This integrated response supports the interpretation of diapause as a coordinated life-history strategy involving resource reallocation towards survival. Additionally, diapause expression varied among strains, with the Mogden strain showing reduced sensitivity compared with Pirbright and hybrid populations, highlighting the role of genetic background in diapause plasticity. These findings demonstrate that diapause in Culex pipiens is a multi-trait, plastic phenotype with important implications for overwintering success and the seasonal dynamics of arbovirus transmission in temperate regions.

Wolbachia is a bacterial endosymbiont that is primarily transmitted from mother to offspring. To increase their transmission, some strains manipulate their hosts reproduction to favor female offspring, such as by inducing parthenogenesis. Here, we assess whether Wolbachia induces parthenogenesis in recently discovered parthenogenetic populations of the ladybug Nephus voeltzkowi by treating females with an antibiotic. Females from sexual populations, which we show are not infected by Wolbachia, serve as a control. Our results demonstrate that the treatment decreases Wolbachia load, subsequently reducing egg production and development among parthenogenetic females, while having no effect on sexual females. Wolbachia load and reproduction then rebound when the treatment is removed. This suggests that the Wolbachia infection is necessary for successful reproduction in the parthenogenetic females, and it may play a two-part role by facilitating egg laying and late embryo development. The cooccurrence of Wolbachia infection and parthenogenesis in N. voeltzkowi, as well as Wolbachias manipulation of host reproduction makes a likely candidate of Wolbachia-induced parthenogenesis outside of haplo-diploids. Understanding how Wolbachia can impact diverse insect reproductive systems can shed a light on the extent in which these bacteria can manipulate hosts for their own gain.

BACKGROUNDThe soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is a pest of soybean in North America that can cause significant yield loss when outbreaks are not managed. Current management tactics primarily rely on inexpensive pyrethroids, but the sustainability of this option is threatened by insecticide-resistance in A. glycines populations across the Upper-Midwest United States. Field-evolved resistance is associated with mutations in the voltage-gated sodium channel subunit h1 (vgsc-h1) gene. RESULTSFour double-stranded RNA (dsRNA) molecules, each matching the sequence of a vgsc-h1 transcript variant ("Specific dsRNAs"), were topically applied to aphids with a genotype carrying the corresponding allele. The mortality of pyrethroid resistant aphids exposed to a Specific dsRNA increased in a dose-dependent manner when applied alone or with a constant concentration of lambda-cyhalothrin, plateauing at 1000 ng ul-1. Synergism was detected between two of four combinations of the Specific dsRNAs and lambda-cyhalothrin. These results were mirrored by the topical application of a single dsRNA with the consensus sequence of all vgsc-h1 variants ("Combined dsRNA"). Mortality was consistently higher in aphids treated with either Specific dsRNA or the Combined dsRNA, alone or with lambda-cyhalothrin, compared to insecticide alone. The number of nymphs produced per female treated with the Specific or Combined dsRNA alone decreased significantly compared to untreated controls. CONCLUSIONThis study demonstrates that the topical application of dsRNAs targeting vgsc-h1 increases the susceptibility and reduces the reproductive capacity of pyrethroid resistant soybean aphids, potentially providing a novel tool for the management of insecticide-resistant aphid populations.

ObjectivesTo estimate the pooled prevalence of Wolbachia infection in biting midges (Ceratopogonidae) across Southwest Asia and to evaluate ecological and biological factors associated with infection patterns. Study DesignSystematic review and meta-analysis. MethodsA comprehensive search of international and regional databases (PubMed, Scopus, Web of Science, Embase, SID, MagIran) was conducted without date restriction. Eligible studies included those using molecular techniques to detect Wolbachia in Ceratopogonidae collected from Southwest Asia. Pooled prevalence was calculated using a random-effects model. Subgroup and meta-regression analyses were performed to assess variations by country, species, altitude, habitat type, and sex. Heterogeneity and publication bias were evaluated using I{superscript 2}, Cochrans Q, and Eggers tests in accordance with PRISMA guidelines. ResultsTwenty-four studies comprising 14,832 midges from six countries were included. The pooled prevalence of Wolbachia infection was 32.6% (95% CI: 28.4-36.9%; I{superscript 2}=78.3%). Iran showed the highest prevalence (38.2%), and Culicoides imicola was the most frequently infected species (36.8%). Higher prevalence was associated with lower altitudes (<500 m; P=0.012), rural habitats (P=0.034), and female midges (P=0.008). Limited evidence suggested the presence of cytoplasmic incompatibility and reduced bluetongue virus competence in infected midges. ConclusionsWolbachia infection is common among Ceratopogonidae in Southwest Asia and is influenced by ecological and biological factors. These findings highlight the potential of Wolbachia as a biocontrol tool in regional vector management, underscoring the need for further experimental and strain-level studies.

Adult mosquitoes rely on plant-derived sugars for survival, reproduction, and flight, yet the plant taxa that mosquitoes encounter in nature and the odors that make those plants attractive remain poorly understood. Most studies of mosquito attraction to plant odors have focused on candidate plants selected a priori, rather than plants linked to field-collected mosquitoes. Here, we combined plant DNA barcoding, semi-field behavioral assays, and volatile profiling to identify field-associated plant resources relevant to Aedes aegypti. Plant DNA recovered from mosquitoes collected across three Florida counties revealed broad plant associations, including 90 genera spanning 37 families, with several taxa recurring across counties or appearing prominently within particular localities. Behavioral experiments in semi-field sticky-trap assays found that five field-associated plant taxa were significantly attractive relative to blank controls, indicating that taxa associated with mosquitoes in nature can also function as attractive cues under semi-field conditions. GC-MS analyses of headspace collections from 42 plant taxa detected 211 volatile compounds and revealed substantial variation in both total emission rate and odor composition among taxa. Although several compounds, including -pinene, limonene, 4-ethylacetophenone, 2-ethyl-1-hexanol, 4-ethylbenzaldehyde, and caryophyllene, were broadly distributed across plant groups, volatile profiles differed significantly among taxa and shared compounds often occurred at markedly different proportional abundances. The five behaviorally tested taxa likewise showed both overlap and divergence, sharing 17 compounds across all five taxa while differing in dominant constituents and total emissions. Together, these results show that Ae. aegypti interacts with a diverse set of plants in the field, and suggests nectar-seeking is shaped not simply by plant identity or total odor abundance, but by the composition and proportional structure of plant odors.

O_LIDNA barcoding of the mitochondrial cytochrome c oxidase I (COI) gene is widely used to characterise insect diversity and distributions; however, its potential to reveal information on species interactions, including host-symbiont associations, remains largely unexplored. Here, we assess whether COI amplicon data can be used to identify Wolbachia - one of the most widely distributed bacterial symbionts known to profoundly affect their hosts biology. C_LIO_LIWe demonstrate that several commonly used invertebrate COI primer sets perfectly match many reference Wolbachia genomes, leading to frequent co-amplification. C_LIO_LIBy screening 7,901 individual-insect COI amplicon libraries obtained with the popular BF3-BR2 primer set, we detected Wolbachia sequences in over 35% of samples, revealing that co-amplification is indeed widespread. After removing low-abundance reads, Wolbachia detection based on COI amplicons showed over 90% agreement with simultaneously generated 16S-V4 rRNA amplicon data from the same specimens. The degree of agreement, however, varied depending on the thresholds used, among datasets and insect clades. C_LIO_LIFurther, we show that Wolbachia abundance inferred from COI amplicons correlated with their abundance in metagenomic datasets for 152 specimens, supporting the quantitative relevance of the signal. C_LIO_LIFinally, we find that Wolbachia COI sequences provide greater phylogenetic resolution than 16S-V4 rRNA data (mean pairwise genetic distance of COI sequences - 9.6%, 16S-V4 rRNA - 2.8%), and the reconstructed Wolbachia COI-based genotype network largely agrees with genome-based phylogenies. C_LIO_LICollectively, our results demonstrate that off-target Wolbachia sequences recovered from standard insect COI barcoding data may reliably detect symbiont presence, provide phylogenetic insight, and guide sample selection for metagenomics. Given the rapid expansion of global insect barcoding initiatives, these findings highlight an opportunity for cost-effective monitoring of their most prevalent bacterial symbionts, offering new perspectives on how host-microbe interactions may shape insect communities. C_LI

Wolbachia is an incredibly widespread maternally transmitted bacterium in arthropods that can alter host physiology, nutrition, reproduction, and immunity. In some cases, multiple Wolbachia strains infect the same host and are stably transmitted alongside each other. This raises the question of how multiple intracellular symbionts interact with each another and with the host to ensure stable transmission. Here, we use fluorescence in situ hybridizations and confocal microscopy to investigate co-transmission in a naturally occurring co-infection of two Wolbachia strains in Drosophila simulans: wHa and wNo. We find significant differences in spatial occupancy and abundance between the co-transmitted strains across stages of oogenesis and embryogenesis. We show that wHa and wNo have biases for different niches during oogenesis, and their strain-specific abundance is driven by egg chamber development, mating status, and their interaction. After differential curing of the co-infection, we find that wNo is dependent on wHa for vertical transmission, but not vice versa. Additionally, while wHa localization patterns are unchanged by loss of co-infection, abundance of wHa in the ovaries increases when wNo is removed. Understanding how symbiont co-infections achieve stability has important implications for the ongoing use of Wolbachia as a tool for insect management programs, but also for our understanding of the ecology of intracellular communities more broadly.

BackgroundHerpesviruses are a group of double-stranded DNA viruses known to infect a wide range of vertebrates and establish life-long latent infections. While bats serve as natural reservoir hosts for numerous viral families, relatively few bat herpesviruses have been successfully isolated. In this study, we report the isolation and characterization of two novel alphaherpesvirus strains obtained from Rousettus aegyptiacus bats in Coastal Kenya. MethodsThe samples of oral and rectal swabs were collected from three different species of bats from coastal Kenya between October 2024 and April 2025; the bat species collected include Hipposideros spp., Coleura afra, and Rousettus aegyptiacus. Virus isolation was performed by inoculation of samples in Vero E6 cells and subsequent monitoring for cytopathic effects (CPE). Total nucleic acids were extracted from CPE positive cultures and subjected to library preparation to enable unbiased detection of both RNA and DNA viruses. The libraries were sequenced using next-generation sequencing with Illumina MiSeq platform. Subsequently, bioinformatic analysis was carried out to identify the virus, generate consensus genomes as well as phylogenetic analysis to determine the placement of identified viruses. ResultsTwo samples from R. aegyptiacus (KIK_460_O and KIK_465_O) induced typical CPE within five days. Sequencing and assembly yielded partial consensus sequences of approximately 60 kb (KIK_460_O) and 70 kb (KIK_465_O), representing extended genomic data for a bat-associated alphaherpesvirus. This virus has a genome of about 140kb, indicating that our partial assemblies account for about 43-50% of the total genome. Both isolates were found to be closely related to Dzifa herpesvirus, an alphaherpesvirus previously identified in Kilifi, Kenya. Alphaherpesvirus was identified based on partial sequencing of UL19 (3,787bp) and UL30 (2,846bp) genes. The two isolates were found to be identical at the UL19 gene, showing that they belonged to the same virus strain. Phylogenetic analysis showed that the novel alphaherpesvirus belongs to primate alphaherpesviruses under the subfamily Alphaherpesvirinae. ConclusionThis study reports the isolation and genomic characterization of a novel fruit bat alphaherpesvirus from Kenyan Rousettus aegyptiacus bats. The partial genome assembly (60-70 kb) represent the first extended genomic data for this virus, covering approximately 43-50% of the estimated 140 kb complete genome. The phylogenetic placement of this alphaherpesvirus near primate viruses, especially Pteropodid alphaherpesvirus 1, suggests bat-association and needs further investigation into its zoonotic potential.

BackgroundSynonymous mutations, once considered neutral, can affect translation efficiency through mRNA folding and splicing, generating codon usage bias. This bias is often linked to genomic GC content, which also influences gene regulation. In the parasitoid wasp Lysiphlebus fabarum, GC content was previously shown to shift between developmental stages, with larvae showing higher GC than adults. Whether this phenomenon is widespread among insects remains unknown. ResultsTranscriptomic data from six insect species spanning Diptera, Hymenoptera, and Lepidoptera was used to compare GC content between expressed genes in larvae and adults. In five species, larval transcripts exhibited higher GC content than adult transcripts. Differential expression analysis revealed that stage-biased genes displayed consistent GC shifts, and orthologous gene families with representatives across species showed particularly GC-rich larval-biased genes in Hymenoptera and Diptera. At the genome scale, modeling in 317 insect species demonstrated an association between parasitic lifestyle and reduced mean GC content in Hymenoptera and Diptera, providing a possible ecological explanation for AT-rich genomes. ConclusionsOur results show that GC content is dynamic across developmental stages, independent of overall genome composition. Stage-specific GC enrichment may reflect adaptive codon usage optimizing translation during energetically demanding life-history stages such as larval development. Furthermore, the association between parasitism and reduced genomic GC highlights how ecological lifestyle might with genome content and evolution. Lastly, this work identifies candidate genes underlying stage-specific GC bias and provides new insights into the interplay between molecular evolution, development, and parasitic adaptation in insects.

The vine mealybug, Planococcus ficus, is a globally invasive pest of grapevine and a vector of leafroll viruses. Like other mealybugs, it reproduces through paternal genome elimination, a sex-determination system that operates without sex chromosomes and is associated with extreme sexual dimorphism. To characterize genome organization and sex-biased expression in this species, we generated a long-read reference genome spanning 369 Mb with 23,489 annotated genes and macrosynteny conserved with the citrus mealybug, Planococcus citri. Resequencing of four California field individuals yielded a first whole-genome estimate of nucleotide diversity and 132 microsatellite markers for population monitoring. Among 2,129 candidate secreted proteins, a conserved core is shared with P. citri, but each species carries a distinct set of lineage-specific effectors. Comparing adult male and female transcriptomes, we found sex-biased expression to be pervasive and skewed toward females: 41% of tested genes differed between the sexes, with female-biased genes both more numerous and showing larger fold changes. These female-biased genes were not randomly distributed but concentrated in discrete blocks of coordinately expressed, tandemly duplicated gene families, a pattern not previously described in a mealybug. Male- and female-biased secreted proteins also differed in origin, with male-biased proteins drawn from a conserved repertoire shared with P. citri and female-biased proteins spanning a more lineage-specific pool. Together, these results reveal a female-skewed, spatially clustered architecture of sex-biased expression in a mealybug that lacks sex chromosomes, and provide genomic resources for managing an invasive vineyard pest.

Free-living nematodes are among the most abundant animals on Earth and play critical ecological roles in soil ecosystems. However, the global population structure and evolutionary history of most species remain poorly understood. Here, we analyzed genome-wide variation in Oscheius tipulae using whole-genome sequence data from 31 isolates, including 28 publicly available genomes and three newly collected strains from Korea. Population structure analyses, phylogenomic inference, and ancestry estimation consistently identified three deeply divergent lineages. These analyses did not detect admixture among lineages and collectively supported a predominantly tree-like evolutionary history. Notably, the lineages were structured by latitude rather than geographic proximity. Isolates from similar latitudinal zones clustered together regardless of continental origin, forming three major groups: northern mid-latitude (NML), low-latitude (LL), and southern mid-latitude (SML). This pattern indicates that the lineages have maintained largely independent evolutionary trajectories over extended timescales despite the potential for long-distance dispersal. Furthermore, environmentally associated variants showed significant differentiation among lineages, indicating that environmental selection may contribute to the maintenance of this latitudinally structured diversity. Our results reveal unexpectedly deep global divergence within O. tipulae, and highlight the importance of ecological divergence and long-term lineage retention in shaping the global diversity of this group.

Nutritional symbionts can be essential for their animal hosts. The bacterial symbiont of the leaffooted bug, Leptoglossus zonatus, Caballeronia, is acquired from the environment each generation in the 2nd instar. The symbiont is critical for L. zonatus: aposymbiotic bugs are unable to reproduce. We hypothesized that symbiotic bugs excrete Caballeronia where juveniles might find and consume them. We inoculated L. zonatus with GFP-labelled Caballeronia and examined feces of each life stage. We found that Caballeronia is excreted almost exclusively in the adult stage. We then asked if 2nd instar nymphs could acquire Caballeronia from feces. Nymphs were provided with a) feces from adults fed GFP-labelled Caballeronia, b) GFP-Caballeronia in culture, or c) water only. We found that feces-fed bugs had similar rates of symbiont acquisition to those fed Caballeronia in culture, indicating that feces can be a source of Caballeronia for L. zonatus. However, compared to culture fed individuals, bugs fed feces had reduced survivorship and required longer to develop, and surviving adults had reduced mass. Bacterial motility assays showed that in contrast to cultured Caballeronia cells, Caballeronia in feces were non-motile. These results show suggest that feces can be a source of Caballeronia, at least in some environments, however transmission mode can influence success of the offspring.

Drosophila RNA viruses often persist in wild and lab populations, yet their tissue and cellular tropism is poorly understood. In the Fly Cell Atlas (a comprehensive Drosophila single-nucleus transcriptome) data, we detected four RNA virus infections: Nora virus, Drosophila A virus, Drosophila C virus, and Newfield virus. Nora and Drosophila A virus were the most abundant and widespread across tissues and cell types, while Drosophila C virus and Newfield virus RNA transcript were only found in oenocyte and fat body tissues. We found transcriptional changes associated with viral infection in canonical viral immunity genes (e.g. Vago, vir-1). Additionally, we observed that during persistent viral infections, transposable element (TE) transcripts were upregulated in somatic cells. TEs are traditionally associated with the germline, but recent studies and our data suggest they are also expressed in somatic cells. Using the Fly Cell Atlas data, we found that distinct somatic cell types express specific TE subtypes, indicating regulated and cell-type specific TE activity often overlooked in transcriptomic studies. We present Fly Viral Atlas (https://flyviralatlas.shinyapps.io/home/), a single-nucleus level atlas of RNA viruses and TE expressions in Drosophila, providing new insights into viral tropism and TE dynamics across cell types and tissues.

Xylosandrus crassiusculus (Motschulsky), the granulate ambrosia beetle, was one of the first highly-destructive ambrosia beetles introduced into the southern U.S in the 1970s where it was found in South Carolina (Kovach 1986). The Redbay ambrosia beetle, Xyleborus glabratus Eichhoff, was first detected in the U.S. in South Georgia in 2002. This beetle and its associated fungi, the laurel wilt fungus Raffaelea laurelensis and others have caused substantial destruction to native redbay (Persea borbonia) in GA, SC, FL and elsewhere. This beetle-pathogen complex also poses a threat to commercial avocado production in the U.S., Central and South America as well as to valuable other Persea spp. and related plants (Laureacea) that are known hosts. As an addition here, 10 years of the spring appearances (Fig.1) of X. crassiusculus in North Florida is offered for future comparisons. A second unusual appearance is the finding and working with UV mulch and ethanol, as a surprising attraction of X. crassiusculus and other ambrosia beetles including X. glabratus. It was also found that the ambrosia beetles do not respond to yellow and green as expected by most. Also, adding burlap was found to be attractive (increases dead and dying appearing trees) as is silver metallic like UV mulch, while camouflage (camo) was found to work like yellow and green. These occurrences led to the invention and development of UV mulch with new traps to better monitor ambrosia beetles. New traps led to new uses for yellow, green and camo to monitor and decrease damage and losses from ambrosia beetles. The data are presented as evaluated and appear in the figures, discussion and a supplemental section. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=139 SRC="FIGDIR/small/733798v1_fig1.gif" ALT="Figure 1"> View larger version (30K): org.highwire.dtl.DTLVardef@1006101org.highwire.dtl.DTLVardef@1e0a3d6org.highwire.dtl.DTLVardef@1244d1borg.highwire.dtl.DTLVardef@423cb7_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOFigure 1:C_FLOATNO Relative timing of annual emergence of Xylosandrus crassiusculus in north Florida. Collected over 10 years using 5 Baker traps with a 10% ethanol/water solution. Data are from years as marked. Note: data from year 2003 was not collected. C_FIG

Segregated variation between populations is a fundamental evolutionary process leading to parasite specialization, yet the resulting impacts on infection heterogeneity within populations are theoretically and empirically understudied. We asked whether the distribution of host susceptibility to infection within populations carries the signatures of geographic structure from pathogen local adaptation, maladaptation, or generalism in a nuclear polyhedrosis virus that infects the Gulf Fritillary butterfly Dione vanillae. For this virus, there is genetic support for two geographically distinct groups within San Diego County, based on whole genome sequencing of 16 virus isolates. Reciprocal laboratory infections showed evidence of two contrasting viral life history strategies: a generalist phenotype that consistently infected variable hosts and a specialist that performed slightly better in its local host population. As predicted by our theoretical model, the more consistent infection displayed by the generalist across populations corresponded to lower heterogeneity in susceptibility within populations, modeled as gamma distribution. Furthermore, the generalist phenotype was collected over a wider geographic range despite having a tenfold-lower mean infection rate than the specialist, suggesting that a strategy of more consistent infection provides key fitness advantages across diverse host populations. Intriguingly, when there is variation in host susceptibility, interpretations of pathogen local adaptation are dose-dependent. Measuring infectivity across multiple doses enables estimation of the whole distribution of susceptibility, which provides more reliable identification of pathogen specialization to its local host. Our work demonstrates how trait distributions and not only their mean values can carry quantifiable signatures of eco-evolutionary processes in interspecific interactions.

BackgroundWest Nile virus (WNV) is a vector-borne zoonotic pathogen maintained in an enzootic cycle between birds and mosquitoes which is considered a significant public health concern in Europe, particularly in relation to its recent increase in reported human cases and range expansion. While a comprehensive understanding of the viruss epidemiological dynamics is essential to inform effective prevention and control strategies, to date significant knowledge gaps remain in quantifying interspecific differences within the complex avian communities involved in WNV circulation. Globally, WNV-infection has indeed been documented across more than 300 bird species, however, whether and how inter-specific differences in avian hosts traits affect the spread of WNV is still largely unknown. A substantial body of research has investigated how epidemiological traits, such as the duration of infection and competence, influence WNV dynamics. However, much less is known about the role of avian demography. Methodology/Principal findingsWe therefore investigated through mathematical modelling the role of avian demographic traits in shaping patterns of mosquito WNV infection dynamics in northern Italy (Lombardy Region, 2016-2018). We focused on the effects of annual offspring production, timing and synchrony of breeding which ultimately affect seasonal abundance of competent avian hosts. We highlighted that timing of breeding has the greatest effect on the number of infected mosquitoes, while annual offspring production influences the timing of the infection peak. Our simulations provide evidence that non-corvid species can have a key impact on WNV transmission. Conclusion/SignificanceThese results can support future research by providing priority bird species to direct further studies and by suggesting that the acknowledgment of spatio-temporal variation in the abundance of competent avian hosts plays a key role in the development of effective surveillance strategies and mosquito control actions. Author summaryWest Nile virus (WNV) is endemic in Italy and represents a significant public health threat in Europe, with increasing cases of severe neuroinvasive disease in humans in recent years. Surveillance data reveal marked spatial and temporal variability in infection dynamics, suggesting that key drivers of WNV transmission remain poorly understood. The contribution of different bird species (over 300 are implicated in the WNV cycle) is often overlooked despite evidence that species-specific traits are critical determinants of WNV infection dynamics. Few studies have examined birds demographic traits, despite their well-established importance in shaping infection dynamics across diseases. Given the challenges in collecting detailed wildlife data, we employed mechanistic models to explore transmission scenarios and test whether avian demographic traits influence bird species roles in WNV transmission and maintenance in Lombardy. Our findings demonstrate that brood size, hatching synchrony, and hatching time significantly affect estimated WNV prevalence in mosquitoes.