Host Reproduction Research Articles

Composition and diversity of the gut microbiota across different life stages of American cockroach (Periplaneta americana).

Periplaneta americana, one of the most widely distributed insects all over the world, can survive and reproduce in harsh environment which may be closely related to the critical roles of intestinal microorganisms in its multiple physiological functions. However, the composition and structure of gut microbiota throughout different life stages and its effects on the strong resilient and environmental adaptability of P. americana remain unclear. In this study, the gut microbiota across life stages including ootheca (embryos), nymph and adult of P. americana were investigated by 16S rRNA high-throughput sequencing. Multivariate statistical analysis showed the richness and diversity of bacterial communities were significantly different among ootheca, nymph and adult stage of P. americana. Taxonomic analysis showed Blattabacterium was the dominant genus in bacterial community of ootheca while the nutrient absorption-related genera including Christensenellaceae and Ruminococcaceae showed high relative abundance in nymph samples. Moreover, functional prediction analysis showed the metabolic categories in ootheca might have more influence on the basic life activities of the host than improved production and viability, while it was more associated to the society activities, reproduction and development of host in nymph and adult. It was suggested that the gut microbiota in each life stage might meet the requirements for environmental adaptability and survival of P. americana via transforming the composition and structure with specific metabolic capabilities. Overall, these results provided a novel sight to better understand the strong vitality and adaptability throughout life stages of P. americana.

The rediscovery of the putative ant social parasite Manica parasitica syn. nov. (Hymenoptera: Formicidae) reveals an unexpected endoparasite syndrome.

Parasitism is ubiquitous across the tree of life, and parasites comprise approximately half of all animal species. Social insect colonies attract many pathogens, endo- and ectoparasites, and are exploited by social parasites, which usurp the social environment of their hosts for survival and reproduction. Exploitation by parasites and pathogens versus social parasites may cause similar behavioural and morphological modifications of the host. Ants possess two overlapping syndromes: the endo- and social parasite syndromes. We rediscovered two populations of the putative social parasite Manica parasitica in the Sierra Nevada, and tested the hypothesis that M. parasitica is an independently evolving social parasite. We evaluated traits used to discriminate M. parasitica from its host Manica bradleyi, and examined the morphology of M. parasitica in the context of ant parasitic syndromes. We find that M. parasitica is not a social parasite. Instead, M. parasitica represents cestode-infected M. bradleyi. We propose that M. parasitica should be regarded as a junior synonym of M. bradleyi. Our results emphasize that an integrative approach is essential for unravelling the complex life histories of social insects and their symbionts.

The nematode tapeworm: rediscovery of the bizarre parasite of nematodes, Spirogyromyces vermicola Tzean & Barron (Fungi, incertae sedis) in northeastern Mexico

We report the second world observation of the bizarre nematode-parasitic fungus-like organism, Spirogyromyces vermicola, from forest soil at Saltillo, Mexico. It is a benign parasite of nematodes that fills their intestine. Its phylogenetic position remains a mystery, but its morphology and development are reminiscent of Harpellales and Orphellales in the Kickxellomycotina. Spirogyromyces was cultivated in vivo in the original host (Rhabditis) and in Caenorhabditis elegans. Spirogyromyces proliferated in both hosts, and it did not appear to affect significantly health, reproduction, or numbers of hosts. The rediscovery of Spirogyromyces will highlight its potential in the study of parasitic systems in nematodes, including Caenorhabditis research.

Reconciling contrasting effects of nitrogen on host immunity and pathogen transmission using stoichiometric models.

Hosts rely on the availability of nutrients for growth, and for defense against pathogens. At the same time, changes in host nutrition can alter the dynamics of pathogens that rely on their host for reproduction. For primary producer hosts, enhanced nutrient loads may increase host biomass or pathogen reproduction, promoting faster density-dependent pathogen transmission. However, the effect of elevated nutrients may be reduced if hosts allocate a growth-limiting nutrient to pathogen defense. In canonical disease models, transmission is not a function of nutrient availability. Yet, including nutrient availability is necessary to mechanistically understand the response of infection to changes in the environment. Here, we explore the implications of nutrient-mediated pathogen infectivity and host immunity on infection outcomes. We developed a stoichiometric disease model that explicitly integrates the contrasting dependencies of pathogen infectivity and host immunity on nitrogen (N) and parameterized it for an algal-host system. Our findings reveal dynamic shifts in host biomass build-up, pathogen prevalence, and the force of infection along N supply gradients with N-mediated host infectivity and immunity, compared with a model in which the transmission rate was fixed. We show contrasting responses in pathogen performance with increasing N supply between N-mediated infectivity and N-mediated immunity, revealing an optimum for pathogen transmission at intermediate N supply. This was caused by N limitation of the pathogen at a low N supply and by pathogen suppression via enhanced host immunity at a high N supply. By integrating both nutrient-mediated pathogen infectivity and host immunity into a stoichiometric model, we provide a theoretical framework that is a first step in reconciling the contrasting role nutrients can have on host-pathogen dynamics.

16S rRNA gene-based meta-analysis of the reptile gut microbiota reveals environmental effects, host influences and a limited core microbiota.

An animal's gut microbiota plays an important role in host health, reproduction and digestion. However, many studies focus on only a few individuals or a single species, limiting our ability to recognize emergent patterns across a wider taxonomic grouping. Here, we compiled and reanalysed published 16S rRNA gene sequence data for 745 gut microbiota samples from 91 reptile species using a uniform bioinformatics pipeline to draw broader conclusions about the taxonomy of the reptile gut microbiota and the forces shaping it. Our meta-analysis revealed the significant differences in alpha- and beta-diversity across host order, environment, diet, habitat and conservation status, with host diet and order contributing the most to these differences. We identified the principal bacterial phyla present in the reptile gut microbiota as Bacteroidota, Proteobacteria (mostly Gamma class), and Firmicutes, and detected the bacterial genus Bacteroides in most reptile individuals, thus representing a putative 'core' microbiota. Our study provides novel insights into key drivers of the reptile gut microbiota, highlights existing knowledge gaps and lays the groundwork for future research on these fascinating hosts and their associated microbes.

Regulation and remodeling of microbial symbiosis in insect metamorphosis

Many insects are dependent on microbial mutualists, which are often harbored in specialized symbiotic organs. Upon metamorphosis, insect organs are drastically reorganized. What mechanism regulates the remodeling of the symbiotic organ upon metamorphosis? How does it affect the microbial symbiont therein? Here, we addressed these fundamental issues of symbiosis by experimentally manipulating insect metamorphosis. The stinkbug Plautia stali possesses a midgut symbiotic organ wherein an essential bacterial symbiont resides. By RNAi of master regulator genes for metamorphosis, Kr-h1 over nymphal traits and E93 over adult traits, we generated precocious adults and supernumerary nymphs of P. stali, thereby disentangling the effects of metamorphosis, growth level, developmental stage, and other factors on the symbiotic system. Upon metamorphosis, the symbiotic organ of P. stali was transformed from nymph type to adult type. The supernumerary nymphs and the precocious adults, respectively, developed nymph-type and adult-type symbiotic organs not only morphologically but also transcriptomically, uncovering that metamorphic remodeling of the symbiotic organ is under the control of the MEKRE93 pathway. Transcriptomic, cytological, and biochemical analyses unveiled that the structural and transcriptomic remodeling of the symbiotic organ toward adult emergence underpins its functional extension to food digestion in addition to the original role of symbiont retention for essential nutrient production. Notably, we found that the symbiotic bacteria in the adult-type symbiotic organ up-regulated genes for production of sulfur-containing essential amino acids, methionine and cysteine, that are rich in eggs and sperm, uncovering adult-specific symbiont functioning for host reproduction and highlighting intricate host-symbiont interactions associated with insect metamorphosis.

Does the corn leafhopper Dalbulus maidis (DeLong & Wolcott) (Hemiptera: Cicadellidae) reproduce in hosts other than maize?

The corn leafhopper Dalbulus maidis (DeLong & Wolcott) (Hemiptera: Cicadellidae) is a specialist insect vector of the corn stunting disease complex. This leafhopper has been reported from different overwintering plants, and more information is required regarding other potential Brazilian plants that may serve as reproductive hosts for this specie. The present study aimed to evaluate possible plants for leafhopper reproduction usually found near the maize fields and the D. maidis reproductive differences among maize genotypes. Three trials were conducted to assess D. maidis survival and oviposition on different maize genotypes and other potential host plants. Survival, nymph presence, oviposition, and nymph eclosion rates were observed. No nymphs were observed in plants other than maize. The number of D. maidis adults was influenced by the different maize inbreds, and the mean number of laid eggs varied across the tested maize materials. Oviposition and nymph emergence was observed in pearl millet [Pennisetum glaucum (L.) R. Br., Poaceae] when D. maidis adults were offered only this plant as substrate, although significantly lower than those recorded on maize. Our results suggest that eliminating maize plants in the off-season could be used as a tool to reduce D. maidis reproduction, thereby minimizing the vector population size in the following season.

Bacterial Communities of the Internal Reproductive and Digestive Tracts of Virgin and Mated Tuta absoluta.

Microorganisms can affect host reproduction, defense, and immunity through sexual or opportunistic transmission; however, there are few studies on insect reproductive organs and intestinal bacterial communities and their effects on mating. Tuta absoluta is a worldwide quarantine pest that seriously threatens the production of Solanaceae crops, and the microbial community within tomato leafminers remains unclear. In this study, 16s rRNA sequencing was used to analyze bacterial communities related to the reproductive organs and intestinal tracts of tomato leafminers (the sample accession numbers are from CNS0856533 to CNS0856577). Different bacterial communities were found in the reproductive organs and intestinal tracts of females and males. Community ecological analysis revealed three potential signs of bacterial sexual transmission: (1) Mating increased the similarity between male and female sex organs and intestinal communities. (2) The bacteria carried by mated individuals were found in unmated individuals of the opposite sex but not in unmated individuals of the same sex. (3) The bacteria carried by unmated individuals were lost after mating. In addition, the abundances of bacterial communities carried by eggs were significantly higher than those of adult worms. Our results confirm that mating leads to the transfer of bacterial communities in the reproductive organs and gut of tomato leafminers, and suggest that this community strongly influences the reproductive process.

Tetracycline inhibits tick host reproduction by modulating bacterial microbiota, gene expression and metabolism levels.

Ticks are disease vectors that are a matter of worldwide concern. Antibiotic treatments have been used to explore the interactions between ticks and their symbiotic microorganisms. In addition to altering the host microbial community, antibiotics can have toxic effects on the host. In the tick Haemaphysalis longicornis, engorged females showed reproductive disruption after microinjection of tetracycline. Multi-omics approaches were implemented to unravel the mechanisms of tick reproductive inhibition in this study. There were no significant changes in bacterial density in the whole ticks on Day (D)2 or D4 after tetracycline treatment, whereas the bacterial microbial community was significantly altered, especially on D4. The relative abundances of the bacteria Staphylococcus, Bacillus and Pseudomonas decreased after tetracycline treatment, whereas the relative abundances of Coxiella and Rhodococcus increased. Ovarian transcriptional analysis revealed a cumulative effect of tetracycline treatment, as there was a significant increase in the number of differentially expressed genes with treatment time and a higher number of downregulated genes. The tick physiological pathways including lysosome, extracellular matrix (ECM)-receptor interaction, biosynthesis of ubiquinone and other terpenoids-quinones, insect hormone biosynthesis, and focal adhesion were significantly inhibited after 4 days of tetracycline treatment. Metabolite levels were altered after tetracycline treatment and the differences increased with treatment time. The differential metabolites were involved in a variety of physiological pathways; the downregulated metabolites were significantly enriched in the nicotinate and nicotinamide metabolism, galactose metabolism, and ether lipid metabolism pathways. These findings indicate that tetracycline inhibits tick reproduction through the regulation of tick bacterial communities, gene expression and metabolic levels. The results may provide new strategies for tick control. © 2023 Society of Chemical Industry.

Cytoplasmic incompatibility and female fecundity associated with Wolbachia infection in a cricket species

Abstract Wolbachia is a maternally inherited endosymbiont of the phylum α‐Proteobacteria that is found widely in arthropods and nematodes. Cytoplasmic incompatibility (CI) is the commonest endosymbiotic manipulation among arthropods, namely reduced embryo viability when Wolbachia‐infected males fertilize Wolbachia‐uninfected females. In this study, endosymbiont infection was investigated and crossing experiments were performed in the wing‐dimorphic cricket Velarifictorus aspersus (Walker) (Orthoptera: Gryllidae) to clarify the effects of Wolbachia on host reproduction. All the tested individuals were infected with two Wolbachia strains, wAsp‐a and wAsp‐f, which belong to supergroup A and supergroup F, respectively. There were no obvious differences in the duration of nymph development or the proportions of females between the Wolbachia‐infected and Wolbachia‐free lines. However, crossing Wolbachia‐infected males with uninfected females reduced the hatching rate by 28% compared with that when infected males were crossed with infected females. The number of eggs laid by Wolbachia‐free females was significantly lower than laid by infected females, either mating with infected males or uninfected males. These results suggest that Wolbachia induced incomplete CI and enhanced female fertility in V. aspersus. Because no homologous cifA and cifB genes, which are involved in CI, were found in supergroups C, D and F, it might be considered that the CI of V. aspersus was induced by strain wAsp‐a of supergroup A. Moreover, the significant increase in the density of wAsp‐a Wolbachia with nymph development might be related to the regulation of CI.

Coevolutionary stability of host-symbiont systems with mixed-mode transmission

The coevolution of hosts and symbionts based on virulence and mode of transmission is a complex and diverse biological phenomenon. We introduced a conceptual model to study the stable coexistence and coevolution of an obligate symbiont (mutualist or parasite) with mixed-mode transmission and its host. Using an age-structured Leslie model for the host, we demonstrated how the obligate symbiont could modify the host’s life history traits (survival and fecundity) and the long-term growth rate of the infected lineage. When the symbiont is vertically transmitted, we found that the host and its symbiont could maximize the infected lineage’s evolutionary success (multi-level selection). Our model showed that symbionts’ effect on host longevity and reproduction might differ, even be opposing, and their net effect might often be counterintuitive. The evolutionary stability of the ecologically stable coexistence was analyzed in the framework of coevolutionary dynamics. Moreover, we found conditions for the ecological and evolutionary stability of the resident host-symbiont pair, which does not allow invasion by rare mutants (each mutant dies out by ecological selection). We concluded that, within the context of our simplified model conditions, a host-symbiont system with mixed-mode transmission is evolutionarily stable unconditionally only if the host can maximize the Malthusian parameters of the infected and non-infected lineages using the same strategy. Finally, we performed a game-theoretical analysis of our selection situation and compared two stability definitions.

New Hosts, Distribution, and Color Trap Preferences of the Invasive Thrips Scirtothrips dorsalis (Thysanoptera: Thripidae) in Mexico

Abstract Scirtothrips dorsalis Hood (Thysanoptera: Thripidae) is an insect of Asian origin and is currently distributed in several countries around the world. It has highly polyphagous habits and has been reported as a primary pest of different fruit, horticultural, and ornamental crops. This species was reported in Mexico in 2020, however, due to its invasive nature and its rapid adaptation to new ecosystems, it is probably present in other regions of the country. The lack of information on this pest has resulted in misidentifications and misdiagnosis at the field level by phytosanitary technicians. In the present work, we found that S. dorsalis is distributed in the states of Veracruz, Sinaloa, Jalisco, and Michoacán in Mexico occupying sites with different climates (warm and temperate) and elevations from 6 to 1,721 m above sea level. Plant reproductive hosts were blackberry (Rubus sp.), blueberry (Vaccinium sp.), Persian lime (Citrus latifolia Tanaka), mango (Mangifera indica L.), and pear (Pyrus communis L.). Through an evaluation of the response of adults toward chromatic traps, we found that this species greatly prefers yellow (×5.40) compared with blue color. More studies are needed on detection and control measures in order to reduce the distribution and economic impact caused by this insect pest in Mexico.

Changes in the gut bacterial community affect miRNA profiles in Riptortus pedestris under different rearing conditions

Insects possess complex and dynamic gut microbial system, which contributes to host nutrient absorption, reproduction, energy metabolism, and protection against stress. However, there are limited data on interactions of host-gut bacterial microbiota through miRNA (microRNA) regulation in a significant pest, Riptortus pedestris. Here, we performed the 16S rRNA amplicon sequencing and small RNA sequencing from the R. pedestris gut under three environmental conditions and antibiotic treatment, suggesting that we obtained a large amount of reads by assembly, filtration and quality control. The 16S rRNA amplicon sequencing results showed that the abundance and diversity of gut bacterial microbiota were significantly changed between antibiotic treatment and other groups, and they are involved in metabolism and biosynthesis-related function based on functional prediction. Furthermore, we identified different numbers of differentially expressed unigenes (DEGs) and differentially expressed miRNAs (DEMs) based on high-quality mappable reads, which were enriched in various immune-related pathways, including Toll-like receptor, RIG-I-like receptor, NOD-like receptor, JAK/STAT, PI3K/Akt, NF-κB, MAPK signaling pathways, and so forth, using GO and KEGG enrichment analysis. Later on, the identified miRNAs and their target genes in the R. pedestris gut were predicted and randomly selected to construct an interaction network. Finally, our study indicated that alterations in the gut bacterial microbiota are significantly positively or negatively associated with DEMs of the Toll/Imd signaling pathway with Pearson correlation analysis. Taken together, the results of our study lay the foundation for further deeply understanding the interactions between the gut microbiota and immune responses in R. pedestris through miRNA regulation, and provide the new basis for pest management in hemipteran pests.

Galls formed by Aceria genistae (Acari: Eriophyidae) alter reproduction of the invasive weed Scotch broom (Cytisus scoparius) in the USA

ABSTRACT The Scotch broom gall mite, Aceria genistae, is an adventive herbivore of Cytisus scoparius (Scotch broom), an invasive non-native shrub in California, USA. Although feeding by these mites clearly induces localised tissue distortion, the effect of A. genistae on overall host vigour and reproduction has not been assessed. Here we compare biomass allocation across various plant organs between two groups, heavily or lightly galled plants, at three northern California sites. Most structural components, including plant height, stem biomass, and leaf biomass, were similar regardless of galling intensity. However, both canopy volume and seeds per plant were reduced in heavily versus lightly galled plants; seeds were reduced up to 80% among larger plants. Collectively, these data suggest A. genistae galls are produced at the cost of seed production. Aceria genistae is a relatively new arrival in California but is already causing measurable effects to plant performance, which are expected to increase over time as mite populations increase and its range expands. Intentionally redistributing this mite is currently illegal in the USA, and this research is part of a broader investigation to inform the biological control agent permit process.

The effects of lotus-fish co-culture on the gut microbiome of Hefang crucian carp (Carassis auratus)

Gut microbiome plays an important role in host's development and reproduction. Lotus-fish co-culture (LFC) is a popular integrated agriculture–aquaculture farming system in China. However, there is still a relative dearth of information on how changes of aquaculture modes will affect the fish gut microbiome. In the present study, metagenomic sequencing was used to compare gut bacteria of the hybrid fish Hefang crucian carp (Carassius cuuieri ♀ × C. auratus var. red ♂) cultured in LFC and intensive pond culture (IPC) systems. The results indicated that aquaculture modes exerted great influences on the fish gut bacterial community. A significantly higher gut bacterial diversity was found in LFC than that in IPC (P < 0.05). The relative abundances of Actinobacteria and Chloroflexi were apparently higher in LFC than those in IPC, whereas Planctomycetota, Firmicutes, and Verrucomicrobia showed opposite patterns. Besides, gut bacterial metabolic potentials involved in energy metabolism, carbohydrate metabolism, amino acid metabolism, environmental information processing, and cellular processes were significantly increased in LFC compared to those in IPC. On the contrary, the bacterial functional potentials related to nucleotide metabolism, DNA mismatch repair, as well as homologous recombination were significantly stimulated in the IPC system. Source‐tracking analysis suggested that fish gut bacterial community in IPC was originated mainly from water sources, whereas the gut bacterial community in LFC was originated from more unknown sources and soil sources. Our results provided new insight into the influence of aquaculture modes on the microbial community diversity and functionality in aquatic animals and highlighted the importance of environment microbiome in reshaping the gut microbes.

Self-stabilization mechanism encoded by a bacterial toxin facilitates reproductive parasitism

A wide variety of maternally transmitted endosymbionts in insects are associated with reproductive parasitism, whereby they interfere with host reproduction to increase the ratio of infected females and spread within populations.1,2 Recent successes in identifying bacterial factors responsible for reproductive parasitism3,4,5,6,7 as well as further omics approaches8,9,10,11,12 have highlighted the common appearance of deubiquitinase domains, although their biological roles-in particular, how they link to distinct manipulative phenotypes-remain poorly defined. Spiroplasma poulsonii is a helical and motile bacterial endosymbiont of Drosophila,13,14 which selectively kills male progeny with a male-killing toxin Spaid (S.poulsonii androcidin), which encodes an ovarian tumor (OTU) deubiquitinase domain.6 Artificial expression of Spaid in flies reproduces male-killing-associated pathologies that include abnormal apoptosis and neural defects during embryogenesis6,15,16,17,18,19; moreover, it highly accumulates on the dosage-compensated male X chromosome,20 congruent with cellular defects such as the DNA damage/chromatin bridge breakage specifically induced upon that chromosome.6,21,22,23 Here, I show that without the function of OTU, Spaid is polyubiquitinated and degraded through the host ubiquitin-proteasome pathway, leading to the attenuation of male-killing activity as shown previously.6 Furthermore, I find that Spaid utilizes its OTU domain to deubiquitinate itself in an intermolecular manner. Collectively, the deubiquitinase domain of Spaid serves as a self-stabilization mechanism to facilitate male killing in flies, optimizing a molecular strategy of endosymbionts that enables the efficient manipulation of the host at a low energetic cost.

Priority host plants of the Queensland fruit fly, Bactrocera tryoni (Froggatt), based on the host reproduction number for tephritid management, surveillance and trade

The Host Reproduction Number (HRN) is a measure of the number of adult fruit flies that can emerge from one kilogram of fruit. HRN is a useful tool in surveillance, management and trade. I reviewed the literature for Queensland fruit fly (Qfly) and found data on 297 hosts. There were 81 Qfly hosts with HRN data and 216 Qfly hosts with no HRN data. The HRN will help to inform and triage hosts for target surveillance and management programs. Additionally, HRN will inform disinfestation activities pertaining to incursion response management, risk mitigation and trade options. There is a need for scientists to report HRN in a consistent manner so that Qfly management programs and trade protocols might be optimised.

“Till death do us apart”: The common destiny of brown hare and its parasite community

Although parasites may threaten individual hosts' survival and reproduction, their role as an essential part of ecosystem functioning and biodiversity has been recognized. In Northern Italy, the hare population has evidently declined since 2008.This paper aims to assess the relationship between host demographic trends and helminth parasite community diversity in a two-year survey in Northern Italy to evaluate the impact of parasites on hosts and confirm the hypothesis that endangered host populations are poor in parasites.In 2013 and 2015 the viscera of 54 and 61 hares legally hunted in agro-ecosystems of the Po Plain were collected. This area is characterized by heavy anthropic pressure: more than 60% of the landscape is represented by agricultural or urbanized territories.No intestinal cestodes were detected. Trichuris sp. and Micipsella numidica were collected in 2015 only; Trichostrongylus retortaeformis, Taenia pisiformis cysticercosis and bronchopulmonary lesions caused by small strongyles were observed in both years. The richness and evenness appeared increased in the second year of the survey, although lower than those obtained by literature data from similar populations examined in the last two decades of 1900.The dominant helminth, T. retortaeformis, was more abundant in individuals with higher weight, while pathological findings were mostly unrelated to this nematode infection; this is consistent with a reduced action, even no harm, of the parasites on the individual host or population level.Our results suggest that the conservation of hosts, environment, and parasites cannot be achieved separately and that parasites and wildlife hosts' destinies are intimately linked, confirming the complexity of ecosystems and the need to contemplate parasite biodiversity in conservation strategies.

Phenotypic plasticity in an egg parasitoid affects olfactory response to odors from the plant–host complex

Female egg parasitoids must optimize their ability to find a suitable host for reproduction in a limited foraging time. Odorant cues associated with the plant–host complex play an essential role in guiding females toward the host. However, parasitoid response is not always identical within the same genotype, and it could be influenced by the environment. This phenotypic plasticity affects parasitoid behavior and morphology and is directly linked to rearing conditions. Yet, how plasticity influences olfactory responses of egg parasitoids toward plant–host odors is largely unexplored. Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae) is an effective biocontrol agent of the invasive brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae). Laboratory no-choice and choice tests showed T. japonicus potential to develop in eggs of non-target Pentatomidae. In Y-tube olfactometer we evaluated the olfactory responses of T. japonicus reared on different hosts toward plant–host derived volatiles associated with H. halys and two other stink bug species. Parasitoids reared on the main host H. halys positively responded only to odors from V. faba–H. halys complex. When reared on alternative hosts, T. japonicus was smaller and did not exhibit attraction to any stimuli, although egg load was only partially affected. Host-induced phenotypic plasticity should be considered when evaluating parasitoids for classical biological control.

Environmental microbes promote phenotypic plasticity in reproduction and sleep behaviour.

The microbiome has been hypothesized as a driving force of phenotypic variation in host organisms that is capable of extending metabolic processes, altering development and in some cases, conferring novel functions that are critical for survival. Only a few studies have directly shown a causal role for the environmental microbiome in altering host phenotypic features. To assess the extent to which environmental microbes induce variation in host life-history traits and behaviour, we inoculated axenic Drosophila melanogaster with microbes isolated from drosophilid populations collected from two different field sites and generated two populations with distinct bacterial and fungal profiles. We show that microbes isolated from environmental sites with modest abiotic differences induce large variation in host reproduction, fatty acid levels, stress tolerance and sleep behaviour. Importantly, clearing microbes from each experimental population removed the phenotypic differences. The results support the causal role of environmental microbes as drivers of host phenotypic plasticity and potentially, rapid adaptation and evolution.