Biology subjects

Hance, T.

Publications and source records attributed to Hance, T..

9 recordsLinked to original sources

bioRxiv2026

The two-component microbial system of the black soldier fly larvae (BSFL) gut: a plastic microbiota in the midgut, but a stable one in the hindgut

Due to their highly polyphagous capacities, black soldier fly (Hermetia illucens) larvae (BSFL) are increasingly valued for their ability to convert organic waste into valuable biomass that can be used for a variety of purposes. These remarkable digestive capabilities are highly dependent on an extremely plastic gut microbiota. However, the distribution and functioning of bacterial communities in the various gut compartments - particularly in the hindgut - remain little understood. In this study, we used a metabarcoding approach based on 16S gene sequencing to investigate the effect of three carbohydrate-rich diets with distinct molecular compositions on the functional diversity of the BSFL gut microbiota. Our results showed that the midgut harbors a highly substrate-sensitive microbiota, with a high abundance of Actinomyces spp., regardless of the substrate. A bacterial diversity oriented toward fatty acid biosynthesis pathways is promoted by starch-rich environment, whereas a lignocellulosic substrate fosters a midgut microbiota dominated by Paenibacillus spp. In contrast, the hindgut exhibits a distinctly stable and homogeneous bacterial composition dominated by Dysgonomonas spp. Overall, our results provide clear evidence of a two-compartment microbial system, in which the midgut primarily serves as a substrate-adaptive primary degradation chamber, while the hindgut functions as a stable terminal compartment for the final processing of residual substrates and the recycling of nutrients. These findings contribute to our understanding of the functional diversity of the bacterial microbiota along the BSFL digestive tract, which is a key factor in explaining this insect's remarkable polyphagous behavior and optimizing its use for industrial purposes.

microbiology↗

bioRxiv2025

Gene flow from the European wild apple and selection shaped the domesticated apple (Malus domestica Borkh.) genome

How selection and demography shape genomes of long-lived crops remains largely unresolved. Using apple (Malus domestica) as a model, we integrate 218 whole genomes (68 cultivated dessert/cider; 150 wild: M. sieversii, M. orientalis, M. sylvestris), RNA-seq, and a flowering-time GWAS to resolve how these forces forged the cultivated apple genome. Despite weak neutral differentiation and widespread admixture, dessert and cider apples form distinct gene pools that derive primarily from M. sieversii-M. orientalis rather than European M. sylvestris. We find no evidence of a strong domestication bottleneck, as expected in perennials. Demography-aware selection scans reveal largely non-overlapping targets: dessert shows more hard sweeps at genes linked to fruit quality, disease resistance, and flowering, whereas cider shows proportionally more soft sweeps and balancing selection; RNA-seq differential expression supports these candidates. Wild-to-crop introgression from M. sylvestris is extensive but heterogeneous by context: some introgressed tracts concentrate in hard-sweep regions and approach fixation (consistent with rapid, targeted uptake), whereas others persist at intermediate frequencies with soft-sweep signatures (consistent with diffuse, recurrent introgression of adaptive alleles). Extending to the phenotype, the lead chromosome 9 flowering-time association lies within an introgressed segment near a transposable element and is separated from sweep peaks, consistent with regulatory/polygenic control. Cultivated apples carry a lower predicted deleterious load than wild relatives. Together, these results provide one of the most comprehensive population genomic portraits of a perennial fruit tree domestication, clarifying how selection and adaptive introgression jointly shaped the cultivated apple genome architecture and yielding actionable targets for breeding and conservation. Significance statementPerennial crops are underexplored compared to annuals, leaving open the question of how selection, gene flow, and demography shape their genomes. Using the apple tree (Malus domestica), we analyzed 218 genomes, along with expression and trait data. Despite weak genome-wide differences, dessert and cider apples form distinct gene pools. Widespread gene flow from the European wild apple supplied adaptive alleles, with contrasting dynamics: in cider, a few introgressed DNA segments rose rapidly; in dessert, many variants shifted gradually. Cultivated apples also carry a lower predicted burden of harmful mutations than wild relatives. Together, these results redefine perennial domestication and pinpoint genomic targets to accelerate breeding and conservation.

genetics↗

bioRxiv2022

The di-symbiotic systems in the aphids Sipha maydis and Peryphillus lyropictus provide a contrasting picture of recent co-obligate nutritional endosymbiosis in aphids

Dependence on multiple nutritional bacterial symbionts forming a metabolic unit has repeatedly evolved in many insect species that feed on nutritionally unbalanced diets such as plant sap. This is the case for aphids of the subfamilies Lachninae and Chaitophorinae, which have evolved di-symbiotic systems in which the ancient obligate nutritional symbiont Buchnera aphidicola is metabolically complemented by an additional nutritional symbiont acquired more recently. Deciphering how different symbionts integrate both metabolically and anatomically in such systems is crucial to understanding how complex nutritional symbiotic systems function and evolve. In this study, we sequenced and analyzed the genomes of the symbionts B. aphidicola and Serratia symbiotica associated with the Chaitophorinae aphids Sipha maydis and Periphyllus lyropictus. Our results show that, in these two species, B. aphidicola and S. symbiotica complement each other metabolically (and their hosts) for the biosynthesis of essential amino acids and vitamins but with distinct metabolic reactions supported by each symbiont depending on the host species. Furthermore, the S. symbiotica symbiont associated with S. maydis appears to be strictly compartmentalized into the specialized host cells housing symbionts in aphids, the bacteriocytes, whereas the S. symbiotica symbiont associated with P. lyropictus exhibits a highly invasive phenotype, presumably because it is capable of expressing a larger set of virulence factors, including a complete flagellum for bacterial motility. Such contrasting levels of metabolic and anatomical integration for two S. symbiotica symbionts that were recently acquired as nutritional co-obligate partners reflect distinct coevolutionary processes specific to each association.

microbiology↗

bioRxiv2021

Assessing the optimal frequency of early parasitoid releases in an apple orchard to control Dysaphis plantaginea: a proof of concept study

Alternative measures to pesticides to control the rosy apple aphid Dysaphis plantaginea are being developed. Naturally occurring predators and parasitoids often fail to reduce aphid abundance below the economic threshold in orchards, because they are active too late after the aphid first infestation. We tested the efficiency of mass release of two parasitoid species, Aphidius matricariae and Ephedrus cerasicola, early in the season to match the presence of aphid fundatrix (sensitive stages). In this trial focusing on an organic apple orchard, three releases were done either every week or every two weeks to test the effect of the release frequency, during two consecutive years. The number of aphid colonies and aphid number per tree were monitored from late March to late May. Degree-days necessary for parasitoid emergence in the field after release were calculated. We show that a sufficient level of aphid control by parasitoids is reached during the first month of the survey, but control mostly fails during the second part of the monitoring session, for both release treatments, and compared to the neem oil control treatment. The relative effects of release frequencies were different between years probably because of interannual differences in aphid population dynamics and initial infestation in orchards. The field survey and the degree-day model suggest that parasitoid releases, at either frequency, are promising candidates for biological control of the rosy aphid, although the method still needs proper calibration. This conclusion needs to be reinforced by repeating the study in more orchards, but our case study lays the first empirical basis that will help to develop future control methods of aphids by parasitoid releases in apple orchards. We argue that releases should be done one to two weeks before first aphid detection to account for long development times of parasitoids at relatively low temperatures.

ecology↗

bioRxiv2021

Ubiquity of the Symbiont Serratia symbiotica in the Aphid Natural Environment: Distribution, Diversity and Evolution at a Multitrophic Level

Bacterial symbioses are significant drivers of insect evolutionary ecology. However, despite recent findings that these associations can emerge from environmentally derived bacterial precursors, there is still little information on how these potential progenitors of insect symbionts circulates in the trophic systems. The aphid symbiont Serratia symbiotica represents a valuable model for deciphering evolutionary scenarios of bacterial acquisition by insects, as its diversity includes intracellular host-dependent strains as well as gut-associated strains that have retained some ability to live independently of their hosts and circulate in plant phloem sap. These strains represent a potential reservoir for the emergence of new and more intimate symbioses. Here, we conducted a field study to examine the distribution and diversity of S. symbiotica found in aphid populations, as well as in different compartments of their surrounding environment. A total of 250 aphid colonies, 203 associated insects, and 161 plant samples associated with aphid colonies were screened for S. symbiotica. Twenty percent of aphids were infected with S. symbiotica, and the symbiont includes a wide diversity of strains with varied tissue tropism corresponding to different lifestyle. We also showed that the prevalence of S. symbiotica is influenced by seasonal temperatures. For the first time, we found that S. symbiotica was present in non aphid species and in host plants, and that the prevalence of the bacterium in these samples was higher when associated aphid colonies were infected. Furthermore, phylogenetic analyses suggest the existence of horizontal transfers between the different trophic levels examined. These results provide a completely new picture of the ubiquity of an insect symbiont in nature. They suggest that ecological interactions promote the dissemination of strains that are still free-living and poorly specialized, and for which plants are a proabable reservoir for the acquisition of new bacterial partners in insects.

evolutionary biology↗

bioRxiv2020

Impact of the host stage on the pear psyllid parasitoid Trechnites insidious, behaviour and fitness

O_LIPear is one of the most important fruit crops of temperate regions. The control of its mains pest, Cacopsylla pyri, is still largely based on the use of chemical pesticides, with all that this implies in terms of negative effects on the environment and health. C_LIO_LIWithin the context of integrated pest management, innovative and ecologically sustainable strategies must be developed for. Although Trechnites insidiosus is the most abundant parasitoid of C. pyri, its biology and its potential as a control agent have been little studied. C_LIO_LIIn this paper, we conducted experiments to evaluate the behavior of the specialist parasitoid T. insidiosus when exposed to different larval instars of the pear psyllid C. pyri, and to assess the quality of the next generation of parasitoids. C_LIO_LIWe found that although T. insidiosus accepts all host instars for oviposition, the third and fourth instars were the most suitable host in terms of behavioral acceptance and progeny development. C_LIO_LIOur study is a first step for further studies on the interaction between psyllids and parasitoids and provides evidence that the specialist parasitoid T. insidiosus is a promising candidate for biological control strategies of the pear psyllid C. pyri. C_LI

zoology↗

bioRxiv2020

Phenotypic plasticity explains violation of Dollo's law

Over the last few decades, numerous examples have been described where a trait that was once lost during the course of evolution had been regained. Here, we argue that such reverse evolution can also become apparent when trait expression is plastic in response to the environment. We tested this hypothesis for the loss and regain of fat synthesis in parasitic wasps. Wasps from lineages that supposedly regained lipogenic ability ~80 million years ago were grown under a fat-poor or fat-rich environment. In line with our hypothesis, it turned out that fat synthesis had not been lost and regained, but was only switched on in low-fat environments. Functional protein domains of key lipogenesis genes were also found in other parasitoid species, suggesting that plasticity of fat synthesis may be more widespread in parasitoids. Individual-based simulations then revealed that a switch for plastic expression can remain functional in the genome for thousands of generations, even if it is only used sporadically. The evolution of plasticity may thus also explain other examples of apparent reverse evolution.

evolutionary biology↗

bioRxiv2019

Trans-generational effects on diapause and life-history-traits of an aphid parasitoid

Transgenerational effects act on a wide range of insects life-history traits and can be involved in the control of developmental plasticity, such as diapause expression. Decrease in or total loss of winter diapause expression recently observed in some species could arise from inhibiting maternal effects. In this study, we explored transgenerational effects on diapause expression and traits in one industrial and one wild strain of the aphid parasitoid Aphidius ervi. These strains were reared under short photoperiod (8:16 h LD) and low temperature (14 {degrees}C) conditions over two generations. Diapause levels, developmental times, physiological and morphological traits were measured. Diapause levels increased after one generation in the wild but not in the industrial strain. For both strains, the second generation took longer to develop than the first one. Tibia length and wing surface decreased over generations while fat content increased. A crossed-generations experiment focusing on the industrial parasitoid strain showed that offspring from mothers reared at 14 {degrees}C took longer to develop, were heavier, taller with wider wings and with more fat reserves than those from mothers reared at 20 {degrees}C (8:16 h LD). No effect of the mother rearing conditions was shown on diapause expression. Additionally to direct plasticity of the offspring, results suggest transgenerational plasticity effects on diapause expression, development time, and on the values of life-history traits. We demonstrated that populations showing low diapause levels may recover higher levels through transgenerational plasticity in response to diapause-induction cues, provided that environmental conditions are reaching the induction-thresholds specific to each population. Transgenerational plasticity is thus important to consider when evaluating how insects adapt to changing environments.

ecology↗

bioRxiv2018

New Insights into the Nature of Symbiotic Associations in Aphids: Initial Steps Involved in Aphid Gut Infection by Serratia symbiotica Bacteria

Symbiotic microorganisms are widespread in nature and can play a major role in the ecology and evolution of animals. The aphid-Serratia symbiotica bacterium interaction provides a valuable model to study mechanisms behind these symbiotic associations. The recent discovery of cultivable S. symbiotica strains having the possibility of free-living lifestyle allowed us to simulate their environmental acquisition by aphids to examine the mechanisms involved in this infection pathway. Here, after oral ingestion, we analyzed the infection dynamic of cultivable S. symbiotica strains during the hosts lifetime using qPCR and fluorescence techniques and determined the immediate fitness consequences of these bacteria on their new host. We further examined the transmission behavior and phylogenetic position of cultivable strains. Usually, S. symbiotica are considered as maternally-transmitted bacteria living within aphid body cavity and bringing some benefits to their hosts despite their costs. Otherwise, our study revealed that cultivable S. symbiotica are predisposed to establish a symbiotic association with new aphid host, settling in its gut. We showed that cultivable S. symbiotica colonized the entire aphid digestive tract following infection, after which the bacterium multiplied exponentially during aphid development. Our results further revealed that gut colonization by the bacteria induce a fitness cost to their hosts. Nevertheless, it appeared that they also offer an immediate protection against parasitoids. Interestingly, cultivable S. symbiotica seem to be extracellularly transmitted, possibly through the honeydew. These findings provide new insights into the nature of symbiosis in aphids and the mechanisms underpinning these interactions.\n\nImportanceFor the first time, our study provides experimental data that highlight a new kind of symbiotic associations in aphids. By successfully isolating microbial symbiont from aphids and by cultivating it in vitro in our laboratory, we established artificial association by simulating new bacterial acquisitions involved in aphid gut infection. Our results showed the early stages involved in this route of infection. Until now, Serratia symbiotica is considered as a maternally-transmitted aphid endosymbiont. Nevertheless, here, we showed that our cultivable strains having an intermediate status between a strict free-living bacterium and a facultative endosymbiont, occupy and replicate in aphid gut and seem to be transmitted over generations through an environmental transmission mechanism. Moreover, they are both parasites and mutualists given the context, as many of the endosymbionts in aphids. Our findings give new perception of associations involved in aphids symbiosis.

evolutionary biology↗