Search

International audience; Lower plant resistance to herbivores following domestication has been suggested as the main cause for higher feeding damage in crops than in wild progenitors. While herbivore compensatory feeding has also been proposed as a possible mechanism for raised damage in crops with low nutritional quality, predictions regarding the effects of plant domestication on nutritional quality for herbivores remain unclear. In particular, data on primary metabolites, even major macronutrients, measured in the organs consumed by herbivores, are scarce. In this study, we used a collection of 10 accessions of wild ancestors and 10 accessions of modern progenies of Triticum turgidum to examine whether feeding damage and selectivity by nymphs of Locusta migratoria primarily depended on five leaf traits related to structural resistance or nutrient profiles. Our results unexpectedly showed that locusts favored wild ancestors over domesticated accessions and that leaf toughness and nitrogen and soluble protein contents increased with the domestication process. Furthermore, the quantitative relationship between soluble protein and digestible carbohydrates was found to poorly meet the specific requirements of the herbivore, in all wheat accessions, both wild and modern. The increase in leaf structural resistance to herbivores in domesticated tetraploid wheat accessions suggested that resource allocation trade-offs between growth and herbivory resistance may have been disrupted by domestication in the vegetative organs of this species. Since domestication did not result in a loss of nutritional quality in the leaves of the tetraploid wheat, our results rather provides evidence for a role of the content of plants in nonnutritive nitrogenous secondary compounds, possibly deterrent or toxic, at least for grasshopper herbivores.

The data obtained from the experiments and scripts used for analyses can be found in the data repository of CIRAD Dataverse (https://doi.org/10.18167/DVN1/D3OP8O).; International audience; Highlights:• We hypothesize that attraction to fresh faeces enhance locust hopper band cohesion.• We exposed third instar hoppers of desert locust to faeces odours of different ages.• We observed an attraction of faeces explained by 11 volatile organic compounds.• Latecomers could get back to the band following faeces’ odours after 24 h.Abstract:Collective motion is one of the most impressive common features of gregarious locusts: once formed, bands and swarms get moving for long distances. It was shown that visual perception of neighbours plays a key role in maintaining marching behaviour at a local scale. But at a larger scale, mechanisms underlying band cohesion are less understood. It was shown in several field studies that individuals separated from the band were able to get back to the group, even after being separated since a night. In this context, faeces’ odours could be a possible indicator of the recent passage of a group. In this study, we tested if nymphs are attracted by faeces’ odours and if this effect is modulated by the age of the faeces. To this end, we conducted individual olfactometric behavioural assays of instar hoppers of desert locust, Schistocerca gregaria, exposed to odours of 1 h-old and 24 h-old faeces. We also used Gas Chromatography-Mass Spectrometry (GC–MS) to identify odours’ volatile organic compounds from faeces. The results of behavioural assays indicated a strong attractive effect of faeces, with no preference for one of the two faecal age classes. Nymphs spent significantly more time in the side of the olfactometer where the faeces’ odours came from, and 72.7% of tested individuals chose this side first. We filtered and annotated 11 volatile organic compounds present in both fresh and old faeces in GC–MS analyses, including guaiacol and phenol, which are known to cause an aggregative effect on desert locusts. As the attractive effect lasted over 24 h, band’s faeces could still have an attractive effect when individuals are separated from the band since one day. In this situation, latecomers individuals would be able to get back to the group by following the traces of their predecessors.

Phenotypic plasticity in body size is a product of modification of the developmental pathway. Although hatchlings of the desert locust, Schistocerca gregaria, show egg size-dependent plasticity in body size, it remains unclear how embryogenesis during egg development regulates final embryonic body size. To determine the developmental pathway causing body size variation at hatching, we examined egg and embryonic development at the early, middle, and late egg developmental stages in S. gregaria by comparing small and large eggs. Crowd-reared females produced larger eggs than isolated-reared females. The daily egg developmental rate was similar between small and large eggs: eggs dramatically absorbed external water after days 3 to 7 and nearly doubled the initial egg weight at the late stage of day 12. Morphological measurements of eggs and embryos at different days after oviposition revealed that large eggs were longer than small eggs throughout developmental stages. However, embryo length was similar between small and large eggs at the early stage (anatrepsis). Embryos begin to absorb yolk into their bodies after blastokinesis. The size of large-egg embryos increased significantly from the middle stage (katatrepsis) due to absorption of more yolk than small eggs. Egg length and embryo length were conspicuously larger in large eggs than in small eggs on day 12 of late katatrepsis. These results suggest that egg size did not influence the egg developmental rate and initial embryo size. Large eggs had more yolk and space, resulting in larger final embryos than small eggs. The amount of yolk and size of eggshells during katatrepsis could play a key role in determining hatchling body size in S. gregaria.

A better understanding of the factors affecting host plant use by spotted-wing drosophila (Drosophila suzukii) could aid in the development of efficient management tools and practices to control this pest. Here, proxies of both preference (maternal oviposition behavior) and performance (adult emergence) were evaluated for 12 different fruits in the form of purees. The effect of the chemical composition of the fruits on preference and performance traits was then estimated. We synthesized the literature to interpret our findings in the light of previous studies that measured oviposition preference and larval performance of D. suzukii. We show that fruit identity influences different parts of the life cycle, including oviposition preference under both choice and no-choice conditions, emergence rate, development time, and number of emerging adults. Blackcurrant was always among the most preferred fruit we used, while grape and tomato were the least preferred fruits. Larvae performed better in cranberry, raspberry, strawberry, and cherry than in the other fruits tested. We found that fruit chemical compounds can explain part of the effect of fruit on D. suzukii traits. In particular, oviposition preference under choice conditions was strongly influenced by fruit phosphorus content. In general, the consensus across studies is that raspberry, blackberry, and strawberry are among the best hosts while blackcurrant, grape and rose hips are poor hosts. Our results generally confirm this view but also suggest that oviposition preferences do not necessarily match larval performances. We discuss opportunities to use our results to develop new approaches for pest management.

Orthoptera are infected by about 60 species of gregarines assigned to the genus Gregarina Dufour, 1828. Among these species, Gregarina garnhami Canning, 1956 from Schistocerca gregaria (Forsskål, 1775) was considered by Lipa et al. in 1996 to be synonymous with Gregarina acridiorum (Léger 1893), a parasite of several orthopteran species including Locusta migratoria (Linné, 1758). Here, a morphological study and molecular analyses of the SSU rDNA marker demonstrate that specimens of S. gregaria and specimens of L. migratoria are infected by two distinct Gregarina species, G. garnhami and G. acridiorum, respectively. Validation of the species confirms that molecular analyses provide useful taxonomical information. Phenotypic plasticity was clearly observed in the case of G. garnhami: the morphology of its trophozoites, gamonts and syzygies varied according to the geographical location of S. gregaria and the subspecies infected.La taxonomie intégrative confirme que Gregarina garnhami et G. acridiorum (Apicomplexa, Gregarinidae), parasites de Schistocerca gregaria et Locusta migratoria (Insecta, Orthoptera), sont des espèces distinctes.Les orthoptères sont parasités par environ soixante espèces de grégarines affiliées au genre Gregarina Dufour, 1828. Parmi ces espèces Gregarina garnhami Canning, 1956 décrite chez Schistocerca gregaria (Forskål, 1775), a été mise en synonymie par Lipa et al. en 1996 avec Gregarina acridiorum (Léger 1893), parasite de plusieurs espèces d’orthoptères dont Locusta migratoria (Linné, 1758). Ici, une étude morphologique et des analyses moléculaires du marqueur SSU rDNA démontrent que les spécimens de S. gregaria et ceux de L. migratoria sont infectés par 2 espèces distinctes de grégarines, Gregarina garnhami et Gregarina acridiorum, respectivement. La validation de ces espèces confirme l’importance des informations fournies par les analyses moléculaires dans les études taxonomiques. Une plasticité phénotypique a été clairement observée dans le cas de G. garnhami : la morphologie de ses trophozoïtes, gamontes et syzygies varie selon la localisation géographique et la sous-espèce de S. gregaria infectée.

Ce rapport est disponible dans : BioRxiv. This article has been peer-reviewed and recommended by Peer Community in Evolutionary Biology; Experiments comparing native to introduced populations or distinct introduced populations to each other show that phenotypic evolution is common and often involves a suit of interacting phenotypic traits. We define such sets of traits that evolve in concert and contribute to the success of invasive populations as an ‘invasion syndrome’. The invasive Harlequin ladybird Harmonia axyridis displays such an invasion syndrome with, for instance, females from invasive populations being larger and heavier than individuals from native populations, allocating more resources to reproduction, and spreading reproduction over a longer lifespan. Invasion syndromes could emerge due to selection acting jointly and directly on a multitude of traits, or due to selection on one or a few key traits that drive correlated indirect responses in other traits. Here, we investigated the degree to which the H. axyridis invasion syndrome would emerge in response to artificial selection on either female body mass or on age at first reproduction, two traits involved in their invasion syndrome. To further explore the interaction between environmental context and evolutionary change in molding the phenotypic response, we phenotyped the individuals from the selection experiments in two environments, one with abundant food resources and one with limited resources. The two artificial selection experiments show that the number of traits showing a correlated response depends upon the trait undergoing direct selection. Artificial selection on female body mass resulted in few correlated responses and hence poorly reproduced the invasion syndrome. In contrast, artificial selection on age at first reproduction resulted in more widespread phenotypic changes, which nevertheless corresponded only partly to the invasion syndrome. The artificial selection experiments also revealed a large impact of diet on the traits, with effects dependent on the trait considered and the selection regime. Overall, our results indicate that direct selection on multiple traits was likely necessary in the evolution of the H. axyridis invasion syndrome. Furthermore, they show the strength of using artificial selection to identify the traits that are correlated in different selective contexts, which represents a crucial first step in understanding the evolution of complex phenotypic patterns, including invasion syndromes.

International audience; In Europe, Puumala virus (PUUV) is responsible for nephropathia epidemica (NE), a mild form of hemorrhagic fever with renal syndrome (HFRS). Despite the presence of its reservoir, the bank vole, on most of French territory, the geographic distribution of NE cases is heterogeneous and NE endemic and non-endemic areas have been reported. In this study we analyzed whether bank vole-PUUV interactions could partly shape these epidemiological differences. We performed crossed-experimental infections using wild bank voles from French endemic (Ardennes) and non-endemic (Loiret) areas and two French PUUV strains isolated from these areas. The serological response and dynamics of PUUV infection were compared between the four cross-infection combinations. Due to logistical constraints, this study was based on a small number of animals. Based on this experimental design, we saw a stronger serological response and presence of PUUV in excretory organs (bladder) in bank voles infected with the PUUV endemic strain. Moreover, the within-host viral diversity in excretory organs seemed to be higher than in other non-excretory organs for the NE endemic cross-infection but not for the NE non-endemic cross-infection. Despite the small number of rodents included, our results showed that genetically different PUUV strains and in a lesser extent their interaction with sympatric bank voles, could affect virus replication and diversity. This could impact PUUV excretion/transmission between rodents and to humans and in turn at least partly shape NE epidemiology in France.

The process of local adaptation involves differential changes in fitness over time across different environments. While experimental evolution studies have extensively tested for patterns of local adaptation at a single time point, there is relatively little research that examines fitness more than once during the time course of adaptation. We allowed replicate populations of the fruit pest Drosophila suzukii to evolve in one of eight different fruit media. After five generations, populations with the highest initial levels of maladaptation had mostly gone extinct, whereas experimental populations evolving on cherry, strawberry and cranberry media had survived. We measured the fitness of each surviving population in each of the three fruit media after five and after 26 generations of evolution. After five generations, adaptation to each medium was associated with increased fitness in the two other media. This was also true after 26 generations, except when populations that evolved on cranberry medium developed on cherry medium. These results suggest that, in the theoretical framework of a fitness landscape, the fitness optima of cherry and cranberry media are the furthest apart. Our results show that studying how fitness changes across several environments and across multiple generations provides insights into the dynamics of local adaptation that would not be evident if fitness were analyzed at a single point in time. By allowing a qualitative mapping of an experimental fitness landscape, our approach will improve our understanding of the ecological factors that drive the evolution of local adaptation in D. suzukii.

Depuis 2006, le laboratoire de préservation des bois du Cirad est accrédité par le COFRAC (Comité français d'accréditation - accréditation n°1-1686) pour ses essais sur la durabilité des bois et produits dérivés du bois et sur l'efficacité protectrice des produits de préservation et des produits anti-termites. La mise en place de la fonction métrologie au laboratoire de préservation du bois est un facteur clé de l'amélioration continue des pratiques. De tous les essais de caractérisation des bois, les essais de résistance aux agents biologiques de détérioration sont les plus délicats. Ils visent en effet à évaluer et à quantifier l'impact d'organismes vivants, comme les champignons et les termites, sur une matière lignocellulosique. On apprécie facilement l'importance de la variabilité de cet impact lié lui-même à la diversité de ces organismes. La validité et la fiabilité des résultats dépendront ainsi directement de la qualité du processus métrologique mis en oeuvre, comprenant le choix des appareils de mesure, leur gestion et leur mise en conformité avec les normes internationales. Mots clés: Métrologie, accréditation, traçabilité, incertitude, essais biologiques.

A new naphthoquinone derivative was isolated from the heartwood of the teak stem. The chemical structure of this new compound, 40,50-dihydroxy-epiisocatalponol, was determined using 1-D and 2-D nuclear magnetic resonance experiments, vibrational circular dichroism, HRMS, and optical rotation. We showed that this new naphthoquinone derivative plays a key role in the variability of decay resistance in teak wood. A high negative correlation was found between its concentration and the mass losses of the wood samples after exposure to the brown rot Antrodia sp., the fungus that is the most virulent against teak (R ¼ _0.9; r < 0.0001). In-vitro bioassays allowed us to demonstrate that 40,50-dihydroxyepiisocatalponol acted as a fungicide against Trametes versicolor (white rot) at 58 mg ml-1 (0.22 mM). Overall, our results demonstrated that the concentration of 40,50-dihydroxy-epiisocatalponol could be used as a new tool to evaluate teak wood durability.

BACKGROUND: Termites are degradation agents that inflict severe damage on wood. Some long-lasting Amazonian trees can resist these insects by producing toxic secondary metabolites. These metabolites could potentially replace synthetic termiticidal products which are becoming more restricted to use. RESULTS: Sextonia rubra is resistant to termite-induced degradation. It has been demonstrated that this species naturally produces an ethyl-acetate-soluble termiticidal metabolite, rubrynolide, to protect its wood. Assays in the presence of tropical and invasive termites established that both rubrynolide and crude ethyl acetate extract from S. rubra wood can be used as a treatment for the protection of sensitive woods against termites. CONCLUSION: Rubrynolide and S. rubra extract are promising candidates for the replacement of synthetic termiticides.

No desenvolvimento de painéis, deve-se dar destaque a ensaios que remetam à aplicabilidade final do produto, como os ensaios de durabilidade ao ataque de fungos e cupins. Nesse contexto, painéis confeccionados com diferentes percentuais de partículas de bagaço de cana-de-açúcar (Saccharum sp.) e fibras de eucalipto (Eucalyptus grandis), aglutinados com duas dosagens de resina ureia formol (13% e 16%), foram submetidos à avaliação de resistência biológica (bioensaios) ao ataque de cupins e fungos, ensaio fundamental na definição de uso e aplicação do produto final. Foram utilizados cupins da espécie Reticulitermes santonensis, rhinotermitidade, e fungos da espécie Pleurotus ostreatus, basidiomiceto de podridão-branca, de acordo com procedimentos da normatização AFNOR. De modo geral, os novos painéis confeccionados apresentaram-se não resistentes aos bioensaios realizados e houve similaridade na dinâmica de ataque e perda de massa entre as diferentes dosagens de resina praticadas, remetendo à necessidade da aplicação de revestimento protetor na superfície dos painéis ou adição de produtos fungicidas e cupinicidas. Trials referring applicability of the final product, such as durability tests to fungi and termites are crucial in developing panels. Therefore, panels made with different percentages of sugarcane bagasse particles (Saccharum sp.) and eucalyptus fiber (Eucalyptus grandis), bounded with two dosages of urea formaldehyde resin (13% and 16%), were evaluated for biological resistance (bioassays) to termites and fungi, which is fundamental in defining use and application of the final product. We used the termite species Reticulitermes santonensis, rhinotermitidade, and the fungy Pleurotus ostreatus, a white rot basidiomycete, according to AFNOR standardization procedures. In general, the new panels were not resistant to bioassays and there was a similarity in the dynamics of attack and mass loss among the different doses of resin applied, thus evidencing the need of applying protective coating on the panels surface or adding termiticide and fungicide products.

Investigations were carried out on the efficacy of extracts from seven Amazonian woods (Bagassa guianensis, Manilkara huberi, Sextonia rubra, Vouacapoua americana, Andira surinamensis, Handroanthus serratifolius, and Qualea rosea) with varying natural durability to reduce soft-rot degradation in a 6-wk soil-bed test. Six of the wood extracts had shown efficacy against soft-rot fungi. In particular, the preservation efficacies of B. guianensis, H. serratifolius, and S. rubra extracts were highly significant up to retention levels of 23, 25, and 12 kg m−3, respectively. Three extracts (A. surinamensis, H. serratifolius, and Q. rosea) were then tested against Gloeophyllum trabeum (brown rot) and Trametes versicolor (white rot), in an agar-block test. H. serratifolius wood extract was very efficient at protecting P. sylvestris samples at 5.1 kg m−3 against the brown rot. This extract could be used as a basis for new wood protectant formulations.

National audience

National audience; The life-history traits of organisms can be driven by the environment. Specifically, the nutritional composition of resources can influence life-history traits in insects. In Drosophila, the ratio of protein to carbohydrate (the P:C ratio) strongly influences life history traits. However, natural resources used by Drosophila species vary in many other factors. We compare how well P:C ratios of fruit resources predict life history traits in , relative to other measures of fruit composition and fruit identity, which integrates all aspects of the resource. We evaluate how 12 different fruit purees influenced life-history traits in . Fecundity (eggs laid in 24 hours) on each fruit medium was measured in a choice and a nochoice environment. We also evaluated development time, the rate of survival from egg to adult, and the total number of adults as an estimate of total fitness. We then test whether fruit identity, composition or P:C ratio best predict life history. Fruit influenced the entire life cycle, including oviposition and larval performance as well as the number of adults produced in the next generation. Variation in these traits is best explained by fruit identity, then composition, and lastly by the P:C ratio. These results highlight the importance of considering a resource as a whole. Considering only the ratio of protein to carbohydrates is not sufficient for understanding variation in key life-history traits.