Biodiversity of hymenopteran parasitoids

Host-natural enemy communities in a changing world: The impact of forest loss on cavity-nesting Hymenoptera and their natural enemies

Cavity-nesting bees and wasps provide important ecosystem services for humans. This study aimed to understand how the replacement of forests with non-forest habitats affects the structure and interaction network of cavity-nesting bees, wasps, and their natural enemies. From 1,536 trap-nests distributed across 48 sites, we collected a total of 541 built nests, from which 1,420 hosts and 254 natural enemies emerged. We found no significant differences in species abundance, richness, or diversity between forest and matrix environments. However, abundance evenness was higher in forests. Interestingly, host species composition differed between forests and matrix areas, while natural enemy composition remained similar. Similarly, network metrics did not differ significantly between the two environments. Despite this apparent resistance of cavity-nesting hymenopteran communities to forest loss, many species are highly specialized in utilizing wooded areas and are not adapted to other environments. As a result, we risk losing not only specific and rare species but also their unique ecological functions. We emphasize the need to include these forest-dependent species in more conservation plans, as most remain poorly studied, from basic aspects of their natural history to applied research on their ecological functions and economic relevance. Future studies should also investigate the potential unseen effects of host composition shifts and the increased dominance of certain species in matrix areas on biodiversity patterns. This could provide clearer insights for improving conservation and management strategies.

Insect-flower interactions, ecosystem functions, and restoration ecology in the northern Sahel: current knowledge and perspectives

Actions for ecological restoration under the Great Green Wall (GGW) initiative in the northern Sahel have been plant focused, paying scant attention to plant-animal interactions that are essential to ecosystem functioning. Calls to accelerate implementation of the GGW make it timely to develop a more solid conceptual foundation for restoration actions. As a step towards this goal, we review what is known in this region about an important class of plant-animal interactions, those between plants and flower-visiting insects. Essential for pollination, floral resources also support insects that play important roles in many other ecosystem processes. Extensive pastoralism is the principal subsistence mode in the region, and while recent analyses downplay the impact of livestock on vegetation dynamics compared to climatic factors, they focus primarily on rangeland productivity, neglecting biodiversity, which is critical for long-term sustainability. We summarise current knowledge on insect-flower interactions, identify information gaps, and suggest research priorities. Most insect-pollinated plants in the region have open-access flowers exploitable by diverse insects, an advantageous strategy in environments with low productivity and seasonal and highly variable rainfall. Other plant species have diverse traits that constrain the range of visitors, and several distinct flower types are represented, some of which have been postulated to match classical "pollination syndromes". As in most ecosystems, bees are among the most important pollinators. The bee fauna is dominated by ground-nesting solitary bees, almost all of which are polylectic. Many non-bee flower visitors also perform various ecosystem services such as decomposition and pest control. Many floral visitors occupy high trophic levels, and are indicators of continued functioning of the food webs on which they depend. The resilience of insect-flower networks in this region largely depends on trees, which flower year-round and are less affected by drought than forbs. However, the limited number of abundant tree species presents a potential fragility. Flowering failure of a crucial "hub" species during exceptionally dry years could jeopardise populations of some flower-visiting insects. Furthermore, across Sahelian drylands, browsers are increasingly predominant over grazers. Although better suited to changing climates, browsers exert more pressure on trees, potentially weakening insect-flower interaction networks. Understanding the separate and combined effects of climate change and land-use change on biotic interactions will be key to building a solid foundation to facilitate effective restoration of Sahelian ecosystems.

Larval and Larval-Pupal Parasitoids Associated with Major Owlet Moth Pests of Soybean and Maize in the Brazilian Savanna: Measures to Preserve Them in Crop Succession

Owlet moths (Lepidoptera: Noctuoidea) are among the most threatening pests of soybean and maize systems under intensive cropping in tropical and subtropical regions. Their high dispersal, larval polyphagia, and voracious feeding behavior often lead to severe grain production losses. Many parasitoids are associated with owlet moths; however, the ecological importance of larval parasitism in the soybean-maize crop rotation of the Brazilian savanna remains uncertain. We assessed larval parasitism in major lepidopteran pests of soybean and maize crops over three agricultural seasons in eight fields across Brazil's central-west region. Parasitic wasps were more common than tachinids on larvae of all lepidopteran species in both soybean and maize fields over the years. The larval parasitism rate by wasps averaged 9.7% in soybean fields and 13.6% in maize fields, whereas tachinids accounted for only 1.7% of parasitized larvae across both crops. The parasitism rate of Anticarsia gemmatalis Hübner was low in all soybean fields (< 4.9%), in contrast to the ones for Chrysodeixis includens (Walker) (5.9 to 32.5%) and the Spodoptera Guenée complex (4.2 to 29.2%). In maize, parasitism rates of Spodoptera frugiperda (J.E. Smith) ranged from 8.4 to 26.0% among fields, primarily by Ichneumonidae. The consistent presence of wasps, such as Cotesia Cameron and Campoletis Förster, parasitizing multiple hosts across all soybean and maize fields and seasons highlights their role in the natural biological control of caterpillars in the soybean-maize crop succession. In this sense, this study discusses relevant aspects of conservation biological control within multiple cropping systems.

Unraveling the venom constituents of the endoparasitoid Aphidius gifuensis with an emphasis on the discovery of a novel insecticidal peptide

BACKGROUND

Venom serves as a pivotal parasitic factor employed by parasitoid wasps to manipulate their hosts, creating a favorable environment for the successful growth of their progeny, and ultimately kill the host. The bioactive molecules within parasitoid venoms exhibit insecticidal activities with promising prospects for agricultural applications. However, knowledge regarding the venom components of parasitoids and the discovery of functional biomolecules from them remains limited.

RESULTS

In this study, 30 venom proteins were identified from the endoparasitoid Aphidius gifuensis through the application of a transcriptomic approach. These proteins were categorized into five groups: hydrolase, molecular chaperone, transferase, other functional protein, and hypothetical protein with unknown function. Particularly noteworthy is the abundant expression of the peptide Vn1 in the venom apparatus of A. gifuensis, indicating its pivotal role in venom activity. Consequently, Vn1 was chosen for further functional analysis, exhibiting insecticidal activity against Tenebrio molitor pupae. Further assessment for revealing its mode of action disclosed that Vn1 impacts genes related to immune response, environmental information processing, metabolism, and response to external stimuli in T. molitor, suggesting its involvement in the intricate parasitoid wasp-host interaction.

CONCLUSION

The findings of this study significantly contribute to our knowledge of the composition and functionality of A. gifuensis venom, establishing a foundation for further investigation into the biological roles of the identified venom constituents. The insecticidal Vn1 isolated from the venom of this parasitoid represents a valuable resource for the development of innovative biocontrol agents with potential applications in agriculture. © 2024 Society of Chemical Industry.

A chromosome-level genome assembly of Meteorus pulchricornis Wesmael (Hymenoptera: Braconidae)

Meteorus pulchricornis Wesmael (Hymenoptera: Braconidae) is an important parasitoid of lepidopteran insects. So far, only three scaffold-level genomes have been published for the genus Meteorus. In this study, we present a high-quality, chromosome-level genome assembly of M. pulchricornis, characterized by high accuracy and contiguity. This assembly was achieved using Oxford Nanopore Technologies long-read, MGI-SEQ short-read, and Hi-C sequencing methods. The final assembly was 158.5 Mb in genome size, with 153.8 Mb (97.03%) assigned to ten pseudochromosomes. The scaffold N50 length reached 17.51 Mb, and the complete Benchmarking Universal Single-Copy Orthologs (BUSCO) score was 99.3%. The genome contains 28.29 Mb of repetitive elements, accounting for 18.39% of the total genome size. We identified 12,342 protein-coding genes, of which 12,308 genes were annotated functionally. Our investigation into gene family evolution in M. pulchricornis showed that 563 gene families expanded, 1,739 contracted, and 58 underwent rapid evolution. The high-quality genome assembly we report here is advantageous for further research on parasitoid wasps and provides a foundational data resource for natural enemy studies.

Parasitoid speciation and diversification

Parasitoid wasps may well be the most species-rich animal group on Earth, and host-parasitoid interactions may thereby be one of the most common types of species interactions. Understanding the major mechanisms underlying diversification in parasitoids should be a high priority, not the least in order to predict consequences from high extinction rates currently observed. The two major hypotheses explaining host-associated diversification are the escape-and-radiate hypothesis and the oscillation hypothesis, where the former assumes that key innovations are major drivers of radiation bursts, whereas the latter rather assumes that diversification depends on processes acting on the standing genetic variation that influences host use. This paper reviews the recent literature on parasitoid speciation in light of these major hypotheses to identify potential key innovations and host use variability underlying diversification. The paper also calls upon recent theoretical advances from a similar system, plant-butterfly interactions, to provide shortcuts in the development of theories explaining the high diversity of parasitoid wasps.

Female-Biased Odorant Receptor MmedOR48 in the Parasitoid Microplitis mediator Broadly Tunes to Plant Volatiles

Odorant receptors (ORs) play a crucial role in insect chemoreception. Here, a female-biased odorant receptor MmedOR48 in parasitoid Microplitis mediator was fully functionally characterized. The qPCR analysis suggested that the expression level of MmedOR48 increased significantly after adult emergence and was expressed much more in the antennae. Moreover, an in situ hybridization assay showed MmedOR48 was extensively located in the olfactory sensory neurons. In two-electrode voltage clamp recordings, recombinant MmedOR48 was broadly tuned to 23 kinds of volatiles, among which five plant aldehyde volatiles excited the strongest current recording values. Subsequent molecular docking analysis coupled with site-directed mutagenesis demonstrated that key amino acid residues Thr142, Gln80, Gln282, and Thr312 together formed the binding site in the active pocket for the typical aldehyde ligands. Furthermore, ligands of MmedOR48 could stimulate electrophysiological activities in female adults of the M. mediator. The main aldehyde ligand, nonanal, aroused significant behavioral preference of M. mediator in females than in males. These findings suggest that MmedOR48 may be involved in the recognition of plant volatiles in M. mediator, which provides valuable insight into understanding the olfactory mechanisms of parasitoids.

Coordinated molecular and ecological adaptations underlie a highly successful parasitoid

The success of an organism depends on the molecular and ecological adaptations that promote its beneficial fitness. Parasitoids are valuable biocontrol agents for successfully managing agricultural pests, and they have evolved diversified strategies to adapt to both the physiological condition of hosts and the competition of other parasitoids. Here, we deconstructed the parasitic strategies in a highly successful parasitoid, Trichopria drosophilae, which parasitizes a broad range of Drosophila hosts, including the globally invasive species D. suzukii. We found that T. drosophilae had developed specialized venom proteins that arrest host development to obtain more nutrients via secreting tissue inhibitors of metalloproteinases (TIMPs), as well as a unique type of cell-teratocytes-that digest host tissues for feeding by releasing trypsin proteins. In addition to the molecular adaptations that optimize nutritional uptake, this pupal parasitoid has evolved ecologically adaptive strategies including the conditional tolerance of intraspecific competition to enhance parasitic success in older hosts and the obligate avoidance of interspecific competition with larval parasitoids. Our study not only demystifies how parasitoids weaponize themselves to colonize formidable hosts but also provided empirical evidence of the intricate coordination between the molecular and ecological adaptations that drive evolutionary success.

The Viromes of Six Ecosystem Service Provider Parasitoid Wasps

Parasitoid wasps are fundamental insects for the biological control of agricultural pests. Despite the importance of wasps as natural enemies for more sustainable and healthy agriculture, the factors that could impact their species richness, abundance, and fitness, such as viral diseases, remain almost unexplored. Parasitoid wasps have been studied with regard to the endogenization of viral elements and the transmission of endogenous viral proteins that facilitate parasitism. However, circulating viruses are poorly characterized. Here, RNA viromes of six parasitoid wasp species are studied using public libraries of next-generation sequencing through an integrative bioinformatics pipeline. Our analyses led to the identification of 18 viruses classified into 10 families (Iflaviridae, Endornaviridae, Mitoviridae, Partitiviridae, Virgaviridae, Rhabdoviridae, Chuviridae, Orthomyxoviridae, Xinmoviridae, and Narnaviridae) and into the Bunyavirales order. Of these, 16 elements were described for the first time. We also found a known virus previously identified on a wasp prey which suggests viral transmission between the insects. Altogether, our results highlight the importance of virus surveillance in wasps as its service disruption can affect ecology, agriculture and pest management, impacting the economy and threatening human food security.

Terebra steering in chalcidoid wasps

Various chalcidoid wasps can actively steer their terebra (= ovipositor shaft) in diverse directions, despite the lack of terebral intrinsic musculature. To investigate the mechanisms of these bending and rotational movements, we combined microscopical and microtomographical techniques, together with videography, to analyse the musculoskeletal ovipositor system of the ectoparasitoid pteromalid wasp Lariophagus distinguendus (Förster, 1841) and the employment of its terebra during oviposition. The ovipositor consists of three pairs of valvulae, two pairs of valvifers and the female T9 (9th abdominal tergum). The paired 1st and the 2nd valvulae are interlocked via the olistheter system, which allows the three parts to slide longitudinally relative to each other, and form the terebra. The various ovipositor movements are actuated by a set of nine paired muscles, three of which (i.e. 1st valvifer-genital membrane muscle, ventral 2nd valvifer-venom gland reservoir muscle, T9-genital membrane muscle) are described here for the first time in chalcidoids. The anterior and posterior 2nd valvifer-2nd valvula muscles are adapted in function. (1) In the active probing position, they enable the wasps to pull the base of each of the longitudinally split and asymmetrically overlapping halves of the 2nd valvula that are fused at the apex dorsally, thus enabling lateral bending of the terebra. Concurrently, the 1st valvulae can be pro- and retracted regardless of this bending. (2) These muscles can also rotate the 2nd valvula and therefore the whole terebra at the basal articulation, allowing bending in various directions. The position of the terebra is anchored at the puncture site in hard substrates (in which drilling is extremely energy- and time-consuming). A freely steerable terebra increases the chance of contacting a potential host within a concealed cavity. The evolution of the ability actively to steer the terebra can be considered a key innovation that has putatively contributed to the acquisition of new hosts to a parasitoid's host range. Such shifts in host exploitation, each followed by rapid radiations, have probably aided the evolutionary success of Chalcidoidea (with more than 500,000 species estimated).