Wasp Host Research Articles

Ultrastructural and genomic characterization of a second banchine polydnavirus confirms the existence of shared features within this ichnovirus lineage

Polydnaviruses (PDVs) are symbiotic viruses carried by endoparasitic wasps and transmitted to caterpillar hosts during parasitization. Although they share several features, including a segmented dsDNA genome, a unique life cycle where replication is restricted to the wasp host, and immunodepressive/developmental effects on the caterpillar host, PDVs carried by ichneumonid and braconid wasps (referred to as ichnoviruses and bracoviruses, respectively) have different evolutionary origins. In addition, ichnoviruses (IVs) form two distinct lineages, with viral entities found in wasps belonging to the subfamilies Campopleginae and Banchinae displaying strikingly different virion morphologies and genomic features. However, the current description for banchine IVs is based on the characterization of a single species, namely that of the Glypta fumiferanae IV (GfIV). Here we provide an ultrastructural and genomic analysis of a second banchine IV isolated from the wasp Apophua simplicipes, and we show that this virus shares many features with GfIV, including a multi-nucleocapsid virion, an aggregate genome size of ~300 kb, genome segments <5 kb, an impressively high degree of genome segmentation and a very similar gene content (same gene families in both viruses). Altogether, the data presented here confirm the existence of shared characteristics within this banchine IV lineage.

Genotype‐by‐genotype specificity remains robust to average temperature variation in an aphid/endosymbiont/parasitoid system

Genotype-by-genotype interactions demonstrate the existence of variation upon which selection acts in host-parasite systems at respective resistance and infection loci. These interactions can potentially be modified by environmental factors, which would entail that different genotypes are selected under different environmental conditions. In the current study, we checked for a G × G × E interaction in the context of average temperature and the genotypes of asexual lines of the endoparasitoid wasp Lysiphlebus fabarum and isolates of Hamiltonella defensa, a protective secondary endosymbiont of the wasp's host, the black bean aphid Aphis fabae. We exposed genetically identical aphids harbouring different isolates of H. defensa to three asexual lines of the parasitoid and measured parasitism success under three different temperatures (15, 22 and 29 °C). Although there was clear evidence for increased susceptibility to parasitoids at the highest average temperature and a strong G × G interaction between the host's symbionts and the parasitoids, no modifying effect of temperature, that is, no significant G × G × E interaction, was detected. This robustness of the observed specificity suggests that the relative fitness of different parasitoid genotypes on hosts protected by particular symbionts remains uncomplicated by spatial or temporal variation in temperature, which should facilitate biological control strategies.

The mechanism of pollinator specificity between two sympatric fig varieties: a combination of olfactory signals and contact cues

Pollinator specificity facilitates reproductive isolation among plants, and mechanisms that generate specificity influence species boundaries. Long-range volatile attractants, in combination with morphological co-adaptations, are generally regarded as being responsible for maintaining extreme host specificity among the fig wasps that pollinate fig trees, but increasing evidence for breakdowns in specificity is accumulating. The basis of host specificity was examined among two host-specific Ceratosolen fig wasps that pollinate two sympatric varieties of Ficus semicordata, together with the consequences for the plants when pollinators entered the alternative host variety. The compositions of floral scents from receptive figs of the two varieties and responses of their pollinators to these volatiles were compared. The behaviour of the wasps once on the surface of the figs was also recorded, together with the reproductive success of figs entered by the two Ceratosolen species. The receptive-phase floral scents of the two varieties had different chemical compositions, but only one Ceratosolen species displayed a preference between them in Y-tube trials. Specificity was reinforced at a later stage, once pollinators were walking on the figs, because both species preferred to enter figs of their normal hosts. Both pollinators could enter figs of both varieties and pollinate them, but figs with extra-varietal pollen were more likely to abort and contained fewer seeds. Hybrid seeds germinated at normal rates. Contact cues on the surface of figs have been largely ignored in previous studies of fig wasp host preferences, but together with floral scents they maintain host specificity among the pollinators of sympatric F. semicordata varieties. When pollinators enter atypical hosts, post-zygotic factors reduce but do not prevent the production of hybrid offspring, suggesting there may be gene flow between these varieties.

Host activity and wasp experience affect parasitoid wasp foraging behaviour and oviposition on nematode‐infected larvae of the forestry pest Hylobius abietis

1. Entomopathogenic nematodes (EPN) are currently being used as introduced biological control agents against the larvae of the native European forestry pest Hylobius abietis L. which develop under the bark of stumps and roots of newly dead conifer trees.2. The potential for resource competition between gregarious ectoparasitoid Bracon hylobii Ratz and EPN by recording oviposition and related behaviours of B. hylobii females on EPN‐infected H. abietis larvae was investigated. Wasps did not parasitise EPN‐infected host larvae that were dead when presented, but naÏve and experienced wasps parasitised live EPN‐infected hosts. NaÏve wasps parasitised live EPN‐infected hosts significantly less frequently than healthy hosts only when the infected larvae were close to death (i.e. died during 24‐h trial). Parasitism by experienced wasps was unaffected by host infection.3. Wasp probing and oviposition were positively associated with the amount of host movement. Preventing H. abietis larvae from chewing on bark significantly reduced parasitism by naÏve, but not experienced wasps.4. The number of eggs per clutch was not affected by bark chewing or EPN‐infection of H. abietis larvae.5. NaÏve and experienced B. hylobii parasitised two abnormal hosts (larvae of coleopteran Rhagium bifasciatum Fabricius and lepidopteran Galleria mellonella L.), both of which moved and chewed on bark during trials.6. It was concluded that B. hylobii can use vibrational cues generated by host movement and feeding to locate hosts at short range and accepts unsuitable (EPN‐infected or abnormal) hosts as long as these create such cues. The implications for competition between B. hylobii and EPN and possible ways of minimising it when applying EPN are discussed.

Codivergence and multiple host species use by fig wasp populations of the Ficus pollination mutualism.

BackgroundThe interaction between insects and plants takes myriad forms in the generation of spectacular diversity. In this association a species host range is fundamental and often measured using an estimate of phylogenetic concordance between species. Pollinating fig wasps display extreme host species specificity, but the intraspecific variation in empirical accounts of host affiliation has previously been underestimated. In this investigation, lineage delimitation and codiversification tests are used to generate and discuss hypotheses elucidating on pollinating fig wasp associations with Ficus.ResultsStatistical parsimony and AMOVA revealed deep divergences at the COI locus within several pollinating fig wasp species that persist on the same host Ficus species. Changes in branching patterns estimated using the generalized mixed Yule coalescent test indicated lineage duplication on the same Ficus species. Conversely, Elisabethiella and Alfonsiella fig wasp species are able to reproduce on multiple, but closely related host fig species. Tree reconciliation tests indicate significant codiversification as well as significant incongruence between fig wasp and Ficus phylogenies.ConclusionsThe findings demonstrate more relaxed pollinating fig wasp host specificity than previously appreciated. Evolutionarily conservative host associations have been tempered by horizontal transfer and lineage duplication among closely related Ficus species. Independent and asynchronistic diversification of pollinating fig wasps is best explained by a combination of both sympatric and allopatric models of speciation. Pollinator host preference constraints permit reproduction on closely related Ficus species, but uncertainty of the frequency and duration of these associations requires better resolution.

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In a mutualistic relation between a potter wasp, Allodynerus delphinalis (Giraud) (Hymenoptera: Vespidae), and its specific parasitic mite, Ensliniella parasitica Vitzthum (Winterschmidtiidae), behaviour of the mite guarding the wasp and attacking their common natural enemy, Melittobia acasta (Walker) (Hymenoptera: Eulophidae), was examined.While mite attacks to M. acasta occurred by accidental physical contact, the counterattack by the parasitoid occurred 24 h after both were released onto their mutual host. The two organisms fought until one of them died in our experimental arena, which the parasitoid could not escape from to avoid combat. It was not possible to determine what the behaviour of the parasitoid would be had it been able to escape. Mite phoretic behaviour was also examined to understand the mechanism by which both the host wasp and the mite could reap reciprocal benefits from the presence of acarinaria on the wasp. The results suggested that the newly emerged host wasp might have an attractant to collect the necessary number of mites in an acarinarium, which would later function as guards of its offspring, given that around 46% of mite deutonymphs were able to migrate into one of the acarinaria within only 10 min after they were put together in an experimental arena. To more fully understand the strategy of each organism involved in this mutualism, further observation on their behaviour is needed.

Torymus sinensis: a viable management option for the biological control of Dryocosmus kuriphilus in Europe?

The chestnut gall wasp Dryocosmus kuriphilus is a global pest of chestnut (Castanea spp). Established as a pest in the mid-twentieth century in Japan, Korea and North America, this species was first reported in Europe in 2002. Following the successful release of a biological control agent Torymus sinensis in Japan, this parasitoid species has been released in Italy since 2005. Here we discuss the potential of T. sinensis as a viable management option for the biological control of D. kuriphilus in central Europe. We suggest that more consideration should be given to determining, (i) the conditions under which T. sinensis may attack alternative native gall wasp hosts and (ii) the likelihood of hybridization of this species with native Torymus. Both issues are central to predicting unassisted range expansion by released T. sinensis, and to assess the environmental risks associated with a more widespread release of this species in Europe.

Immunosuppression induced by expression of a viral RNase enhances susceptibility of Plutella xylostella to microbial pesticides

Abstract Polydnaviruses are a group of insect DNA viruses and are characterized in their segmented genome that is located in the chromosome(s) of host wasps. A polydnavirus, Cotesia plutellae bracovirus (CpBV), encodes a viral ribonuclease (RNase) T2 in a specific segment #3 (CpBV‐S3). This study tested its effect on gene expression associated with host immune responses in the diamondback moth, Plutella xylostella. Micro‐injection of CpBV‐S3 into nonparasitized larvae induced expression of its two encoded genes, CpBV‐ORF301 (=CpBV‐RNase T2) and CpBV‐ORF302. In response to a bacterial challenge, four antimicrobial peptide genes (hemolin, gloverin, cecropin and lysozyme) and six phenoloxidase (PO)–associated genes (proPO‐activating proteinase, PO, serine proteinase homolog and serpins 1–3) were up‐regulated in their expressions. However, the transient expression of CpBV‐S3 suppressed the expressions of cecropin, PO and serpin 1. Double‐stranded RNA specific to the viral RNase T2 could specifically knockdown the viral gene expression and restored the three gene expressions suppressed in the larvae injected with CpBV‐S3. The inhibitory activity of the viral RNase T2 on the target genes was further proven by the suppression of PO activation in response to bacterial challenge in the larvae injected with CpBV‐S3. This immunosuppression by the expression of the viral RNase T2 resulted in significant increase of pathogen susceptibility of P. xylostella against Bacillus thuringiensis or baculovirus infection.

Host location by the fruit fly parasitoid Diachasmimorpha krausii: role of fruit fly species, life stage and host plant

1 Diachasmimorpha krausii is a braconid parasitoid of larval tephritid fruit flies, which feed cryptically within host fruit. At the ovipositor probing stage, the wasp cannot discriminate between hosts that are physiologically suitable or unsuitable for offspring development and must use other cues to locate suitable hosts. 2 To identify the cues used by the parasitoid to find suitable hosts, we offered, to free flying wasps, different combinations of three fruit fly species (Bactrocera tryoni, Bactrocera cacuminata, Bactrocera cucumis), different life stages of those flies (adults and larvae) and different host plants (Solanum lycopersicon, Solanum mauritianum, Cucurbita pepo). In the laboratory, the wasp will readily oviposit into larvae of all three flies but successfully develops only in B. tryoni. Bactrocera tryoni commonly infests S. lycopersicon (tomato), rarely S. mauritianum (wild tobacco) but never C. pepo (zucchini). The latter two plant species are common hosts for B. cacuminata and B. cucumis, respectively. 3 The parasitoid showed little or no response to uninfested plants of any of the test species. The presence of adult B. tryoni, however, increased parasitoid residency time on uninfested tomato. 4 When the three fruit types were all infested with larvae, parasitoid response was strongest to tomato, regardless of whether the larvae were physiologically suitable or unsuitable for offspring development. By contrast, zucchini was rarely visited by the wasp, even when infested with B. tryoni larvae. 5 Wild tobacco was infrequently visited when infested with B. cacuminata larvae but was more frequently visited, with greater parasitoid residency time and probing, when adult flies (either B. cacuminata or B. tryoni) were also present. 6 We conclude that herbivore-induced, nonspecific host fruit wound volatiles were the major cue used by foraging D. krausii. Although positive orientation to infested host plants is well known from previous studies on opiine braconids, the failure of the wasp to orientate to some plants even when infested with physiologically suitable larvae, and the secondary role played by adult fruit flies in wasp host searching, are newly-identified mechanisms that may aid parasitoid host location in environments where both physiologically suitable and unsuitable hosts occur.

Pollinator sharing in dioecious figs (Ficus: Moraceae)

As one of the most specialized pollination syndromes, the fig (Ficus)–fig wasp (Agaonidae) mutualism can shed light on how pollinator behaviour and specificity affect plant diversification through processes such as reproductive isolation and hybridization. Pollinator sharing among species has important implications for Ficus species delimitation and the evolutionary history of the mutualism. Although agaonid wasp pollinators are known to visit more than one host species in monoecious figs, pollinator sharing has yet to be documented in dioecious figs. The present study investigated the frequency of pollinator sharing among sympatric, closely-related dioecious figs in Ficus sections Sycocarpus and Sycidium. Molecular and morphological species identification established the associations between pollinating agaonid wasp species and host fig species. Cytochrome oxidase I was sequenced from 372 Ceratosolen pollinators of Ficus section Sycocarpus and 210 Kradibia pollinators of Ficus section Sycidium. The association between fig species and morphologically distinct clades of pollinator haplotypes was predominantly one-to-one. In Ceratosolen, six of 372 pollinators (1.5%) visited fig species other than the predominant host. No pollinator sharing was detected between the two Sycidium host species, although a rare hybrid shared Kradibia pollinators with both parental species. These findings point to low rates of pollinator sharing among closely-related dioecious fig species in sympatry, and perhaps lower rates than among monoecious figs. Such rare events could be evolutionarily important as mechanisms for gene flow among fig species. Differences in rates of pollinator sharing among fig lineages might explain the conflicting phylogenetic patterns inferred among monoecious figs, dioecious figs, and their respective pollinators. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103, 546–558.

Spatial and temporal aspects of the relationships between Latibulus argiolus (Rossi) (Hymenoptera: Ichneumonidae) parasitoid and the resocial host wasp Polistes nimpha (Christ) (Hymenoptera: Vespidae)

The observations have shown that under the conditions of the Proval‘skaya steppe of the Lugansk nature reserve females of the first generation of parasitoid Latibulus argiolus display a behavioral response to the distribution of the host, the resocial wasp Polistes nimpha. L. argiolus females concentrate their searching activity on the sites with a high host colony density, and their distribution depends on the nest size. When the parasitoid number increases, they start parasitizing the host earlier, sometimes even before worker emergence. The density-dependent behavioral response observed in the nature is conditioned in the first place by the influence of the numerical response component since when the parasitoid number increases, they start parasitizing the host earlier, sometimes even before worker emergence.

Herbivore‐induced plant volatiles enhance the ability of parasitic wasps to find hosts on a plant

AbstractWe previously reported that cabbage plants emitted volatiles in response to herbivory by diamondback moth (DBM) larvae and that a cocktail of four induced volatile compounds (n‐heptanal, sabinene, α‐pinene and (Z)‐3‐hexenyl acetate) attracted Cotesia vestalis, a wasp parasitoid of DBM larvae (Shiojiri et al., PLOS ONE, 2010). Here, we describe the behaviour of the wasp in response to exposure to the cocktail and a solvent (control) on crucifer plants (Brassica rapa) with DBM larvae. Wasps showed longer residence and search times on plants with the cocktail than they did on control plants. Further, both wasp–host encounters and oviposition frequencies were significantly higher on plants associated with the cocktail and the rates of parasitism on plants with the cocktail increased due to longer residence and increased searching activity by the parasitoid on the plant. These results indicate that the host‐searching activity of the parasitoid C. vestalis is enhanced on host‐infested plants by the DBM‐induced plant volatiles.

Chemical Analyses of Wasp-Associated Streptomyces Bacteria Reveal a Prolific Potential for Natural Products Discovery

Identifying new sources for small molecule discovery is necessary to help mitigate the continuous emergence of antibiotic-resistance in pathogenic microbes. Recent studies indicate that one potentially rich source of novel natural products is Actinobacterial symbionts associated with social and solitary Hymenoptera. Here we test this possibility by examining two species of solitary mud dauber wasps, Sceliphron caementarium and Chalybion californicum. We performed enrichment isolations from 33 wasps and obtained more than 200 isolates of Streptomyces Actinobacteria. Chemical analyses of 15 of these isolates identified 11 distinct and structurally diverse secondary metabolites, including a novel polyunsaturated and polyoxygenated macrocyclic lactam, which we name sceliphrolactam. By pairing the 15 Streptomyces strains against a collection of fungi and bacteria, we document their antifungal and antibacterial activity. The prevalence and anti-microbial properties of Actinobacteria associated with these two solitary wasp species suggest the potential role of these Streptomyces as antibiotic-producing symbionts, potentially helping defend their wasp hosts from pathogenic microbes. Finding phylogenetically diverse and chemically prolific Actinobacteria from solitary wasps suggests that insect-associated Actinobacteria can provide a valuable source of novel natural products of pharmaceutical interest.

A Numerical Analysis Model Allows Quantification of Lifespan-Dependent and Random Kinetic Processes Contributing to the Thrombocytopenia of Murine WAS.

AbstractAbstract 3684In vivo platelet consumption is thought to be due to two kinetically distinct types of process: random processes, such as hemostasis and/or immune-mediated clearance, and lifespan-dependent apoptosis. The Mills Dornhorst equation, which has been used to model platelet consumption, has several theoretical and practical drawbacks: 1) It assumes apoptosis is instantaneous, an assumption at odds with the lack of linearity that in vivo platelet consumption data shows at late points in the population lifespan; 2) It does not allow an explicit solution for the random consumption rate constant; and 3) It cannot be applied to in vivo platelet consumption data generated with allogeneic platelets. While a recent alternative model (Dowling et al., Blood. 2010 Jun 7. [Epub ahead of print]) offers a solution to the first of these problems, it does not address the others – and its application to platelet consumption data requires the estimation of a large number of kinetic modeling parameters (seven). Here we use a simpler numerical analysis model to quantify random and lifespan-dependent platelet consumption processes in normal and thrombocytopenic (WASP(-)) mice. Increased platelet turnover is thought to contribute the thrombocytopenia of WAS.Numerical analysis is a well established algorithm-based alternative to the use of analytic models such as the Dornhorst equation. Our model applies three parameter values (a random consumption rate constant, a “nominal lifespan”, and a random apoptosis rate constant) to a matrix comprising a series of platelet cohorts (in columns) which are sequentially produced and fractionally consumed in a series of time intervals (rows). Cohorts are consumed at a random (exponential) rate until they reach their nominal lifespan, after which they are consumed at a rate equal to the sum of the first rate and a random apoptosis rate. The summed cohort values achieved after equilibration of production and consumption comprise the population platelet count. Continued platelet consumption (after production is halted) then serves to model in vivo platelet consumption data, a process which takes into account consumption rate-dependent variation in the starting population's age distribution.A least squares fitting procedure is used to find parameter values which best fit observed platelet consumption data obtained with fluorescently tagged WT platelets in WT recipients, and WASP(-) platelets in WASP(-) recipients. Comparison of the resultant absolute random platelet consumption rate to known thresholds for thrombocytpenia-induced hemorrhage allows estimation of the effects of platelet preparation and labeling on the observed consumption rate (the “preparation lesion”). Inferred platelet lifespan distributions are in turn used to model the consumption of WT platelets in WASP(-) recipients, and of WASP(-) platelets in WT recipients. This type of comparison is not feasible with the MIlls-Dornhorst model.Our findings suggest that rapid random in vivo consumption due to an intrinsic (“cis”) platelet defect contributes significantly to the thrombocytopenia of murine WAS. Platelet production is increased in WASP(-) mice, but not as much as would be expected from the increased number of megakaryocytes in bone marrow and spleen. This result supports the idea that thrombopoiesis per megakaryocyte is inhibited by WASP deficiency. No significant “trans” effect of host WASP deficiency on the consumption rate of transfused WT platelets is seen, the differing appearances of raw platelet consumption data notwithstanding. However, the method also allows quantification of a significant “cis/trans” contribution of host WASP deficiency to the rapid consumption of WASP(-) platelets. The mechanism for the cis/trans effect is unknown.Application of this numerical analysis method to clinical platelet consumption data for thrombocytopenias of unknown etiology should allow quantification of the separate contributions of impaired platelet production and accelerated platelet consumption in such cases. Disclosures:No relevant conflicts of interest to declare.

A SERI technique reveals an immunosuppressive activity of a serine-rich protein encoded in Cotesia plutellae bracovirus

Polydnavirus genome is segmented and dispersed on host wasp chromosome. After replication, the segments form double- stranded circular DNAs and embedded in viral coat proteins. These viral particles are delivered into a parasitized host along with parasitoid eggs. A serine-rich protein (SRP) is predicted in a polydnavirus, Cotesia plutellae bracovirus (CpBV), genome in its segment no. 33 (CpBV-S33), creating CpBVSRP1. This study explored its expression and physiological function in the diamondback moth, Plutella xylostella, larvae parasitized by C. plutellae. CpBV-SRP1 encodes 122 amino acids with 26 serines and several predicted phosphorylation sites. It is persistently expressed in all tested tissues of parasitized P. xylostella including hemocyte, fat body, and gut. Its physiological function was analyzed by injecting CpBV-S33 and inducing its expression in nonparasitized P. xylostella by a technique called SERI (segment expression and RNA interference). The expression of CpBV-SRP1 significantly impaired the spreading behavior and total cell count of hemocytes of treated larvae. Subsequent RNA interference of CpBV-SRP1 rescued the immunosuppressive response. This study reports the persistent expression of CpBV-SRP1 in a parasitized host and its parasitic role in suppressing the host immune response by altering hemocyte behavior and survival.

Experimental Evidence that a Desert Parasitoid Keeps its Host Cool

The wasp parasitoid Pseudopompilus humboldti (Hymenoptera; Pompilidae) in the Negev desert of Israel stores its paralyzed host, the spider Stegodyphus lineatus (Araneae; Eresidae), at the entrance of the spider's nest. The spider is moved by the wasp from the depth of the nest to the entrance in spite of increased exposure to visually-searching predators, such as birds. We examined the hypothesis that this behaviour has evolved to prevent the wasp's host from overheating in this hot desert. Experimental manipulations of the position of the parasitized spiders demonstrated that spiders and wasp larvae could not survive the heat experienced deep in the spider's nest during summer. By contrast, in the cooler nest entrance, spiders and larvae survived, if they were overlooked by predators. This host-storing behaviour is an adaptive trade-off between thermoregulatory requirements and predation risk. This appears to be the first evidence that a parasitoid manipulates the temperature of its host, albeit for its own ultimate gain.

Transient expression of specific Cotesia plutellae bracoviral segments induces prolonged larval development of the diamondback moth, Plutella xylostella

A polydnavirus, Cotesia plutellae bracovirus (CpBV), possesses a segmented and dispersed genome that is located on chromosome(s) of its symbiotic endoparasitic wasp, C. plutellae. When the host wasp parasitizes larvae of the diamondback moth, Plutella xylostella, at least 27 viral genome segments are delivered to the parasitized host along with the wasp egg. The parasitized P. xylostella exhibits significant immunosuppression and a prolonged larval development. Parasitized larvae take about 2 days longer than nonparasitized larvae to develop until the wandering stage of the final larval instar, and die after egress of the full grown wasp larvae. Developmental analysis using juvenile hormone and ecdysteroid analogs suggests that altering endocrine signals could induce the retardation of larval developmental rate in P. xylostella. In this study we used a transient expression technique to micro-inject individual CpBV genome segments, and tested their ability to induce delayed larval development of P. xylostella. We demonstrated that a CpBV segment was able to express its own encoded genes when it was injected into nonparasitized larvae, in which the expression patterns of the segment genes were similar to those in the larvae parasitized by C. plutellae. Twenty three CpBV genome segments were individually cloned and injected into the second instar larvae of P. xylostella and their effects assessed by measuring the time taken for host development to the cocooning stage. Three CpBV genome segments markedly interfered with the host larval development. When the putative genes of these segments were analyzed, it was found that they did not share any common genes. Among these segments able to delay host development, segment S27 was predicted to encode seven protein tyrosine phosphatases (CpBV-PTPs), some of which were mutated by insertional inactivation with transposons, while other encoded gene expressions were unaffected. The mutant segments were unable to induce prolonged larval development of P. xylostella. These results suggest that CpBV can induce prolonged larval development of P. xylostella, and that at least some CpBV-PTPs may contribute to the parasitic role probably by altering titers of developmental hormones.

Natural enemy diversity reduces temporal variability in wasp but not bee parasitism

Biodiversity may enhance and stabilise ecosystem functioning, but little evidence exists for diversity–function relationships involving multitrophic interactions in real landscapes. In multitrophic communities diversity may vary at different trophic levels, with either synergistic or antagonistic effects on ecosystem functioning. Intensification of land-use systems is often found to reduce diversity, which in turn may lead to reduced associated ecological functions in natural food webs, such as host-parasite interactions. In this study we investigated the relationship between the number of natural enemy and host species and the mean rate and temporal variability of parasitism (inverse of stability), along an intensification gradient of coffee agroforests in Ecuador. We used standardised trap nests for bees and wasps and their natural enemies in 14 agroforests, and evaluated these monthly over a period of 17 months. We found that parasitism rates of wasps and bees increased with increasing number of enemy species and decreased with increasing number of host species. Temporal variability in parasitism rates decreased with increasing number of enemy species and increased with temporal variability in enemy species richness; however, these effects were restricted to wasp hosts. Intensification of agroforests did not significantly affect species richness of hosts or enemies or their relation to parasitism and its temporal variability. We conclude that high enemy diversity may enhance parasitism rates and that high host diversity may provide resistance against consumption. Furthermore, we show that a diverse and stable enemy community may also have a stabilizing effect on parasitism rates. However, these effects may be host-guild specific, as these relations were restricted to wasps.

Diversity and Phylogeny of Cardinium (Bacteroidetes) in Armored Scale Insects (Hemiptera: Diaspididae)

Abstract Species of Cardinium are intracellular endosymbionts of arthropods. They are known to interfere with the mode of reproduction in some parasitoid wasp and mite hosts, and they are associated with parthenogenesis in the oleander scale, Aspidiotus nerii Bouché (Hemiptera: Diaspididae). Here, we survey A. nerii more broadly for presence of Cardinium species. In total, we tested 593 individuals in 301 populations, representing 132 identified species of armored scale insects, by using polymerase chain reaction (PCR) and sequencing of 16S rDNA. We obtained positive PCR results in 67 individuals of 34 populations, representing 20 species and one unidentified individual. Sequencing of these PCR products yields 20 new Cardinium haplotypes, raising the number of known insect-associated Cardinium haplotypes from 15 to 35. The new host-list elucidates the ecology of Cardinium, which in insects seems to be specialized on plant-feeding Hemiptera and associated parasitoid Hymenoptera. A phylogenetic analysis of all known insect-associated Cardinium 16S sequences reveals deep diversity in armored scale insects and implies horizontal transfer of Cardinium among armored scale insects and their parasitoids.

Global transcriptional profile of Tranosema rostrale ichnovirus genes in infected lepidopteran hosts and wasp ovaries

The ichnovirus TrIV, transmitted by the endoparasitic wasp Tranosema rostrale to its lepidopteran host during oviposition, replicates asymptomatically in wasp ovaries and causes physiological dysfunctions in parasitized caterpillars. The need to identify ichnoviral genes responsible for disturbances induced in lepidopteran hosts has provided the impetus for the sequencing and annotation of ichnovirus genomes, including that of TrIV. In the latter, 86 putative genes were identified, including 35 that could be assigned to recognized ichnoviral gene families. With the aim of assessing the relative importance of each TrIV gene, as inferred from its level of expression, and evaluating the accuracy of the gene predictions made during genome annotation, the present study builds on an earlier qPCR quantification of transcript abundance of TrIV rep ORFs, in both lepidopteran and wasp hosts, extending it to other gene families as well as to a sample of unassigned ORFs. We show that the majority (91%) of putative ORFs assigned to known gene families are expressed in infected larvae, while this proportion is lower (67%) for a sample taken among the remaining ORFs. Selected members of the TrV and rep gene families are shown to be transcribed in infected larvae at much higher levels than genes from any other TrIV gene family, pointing to their likely involvement in host subjugation. In wasp ovaries, the transcriptional profile is dominated by a rep gene and a member of a newly described gene family encoding secreted proteins displaying a novel cysteine motif, which we identified among previously unassigned ORFs.