Sex-Specific Transcriptomic Changes in the Villous Tissue of Placentas of Pregnant Women Using a Selective Serotonin Reuptake Inhibitor.

About 5% of pregnant women are treated with selective serotonin reuptake inhibitor (SSRI) antidepressants to treat their depression. SSRIs influence serotonin levels, a key factor in neural embryonic development, and their use during pregnancy has been associated with adverse effects on the developing embryo. However, the role of the placenta in transmitting these negative effects is not well understood. In this study, we aim to elucidate how disturbances in the maternal serotonergic system affect the villous tissue of the placenta by assessing whole transcriptomes in the placentas of women with healthy pregnancies and women with depression and treated with the SSRI fluoxetine during pregnancy. Twelve placentas of the Biology, Affect, Stress, Imaging and Cognition in Pregnancy and the Puerperium (BASIC) project were selected for RNA sequencing to examine differentially expressed genes: six male infants and six female infants, equally distributed over women treated with SSRI and without SSRI treatment. Our results show that more genes in the placenta of male infants show changed expression associated with fluoxetine treatment than in placentas of female infants, stressing the importance of sex-specific analyses. In addition, we identified genes related to extracellular matrix organization to be significantly enriched in placentas of male infants born to women treated with fluoxetine. It remains to be established whether the differentially expressed genes that we found to be associated with SSRI treatment are the result of the SSRI treatment itself, the underlying depression, or a combination of the two.

Circadian entrainment to red-light Zeitgebers and action spectrum for entrainment in the jewel wasp Nasonia vitripennis.

Light is the most important environmental cue for the circadian system of most organisms to stay synchronized to daily environmental changes. Like many other insects, the wasp Nasonia vitripennis has trichromatic compound eye-based colour vision and is sensitive to the light spectrum ranging from UV to green. We recently described a red-sensitive, ocelli-based photoreceptor, but its contribution to circadian entrainment remains unclear. In this study, we investigated the possibility of Nasonia circadian light entrainment under long-wavelength red LED light-dark cycles and characterized the strength of red light as a potential Zeitgeber. Additionally, we measured the possibility of entrainment under various light intensities (from 5·1012 to 4·1015 photons·cm-2·s-1) and a broader range of wavelengths (455-656 nm) to construct corresponding action spectra for characterizing all circadian photoreceptors involved in photic entrainment. We also conducted electroretinogram (ERG) recordings for each wavelength in the compound eyes. Our findings demonstrate that Nasonia can entrain under red light dark cycles, and the sensory pathway underlying the red-light Zeitgeber response may reside in the ocelli. Combined with findings from previous research, we pose that blue- and green-sensitive rhodopsin photoreceptor cells function as the major circadian photoreceptors in both circadian entrainment by light-dark cycles and circadian phase shifts by light pulses, whereas the red-sensitive photoreceptor cell requires higher light intensity for its role in circadian entrainment by light-dark cycles.

Transcriptomic Analysis of Light-Induced Genes in Nasonia vitripennis: Possible Implications for Circadian Light Entrainment Pathways.

Circadian entrainment to the environmental day-night cycle is essential for the optimal use of environmental resources. In insects, opsin-based photoreception in the compound eye and ocelli and CRYPTOCHROME1 (CRY1) in circadian clock neurons are thought to be involved in sensing photic information, but the genetic regulation of circadian light entrainment in species without light-sensitive CRY1 remains unclear. To elucidate a possible CRY1-independent light transduction cascade, we analyzed light-induced gene expression through RNA-sequencing in Nasonia vitripennis. Entrained wasps were subjected to a light pulse in the subjective night to reset the circadian clock, and light-induced changes in gene expression were characterized at four different time points in wasp heads. We used co-expression, functional annotation, and transcription factor binding motif analyses to gain insight into the molecular pathways in response to acute light stimulus and to form hypotheses about the circadian light-resetting pathway. Maximal gene induction was found after 2 h of light stimulation (1432 genes), and this included the opsin gene opblue and the core clock genes cry2 and npas2. Pathway and cluster analyses revealed light activation of glutamatergic and GABA-ergic neurotransmission, including CREB and AP-1 transcription pathway signaling. This suggests that circadian photic entrainment in Nasonia may require pathways that are similar to those in mammals. We propose a model for hymenopteran circadian light-resetting that involves opsin-based photoreception, glutamatergic neurotransmission, and gene induction of cry2 and npas2 to reset the circadian clock.

Phenological mismatch affects individual fitness and population growth in the winter moth.

Climate change can severely impact species that depend on temporary resources by inducing phenological mismatches between consumer and resource seasonal timing. In the winter moth, warmer winters caused eggs to hatch before their food source, young oak leaves, became available. This phenological mismatch changed the selection on the temperature sensitivity of egg development rate. However, we know little about the fine-scale fitness consequences of phenological mismatch at the individual level and how this mismatch affects population dynamics in the winter moth. To determine the fitness consequences of mistimed egg hatching relative to timing of oak budburst, we quantified survival and pupation weight in a feeding experiment. We found that mismatch greatly increased mortality rates of freshly hatched caterpillars, as well as affecting caterpillar growth and development time. We then investigated whether these individual fitness consequences have population-level impacts by estimating the effect of phenological mismatch on population dynamics, using our long-term data (1994-2021) on relative winter moth population densities at four locations in The Netherlands. We found a significant effect of mismatch on population density with higher population growth rates in years with a smaller phenological mismatch. Our results indicate that climate change-induced phenological mismatch can incur severe individual fitness consequences that can impact population density in the wild.

Social modulation of oogenesis and egg laying in Drosophila melanogaster.

Being part of a group facilitates cooperation between group members but also creates competition for resources. This is a conundrum for gravid females, whose future offspring benefit from being in a group only if there are enough resources relative to group size. Females may therefore be expected to modulate reproductive output depending on social context. In the fruit fly Drosophila melanogaster, females actively attract conspecifics to lay eggs on the same resources, generating groups in which individuals may cooperate or compete. The genetic tractability of this species allows dissecting the mechanisms underlying physiological adaptation to social context. Here, we show that females produce eggs increasingly faster as group size increases. By laying eggs faster when grouped than when isolated, females reduce competition between offspring and increase offspring survival. In addition, grouped females lay eggs during the day, while isolated females lay them at night. We show that responses to the presence of others requires visual input and that flies from any sex, mating status, or species can trigger these responses. The mechanisms of this modulation of egg laying by group is connected to a lifting of the inhibition of light on oogenesis and egg laying, possibly mediated in part by an increase in juvenile hormone activity. Because modulation of reproduction by social context is a hallmark of animals with higher levels of sociality, our findings in a species considered solitary question the validity of this nomenclature and suggest a widespread and profound influence of social context on reproduction.

Rapid but narrow - Evolutionary adaptation and transcriptional response of Drosophila melanogaster to toxic mould.

Insects have adapted to a multitude of environmental conditions, including the presence of xenobiotic noxious substances. Environmental microorganisms, particularly rich on ephemeral resources, employ these noxious chemicals in a chemical warfare against predators and competitors, driving co-evolutionary adaptations. In order to analyse how environmental microbes may be driving such evolutionary adaptations, we experimentally evolved Drosophila melanogaster populations by exposing larvae to the toxin-producing mould Aspergillus nidulans that infests the flies' breeding substrate. To disentangle the effects of the mycotoxin Sterigmatocystin from other substrate modifications inflicted by the mould, we used the following four selection regimes: (i) control without fungus, (ii) A. nidulans wild type, (iii) a mutant of A. nidulans ΔlaeA with impaired toxin production, (iv) synthetic Sterigmatocystin. Experimental evolution was carried out in five independent D. melanogaster populations each, for a total of 11 generations. We further combined our evolution experiment with transcriptome analysis to identify evolutionary shifts in gene expression due to the selection regimes and mould confrontation. Populations that evolved in presence of the toxin-producing mould or the pure mycotoxin rapidly adapted to the respective conditions and showed higher viability in subsequent confrontations. Yet, mycotoxin-selected populations had no advantage in A. nidulans wild type confrontation. Moreover, distinctive changes in gene expression related to the selection-regime contrast were only associated with the toxin-producing-fungus regime and comprised a narrow set of genes. Thus, it needs the specific conditions of the selection agent to enable adaptation to the fungus.

Aggregation pheromones have a non-linear effect on oviposition behavior in Drosophila melanogaster.

Female fruit flies (Drosophila melanogaster) oviposit at communal sites where the larvae may cooperate or compete for resources depending on group size. This offers a model system to determine how females assess quantitative social information. We show that the concentration of pheromones found on a substrate increases linearly with the number of adult flies that have visited that site. Females prefer oviposition sites with pheromone concentrations corresponding to an intermediate number of previous visitors, whereas sites with low or high concentrations are unattractive. This dose-dependent decision is based on a blend of 11-cis-Vaccenyl Acetate (cVA) indicating the number of previous visitors and heptanal (a novel pheromone deriving from the oxidation of 7-Tricosene), which acts as a dose-independent co-factor. This response is mediated by detection of cVA by odorant receptor neurons Or67d and Or65a, and at least five different odorant receptor neurons for heptanal. Our results identify a mechanism allowing individuals to transform a linear increase of pheromones into a non-linear behavioral response.

Circadian rhythm entrainment of the jewel wasp, Nasonia vitripennis, by antagonistic interactions of multiple spectral inputs.

Circadian light entrainment in some insects is regulated by blue-light-sensitive cryptochrome (CRY) protein that is expressed in the clock neurons, but this is not the case in hymenopterans. The hymenopteran clock does contain CRY, but it appears to be light-insensitive. Therefore, we investigated the role of retinal photoreceptors in the photic entrainment of the jewel wasp Nasonia vitripennis. Application of monochromatic light stimuli at different light intensities caused phase shifts in the wasp's circadian activity from which an action spectrum with three distinct peaks was derived. Electrophysiological recordings from the compound eyes and ocelli revealed the presence of three photoreceptor classes, with peak sensitivities at 340 nm (ultraviolet), 450 nm (blue) and 530 nm (green). An additional photoreceptor class in the ocelli with sensitivity maximum at 560-580 nm (red) was found. Whereas a simple sum of photoreceptor spectral sensitivities could not explain the action spectrum of the circadian phase shifts, modelling of the action spectrum indicates antagonistic interactions between pairs of spectral photoreceptors, residing in the compound eyes and the ocelli. Our findings imply that the photic entrainment mechanism in N. vitripennis encompasses the neural pathways for measuring the absolute luminance as well as the circuits mediating colour opponency.

Towards evolutionary predictions: Current promises and challenges.

Evolution has traditionally been a historical and descriptive science, and predicting future evolutionary processes has long been considered impossible. However, evolutionary predictions are increasingly being developed and used in medicine, agriculture, biotechnology and conservation biology. Evolutionary predictions may be used for different purposes, such as to prepare for the future, to try and change the course of evolution or to determine how well we understand evolutionary processes. Similarly, the exact aspect of the evolved population that we want to predict may also differ. For example, we could try to predict which genotype will dominate, the fitness of the population or the extinction probability of a population. In addition, there are many uses of evolutionary predictions that may not always be recognized as such. The main goal of this review is to increase awareness of methods and data in different research fields by showing the breadth of situations in which evolutionary predictions are made. We describe how diverse evolutionary predictions share a common structure described by the predictive scope, time scale and precision. Then, by using examples ranging from SARS-CoV2 and influenza to CRISPR-based gene drives and sustainable product formation in biotechnology, we discuss the methods for predicting evolution, the factors that affect predictability and how predictions can be used to prevent evolution in undesirable directions or to promote beneficial evolution (i.e. evolutionary control). We hope that this review will stimulate collaboration between fields by establishing a common language for evolutionary predictions.

Transcriptional regulation underlying the temperature response of embryonic development rate in the winter moth.

Climate change will strongly affect the developmental timing of insects, as their development rate depends largely on ambient temperature. However, we know little about the genetic mechanisms underlying the temperature sensitivity of embryonic development in insects. We investigated embryonic development rate in the winter moth (Operophtera brumata), a species with egg dormancy which has been under selection due to climate change. We used RNA sequencing to investigate which genes are involved in the regulation of winter moth embryonic development rate in response to temperature. Over the course of development, we sampled eggs before and after an experimental change in ambient temperature, including two early development weeks when the temperature sensitivity of eggs is low and two late development weeks when temperature sensitivity is high. We found temperature-responsive genes that responded in a similar way across development, as well as genes with a temperature response specific to a particular development week. Moreover, we identified genes whose temperature effect size changed around the switch in temperature sensitivity of development rate. Interesting candidate genes for regulating the temperature sensitivity of egg development rate included genes involved in histone modification, hormonal signalling, nervous system development and circadian clock genes. The diverse sets of temperature-responsive genes we found here indicate that there are many potential targets of selection to change the temperature sensitivity of embryonic development rate. Identifying for which of these genes there is genetic variation in wild insect populations will give insight into their adaptive potential in the face of climate change.

Evolution of parasitoid host preference and performance in response to an invasive host acting as evolutionary trap.

The invasion of a novel host species can create a mismatch in host choice and offspring survival (performance) when native parasitoids attempt to exploit the invasive host without being able to circumvent its resistance mechanisms. Invasive hosts can therefore act as evolutionary trap reducing parasitoids' fitness and this may eventually lead to their extinction. Yet, escape from the trap can occur when parasitoids evolve behavioral avoidance or a physiological strategy compatible with the trap host, resulting in either host-range expansion or a complete host-shift. We developed an individual based model to investigate which conditions promote parasitoids to evolve behavioral preference that matches their performance, including host-trap avoidance, and which conditions lead to adaptations to the unsuitable hosts. The model was inspired by solitary endo-parasitoids attacking larval host stages. One important aspect of these conditions was reduced host survival during incompatible interaction, where a failed parasitization attempt by a parasitoid resulted not only in death of her offspring but also in host killing. This non-reproductive host mortality had a strong influence on the likelihood of establishment of novel host-parasitoid relationship, in some cases constraining adaptation to the trap host species. Moreover, our model revealed that host-search efficiency and genetic variation in host-preference play a key role in the likelihood that parasitoids will include the suboptimal host in their host range, or will evolve behavioral avoidance resulting in specialization and host-range conservation, respectively. Hence, invasive species might change the evolutionary trajectory of native parasitoid species, which is important for predicting biocontrol ability of native parasitoids towards novel hosts.

Houseflies harbor less diverse microbiota under laboratory conditions but maintain a consistent set of host-associated bacteria.

The housefly (Musca domestica) is a wide-ranging insect, often associated with decaying matter from livestock and humans. The septic environments in which houseflies live are believed to be a rich source for microbial acquisition. Although the housefly can harbor a wide range of microorganisms, it is not yet well known which microbes are always recurrent, which are dispensable and which environmentally dependent. In the present study, we aim at identifying which microbes are recurrently associated with the housefly gut throughout the species' life cycle and whether their acquisition relies on the fly's living environment. We surveyed three housefly strains-two of them kept under standard laboratory conditions for a long time and one wild-caught. To track any shifts happening throughout the lifecycle of the housefly and to test the consistency of the revealed microbial communities, we sampled houseflies at five developmental stages over the course of four consecutive generations. Both the bacterial and fungal microbiota of five developmental stages were studied for all samples, using amplicon sequencing for the 16S and ITS1 rRNA gene, respectively. Results revealed diverse microbial communities yet consistent for each of the two distinct sampling environments. The wild-caught population showed a more diverse and more distinct gut microbiota than the two laboratory strains, even though the strain was phylogenetically similar and shared geographic origin with one of them. Two bacterial genera, Myroides and Providencia, and two yeasts, Trichosporon and Candida tropicalis, were present in all sampled larvae and pupae, regardless of the strain. Analysis of the provided diet revealed that the flies acquired the yeasts through feeding. Our main findings show that houseflies might lose microbial diversity when reared in controlled environments, however they can maintain a consistent set of bacteria. We conclude that although the environment can facilitate certain microbial transmission routes for the housefly, and despite the fungal microbiota being largely acquired through diet, the larval bacterial gut microbiome remains relatively consistent within the same developmental stage.

Coenzyme A precursors flow from mother to zygote and from microbiome to host.

Coenzyme A (CoA) is essential for metabolism and protein acetylation. Current knowledge holds that each cell obtains CoA exclusively through biosynthesis via the canonical five-step pathway, starting with pantothenate uptake. However, recent studies have suggested the presence of additional CoA-generating mechanisms, indicating a more complex system for CoA homeostasis. Here, we uncovered pathways for CoA generation through inter-organismal flows of CoA precursors. Using traceable compounds and fruit flies with a genetic block in CoA biosynthesis, we demonstrate that progeny survive embryonal and early larval development by obtaining CoA precursors from maternal sources. Later in life, the microbiome can provide the essential CoA building blocks to the host, enabling continuation of normal development. A flow of stable, long-lasting CoA precursors between living organisms is revealed. This indicates the presence of complex strategies to maintain CoA homeostasis.

Adaptations and counter-adaptations in Drosophila host-parasitoid interactions: advances in the molecular mechanisms.

Both hosts and parasitoids evolved a diverse array of traits and strategies for their antagonistic interactions, affecting their chances of encounter, attack and survival after parasitoid attack. This review summarizes the recent progress that has been made in elucidating the molecular mechanisms of these adaptations and counter-adaptations in various Drosophila host-parasitoid interactions. For the hosts, it focuses on the neurobiological and genetic control of strategies in Drosophila adults and larvae of avoidance or escape behaviours upon sensing the parasitoids, and the immunological defences involving diverse classes of haemocytes. For the parasitoids, it highlights their behavioural strategies in host finding, as well as the rich variety of venom components that evolved and were partially acquired through horizontal gene transfer. Recent studies revealed the mechanisms by which these venom components manipulate their parasitized hosts in exhibiting escape behaviour to avoid superparasitism, and their counter-strategies to evade or obstruct the hosts' immunological defences.

Timing of increased temperature sensitivity coincides with nervous system development in winter moth embryos.

Climate change is rapidly altering the environment and many species will need to genetically adapt their seasonal timing to keep up with these changes. Insect development rate is largely influenced by temperature, but we know little about the mechanisms underlying the temperature sensitivity of development. Here, we investigate seasonal timing of egg hatching in the winter moth, one of the few species which has been found to genetically adapt to climate change, likely through selection on temperature sensitivity of egg development rate. To study when during development winter moth embryos are most sensitive to changes in ambient temperature, we gave eggs an increase or decrease in temperature at different moments during their development. We measured their developmental progression and time of egg hatching, and used fluorescence microscopy to construct a timeline of embryonic development for the winter moth. We found that egg development rate responded more strongly to temperature once embryos were in the fully extended germband stage. This is the phylotypic stage at which all insect embryos have developed a rudimentary nervous system. Furthermore, at this stage, timing of ecdysone signaling determines developmental progression, which could act as an environment dependent gateway. Intriguingly, this may suggest that, from the phylotypic stage onward, insect embryos can start to integrate internal and environmental stimuli to actively regulate important developmental processes. As we found evidence that there is genetic variation for temperature sensitivity of egg development rate in our study population, such regulation could be a target of selection imposed by climate change.

Artificial selection for nonreproductive host killing in a native parasitoid on the invasive pest, Drosophila suzukii.

Establishment and spread of invasive species can be facilitated by lack of natural enemies in the invaded area. Host-range evolution of natural enemies augments their ability to reduce the impact of the invader and could enhance their value for biological control. We assessed the potential of the Drosophila parasitoid, Leptopilina heterotoma (Hymenoptera: Figitidae), to exploit the invasive pest Drosophila suzukii by focusing on three performance indices: (i) attack rate; (ii) host killing, consisting of killing rate and lethal attack rate (killing efficiency); and (iii) successful offspring development (reproductive success). We found significant intraspecific variation in attack rate and killing rate and lethal attack rate among seven European populations, but offspring generally failed to successfully develop from the D. suzukii host. We crossed these European lines to create a genetically variable source population and performed a half-sib analysis to quantify genetic variation. Using a Bayesian animal model, we found that attack rate and killing rate had a heritability of h 2 = 0.2 , lethal attack rate h 2 = 0.4 , and offspring development h 2 = 0 . We then artificially selected wasps with the highest killing rate of D. suzukii for seven generations to test whether host-killing could be improved. There was a small and inconsistent response to selection in the three selection lines. Realized heritability ( h r 2 ) after four generations of selection was 0.17 but near zero after seven generations of selection. The genetic response might have been masked by an increased D. suzukii fitness resulting from adaptation to laboratory conditions. Our study reveals that native, European, L. heterotoma can attack the invasive pest, D. suzukii and significantly reduce fly survival and that different steps of the parasitization process need to be considered in the evolution of host-range. It highlights how evolutionary principles can be applied to optimize performance of native species for biological control.

DROP: Molecular voucher database for identification of Drosophila parasitoids.

Molecular identification is increasingly used to speed up biodiversity surveys and laboratory experiments. However, many groups of organisms cannot be reliably identified using standard databases such as GenBank or BOLD due to lack of sequenced voucher specimens identified by experts. Sometimes a large number of sequences are available, but with too many errors to allow identification. Here, we address this problem for parasitoids of Drosophila by introducing a curated open-access molecular reference database, DROP (Drosophila parasitoids). Identifying Drosophila parasitoids is challenging and poses a major impediment to realize the full potential of this model system in studies ranging from molecular mechanisms to food webs, and in biological control of Drosophila suzukii. In DROP, genetic data are linked to voucher specimens and, where possible, the voucher specimens are identified by taxonomists and vetted through direct comparison with primary type material. To initiate DROP, we curated 154 laboratory strains, 856 vouchers, 554 DNA sequences, 16 genomes, 14 transcriptomes, and six proteomes drawn from a total of 183 operational taxonomic units (OTUs): 114 described Drosophila parasitoid species and 69 provisional species. We found species richness of Drosophila parasitoids to be heavily underestimated and provide an updated taxonomic catalogue for the community. DROP offers accurate molecular identification and improves cross-referencing between individual studies that we hope will catalyse research on this diverse and fascinating model system. Our effort should also serve as an example for researchers facing similar molecular identification problems in other groups of organisms.

Does Drosophila sechellia escape parasitoid attack by feeding on a toxic resource?

Host shifts can drastically change the selective pressures that animals experience from their environment. Drosophila sechellia is a species restricted to the Seychelles islands, where it specializes on the fruit Morinda citrifolia (noni). This fruit is known to be toxic to closely related Drosophila species, including D. melanogaster and D. simulans, releasing D. sechellia from interspecific competition when breeding on this substrate. Previously, we showed that larvae of D. sechellia are unable to mount an effective immunological response against wasp attack, while larvae of closely-related species can defend themselves from parasitoid attack by melanotic encapsulation. We hypothesized that this inability constitutes a trait loss due to a reduced risk of parasitoid attack in noni. Here we present a lab experiment and field survey aimed to test the hypothesis that specialization on noni has released D. sechellia from the antagonistic interaction with its larval parasitoids. Our results from the lab experiment suggest that noni may be harmful to parasitoid wasps. Our results from the field survey indicate that D. sechellia was found in ripe noni, whereas another Drosophila species, D. malerkotliana, was present in unripe and overripe stages. Parasitic wasps of the species Leptopilina boulardi emerged from overripe noni, where D. malerkotliana was the most abundant host, but not from ripe noni. These results indicate that the specialization of D. sechellia on noni has indeed drastically altered its ecological interactions, leading to a relaxation in the selection pressure to maintain parasitoid resistance.

Seasonal morphotypes of Drosophila suzukii differ in key life-history traits during and after a prolonged period of cold exposure.

Seasonal polyphenism in Drosophila suzukii manifests itself in two discrete adult morphotypes, the "winter morph" (WM) and the "summer morph" (SM). These morphotypes are known to differ in thermal stress tolerance, and they co-occur during parts of the year. In this study, we aimed to estimate morph-specific survival and fecundity in laboratory settings simulating field conditions. We specifically analyzed how WM and SM D. suzukii differed in mortality and reproduction during and after a period of cold exposure resembling winter and spring conditions in temperate climates. The median lifespan of D. suzukii varied around 5 months for the WM flies and around 7 months for the SM flies. WM flies showed higher survival during the cold-exposure period compared with SM flies, and especially SM males suffered high mortality under these conditions. In contrast, SM flies had lower mortality rates than WM flies under spring-like conditions. Intriguingly, reproductive status (virgin or mated) did not impact the fly survival, either during the cold exposure or during spring-like conditions. Even though the reproductive potential of WM flies was greatly reduced compared with SM flies, both WM and SM females that had mated before the cold exposure were able to continuously produce viable offspring for 5 months under spring-like conditions. Finally, the fertility of the overwintered WM males was almost zero, while the surviving SM males did not suffer reduced fertility. Combined with other studies on D. suzukii monitoring and overwintering behavior, these results suggest that overwintered flies of both morphotypes could live long enough to infest the first commercial crops of the season. The high mortality of SM males and the low fertility of WM males after prolonged cold exposure also highlight the necessity for females to store sperm over winter to be able to start reproducing early in the following spring.

Context-Dependence and the Development of Push-Pull Approaches for Integrated Management of Drosophila suzukii.

Sustainable pest control requires a systems approach, based on a thorough ecological understanding of an agro-ecosystem. Such fundamental understanding provides a basis for developing strategies to manipulate the pest's behaviour, distribution, and population dynamics, to be employed for crop protection. This review focuses on the fundamental knowledge required for the development of an effective push-pull approach. Push-pull is a strategy to repel a pest from a crop, while attracting it toward an external location. It often relies on infochemicals (e.g., pheromones or allelochemicals) that are relevant in the ecology of the pest insect and can be exploited as lure or repellent. Importantly, responsiveness of insects to infochemicals is dependent on both the insect's internal physiological state and external environmental conditions. This context-dependency reflects the integration of cues from different sensory modalities, the effect of mating and/or feeding status, as well as diurnal or seasonal rhythms. Furthermore, when the costs of responding to an infochemical outweigh the benefits, resistance can rapidly evolve. Here, we argue that profound knowledge on context-dependence is important for the development and implementation of push-pull approaches. We illustrate this by discussing the relevant fundamental knowledge on the invasive pest species Drosophila suzukii as an example.