Joan van Baaren

University of Rennes | UR1 · UMR CNRS 6553 - Ecosystème-Biodiversité-Evolution (ECOBIO)

Sweet pepper is a crop that benefits from phytosanitary treatments with low environmental impact, especially the successful control of pests through the introduction of biological control agents in greenhouses. However, predators that naturally occur in these surroundings often enter greenhouses. The precise roles of these natural predators and the...

Climate change is ten times faster now than in the last global warming event, 56 million years ago, with temperature and extreme weather dramatically increasing due to human activity. This rapid changes in climate affect all levels of biodiversity. However, despite their high global biodiversity, only 3 percent of global climate change literature i...

Bet-hedging occurs when unreliable environments select for genotypes exhibiting a lower variance in fitness at the cost of a lower mean fitness for each batch of progeny. This means that at the level of the genotype, the production of mostly non-optimal phenotypes may be favored when at least some phenotypes are successful. As extreme unreliable cl...

Warming temperate winters are resulting in increased insect winter activity. With modern agroecosystems largely homogenous, characterised by low floral diversity, competitive interactions may arise between flower-visiting species, with potential implications for the ecosystem services they provide (e.g. biological control and pollination). Flower s...

One method to study the impact of climate change on host-parasitoid relationships is to compare populations along geographical gradients in latitude, altitude or longitude. Indeed, temperatures, which vary along geographic gradients directly shape the life traits of parasitoids and indirectly shift their populations through trophic interactions wit...

Context Flower-visiting insects depend on floral resource availability from both cultivated and semi-natural habitats in agricultural landscapes. Landscape studies exploring insect abundance mainly focus on land cover maps without considering plant species within. Highlighting the functional role of landscapes through the potential floral resources...

By increasing plant diversity in agroecosystems, it has been proposed that one can enhance and stabilize ecosystem functioning by increasing natural enemies’ diversity. Food web structure determines ecosystem functioning as species at different trophic levels are linked in interacting networks. We compared the food web structure and composition of...

Plant viruses transmitted by vector pests are one of the most important worldwide threats to global food production and security. Biological control strategies to enhance natural enemies (parasitoids and predators) have mainly focused on their ability to reduce pest density. In contrast, few studies have examined how natural enemies affect the spre...

Climate warming is considered to be among the most serious of anthropogenic stresses to the environment, because it not only has direct effects on biodiversity, but it also exacerbates the harmful effects of other human‐mediated threats. The associated consequences are potentially severe, particularly in terms of threats to species preservation, as...

All species interact in complex antagonistic or mutualistic networks that may be driven by turnover in species composition due to spatiotemporal environmental filtering. Therefore, studying differences in insect communities along environmental gradients may improve our understanding of the abiotic and biotic factors that shape the structure of trop...

Background Cover crops can be used as a habitat management strategy to enhance the natural enemies and their temporal synchronization with a target pest. We examined the effect of winter oat intercropping within organic plum orchards on the natural enemy abundance and seasonal dynamics on the biological control of plum aphids in spring in Central C...

Physiological thermotolerance and behavioral thermoregulation are central to seasonal cold adaptation in ectothermic organisms. For species with enhanced mobility, behavioral responses may be of greater importance in the cold stress response. Employing the carabid beetles as a study organism, the current study compared physiological thermotolerance...

Intensive agriculture has profoundly altered biodiversity and trophic relationships in agricultural landscapes, leading to the deterioration of many ecosystem services such as pollination or biological control. Information on which spatio-temporal factors are simultaneously affecting crop pests and their natural enemies is required to improve conse...

Identifying which behavioural strategies maximize individual fitness is a key objective in ecology. Organisms are known to adapt their foraging behaviour to their environment in response to abiotic and biotic constraints, such as the distribution of resources or the presence of competitors. For instance, bees are known to avoid recently visited flo...

When organisms coevolve, any change in one species can affect phenotypes and ecology of the other species. Upper trophic levels have to synchronize their life-cycle to both abiotic conditions and lower trophic level species phenotypic variations and phenology. The role such interactions play in ecosystems is central, but their mechanistic bases rem...

Understanding how resource diversification affects ecological interactions, food web structure and ecosystem functioning is essential in both fundamental and applied ecology. While plant diversification strategies (either in‐field or around‐field) are often proposed in agricultural landscapes as practices to improve the biological control of herbiv...

Upon encountering a host, a female parasitoid wasp has to decide whether to learn positive or negative cues related to a host. The optimal female decision will depend on the fitness costs and benefits of learned stimuli. Reward quality is positively related to the rate of behavioral acquisition in processes such as associative learning. Wolbachia,...

The onset of an overwintering strategy to overcome cold temperatures of a species of ectotherms can include remaining active or entering diapause. This in turn will depend on the relative costs of each strategy and therefore, could differ among populations along a latitudinal gradient. Thus, expecting higher levels of diapause in the coldest condit...

In temperate climates, many insects are losing their diapause overwintering strategy as a consequence of warming winters and instead are remaining active all year round. Increased winter activity sees insects vulnerable to the challenging cold temperatures of winter months in a time when food availability is limited. This is true of parasitoid wasp...

The Earth's climate is changing at a rapid pace. To survive in increasingly fluctuating and unpredictable environments, species can either migrate or evolve through rapid local adaptation, plasticity and/or bet-hedging. For small ectotherm insects, like parasitoids and their hosts, phenotypic plasticity and bet-hedging could be critical strategies...

The occurrence of different color patterns in a population of a species can depend on genetic variations or plasticity to environmental conditions. Body color variation is under selection because it is involved in several ecological processes such as camouflage for prey-predator interactions or resistance to environmental variations. Among insects,...

The original article has been corrected.

Abstract Body size is an important biotic factor in evolutionary ecology, since it affects all aspects of insect physiology, life history, and consequently, fitness in ectothermic insects and how species adapt with their environment. It has been linked to temperature, with lower temperatures resulting in larger size. In this study, we tested the c...

In temperate climates, as a consequence of warming winters, an increasing number of ectothermic species are remaining active throughout winter months instead of diapausing, rendering them increasingly vulnerable to unpredictable cold events. One species displaying a shift in overwintering strategy is the parasitoid wasp and biological control agent...

Climate warming is largely attributed to a substantial increase in nighttime rather than in daytime temperatures. However, previous studies concerning the warming effects on species and interspecific interactions mainly focus on changes in average or daytime temperature. Night warming is often overlooked in climate change studies. Importantly, the...

The use of cover crops can promote the abundance and early arrival of populations of natural enemies. Cereal cover crops between orchards rows could encourage the early arrival of the parasitoid Aphidius platensis, as they offer alternative winter hosts (e.g., Rhopalosiphum padi), enhancing the control of Myzus persicae in spring. However, the pref...

Organisms are likely to experience novel photoperiod-temperature conditions, either as a consequence of poleward range shifts or of local changes in phenology. However, constraints of living under short day-length are for now little researched and the ecological and evolutionary effects of photoperiodic conditions independent from temperatures on o...

Resource partitioning is a key ecological mechanism allowing species sharing similar resources to limit competition and coexist. Pollinator communities in European agricultural landscapes are ideal models to study resource partitioning, as floral resources are often limited and honeybees, potential competitors, are widespread. Mass-flowering crops...

In organisms, the energy allocated to different functions, such as between survival and reproduction, can vary according to biotic and/or abiotic constraints, resulting in trade-offs between associated life history traits. Life history strategies adopted by organisms depend notably on their position along the Capital-Income Breeder Continuum (CIBC)...

Transgenerational effects act on a wide range of insects' life-history traits and can be involved in the control of developmental plasticity, such as diapause expression. Decrease in or total loss of winter diapause expression recently observed in some species could arise from inhibiting maternal effects. In this study, we explored transgenerationa...

When a guild of species exploit the same limited resources, interspecific competition induces the exclusion of inferior competitors, in which case, interspecific recognition mechanisms are needed. Here, we address resource partitioning and interspecific competition among three main solitary parasitoid species attacking the same host resource, the a...

Within the optimal foraging theory framework, parasitoids constitute ideal models to elucidate combined physiological and environmental determinism of foraging behavior between current and future fitness gains. Parasitoid females need hosts to lay eggs for their reproduction (immediate gain), but also sugar food resources for their survival (future...

In agricultural areas, the climatic conditions at the northern limit of crop cultures could impact pest regulation. In this paper, we study the aphid-parasitoid-hyperparasitoid network in cereal fields around Saskatoon (SK, Canada), one of the most harsh climatic conditions for cereal crops in the world, with an extremely short growing season. We h...

Los cultivos de cobertura pueden ser una alternativa de manejo en el control biológico de áfidos, al favorecer la diversidad y actividad de enemigos naturales, y al ser hospederos alternativos que proporcionan refugio y alimento. Los parasitoides son usados con frecuencia en el control biológico por su especialización y eficiencia. Los hospederos a...

Life-history traits within ecological communities can be influenced by two opposite pressures, the first one being community-wide density-dependent processes like competition (internal filters), and the second regional environmental conditions (external filters). While species belonging to a guild may present contrasting traits as a means of niche...

1. In the context of global change, modifications in winter conditions may disrupt the seasonal phenology patterns of organisms, modify the synchrony of closely interacting species and lead to unpredictable outcomes at different ecological scales. 2. Parasites are present in almost every food web and their interactions with hosts greatly contribute...

Differentiation of traits among populations can evolve by drift when gene flow is low relative to drift or selection when there are different local optima in each population (heterogeneous selection), whereas homogeneous selection tends to prevent evolution of such a differentiation. Analyses of geographical variations in venom composition have bee...

Competition among foraging individuals of the same species occurs for several resources including, but not limited to, food, mates, nesting sites and, in parasitoid wasps, hosts. Individuals should therefore adapt their resource exploitation decisions accordingly and learning ability has been shown to be used in intraspecific competition situations...

Transgenerational effects act on a wide range of insects" life-history traits and can be involved in the control of developmental plasticity, such as diapause expression. Decrease in or total loss of winter diapause expression recently observed in some species could arise from inhibiting maternal effects. In this study, we explored transgenerationa...

To overwinter, insects from mild temperate areas can either enter diapause or remain active. Both strategies involve costs and benefits depending on the environment. In the first case, the emerging individuals will resist winter but have a reduced fitness because diapause entails physiological and ecological costs. In the second case, individuals n...

Consequences of inter-annual environmental fluctuations, including those associated with climate change, can have a knock-on effect from individual to community scale. In particular, changes in species seasonal phenology can modify the structure and composition of communities, with potential consequences on their functioning and the provision of ec...

Aphidius ervi Haliday (Hymenoptera: Braconidae) is a major natural enemy of several agricultural pests in North America. Yet little is known about its overwintering strategy, especially concerning the plastic response to photoperiod and temperature that induce diapause. Information on parasitoid overwintering patterns is of great importance if we a...

Consequences of environmental fluctuations, including those associated with climate changes, can have a knock-on effect from individual to community scale. In particular, changes in species seasonal phenology can modify the structure and composition of communities, with potential consequences on their functioning and the provision of ecosystem serv...

When organisms coevolve, any change in one species can induce phenotypic changes in traits and ecology of the other species. The role such interactions play in ecosystems is central, but their mechanistic bases remain underexplored. Upper trophic level species have to synchronize their life-cycle to both abiotic conditions and to lower trophic leve...

An important question in evolutionary ecology is to understand the drivers of phenotypic variations in contrasted environments. Disentangling plasticity from evolutionary responses in such contexts allows a better knowledge of how organisms adapt their phenotypes to changing climates. Various aspects of the seasonal ecology of insect populations ar...

Parasitoids are among the most important and successful groups of natural enemies used in the biological control of insect pests. In most systems, several parasitoid species can parasitize the same pest. The coexistence of parasitoids in agroecosystems and their efficacy as biological control agents may be disrupted by global warming. An increase o...

Most insect species are affected by Human Induced Rapid Environmental Changes (HIREC). Multiple responses to HIREC are observed in insects, such as modifications of their morphology, physiology, behavioural strategies or phenology. Most of the responses involve phenotypic plasticity rather than genetic evolution. Here, we review the involvement of...

Floral nectar has been widely probed to be essential for many parasitoid insects to complete their life cycle. Thermal stress caused by hot temperatures could be reduced if parasitoids are fed. We initially evaluated a group of plants attending several growing and flowering features. The best plants were tested for parasitoids adult longevity with...

Life‐history traits within ecological communities can be influenced by regional environmental conditions (external filters) and community‐wide density‐dependent processes (internal filters). While traits in a regional context may converge to a narrow range of values because of environmental filtering, species belonging to a guild may present contra...

Animals can produce a range of body colors depending on their environment. Coloration polymorphism is under selection because it is involved in several ecological processes such as camouflage and prey-predators interactions. Among insects, aphids are known to produce difference body color morphs depending on their biotic and abiotic environment and...

For generalist parasitoids such as those belonging to the Genus Aphidius, the choice of host species can have profound implications for the emerging parasitoid. Host species is known to affect a variety of life history traits. However, the impact of the host on thermal tolerance has never been studied. Physiological thermal tolerance, enabling surv...

In agrosystems, the increase in non-crop plant diversity by habitat management in or around arable fields contributes to improved Conservation Biological Control. During winter, plant flower are often used as monospecific ground cover and are expected to die before flowering as a result of recurrent frost events. Decreases in minimal temperature du...

According to bet-hedging theory, individuals that live in unpredictable environments can reduce variation in fitness outcomes by investing in different strategies at the same time. For arthropods, facultative summer diapause may be maternally induced, being expressed only in some offspring and depending on anticipated conditions or previous conditi...

Organisms often live in unpredictable environments and have to adopt life history strategies that optimize their fitness under these conditions. According to bet-hedging theory, individuals can reduce variation in fitness outcomes by investing in different strategies at the same time. For arthropods, facultative summer diapause enables survival dur...

Insects from temperate areas usually enter diapause to overwinter. Climate change may severely impact insect communities through changes in phenology and seasonal ecology. In Western France for instance, there has been a recent change in parasitoid species composition in cereal fields with some species that used to overwinter in diapause over the p...

Nutritional quality during early life can affect learning ability and memory retention of animals. Here we studied the effect of resource quality gained during larval development on the learning ability and memory retention of 2 sympatric strains of similar genetic background of the parasitoid Trichogramma brassicae: one uninfected and one infected...

Temperature is both a selective pressure and a modulator of the diapause expression in insects from temperate regions. Thus, with climate warming, an alteration of the response to seasonal changes is expected, either through genetic adaptations to novel climatic conditions or phenotypic plasticity. Since the 1980s in western France, the winter guil...

Nutritional quality during early life can affect learning ability and memory retention of animals. Here we studied the effect of resource quality gained during larval development on the learning ability and memory retention of 2 sympatric strains of similar genetic background of the parasitoid Trichogramma brassicae: one uninfected and one infected...

Landscape changes are known to exacerbate the impacts of climate change. As such, understanding the combined effect of climate and landscape on agro-ecosystems is vital if we are to maintain the function of agro-ecosystems. The present study aimed to elucidate the effects of agricultural landscape complexity on the microclimate and thermal toleranc...

Populations of herbivorous insects are naturally consumed by other predacious or predatory insect species. These entomophagous insects are thus plant-dwelling organisms that use the plant for several vital functions and are affected by plant traits at the evolutionary, organism and population levels. Many entomophagous species are used for the biol...

Global change is resetting the spatial and ecological equilibrium of complex co-evolutionary relationships between plants and their insect herbivores. We review the mechanisms at play in the responses of plant–insect interactions to global changes, including increased temperature and atmospheric CO2 concentrations, modification of land use and poll...

Populations of herbivorous insects are naturally consumed by other predacious or predatory insect species. These entomophagous insects are thus plant-dwelling organisms that use the plant for several vital functions and are affected by plant traits at the evolutionary, organism and population levels. Many entomophagous species are used for the biol...

Global change is resetting the spatial and ecological equilibrium of complex co-evolutionary relationships between plants and their insect herbivores. We review the mechanisms at play in the responses of planteinsect interactions to global changes, including increased temperature and atmospheric CO2 concentrations, modification of land use and poll...