1. Birds and bats are relevant natural enemies of pests in fruit crops. However, by preying also on arthropod natural enemies, they may act as intraguild predators that can lead to pest release. Disentangling how these two groups intervene in different ecological relationships is thus essential to understand their relative contribution and complementarity in pest control provision.
2. We used dietary DNA metabarcoding to build tri-trophic networks that account for direct and indirect interactions among top predators (birds and bats), mesopredators (spiders) and pests (insects) in apple and blueberry crops. To identify species closely linked to pests, we estimated modularity. To evaluate their topological and tri-trophic role, we quantified their centrality and the extent of distinct predatory pathways in their diets (i.e. direct pest predation, intraguild predation or both). Finally, in the case of birds in apple crop, we tested if the topological and tri-trophic role of species depended on their abundance, degree of insectivory and morphological traits.
3. The network was modular in both crops, with birds and bats occupying distinct modules feeding on different prey. Bats tended to be more directly connected to pests than birds, which were more frequently involved in intraguild predation. Among birds in the apple crop, higher abundance increased direct pest predation, whereas greater insectivory favoured intraguild predation. Morphology further shaped topological position, with smaller species with less pointed wings demonstrating higher centrality values.
4. Birds and bats showed different and complementary roles in pest control service, a pattern consistent among fruit crops. Both vertebrate groups were associated with different prey, and birds were more prone to promote pest release than bats, although such effect was weaker for common and less insectivorous species.
5. Synthesis and applications. Our study highlights that by combining interaction networks, tri-trophic cascades and species traits, we can better understand the role of species on the control of pests in fruit crops. In particular, our results point out that promoting bats and abundant birds may be an efficient strategy to enhance pest control in fruit orchards.

Coevolution in trophic interactions is often considered as a major factor underlying diversification in interacting species. Most focus hitherto has however been on bottom–up processes where host-associated differentiation drives diversification, and less on top–down processes through enemy-associated differentiation. In this paper, we contrast bottom–up and top–down processes as drivers for diversification based both on theoretical reasoning and empirical studies. As a framework, we use the oscillation hypothesis which posits that local differentiation and network rewiring following geographic range shifts are major drivers for diversification. Our conclusion is that speciation through bottom–up and top–down processes likely act on different spatial scales but also that conditions for the interaction are different for hosts and enemies. For example, enemies can select their resource, leading to a specialized attack, but hosts cannot select their attacker, leading to a generalized defense. These differences have the consequence that local adaptation likely proceeds at a faster pace in enemies, and particularly in parasitoids, compared to hosts. Our analysis results in several testable hypotheses but we also argue that further theoretical evolutionary models are needed that combine ecological processes and genetic mechanisms.

Background and aims: Florivory poses a threat to the sexual reproductive success of plants, having both quantitative and qualitative effects by reducing seed yield and seed quality. Plants can resist herbivory, tolerate damage, or employ a mix of these strategies to mitigate fitness costs. Organisms such as detritivores can increase nutrient availability in the rhizosphere, although it remains uncertain how plants invest these additional resources in contexts with and without herbivory, which may be particularly relevant in resource-limited ecosystems. Methods: We investigated the combined effects of detritivore beetle larvae and specialist florivorous pierid caterpillars on a semiarid Brassicaceae herb in a field setting, manipulating the abundance of both detritivores and floral herbivores across a full factorial density gradient. Results: Despite promoting tolerance (surplus production of reproductive tissue) and increasing resistance (increased glucosinolate production), a high density of floral herbivores negatively impacted seed production. However, this mixed plant response led to a non-linear relationship between herbivore density and damage, demonstrating its effectiveness against herbivory. Increasing detritivore density did not affect seed production, nor did it enable plants to better resist or compensate for florivore damage. Instead, high detritivore density had an independent transgenerational effect by increasing the emergence rate of seedlings, thereby favouring seed quality over quantity. Conclusion: Prioritising seed quality over quantity may be an adjustment of the reproductive strategy to ensure seedling establishment in harsh and unpredictable environments at the cost of fewer offspring. This finding underscores the necessity of accounting for transgenerational effects in plant defence theory.

Pesticide use and habitat loss are major anthropogenic drivers of bee decline, raising global concerns about impaired crop pollination. However, the relative importance of these stressors and their combined impact on bee assemblages comprising species with different traits, such as body size or nesting strategy, remains unknown. Here we addressed these key knowledge gaps in a global quantitative synthesis analysing bee assemblage data from 681 crop fields across three continents. We found that both local pesticide hazards and decreasing proportions of semi-natural habitats in surrounding landscapes negatively affected wild bee abundance and species richness in crop fields, while pesticides additionally reduced functional and phylogenetic diversity. Semi-natural habitat availability did not buffer against these negative pesticide effects, nor did we identify any specific traits rending bees more vulnerable to one of the two drivers. Our findings highlight the pressing need to reduce non-target effects of pesticide use and emphasize that conservation and restoration of semi-natural habitats successfully promote wild bees, but are insufficient strategies to mitigate pesticide-driven losses of wild bee pollinators from crop fields.

1. Predation can be a great source of mortality for insect eggs. Thus, female insects use multiple strategies to reduce it. Two common strategies are to aggregate eggs, which may function to satiate egg predators, and various deterrence strategies, such as the addition of faecal strings on top of the egg.
2. We tested the hypothesis that these two strategies work best in combination, where egg aggregation may strengthen the effect of deterrence strategies. We compared egg predation by the predator Paederus riparius both within the species Galerucella lineola (cleaned eggs versus eggs with faecal strings), and between the species G. lineola and G. sagittariae (where the latter species naturally lack faecal strings).
3. Our findings revealed a robust treatment interaction, where faecal strings and egg density affected egg survival when exposed to Paederus riparius. Egg survival increased with egg density for eggs with faecal strings but was constantly low on eggs without faecal strings (cleaned G. lineola eggs or G. sagittariae eggs).
4. This study emphasised that a combination of insect traits may be needed to defend insect eggs against their natural predators.

1. Apple is one of the most important pollinator-dependent fruit crops worldwide. To secure high-quality yields, it is crucial to know which, and to what extent, pollinating insects contribute to its pollination success as measured by fruit set, fruit weight and seed set.
2. We perform a meta-analysis of field studies conducted across multiple orchards on insect-mediated pollination in apple cultivation, using raw data from 29 studies, totalling 532 orchard replicates. We assessed the extent of pollen limitation on different pollination outcomes and assessed the contribution of honeybees, wild bees and bee species richness to apple pollination.
3. Across all studies, we detected strong evidence of pollen limitation for fruit set and seed set, but not for fruit weight. Honeybees were the most abundant flower visitors (average relative visitation of 71.9%) compared to wild bees; but when correcting for their pollination efficiency, the relative pollination contribution of honeybees was lower compared to their relative visitation (vice versa for solitary bees).
4. We conclude that honeybee visitation rate did not influence fruit or seed set; yet increasing honeybee visitation had a small, negative effect on fruit weight. Fruit set was not influenced by wild bee visitation rate, whereas wild bee visitation had a small, but clear positive effect on fruit weight and seed set. Bee species richness had a small, positive effect on seed set; whereas it did not affect fruit set and fruit weight.
5. Syntheses and applications. Our study highlights that pollen limitation is common in this global crop. While managed honeybees are dominant pollinators, a diverse community of wild bees contributes significantly to apple pollination and high-quality yield. The positive effect of wild bees and species richness on fruit weight and seed set demonstrates that wild bee pollination results in better-quality fruit production (increased weight & seed set). Therefore, our synthesis highlights the importance of conserving pollinator diversity to maintain pollination services. The absence of a clear effect of honeybee visitation rate on fruit and seed set, coupled with its negative impact on fruit weight, suggests a need for further optimisation of honeybee management to improve the cost-efficiency of pollination management.

Parasitoid wasps are major causes of mortality of many species, making host immune defences a common target of adaptive evolution, though such targets outside model species are poorly understood. In this study, we used two tests of positive selection to compare across three closely related Galerucella leaf beetles that show substantial differences in their phenotypic response to the shared parasitoid wasp Asecodes parviclava, their main natural enemy. Using a codon-based test, which detects excess amino acid fixations per locus along each species’ lineage, we found more evidence of positive selection on parasitoid-relevant immune genes in the species with the strongest immunocompetence (G. pusilla) compared with the species having weaker immunocompetence (G. tenella and G. calmariensis). Moreover, genes coding for the early phases in the immune response cascade were predominantly among the positively selected immune genes, providing targets for future functional genomic study to pin-point connections between genotypic and phenotypic differences in defences towards a parasitoid wasp. In contrast, genome-wide analyses of the haplotype frequency spectrum, which quantify selection over recent evolutionary time scales, revealed similar signatures of positive selection on immune genes across species. These results advance the field of host-parasitoid dynamics by providing novel insights into the tempo and mode of insect host evolutionary dynamics, and offering a framework for making genotype to phenotype connections for immunocompetence phenotypes.

Gut microbiomes of holometabolous insects can be strongly affected by metamorphosis. Previous studies suggest that microbiome colonization and community development often rely on specialized transmission routes between host life stages. However, there is a lack of comparative studies of microbial community dynamics from different transmission mechanisms. We compared the gut microbial community dynamics across life stages in five Galerucella species that differ in their potential microbial transfer mechanism by sequencing amplicons of the 16S rRNA gene. Females of three of the studied species place a fecal string on top of the egg, which may enhance the transfer of gut microbes, whereas females of the two other species do not. We found that the α-diversity was more stable between life stages in fecal string-placer species compared with the non-fecal string-placer species. Moreover, there were consistent microbiome differences between species, with multiple taxa in each species consistently appearing in all life stages. Fecal strings placed on eggs seem to play an important role in the diversity and dynamics of gut bacteria in Galerucella species, facilitating the vertical transfer of gut bacteria between host insect generations. Alternative, but less efficient, transmission routes appear to occur in non-fecal string-placer species.

Context  Flood disturbances act as strong filters on arthropod communities by excluding species that are not adapted to the high water-tables. Sensitive species can survive in these areas by either migrating to more terrestrial habitats or by using dry refuges within the wetland created by topographical heterogeneity.

Objectives  We examined the role of dry refugia and the scale at which these affect arthropod densities, mainly cursorial species, by using previous information on local dryness-wetness of wetlands.

Methods  We selected sites wiith different flooding regimes within a large fen based on used prior information on local dryness-wetness of wetlands at 2 × 2 m resolution. We then used suction sampling to collect abundance data of beetles and spiders, and related these data to flooding regimes at spatial scales up to 26 × 26 m.

Results  These studies indicated that species within Linyphiidae, Staphylinidae and Chrysomelidae were more abundant in the presence of dry refuges at a scale of 10 × 10 m, whereas Salticidae preferred wetter areas. Species within Carabidae, Lycosidae and a number of other taxon groups were indifferent to these structures. Moreover, the data seem to suggest that mainly habitat generalists benefit from the refuges. Accordingly, those groups that were impartial to the dry refuges included almost exclusively species that can be categorised as wetland specialists.

Conclusions  Small-scale refuges in heterogeneously flooded wetlands may be important to consider for guiding contemporary efforts to restore wetlands as a mean to promote biodiversity.

Wetlands are valuable and diverse environments that contribute to a vast range of ecosystem services, such as flood control, drought resilience, and carbon sequestration. The provision of these ecosystem services depends on their hydrological functioning, which refers to how water is stored and moved within a wetland environment. Since the hydrological functions of wetlands vary widely based on location, wetland type, hydrological connectivity, vegetation, and seasonality, there is no single approach to defining these functions. Consequently, accurately identifying their hydrological functions to quantify ecosystem services remains challenging. To address this issue, we investigate the hydrological regimes of wetlands, focusing on water extent, to better understand their hydrological functions. We achieve this goal using Sentinel-1 SAR imagery and a self-supervised deep learning model (DeepAqua) to predict surface water extent for 43 Ramsar sites in Sweden between 2020 and 2023. Clustering analysis grouped the wetlands based on the water extent predictions into five archetypes based on their hydrological similarity: “spring-surging”, “spring-flooded”, “summer-flooded”, “slow-drying”, and “summer-dry”. The archetypes represent great heterogeneity, with flashy regimes being more prominent at higher latitudes and smoother regimes found preferentially in central and southern Sweden. Additionally, many wetlands show exceptional similarity in the timing and duration of flooding and drying events, which only became apparent when grouped. We attempt to link hydrological functions to the archetypes, whereby headwater wetlands, such as spring-surging wetlands, have the potential to accentuate floods and droughts, while slow-drying wetlands, typical of floodplain wetlands, are more likely to provide services such as flood attenuation and water storage during low flow conditions. Additionally, although wetlands can be classified in a myriad of ways, we propose that classifying wetlands based on the hydrological regime derived from water surface extent is useful for identifying hydrological functions specific to the site and season and when discharge or water level data are not available. Lastly, we foresee that hydrological-regime-based classification can be easily applied to other wetland-rich landscapes to better understand the hydrological functions and identify their respective ecosystem services.