Parasitoid Species Richness Research Articles

Through the green mosaic: Different tropical vegetation types have complementary effects on parasitoid diversity and biological control in organic agroecosystems

Land use change threaten global biodiversity, impacting ecosystem services, especially in diverse tropical regions. Yet, biodiversity conservation does not guarantee ecosystem services provision, given species' variable responses to local and landscape factors. Here, we evaluate how the landscape and local resources affect parasitoid diversity and aphid biological control in a tropical organic crop. Locally, we compared parasitoid communities within the crops and on adjacent non-crop plant strips and evaluated the effect of flower resource abundance on parasitoid diversity. At the landscape scale, we analyzed the effect of natural areas and their specific vegetational types on parasitoid diversity and the scale of these effects. Finally, we evaluated the relationship between biodiversity and biological control. Non-crop plant strips had higher parasitoid species richness and abundance than the crops, but similar species composition. Flower resource abundance in the non-crop strips negatively affected parasitoid richness. Natural areas in the landscape benefited parasitoid richness at a close range (0.42 km) and reduced parasitoid abundance at a wider scale (1.75 km). Forests and savannas increased parasitoid richness and reduced abundance, while grasslands drive parasitoid abundance and may disrupt species richness. Savannah areas, where trees and grasses coexist boosted the positive effects of forests on species richness and of grasslands on abundance. Parasitoid species richness benefited biological control exclusively in communities with intermediate and high number of parasitoid species. Our findings show that natural vegetation types with different wood densities have complementary effects in parasitoid diversity in tropical agroecosystems and represent a useful baseline for development of management and zoning plans.

Rainforest transformation reduces parasitoid wasp diversity—Can the enrichment of flowering vegetation alleviate this?

Abstract In Indonesia, the rapid expansion of oil palm and rubber plantations replaces large areas of tropical rainforest. Rainforest transformation alters the diversity and composition of parasitoid wasp communities, but appropriate management strategies to buffer their decline in rainforest transformation landscapes are not yet developed. Here, we studied the effects of rainforest conversion to smallholder rubber and oil palm plantations on parasitoid wasp species richness, abundance and species composition. We also conducted a flowering vegetation enrichment experiment using the flowering weed Asystasia gangetica in all land‐uses to investigate potential mitigation effects on parasitoid wasp diversity and composition. Rainforest transformation to rubber plantations caused a large decrease in species richness (46%) and abundance (59%) of parasitoid wasps. Community structure of parasitoid wasps differed between forest and monoculture habitats with more habitat‐specialised species in forest and a higher proportion of common species in the monoculture. The experimental flowering vegetation enrichment increased parasitoid wasp species richness by 18% and abundance by 127%. Enrichment also enhanced the presence of unique parasitoid species in plantation and furthermore increased differences in community composition between rainforest and plantations. However, the enrichment experiment was confounded by time, meaning that a multi‐year experiment with targeted controls is necessary for statistically more reliable statements. Our study shows the effect of rainforest transformation to oil palm and rubber plantations on parasitoid wasp communities. Although providing additional flowering vegetation in plantations seems to potentially mitigate diversity loss, further research is needed to confirm and to investigate the mechanisms how flowering plants alleviate negative effects of rainforest transformation on parasitoid communities. Thereby, efficient conservation strategies for parasitoids wasps and their biological control services can be developed for rapidly changing tropical landscapes.

Community structure of parasitoids attacking Schizomyia sasakii (Diptera: Cecidomyiidae) and local adaptation of the gall midge in the Izu region

AbstractInsect community structures and biological interactions vary with the distance from the mainland to islands. Gall inducers are key organisms in local arthropod communities because their galls harbor diverse arthropods. We investigated the parasitoid community of a gall‐inducing cecidomyiid Schizomyia sasakii on the Izu Peninsula and the Izu Islands, Japan. We examined relationships between parasitism by Inostemma sp. and Torymus hirtipennis, and gall characteristics, and analyzed the directional selection on gall characteristics induced by S. sasakii in each locality. The species richness of parasitoids on the Izu Islands decreased with the distance from the Izu Peninsula to each island, and area of respective islands. Inostemma sp. preferably attacked large galls on Ohshima Island, and T. hirtipennis tended to attack relatively small galls in the Izu Peninsula. Directional selection on gall characteristics of S. sasakii favored the induction of larger galls and thicker tissues by S. sasakii on Ohshima Island. In contrast, no directional selection was detected in the gall characteristics on Hachijojima Island. The number of alternative host species of parasitoid may affect variation in parasitoid richness of S. sasakii on distant and small islands, because the species richness of gall midges is necessary to maintain local parasitoid populations. Our study supported the ovipositor limitation hypothesis for the torymid species, related to gall size. The directional selection of parasitoid attacks on the Izu Islands may act to favor the induction of large and hypertrophic galls by S. sasakii to avoid the parasitoids.

Multitrophic arthropod diversity mediates tree diversity effects on primary productivity.

Forests sustain 80% of terrestrial biodiversity and provide essential ecosystem services. Biodiversity experiments have demonstrated that plant diversity correlates with both primary productivity and higher trophic diversity. However, whether higher trophic diversity can mediate the effects of plant diversity on productivity remains unclear. Here, using 5 years of data on aboveground herbivorous, predatory and parasitoid arthropods along with tree growth data within a large-scale forest biodiversity experiment in southeast China, we provide evidence of multidirectional enhancement among the diversity of trees and higher trophic groups and tree productivity. We show that the effects of experimentally increased tree species richness were consistently positive for species richness and abundance of herbivores, predators and parasitoids. Richness effects decreased as trophic levels increased for species richness and abundance of all trophic groups. Multitrophic species richness and abundance of arthropods were important mediators of plant diversity effects on tree productivity, suggesting that optimizing forest management for increased carbon capture can be more effective when the diversity of higher trophic groups is promoted in concert with that of trees.

Diversity and Composition of Arthropods Natural Enemies in Integrated Rice Fish Farming System (Minna padi) and Its Functions in Agroecosystems

Minna Padi is an integrated rice fish farming system that implements environmentally friendly cultivation and creates a sustainable ecosystem. However, the effects of minna padi farming systems on the diversity of natural enemies have not been reported previously. This research was conducted to compare the diversity and abundance of natural enemies [parasitoids and predators] in minna padi and conventional rice fields. Three pairs of minna padi and conventional paddy fields were selected for fields research. Natural enemies were collected in the field research using sweeping nets, yellow sticky traps and pitfall trap every two weeks during the cultivation. The results showed that the abundance of parasitoids was higher in minna padi than that in conventional farming systems. However, the abundance of predators was higher in conventional farming systems. Parasitoid and predator species richness also showed no difference between the two rice farming systems. However, the composition between the two farming systems was different, minna padi was dominated by parasitoids such as Aphonagmus sp. and Eurythoma dentata, while conventional dominated by a predator such as Pardosa pseudoannulata and Plexippus sp.

Parasitoid Wasp Community Dynamics in Vineyards Following Insecticide Application

In order to integrate parasitoid wasps in agroecosystems as biological control agents, we need to understand how insecticides affect the parasitoids in the crops and their surroundings. We investigated the non-target effect of Indoxacarb, an insecticide commonly used against European grapevine moth, on parasitoid wasp communities in vineyards. We focused on characterizing: 1. The dynamics of common wasp species, and 2. Wasp abundance and species richness in the vineyard center, edge, and nearby natural area. Seven vineyards, with neighboring natural areas, were sampled before, and up to 2 weeks after, Indoxacarb applications over 2 years. We expected initial negative effects of spraying in the vineyard with some effect of Indoxacarb drift into the natural habitat, followed by wasp recovery, first in natural areas, then at the vineyard edge and finally in the center. Sticky traps were hung at the vineyard edge and center to evaluate migration into and out of the vineyard. Vacuum sampling was used to obtain parasitoid total abundance and species richness, and the abundances of four common species (43% of the wasps collected). From the vacuum samples we found that total wasp abundance and richness declined after spraying in the vineyards’ margins and center but rose over time in the natural area. Vineyard wasp abundance was restored to pre-spraying levels within 2 weeks. Among the abundant species, Trichogramma sp. and Telenomus sp., which parasitize lepidopteran hosts, declined after spraying, and Trichogramma sp. recovered more quickly than Telenomus sp. Two other abundant species, Lymaenon litoralis and Oligosita sp., did not decline after spraying. In the sticky traps, wasp abundance increased at the vineyard edge but not center after spraying, suggesting that there was migration of wasps at the vineyard edge, into or out of the crop. The results indicate an effect of Indoxacarb on the parasitoid wasp community, particularly on parasitoids of lepidopterans, the target group of Indoxacarb. The results also indicate a potential for recovery of the parasitoid community through migration from neighboring natural vegetation.

Changes in galling insect community on Caryocar brasiliense trees mediated by soil chemical and physical attributes.

The nutrient stress hypothesis predicts that galling insects prevail on host plants growing in habitats with soils of low nutritional quality. Caryocar brasiliense (Caryocaraceae) is host to four different leaf-galling insects. These insects have the potential to cause a reduction in the production of C. brasiliense fruits, an important source of income for many communities in Brazil. We studied the effects of soil physical and chemical characteristics on the abundance, species richness, and diversity of galling insects and their natural enemies on C. brasiliense trees growing under three different soil conditions. Our data corroborate the hypothesis that in nutritionally poor (e.g., lower phosphorus content) and worse physical textures (e.g., sandy) soils, host plants support higher species richness and diversity of galling insects. However, the abundance of Eurytoma sp. (the most common gall in C. brasiliense), was correlated with a higher phosphorus concentration in the soil (better nutritional condition). The percentage of galled leaflets and the area of leaflets occupied by Eurytoma sp galls were higher in the more fertile soil. In this soil, there was greater abundance, species richness, and diversity of parasitoids of Eurytoma sp. (e.g., Sycophila sp.) and predators (e.g., Zelus armillatus). Our data indicate the importance of habitat quality in the composition of the galling insect community and the impact of soil properties in mediating the distribution of these insects in C. brasiliense.

Identifying plant mixes for multiple ecosystem service provision in agricultural systems using ecological networks

Abstract Managing agricultural environments in a way that maximises the provision of multiple ecosystem services is a significant challenge in the development of sustainable and secure food systems. Advances in network ecology provide a way forward, particularly in arable landscapes, as they incorporate mutualistic and antagonistic interactions associated with crop production. Here, we present an approach to identify mixes of non‐crop plant species that provide multiple ecosystem services while minimising disservices. Genetic algorithms were applied to the Norwood Farm ecological network—a comprehensive dataset of antagonistic and mutualistic species interactions on an organic farm in the United Kingdom. We aimed to show how network analyses can be used to select plants supporting a high diversity of insect pollinators and parasitoids of insect pests, but low diversity of herbivores. Further to this, we wanted to understand the trade‐offs in ecosystem service provision associated with conventional management practices that focus on individual ecosystem services. We show that multilayer network analyses can be used to identify mixes of plant species that maximise the species richness of pollinators and parasitoids (natural enemies of insect pests), while minimising the species richness of herbivores. Trade‐offs between ecosystem processes were apparent with several plant species associated with a high species richness of both positive (pollinators and parasitoids) and negative (herbivores) functional taxonomic groups. As a result, optimal plant species mixes for individual ecosystem services were different from the mix simultaneously maximising pollination and parasitism of pest insects, while minimising herbivory. Synthesis and applications. Plant mixes designed solely for maximising pollinator species richness are not optimal for the provision of other ecosystem services and disservices (e.g. parasitism of insect pests and herbivory). The method presented here will allow for the design of management strategies that facilitate the provision of multiple ecosystem services. To this end, we provide a protocol for practitioners to develop their own plant mixes suitable for farm‐scale management. This avenue of predictive network ecology has the potential to enhance agricultural management, supporting high levels of biodiversity and food production by manipulating ecological networks in specific ways.

Reprint of: Tree diversity promotes predatory wasps and parasitoids but not pollinator bees in a subtropical experimental forest

From regional to global scales, anthropogenic environmental change is causing biodiversity loss and reducing ecosystem functionality. Previous studies have investigated the relationship between plant diversity and functional insect communities in temperate and also in tropical grasslands and forests. However, few studies have explored these dynamics in subtropical forests. Here, cavity-nesting Hymenoptera and associated parasitoids were collected across a controlled tree diversity experiment in subtropical China to test how predatory wasps, bees and parasitoids respond to tree species richness. Abundance and species richness of predatory wasps and parasitoids were positively correlated with tree species richness, while bee abundance and bee species richness were unrelated to tree species richness. Our results indicate that tree species richness increases the abundance and species richness of important communities such as predators and parasitoids. Moreover, the results highlight the importance of subtropical forests in maintaining abundance and species richness of key functional insect groups.

The abundance and diversity of fruit flies and their parasitoids change with elevation in guava orchards in a tropical Andean forest of Peru, independent of seasonality.

Lower elevations are generally thought to contain a greater abundance and diversity of insect communities and their natural enemies than higher elevations. It is less clear, however, how changes in seasons influence this pattern. We conducted a 2-year study (2013‒2014) in guava orchards located in a tropical Andean forest of Peru to investigate differences in fruit flies (Diptera: Tephritidae) and their parasitoid communities at two elevations and over two seasons. Fruit fly traps were installed, monitored, and guava fruits were sampled from eight orchards at low (800–950 m above sea level) and high (1,700–1,900 m above sea level) elevations and during the dry and rainy seasons. At each orchard, adult fruit fly trap captures and emergence of fruit flies and their parasitoids from guava fruit were quantified to determine their abundance and species composition. There was a greater abundance and species richness of fruit flies captured in traps at lower elevations, as well as higher abundance and species evenness of fruit flies that emerged from fruit, indicating that lower elevations are associated with larger fruit fly populations. The abundance, species richness and diversity of parasitoids were also greater at lower elevations. Consequently, guava fruit infestation and fruit fly parasitism rates were also greater at lower elevations. Seasonality also influenced fruit fly populations with a greater number of flies emerging from guava fruit and more fruit infested in the rainy season. However, seasonality had no effect on parasitoid population parameters or rate of parasitism, nor did it interact with elevation as an influence of populations of fruit flies or their parasitoids in guava orchards. This study highlights the importance of examining both elevation and seasonality for a better understanding of the population dynamics of fruit flies and their parasitoids in tropical agroecosystems.

Abundance, not diversity, of host beetle communities determines abundance and diversity of parasitoids in deadwood.

Most parasites and parasitoids are adapted to overcome defense mechanisms of their specific hosts and hence colonize a narrow range of host species. Accordingly, an increase in host functional or phylogenetic dissimilarity is expected to increase the species diversity of parasitoids. However, the local diversity of parasitoids may be driven by the accessibility and detectability of hosts, both increasing with increasing host abundance. Yet, the relative importance of these two mechanisms remains unclear. We parallelly reared communities of saproxylic beetle as potential hosts and associated parasitoid Hymenoptera from experimentally felled trees. The dissimilarity of beetle communities was inferred from distances in seven functional traits and from their evolutionary ancestry. We tested the effect of host abundance, species richness, functional, and phylogenetic dissimilarities on the abundance, species richness, and Shannon diversity of parasitoids. Our results showed an increase of abundance, species richness, and Shannon diversity of parasitoids with increasing beetle abundance. Additionally, abundance of parasitoids increased with increasing species richness of beetles. However, functional and phylogenetic dissimilarity showed no effect on the diversity of parasitoids. Our results suggest that the local diversity of parasitoids, of ephemeral and hidden resources like saproxylic beetles, is highest when resources are abundant and thereby detectable and accessible. Hence, in some cases, resources do not need to be diverse to promote parasitoid diversity.

Tree diversity promotes predatory wasps and parasitoids but not pollinator bees in a subtropical experimental forest

From regional to global scales, anthropogenic environmental change is causing biodiversity loss and reducing ecosystem functionality. Previous studies have investigated the relationship between plant diversity and functional insect communities in temperate and also in tropical grasslands and forests. However, few studies have explored these dynamics in subtropical forests. Here, cavity-nesting Hymenoptera and associated parasitoids were collected across a controlled tree diversity experiment in subtropical China to test how predatory wasps, bees and parasitoids respond to tree species richness. Abundance and species richness of predatory wasps and parasitoids were positively correlated with tree species richness, while bee abundance and bee species richness were unrelated to tree species richness. Our results indicate that tree species richness increases the abundance and species richness of important communities such as predators and parasitoids. Moreover, the results highlight the importance of subtropical forests in maintaining abundance and species richness of key functional insect groups.

Integrative taxonomy to assess the species richness of chalcidoid parasitoids (Hymenoptera) associated to Bruchinae (Coleoptera: Chrysomelidae) from Mexico

espanolChalcidoidea es un grupo extremadamente diverso de Hymenoptera y los parasitoides mas comunes, encontrandose asociados con mas de 15 ordenes de hexapodos. La identificacion de especies en esta superfamilia tiende a ser dificil debido a su tamano pequeno, falta de estudios taxonomicos exhaustivos para muchos grupos y convergencia de caracteres morfologicos. El presente estudio tuvo como objetivo identificar las especies de parasitoides (Hymenoptera: Chalcidoidea) asociados con escarabajos Bruchinae (Coleoptera: Chrysomelidae) del centro y sur de Mexico utilizando evidencia morfologica y molecular (gen mitocondrial COI). Se reportan 39 especies de bruchinos asociadas con 8 taxones vegetales. La evidencia morfologica y molecular examinada permitio delimitar 29 especies de chalcidoideos, de las cuales 6 son nuevos registros para el territorio mexicano. Se encontraron inconsistencias en la delimitacion de especies entre los datos morfologicos y moleculares en los generos Eupelmus (Eupelmidae) y Horismenus (Eulophidae). Este estudio destaca la considerable riqueza de especies de Chalcidoidea que esta asociada a los Bruchinae, asi como la necesidad de proporcionar registros confiables de hospedantes para los miembros de este grupo de parasitoides. EnglishChalcidoidea are a highly diverse group of Hymenoptera and the most common parasitoids, being associated to more than 15 hexapod orders. The identification of species in this superfamily is considerably difficult due to their small size, lack of comprehensive taxonomic studies for many groups and convergence of morphological features. In this study, we aimed to identify the chalcidoid species that are associated to bruchine beetles (Chrysomelidae) from central and southern Mexico, using morphological and molecular (mitochondrial COI gene) evidence. We report a total of 39 bruchine species associated to 8 plant taxa. The gathered morphological and molecular evidence allowed to delimit 29 chalcidoid species, 6 of which are new records for Mexico. We found inconsistencies in the species delimitation between the morphological and molecular data in species of Eupelmus (Eupelmidae) and Horismenus (Eulophidae). This study highlights the considerable species richness of chalcidoid taxa that are associated to bruchine beetles, and the need to provide reliable host records for members of this group of parasitoids.

KEANEKARAGAMAN HYMENOPTERA PARASITOID PADA PERKEBUNAN KELAPA SAWIT (Elais guineensis Jacq.) YANG BERBATASAN DENGAN HUTAN SEKUNDER

Secondary forest is primary forest that managed for forest exploitation purposes, so there are many oil palm plantations that are directly adjacent to secondary forest. Hymenopteran parasitoid is a group of the most important insect in the Hymenoptera order, because of its role as natural enemies or biological control agents against insect pests in agricultural ecosystems, including oil palm plantations. The objective of this study was to understand the diversity, species richness and abundance of Hymenopteran parasitoids in oil palm plantations which adjacent to secondary forests. The research was a survey, the purposive sampling method to determine the research location, while to determine the sample points used a systematic random sampling method. For insect collection, insect nets and yellow pan traps were used. The research was carried out in oil palm plantations located in Gunung Selasih and Siguntur Village. In each research unit there were 10 sample points with a distance of each sample point was 100 m along the transect line. The results showed that the total number of Hymenopteran parasitoids collected was 199 individuals belonging to 23 families and 94 morphospecies. Braconidae and Ichneumonidae were the Hymenopteran parasitoids family which its members were found many in the present study.

Understanding insect parasitoids life history behaviour for optimal utilization in biological control of tropical injurious pest - a review

Parasitoids are a key component of most terrestrial ecosystems due to their numbers and ecological significance due to he nature of their life cycle which partly depend on other insects for their survival. They are vitally important for the maintenance of biodiversity being involved in a vast number of trophic interactions including regulatory effect on insect pest populations. There are four insect orders that are particularly prominent for this type of life history. These are Hymenoptera, Diptera, Coleoptera and Neuroptera. The greatest number is found in the order Hymenoptera, which account for nearly 75% of the estimated number of parasitoid species. There are considerable variations in parasitism of insect parasitoids. These may be I diobionts, whose hosts stop development, when they are parasitized and Koinobionts which allow the hosts to continue their development until the parasitoid’s offspring matures. Reports have shown that species richness of koinobionts parasitoids tends to decrease toward the tropics while idiobionts richness does it less severely. Such pattern was howeve intrinsically related to the host feeding niche. In hymenopteran parasitoid complexes however the richness of both idiobionts and koinobionts falls toward the tropics in exophytic hosts, while on endophytic hosts, there are no changes in species richness for both types of parasitoids. Biological control is the central stone of integrated pest management (IPM) paradigm and natural enemies are becoming an increasingly desirable prospect in lieu of chemical insecticides. Although hymenopteran parasitoids are widely used in the control of insect pest due to their Diversity and species richness, Coleopterans parasitoids could be useful in suppressing pest due to the pattern of their parasitism. Host selection strategies of insect parasitoids are largely influenced by chemical signals from plants attacked by insect pest. Their competitive fitness and reproductive success will therefore depend extensively on the ability to employ such signals more efficiently. Keywords: Behaviour, Biological control, Diversity, Insect parasitoids, Plant metabolites

Impact of urbanization on predator and parasitoid insects at multiple spatial scales.

Landscapes are becoming increasingly urbanized, causing loss and fragmentation of natural habitats, with potentially negative effects on biodiversity. Insects are among the organisms with the largest diversity in urbanized environments. Here, we sampled predator (Ampulicidae, Sphecidae and Crabronidae) and parasitoid (Tachinidae) flower-visiting insects in 36 sites in the city of Rome (Italy). Although the diversity of herbivorous insects in urban areas mostly depends on the availability of flowering plants and nesting sites, predators and parasitoids generally require a larger number of resources during their life cycle, and are expected to be particularly influenced by urbanization. As flower-visitors can easily move between habitat patches, the effect of urbanization was tested at multiple spatial scales (local, landscape and sub-regional). We found that urbanization influenced predator and parasitoid flower-visitors at all three spatial scales. At the local scale, streets and buildings negatively influenced evenness of predators and species richness and abundance of parasitoids probably acting as dispersal barrier. At the landscape scale, higher percentage of urban decreased predator abundance, while increasing their evenness, suggesting an increase in generalist and highly mobile species. Area and compactness (i.e. Contiguity index) of urban green interactively influenced predator communities, whereas evenness of parasitoids increased with increasing Contiguity index. At the sub-regional scale, species richness and abundance of predators increased with increasing distance from the city center. Compared to previous studies testing the effect of urbanization, we found little variation in species richness, abundance and evenness along our urbanization gradient. The current insect fauna has been probably selected for its tolerance to habitat loss and fragmentation, being the result of the intensive anthropogenic alteration occurred in the area in the last centuries. Conservation strategies aimed at predator and parasitoid flying insects have to take in account variables at multiple spatial-scales, as well as the complementarity of resources across the landscape.

Multiple plant diversity components drive consumer communities across ecosystems

Humans modify ecosystems and biodiversity worldwide, with negative consequences for ecosystem functioning. Promoting plant diversity is increasingly suggested as a mitigation strategy. However, our mechanistic understanding of how plant diversity affects the diversity of heterotrophic consumer communities remains limited. Here, we disentangle the relative importance of key components of plant diversity as drivers of herbivore, predator, and parasitoid species richness in experimental forests and grasslands. We find that plant species richness effects on consumer species richness are consistently positive and mediated by elevated structural and functional diversity of the plant communities. The importance of these diversity components differs across trophic levels and ecosystems, cautioning against ignoring the fundamental ecological complexity of biodiversity effects. Importantly, plant diversity effects on higher trophic-level species richness are in many cases mediated by modifications of consumer abundances. In light of recently reported drastic declines in insect abundances, our study identifies important pathways connecting plant diversity and consumer diversity across ecosystems.

Parasitoid diversity and parasitism rates in Pampean agricultural mosaics are enhanced by landscape heterogeneity

Abstract Agricultural intensification affects negatively on landscape heterogeneity, biodiversity, biotic interactions and the associated ecological functions. Here, we describe the structure of herbivore–parasitoid interactions by analysing the rates of parasitism and their variability in relation to landscape heterogeneity. Phytometer traps (Commelina erecta L.) infested with a specific leaf miner fly (Liriomyza commelinae Walker) were used to analyse whether landscape heterogeneity influences the parasitism rates and the associated parasitoid diversity. For that reason, phytometers were distributed in 21 sampling sites along rural roads. Not only did landscape heterogeneity influence positively on parasitoid species richness at the site level (local scale), but it also influenced on the percentage of total parasitism and specific parasitism rates of several species. Although the parasitoid diversity was similar at the landscape scale, the evenness of interactions changed substantially among sites. Possibly, the richer plant communities in heterogeneous landscapes provide with a wider combination of resources for parasitoids. The increase in both parasitoid species richness and biological regulation supports the adoption of management strategies that creates heterogeneous farmland mosaics. Landscape heterogeneity may be enhanced by diversifying crop sequences and sowing wildflower strips along field margins. Thus, non‐crop habitats could serve as reservoirs for generalist parasitoids of novel pest species, supplying biological regulation services in agricultural landscapes. We argue that enhancing agrobiodiversity is a key goal to design agroecosystems that ensure food security, equity and sustainability.

Landscape composition, configuration, and trophic interactions shape arthropod communities in rice agroecosystems

Abstract Increasing landscape heterogeneity of agroecosystems can enhance natural enemy populations and promote biological control. However, little is known about the multiscale effects of landscape heterogeneity on arthropod communities in rice agroecosystems, especially in combination with trophic interactions. We examined for the first time how landscape heterogeneity, measured by four independent metrics of landscape composition and configuration at three spatial scales, affected species abundance and species richness of rice arthropods within four functional groups and the abundance of the most common species at 28 sites in the Philippines. We additionally examined the influence of trophic interactions among these functional groups. We found that both the compositional and configurational landscape heterogeneity in combination with trophic interactions determined the structure of rice‐arthropod communities. Herbivore abundance decreased with increasing landscape diversity. The abundance of parasitoids and species richness of both parasitoids and predators increased with the structural connectivity of rice bunds. Fragmentation of the rice landscape had a clear negative effect on most arthropod groups, except for highly mobile predatory arthropods. Abundance of common predators and detritivore species decreased with increasing complexity in the shape of rice patches. Trophic interactions, measured as the abundance of prey, outweighed the importance of landscape heterogeneity for predators. In contrast, parasitoids responded positively to configurational landscape heterogeneity but were unaffected by prey abundance. Synthesis and applications. Our research shows how landscape heterogeneity and trophic interactions have different effects on different functional groups. While predator abundance was solely driven by the availability of prey, all other functional groups in the rice‐arthropod community were significantly affected by the composition and configuration of surrounding landscape features. Landscape management aiming to improve biodiversity and biological control in rice agroecosystems should promote a diversity of land uses and habitat types within 100–300 m radii to reduce the presence of pests. Management practices should also focus on maintaining smaller rice patches and the structural connectivity of rice bunds to enhance populations of the natural enemies of rice pests. Future research should focus on the temporal and spatial manipulation of rice fields to maximize the effects of biological control.

Effects of environmental parameters on the chestnut gall wasp and its complex of indigenous parasitoids.

The chestnut gall wasp (CGW), Dryocosmus kuriphilus, an invasive pest native to China, has caused severe yield and economic losses to chestnut production in Europe since its arrival in 2002. In Southern Italy, the complex of indigenous parasitoids colonizing CGW was monitored between 2013 and 2015, with the aim of estimating the composition of the indigenous parasitoid complex, its ability to control CGW populations, and the interactions of both factors with several measured environmental parameters. We compared results among three differently managed field types. Results showed an increase in the rate of parasitism both when the host population density was lower and in unmanaged chestnut stands with more natural conditions. The percentage of parasitism in galls was related to morphological traits of the galls and to higher seasonal temperatures, which reduced the parasitism intensity because CGW develops earlier under such conditions. The host-parasitoid mortality inside galls varied among sites and was associated mostly with rot fungi during wet spring and summer months. Parasitoid species richness was similar among the study sites, but the proportion of parasitoid species differed between orchards and unmanaged coppice stands. The timing of attack by parasitoids followed a species-specific successional sequence throughout the larva-to-adult life cycle of the CGW. These interactions should be considered in future research on trophic relationships and when modeling invasive scenarios for new pest species.