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Increasing landscape complexity can enhance biodiversity and ecosystem services in agroecosystems. However, policies based on conversion of arable land into semi-natural habitats to increase landscape complexity and ecosystem services can be difficult to implement. Although it appears to be a promising management option, nothing is known about the effect of increasing landscape diversity through crop rotations on the delivery of ecosystem services. In this study, we examined how landscape complexity and crop rotation intensity in the landscape at different spatial scales affect the flow and the stability of natural pest control services in barley fields using manipulative cage experiments. Exclusion experiments revealed that natural enemies can have a strong impact on aphid population growth and that the delivery of pest control services is strongly dependent on the landscape context. We found that the overall level of pest control increased with landscape complexity and that this effect was independent of crop rotation intensity. In addition, the within-field stability in pest control services increased with crop rotation intensity in the landscape, although stability in parasitism rates decreased. Multiple spatial scales analyses showed that the mean level of natural pest control was best predicted by landscape complexity at the 0 center dot 5-km and the 1-km spatial scales. The stability in overall pest control decreased with proportion of ley at the 2 center dot 5-km and the 3-km spatial scales. Synthesis and applications. Our study disentangled, for the first time, the relative effects of landscape complexity and crop rotation intensity on the delivery of an ecosystem service. We show that combined management of semi-natural habitat and crop rotation can stabilize and enhance natural pest control in agricultural landscapes. Our findings have important implications in terms of management options to maintain and enhance ecosystem services in agroecosystems. They suggest that conservation of heterogeneous landscapes, characterized by a higher proportion of semi-natural habitats such as pastures and relatively small fields, is essential for maintaining and enhancing effective biological control in agroecosystems.

1. The loss of semi-natural grasslands in agro-ecosystems has increased the importance of adequate management of remaining grasslands. Recommendations for intensive grazing have been debated because the effects of different management practices may differ between taxa and species. The increased fragmentation of grasslands suggests that the influence of management practices should be studied in a landscape context. 2. We studied four groups of flower visitors, many of which are pollinators, bees (Apoidea), butterflies (Lepidoptera), hoverflies (Syrphidae) and beetles (Coleoptera), in semi-natural grasslands managed at three intensity levels in eight areas in central Sweden. Local characteristics of the grasslands were recorded and landscape diversity was quantified. Vegetation height was correlated with grazing intensity: intensive grazing with the shortest vegetation and abandoned grassland with the tallest. 3. The insect groups responded differently to grazing intensity. Species richness and abundance differed between management regimes for beetles and hoverflies but not for bees and butterflies. 4. The effects of local habitat and landscape composition on species richness, abundance and composition differed between groups. Bee diversity responded to both local and landscape factors. Butterflies were mainly affected by local vegetation height and linear elements in the landscape. More species of hoverflies were recorded in tall vegetation and in landscapes with high forest cover. Beetles responded only to local environment characteristics. 5. Synthesis and applications. We demonstrate the importance of studying different insect groups simultaneously when evaluating habitat and landscape qualities for diversity. The results suggest that planning for conservation of biodiversity at landscape scales may be better than implementing grazing guidelines for individual grasslands. Grazing intensity should vary within or between landscapes to preserve pollinator diversity. Conservation management to encourage flower visitors cannot be generalized to include all groups simultaneously.

The suppression of agricultural pests by natural enemies, including generalist arthropod predators, is an economically important regulating ecosystem service. Besides pests, generalist predators may also consume non-pest extraguild and intraguild prey, which can affect their impact on pest populations. This may either reduce the impact of generalist predators on pest populations, because they are diverted from pest predation, or increase it, as it helps them survive periods of low pest availability. However, the availability of pest prey and alternative, non-pest prey can vary over the crop growing season and between farming systems, potentially affecting predator–prey interactions and the levels of biological control. We have limited information about how farming systems and environmental variation over the crop growing season influence predator diets. This limits our ability to predict the importance of generalist predators as natural enemies of agricultural pests. Here we utilize molecular gut content analyses to assess detection frequencies of extra- and intraguild prey DNA in generalist predator communities in replicated organically and conventionally managed cereal fields at two key periods of the cropping season for aphid biological control. This is done in order to understand how farming system, crop season, prey availability and predator community composition determine the composition of predator diets. Aphid pests and decomposers (springtails) were equally important prey for generalist predators early in the growing season. Later in the season, the importance of aphid prey increased with increasing aphid densities while springtail prédation rates were positively correlated to abundance of this prey at both early and late crop growth stages. Intraguild prédation was unidirectional: carabids fed on spiders, whereas spiders rarely fed on carabids. Carabids had higher detection frequencies for the two most common spider families in organically compared to conventionally managed fields. Our study documents that predation by generalist predator communities on aphid pests increases with pest numbers independently of their generally widespread consumption of alternative, non-pest prey. Therefore, conservation strategies in agricultural fields could promote biological control services by promoting high levels of alternative non-pest prey for generalist predator communities.

Food web structure influences ecosystem functioning and the strength and stability of associated ecosystem services. With their broad diet, generalist predators represent key nodes in the structure of many food webs and they contribute substantially to ecosystem services such as biological pest control. However, until recently it has been difficult to empirically assess food web structure with generalist predators. We utilized DNA-based molecular gut-content analyses to assess the prey use of a set of generalist invertebrate predator species common in temperate agricultural fields. We investigated the degree of specialization of predator-prey food webs at two key stages of the cropping season and analysed the link temperature of different trophic links, to identify non-random predation. We found a low level of specialization in our food webs, and identified warm and cool links which may result from active prey choice or avoidance. We also found a within-season variation in interaction strength between predators and aphid pests which differed among predator species. Our results show a high time-specific functional redundancy of the predator community, but also suggest temporally complementary prey choice due to within-season succession of some predator species.

Because of the dynamic nature of many managed habitats, proper evaluation of conservation efforts calls for models that take into account both spatial and temporal habitat dynamics. We develop a metapopulation model for successional-type systems, in which habitat quality changes over time in a predictable fashion. The occupancy and recruitment of the predatory saproxylic (dependent on dead wood) beetle Harminius undulatus was studied in a managed boreal forest landscape, covering 24449 ha, in central Sweden. In a first step, we analyzed the beetle's occupancy pattern in relation to stand characteristics, and the amounts of present and past habitat in the surrounding landscape. Managed forest is suitable habitat when ≥60 years old, and immediately after cutting, but not between the ages of 10 and 60 years. The observed occupancy of H. undulatus was positively correlated with the stand's age as habitat. We used a metapopulation model to predict the current probability of occurrence in each forest stand, given the spatiotemporal distribution of suitable forest stands during the last 50 years. Metapopulation parameters were estimated by matching predicted spatial distributions with observed spatial distributions. The model predicted observed spatial distributions better than a similar model that assumed constant habitat quality of each forest stand. Thus, metapopulation models for successional-type systems, such as dead wood dependent organisms in managed forest landscapes, should include habitat dynamics. An estimated 82% of the landscape-wide recruitment took place in managed stands, which covered 87% of the forest area, in comparison with 18% in unmanaged stands, which covered 13% of the forest area. Among the managed stand types, 2265;60-year-old stands and 3-7-year-old clear-cuttings contributed to 79% of the total recruitment while 8-59-year-old stands only contributed 3%. The results suggest the following guidelines to improve conditions for H. undulatus and other species with similar habitat requirements: (1) the proportion of the landscape constituted by younger stands should not be allowed to grow too large, (2) the rotation period of managed stands should not be allowed to be too short, and (3) dead wood should be retained and created at final cutting.

The influence of landscape structure on anopheline mosquito density and diversity was studied in a comparison of agricultural and forested landscapes in northern Thailand. Agriculture locations had significantly higher landscape diversity, more patches, smaller mean patch sizes, and more complex patch shapes than forest locations. Mosquito collections were undertaken during both dry and wet seasons from October 1997 to December 1999. The density of two forest-associated species, Anopheles maculatus s.s. and Anopheles minimus s.l., both primary malaria vectors in Thailand, was significantly higher in forest locations in at least one season. The density of two paddy field-associated species, Anopheles aconitus and Anopheles hyrcanus group did not differ between locations. Anopheles aconitus is a secondary malaria vector and An. hyrcanus group is not considered as a vector in Thailand. The density of An. minimus s.l. was positively related to forest mean patch size, various water and paddy field landscape metrics and negatively related to landscape diversity. Anopheles hyrcanus group was also positively related to water metrics. Anopheline species diversity was negatively related to landscape diversity. Forest fragmentation resulting from human economic activities often increases landscape heterogeneity, which may result in a reduction in anopheline species diversity, as was the case in this study. There are indications that the effect of fruit orchards on anopheline diversity might be different in the dry season compared to the wet season. Fruit orchard landscape metrics affected species diversity negatively in the dry season and positively in the wet season. One reason for this could be that pesticides are typically applied in fruit orchards during the dry season. The conversion of forests to fruit orchards is a major land-use change in northern Thailand. These results show the complexity of vector status in northern Thailand and that vector and agriculture pest control are intricately interrelated. It is therefore important to include both the public health and agricultural sectors in controlling malaria vectors in the country. Our results also indicate that if landscape management should be used for malaria control in northern Thailand large-scale reduction and fragmentation of forest cover would be needed. Such drastic actions do not agree well with current global objectives concerning forest and biodiversity conservation

The need to study movement in specific ecosystems in order to understand population dynamics in space is appreciated among ecologists. Ecological data is, however, often collected at small scales making large-scale predictions dubious at best. To examine whether extrapolations across scales are possible, we build observed behaviors affecting movement of three carabid beetle species, Pterostichus cupreus, P. melanarius and P. niger (Coleoptera, Carabidae), into a spatially explicit individual-based model (IBM) to study patterns at a number of spatial scales. Field-tracking recordings of individual beetles are fitted to a biased random walk (BRW) model and inserted into the IBM together with data on settling behavior. Beetles will often stop and rest during their activity periods. A range of probabilities for alternation between active and resting behavior are tested in the model at several prey levels. We found that at large scales, in this case movement over hundreds of meters and several seasons, diffusion is a good approximation for population spread. At small scales of around one meter, BRW describes movement accurately. At intermediate scales we need both BRW, resting, and changes between these behaviors to describe motion effectively in the model. The area covered by the beetles increases linearly over time, while the maximum distance moved does not, indicating an approximately circular expansion and a thorough search of area traversed. Seasonal range and estimated rate of movement differed among species depending on prey availability but was not correlated to body size.

Glucosinolates are a category of secondary products present primarily in species of the order Capparales. When tissue is damaged, for example by herbivory, glucosinolates are degraded in a reaction catalyzed by thioglucosidases, denoted myrosinases, also present in these species. Thereby, toxic compounds such as nitriles, isothiocyanates, epithionitriles and thiocyanates are released. The glucosinolate-myrosinase system is generally believed to be part of the plant's defense against insects, and possibly also against pathogens. In this review, the evolution of the system and its impact on the interaction between plants and insects are discussed. Further, data suggesting additional functions in the defense against pathogens and in sulfur metabolism are reviewed.

Agricultural intensification is recognised as a major driver of biodiversity loss in human-modified landscapes. Several agro-environmental measures at different spatial scales have been suggested to mitigate the negative impact of intensification on biodiversity and ecosystem services. The effect of these measures on the functional structure of service-providing communities remains, however, largely unexplored. Using two distinct landscape designs, we examined how the management options of organic farming at the field scale and crop diversification at the landscape level affect the taxonomic and functional structure of generalist predator communities and how these effects vary along a landscape complexity gradient. Organic farming as well as landscapes with longer and more diversified crop rotations enhanced the activity-density of spiders and rove beetles, but not the species richness or evenness. Our results indicate that the two management options affected the functional composition of communities, as they primarily enhanced the activity-density of functionally similar species. The two management options increased the functional similarity between spider species in regards to hunting mode and habitat preference. Organic farming enhanced the functional similarity of rove beetles. Management options at field and landscape levels were generally more important predictors of community structure when compared to landscape complexity. Our study highlights the importance of considering the functional composition of generalist predators in order to understand how agro-environmental measures at various scales shape community assemblages and ecosystem functioning in agricultural landscapes.

Using genomic AFLP analysis DNA polymorphism was studied in 14 field populations of pollen beetles (Meligethes aeneus), collected during 2004 in six European countries (Denmark, France, Finland, Germany, Sweden, and UK). Using one primer combination 410 polymorphic DNA fragments were obtained based on analysis of single beetles. AFLP profiles were analysed with similarity measures using the Nei and Li coefficient and dendrograms generated. Dendrograms constructed from distance matrices revealed clustering by population origin and assignment analysis generally supported the genotype classification. Principal component analysis of the fourteen groups resulted in wide dispersion but also connections between some groups. The levels of genetic variation within populations explained most of the variation. Migrant analysis suggested a low level of gene flow between pollen beetle populations at different geographical locations indicating little long range dispersal of pollen beetles. However, a Mantel test found no correlation between genetic and geographical distance. Apparently genetic differentiation among populations has a complex background and may involve factors such as local adaptation and founder effects.