Decreased Functional Diversity and Biological Pest Control in Conventional Compared to Organic Crop Fields

Organic farming is one of the most successful agri-environmental schemes, as humans benefit from high quality food, farmers from higher prices for their products and it often successfully protects biodiversity. However there is little knowledge if organic farming also increases ecosystem services like pest control. We assessed 30 triticale fields (15 organic vs. 15 conventional) and recorded vascular plants, pollinators, aphids and their predators. Further, five conventional fields which were treated with insecticides were compared with 10 non-treated conventional fields. Organic fields had five times higher plant species richness and about twenty times higher pollinator species richness compared to conventional fields. Abundance of pollinators was even more than one-hundred times higher on organic fields. In contrast, the abundance of cereal aphids was five times lower in organic fields, while predator abundances were three times higher and predator-prey ratios twenty times higher in organic fields, indicating a significantly higher potential for biological pest control in organic fields. Insecticide treatment in conventional fields had only a short-term effect on aphid densities while later in the season aphid abundances were even higher and predator abundances lower in treated compared to untreated conventional fields. Our data indicate that insecticide treatment kept aphid predators at low abundances throughout the season, thereby significantly reducing top-down control of aphid populations. Plant and pollinator species richness as well as predator abundances and predator-prey ratios were higher at field edges compared to field centres, highlighting the importance of field edges for ecosystem services. In conclusion organic farming increases biodiversity, including important functional groups like plants, pollinators and predators which enhance natural pest control. Preventative insecticide application in conventional fields has only short-term effects on aphid densities but long-term negative effects on biological pest control. Therefore conventional farmers should restrict insecticide applications to situations where thresholds for pest densities are reached

Disruption of LRRK2 Does Not Cause Specific Loss of Dopaminergic Neurons in Zebrafish

Mutations in LRRK2 are genetically linked to Parkinson's disease (PD) but its normal biological function is largely unknown. Sheng et al. recently reported that deletion of the WD40 domain of LRRK2 in zebrafish specifically causes PD-like loss of neurons and behavior defect. However, our similar early study and recent confirming experiments using the same reagents reported by Sheng et al. failed to reproduce the phenotype of the loss of dopaminergic neurons, although the mRNA of LRRK2 was molecularly disrupted. Our study suggests that function of LRRK2 and its usefulness to generate zebrafish PD model needs further evaluation

Conservation of pollinators in traditional agricultural landscapes – New challenges in Transylvania (Romania) posed by EU accession and recommendations for future research

Farmland biodiversity is strongly declining in most of Western Europe, but still survives in traditional low intensity agricultural landscapes in Central and Eastern Europe. Accession to the EU however intensifies agriculture, which leads to the vanishing of traditional farming. Our aim was to describe the pollinator assemblages of the last remnants of these landscapes, thus set the baseline of sustainable farming for pollination, and to highlight potential measures of conservation. In these traditional farmlands in the Transylvanian Basin, Romania (EU accession in 2007), we studied the major pollinator groups-wild bees, hoverflies and butterflies. Landscape scale effects of semi-natural habitats, land cover diversity, the effects of heterogeneity and woody vegetation cover and on-site flower resources were tested on pollinator communities in traditionally managed arable fields and grasslands. Our results showed: (i) semi-natural habitats at the landscape scale have a positive effect on most pollinators, especially in the case of low heterogeneity of the direct vicinity of the studied sites; (ii) both arable fields and grasslands hold abundant flower resources, thus both land use types are important in sustaining pollinator communities; (iii) thus, pollinator conservation can rely even on arable fields under traditional management regime. This has an indirect message that the tiny flower margins around large intensive fields in west Europe can be insufficient conservation measures to restore pollinator communities at the landscape scale, as this is still far the baseline of necessary flower resources. This hypothesis needs further study, which includes more traditional landscapes providing baseline, and exploration of other factors behind the lower than baseline level biodiversity values of fields under agri-environmental schemes (AES)

Landscape potential for pollen provisioning for beneficial insects favours biological control in crop fields

International audienceContext: The importance of landscape complexity for biological control is well-known, but its functional roles are poorly understood.Objectives: We evaluated the landscape capacity to provide floral resources for beneficial insects and its consequences for biological control in fields.Methods:The gut contents of adult hoverflies sampled in 41 cereal fields were analysed to determine which plant species are exploited. The relative value of each habitat in providing adequate pollen resources was evaluated by vegetation survey. Then 15 cereal fields were selected along a gradient of landscape complexity, where the abundance of aphids, hoverfly larvae and aphid parasitism was monitored. The habitat’s proportions in landscape buffers surrounding these fields were used as landscape descriptors and to assess the potential level of pollen resources provision (LP index).Results: Aphid abundance significantly decreased with an increase of the LP index mainly sustained by grassy strips and weeds in fields. However, hoverfly larvae abundance also decreased with the increasing LP index. The enhancement of the aphid parasitism rate with the LP index suggests that aphid parasitoids may benefit from the same floral resources as hoverflies. Their crop habitat specialism may give them a competitive advantage in fields where both aphid and floral resources are abundant.Conclusions: Complex interaction networks involved in biological control may disrupt the expected direct effects of floral resource provisioning for a focal beneficial species. We highlighted fields and grassy strips as habitats provisioning floral resources for which the LP index could be very helpful to optimize agroecological management strategies