Wild pollinators have been shown to enhance the pollination of Brassica napus (oilseed rape) and thus increase its market value. Several studies have previously shown that pollination services are greater in crops adjoining forest patches or other seminatural habitats than in crops completely surrounded by other crops. In this study, we investigated the specific importance of forest edges in providing potential pollinators in B. napus fields in two areas in France. Bees were caught with yellow pan traps at increasing distances from both warm and cold forest edges into B. napus fields during the blooming period. A total of 4594 individual bees, representing six families and 83 taxa, were collected. We found that both bee abundance and taxa richness were negatively affected by the distance from forest edge. However, responses varied between bee groups and edge orientations. The ITD (Inter-Tegular distance) of the species, a good proxy for bee foraging range, seems to limit how far the bees can travel from the forest edge. We found a greater abundance of cuckoo bees (Nomada spp.) of Andrena spp. and Andrena spp. males at forest edges, which we assume indicate suitable nesting sites, or at least mating sites, for some abundant Andrena species and their parasites (Fig. 1). Synthesis and Applications. This study provides one of the first examples in temperate ecosystems of how forest edges may actually act as a reservoir of potential pollinators and directly benefit agricultural crops by providing nesting or mating sites for important early spring pollinators. Policy-makers and land managers should take forest edges into account and encourage their protection in the agricultural matrix to promote wild bees and their pollination services.

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The syndrome “basses richesses” (SBR) is a disease of sugar beet in eastern France associated with two phloem-restricted, nonculturable plant pathogens: a stolbur phytoplasma and a γ-3 proteobacterium, here called SBR bacterium. Three planthopper (Hemiptera: Cixiidae) species were found to live near and within sugar beet fields in eastern France: Cixius wagneri, Hyalesthes obsoletus, and Pentastiridius leporinus. The role of these planthoppers in spreading the two pathogens to sugar beet was studied. Based on its abundance and high frequency of infection with the SBR bacterium, P. leporinus was considered to be the economic vector of SBR disease. C. wagneri, the primary vector of ‘Candidatus Phlomobacter fragariae’ to strawberry in western France, also was found to be infected by the SBR bacterium and to transmit the pathogen to sugar beet. Neither C. wagneri nor P. leporinus were infected by stolbur phytoplasma. Populations of H. obsoletus living on bindweed (Convolvulus arvensis) and nettle (Urtica dioica) collected near sugar beet fields did not carry the SBR bacterium, but were highly infected with two restriction fragment length polymorphism-differentiable stolbur phytoplasma isolates. In transmission assays, only the bindweed phytoplasma isolate was transmissible to and pathogenic on sugar beet. When compared with controls, the bindweed stolbur phytoplasma and SBR bacterium similarly reduced the biomass of sugar beet plants, but the phytoplasma caused greater reductions in taproot biomass and sugar content than the SBR bacterium.

Understanding the processes that shape biodiversity patterns is essential for ecosystem management and conservation. Local environmental conditions are often good predictors of species distribution and variations in habitat quality usually positively correlate to species richness. However, beside habitat limitation, species presence-absence may be constrained by dispersal limitation. We tested the relative importance of both limitations on saproxylic beetle diversity, using forest continuity as a surrogate for dispersal limitation and stand maturity as a surrogate for habitat limitation. Forest continuity relies on the maintenance of a forest cover over time, while stand maturity results in the presence of old-growth habitat features. Forty montane beech-fir forests in the French pre-Alps were sampled, under a balanced sampling design in which forest continuity and stand maturity were crossed. A total of 307 saproxylic beetle species were captured using flightinterception traps and Winkler-Berlese extractors. We explored the response of low-versus high-dispersal species groups to forest continuity and stand maturity. Saproxylic beetle diversity increased significantly with stand maturity and was mostly influenced by variables related to deadwood diversity at the stand scale and suitable habitat availability at the landscape scale. Surprisingly, no evidence of dispersal limitation was found, as diversity patterns were not influenced by forest continuity and associated variables, even for low-dispersal species. Our study demonstrates that in an unfragmented forest landscape, saproxylic beetles are able to colonize recent forests, as long as local deadwood resources are sufficiently diversified (e.g. tree species, position, diameter and/or decay stage).

Abstract. Cixiid planthoppers have been shown to vector phloem-limited prokaryotes associated with plant diseases world-wide. In eastern France, an emerging disease of sugar beet called syndrome "basses richesses" has been associated with phloem-restricted bacteria transmitted by a cixiid planthopper within the genus Pentastiridius. Early investigation suggested the species being Pentastiridius beieri. On the basis of a morphological and phylogenetic study we report the identification of the planthopper as Pentastiridius leporinus. Furthermore we report some biological traits of the species, which shows a surprising ecological adaptation to an annual cropping rotation sugar beet-winter cereals.

Abstract. 1. Intensive forestry has drastically reduced the volume of standing deadwood, even more than total deadwood volume. It has been demonstrated in boreal forests that snags have a high conservation value for many saproxylic species and that the lying or standing aspect of the deadwood makes a difference. The conservation of saproxylic beetles in the changing deadwood landscape of temperate managed forests depends on a deeper understanding of the ecological value of forest stand legacies. 2. Our study questioned whether the retention of oak snags is an important conservation concern in European temperate forests. We analysed the differences in saproxylic beetle fauna between oak snags and logs and explored the diameter effect on log–snag differences. We compared the species composition and richness of saproxylic beetle assemblages in a temperate deciduous forest. Emergence traps were set in a balanced sampling design of 22 ground‐lying logs and 22 oak snags with a range of intermediate decay stages and 2 diameter classes. 3. Oak snags yielded more individuals per volume unit and supported more species than logs, and exhibited significantly dissimilar assemblages from logs and hosted original species. Snags, especially large snags, were more interesting for rare beetle species conservation than logs. The feeding guild structure slightly differed between snags and logs. Overall, log–snag differences depended on the diameter class. 4. We confirm that saproxylic biodiversity would significantly benefit from forestry measures favouring oak snag retention (especially large snags), even though further multi‐scale studies are necessary to develop quantitative retention guidelines.

The decline of many saproxylic species results from the decrease in old-growth structures in European harvested forests. Among conservation tools, protected reserves withdrawn from regular harvesting and extended rotations have been employed to restore old-growth attributes in structurally simplified managed forests, even if the effects of such management actions on forest habitats and biodiversity remain largely unknown.In this study, we compared structural stand features and saproxylic beetle assemblages in two stand classes -recently harvested stands and long-established reserves, where less or more than 30 years had elapsed since last harvest. Habitat and saproxylic beetle data were collected according to standardized protocols in 153 plots in seven lowland deciduous forests.Tangible contrasts in stand features were found between long-established reserves and recently harvested plots. Indeed, most higher-value densities and volumes were found in unharvested areas. The difference was weaker for microhabitat-bearing tree density than for deadwood; some deadwood features, such as volume of large downed and standing deadwood showed a very pronounced difference, thus indicating a marked deleterious effect of forest harvesting on these elements. Deadwood diversity, on the other hand, was only slightly affected and the level of stand openness did not change.The response of saproxylic beetles to delayed harvesting was weaker than the structural changes in deadwood features. Indeed even if only some guilds weakly increased in non-harvested plots, harvesting classes significantly affected the abundance of a quarter of the species tested.Our results tend to question measures such as rotating and temporarily ageing patches. We argue in favor of permanent strict fixed-location reserves. Future work should examine how stands recover old-growth forest attributes and how the associated saproxylic fauna colonizes in the long term. bs_bs_banner Animal Conservation. Print ISSN 1367-9430 Set-aside forests and saproxylic beetles C. Bouget et al. Set-aside forests and saproxylic beetles C. Bouget et al.

Data availabilityThe datasets generated during and/or analyzed during the current study are not publicly available due to further analyses on the data but are available from the corresponding author on reasonable request. Declaration on conflicts of interestThe authors declare that they have no conflict of interest. Total number of characters: 66 681 Number of tables: 5 (+1 in supplementary data) Number of figures: 6 (+ 1 in supplementary data) Reference to pre-print servers (when relevant):The Preprint version of this article is available in the BioRxiv server, https://www.biorxiv.org/content/10.1101/2020.02.11.943753v1 . CC-BY 4.0 International license available under a (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made Forest decline differentially affects trophic guilds of canopy-dwelling beetles Key messageDecline can affect the structure, resources and microclimates of the forest canopy, and potentially have cascading effects on canopy-dwelling species. Our survey shows that an oak decline can promote saproxylic beetles, especially xylophagous ones, and generalist phyllophagous weevils. However, it negatively affects specialist phyllophagous species and has no effect on seminiphagous weevils.