Storage conditions of stockpiled diapausing pupae ofRhagoletis cerasi for obtaining high emergence rates

The authors, members of the IOBC working group on genetic control of the European cherry fruit flyRhagoletis cerasi L., present the summarized results of a joint 4-year experiment aiming at the optimalization of storage conditions for stockpiled pupae. Highest emergence rates are achieved by chilling periods of 5 to 6 months and recommended storage temperatures are close to the developmental threshold of +5°C. Total storage time of pupae should not exceed 14 months.

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Résumé Les auteurs, membres du groupe de travail de l'O.I.L.B. sur la lutte génétique contre la mouche européene de la cerise,Rhagoletis cerasi L., présentent le bilan de 4 ans d'expérimentation en commun en vue de trouver la meilleure méthode de conservation des pupes. Les taux d'émergence imaginale les plus élevés sont obtenus à la suite d'une période de froid de 5 à 6 mois à une température voisine du seuil de développement: 5°C. La durée totale de la conservation au froid des pupes ne doit pas dépasser 14 mois.

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Fourth report of the IOBC working group on genetic control ofR. cerasi.     

Hedges as potential sources ofTyphlodromus pyri,the most important predatory mite in vineyards of Northern Switzerland

This paper presents the results of an acarological survey started in 1984 in hedges bordering vineyards in Northern Switzerland where natural populations of the economically important predatory miteTyphlodromus pyri occur. The objective of these investigations was to identify those plant species in the hedges and forest margins adjacent to vineyards that carry high populations of this important predator, and to evaluate the potential role of hedges as ecological refuges and sources ofT. pyri. We found high and consistent densities ofT. pyri onRubus fruticosus, and less regularly onCornus sanguinea, Corylus avellana andLonicara xylosteum. We conclude that hedges can provide ecological refuges and sources of this economically important predatory mite where earlier applications of inappropriate pesticides have eliminated these important antagonists. However, the inoculative release ofT. pyri along with the increase of the internal ecological diversity of the vineyard achieved by proper management of the green over plants (“weed”) will have a strong influence on predator densities within the vineyards.      

Niche differentiation among invasive Ponto-Caspian <Emphasis Type="Italic">Chelicorophium</Emphasis> species (Crustacea,Amphipoda, Corophiidae) by food particle size

After Chelicorophium curvispinum, two other Ponto-Caspian tube-dwelling, filter-feeding amphipod species (Chelicorophium robustum and Chelicorophium sowinskyi) have colonized several catchments in Central and Western Europe in recent decades. To reveal the mechanism of niche differentiation among them, we measured the mesh sizes of their filtering apparatus and analyzed multi-habitat sampling data from the River Danube using RDA-based variance partitioning between environmental and spatial explanatory variables. Morphometric data showed a clear differentiation among the species by filter mesh size (C. curvispinum?>?C. robustum?>?C. sowinskyi). Field data also indicated the relevance of suspended matter; however, the mere quantity of suspended solids included in the analysis could not explain the abundance patterns effectively. Current velocity, substrate types, and total nitrogen content also had a non-negligible effect; however, their role in the niche differentiation of the species is not evident. In summary, differences in their filter mesh sizes indicate a niche differentiation by food particle size among the invasive Chelicorophium species, allowing their stable coexistence given sufficient size variability in their food source. Consequently, the two recent invaders increase the effectiveness of resource utilization, resulting in a more intensive benthic–pelagic coupling in the colonized ecosystems.     

Current velocity shapes co‐existence patterns among invasive Dikerogammarus species

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Success factors and future prospects of Ponto–Caspian peracarid (Crustacea: Malacostraca) invasions: Is ‘the worst over’?

Ponto–Caspian peracarids (amphipods, isopods, mysids and cumaceans) represent one of the most successful groups of aquatic invaders comprising several high-impact species, such as Chelicorophium curvispinum, Dikerogammarus villosus, or Hemimysis anomala. In the present study we made the first attempt to compare biological traits and the environmental preferences of invasive and non-invasive members of the group based on both literature and field data (Joint Danube Survey 3, 2013) with the goal of identifying factors linked to invasion success and drawing conclusions on future invasion risks. Both datasets indicated substrate preference as an important factor in spontaneous range expansion; all invasive species are lithophilous, whereas the majority of non-invasives are psammo-pelophilous. The remaining seven presently non-invasive lithophilous species deserve special attention when considering potential future invaders; however, due to their rarity and possible negative interactions with earlier colonists we consider the probability of their expansion in the foreseeable future as low. Their potential expansion could most likely be of minor consequence anyway, since no considerable functional novelty can be attributed to them in addition to species already present. In this limited context (regarding habitats dominated by hard substrates and not considering the potential further spread of already invasive species) it might be justified to conclude that ‘the worst is over’. Nevertheless, impending navigation development projects both in the Danube–Main–Rhine and Dnieper–Pripyat–Bug–Vistula systems might favour the future spread of non-lithophilous species, which might imply a new invasion wave of Ponto–Caspian peracarids.