Stable N-isotope signatures of central European ants – assessing positions in a trophic gradient

Studies employing stable isotope technology have greatly contributed to understanding trophic relationships of tropical ants, but temperate-zone ants remain under-explored. We studied δ¹⁵N values of 43 ant species from three subfamilies sampled across central Europe. After statistically accounting for the effects of elevation and geographical location of habitats, which alter the isotopic composition of nitrogen in ecosystems, significant patterns in N-isotope signatures were detected. These signatures hint at differences across ants in the contribution of plant-derived nitrogen obtained via trophobiosis and nectarivory relative to nitrogen obtained via predation and scavenging. In general, Myrmicinae had higher δ¹⁵N values than Formicinae, in line with a greater relative importance of trophobiosis in the latter. The genus Myrmica scored especially high, indicating predominantly predacious nitrogen sources. Remarkably, also the granivore Messor cf. structor had high δ¹⁵N values. This suggests that, despite the major portion of food uptake being made up by plant seeds, this ant could derive substantial fractions of its nitrogen budget from feeding on arthropod corpses or vertebrate faeces. Moreover, this highlights that deductions from observed quantities of ingested food on its relative contribution to ants’ matter balance should be accompanied by isotope analyses. At the other end of the spectrum, Camponotus and Plagiolepis had low δ¹⁵N values. In line with multiple field observations, this suggests a contribution of trophobiosis not only to their energy, but also to their nitrogen budget. Formica and Lasius had intermediate ¹⁵N values, which is in agreement with the current view that these ants have mixed diets with a balance between trophobiosis and predation. A possible influence of endosymbiotic bacteria on the isotope signatures of several genera is discussed. This study provides a first application of stable isotope technology to estimate the role of plant-derived nutrients to the nitrogen budget of a larger range of central European ants. Furthermore, it shows that N-isotope analysis is applicable across extended ecological and geographical gradients. Future studies along this line are promising to complement our current understanding of the nutritional ecology of temperate-zone ants. Received 20 March 2007; revised 17 June and 24 August; accepted 11 September 2007.     

Review of invertebrate biological control agent regulation in Australia, New Zealand, Canada and the USA: recommendations for a harmonized European system

Europe lags far behind Australia, New Zealand, Canada and the USA in terms of implementing regulatory procedures for the import and release of invertebrate biological control agents (IBCAs). A number of standards, documents and guidelines have been produced over recent years in an attempt to harmonize regulation of IBCA introduction into Europe. Despite these efforts, the number of member countries implementing any form of IBCA regulation remains low, with many industries, biological practitioners and regulators fearing that a regulatory system would render the process of approval for IBCA introduction into a country costly and time consuming. Europe’s priority is therefore to formulate a regulatory system that will be readily approved of and adopted by all member countries. In this paper we review the current regulatory processes operating in Australia, New Zealand, Canada and the USA. There is potential for Europe to benefit from the years of experience that these countries have in IBCA regulation. We therefore propose recommendations based on features of the regulatory processes in each of the four countries that work well and that could be adopted to generate a workable Europe‐wide regulatory system.     

Comparative efficacy assessment of fungi,nematodes and insecticides to control western corn rootworm larvae in maize

All three larval instars of Diabrotica virgifera virgifera LeConte (western corn rootworm, Coleoptera: Chrysomelidae) feed on the roots of maize, Zea mays (L.). We assessed the efficacies of the following four agents in controlling these larvae: (1) the entomopathogenic fungus Metarhizium anisopliae (Metsch.) Sorokin (Hypocreales: Clavicipitaceae), (2) the nematode Heterorhabditis bacteriophora Poinar (Nematoda: Rhabditida), (3) a tefluthrin-based soil insecticide and (4) clothianidin-coated seeds. The agents were applied in field plot experiments in southern Hungary in 2006 and 2007. Efficacy was assessed by comparing the number of emerging D. v. virgifera adults and corresponding root damage among treatments and untreated controls. All agents significantly reduced D. v. virgifera numbers and root damage, but the relative success of each treatment was variable. On average across fields and years, the nematode and the two insecticides reduced D. v. virgifera by 65 ± 34% SD, while the fungus reduced D. v. virgifera by 31 ± 7%. According to the node injury scale, the agents prevented 23–95% of potential root damage. Large-scale commercialisation of these biological agents could offer viable and practical control options against D. v. virgifera.