Summary 1.Habitat requirements of solitary bees include nesting sites, food resources and nesting material. We used translocation experiments to establish foraging distances and measured foraging trip duration to analyse how solitary bees cope with the distance between nesting sites and suitable food plants in different habitat types. 2. Maximum foraging distance between nesting site and food patch was 150-600 m for the 16 bee species examined. Foraging distance was correlated positively with body length. Mean foraging trip duration, measured for seven bee species, ranged from 6 to 28 min and was also correlated with body length. In a study of the polylectic species Osmia rufa , we found a significant decrease in foraging trip duration with increasing number of plant species. Logistic regressions showed that the oligolectic Megachile lapponica nested in trap nests with a probability of 50% if the distance between trap nest and food patch was less than 250 m. The oligolectic Chelostoma rapunculi utilized trap nests when the distance to the nearest food patch was less than 300 m. 3. These experiments showed that solitary bees have a rather small foraging range so local habitat structure appears to be of more importance than large-scale landscape structure. All requirements for sustaining viable populations must be within this range. Therefore, it is necessary to maintain and restore a dense network of habitat patches in landscapes to ensure long-term sustainability of wild bee diversity and their ecological function as pollinators.

Summary 0[ Results from four _eld studies show that communities of trap!nesting bees and wasps and their natural enemies are promising bioindicators for ecological change or habitat quality[ These small and easy!to!handle communities can be analysed with respect to "i# species richness and related parameters\ and "ii# ecological functions or interactions[ The communities comprise Hymenoptera "Apidae\ Sphecidae\ Eumen! idae\ Pompilidae# and natural enemies belonging to many insect taxa[ Traps consisted of 049Ð199\ 04Ð19!cm long\ reed internodes\ put into tins or plastic tubes of 02Ð04 cm diameter^wooden posts with 1Ð09 of such reed!_lled tins were exposed in the target habitat[ 1[ Species richness and abundance of bees "but not wasps# were closely related to plant species richness of the habitat\ a measure of the bees| food resource[ However\ availability of nest sites of above!ground nesting species was equally important] meadows with old trees supported greater populations than meadows without trees[ A threefold increase in exposed traps resulted in a twofold increase in species[ 2[ The sensitivity of this bioindicator system pro_ts from the fact that evaluations rely not only on presence:absence data\ descriptive population attributes or diversity indices\ but also on interactions or ecological functions[ Monitoring ecological responses or multitrophic interactions\ and their relationship to species diversity\ is rarely done but much needed[ Ecological functions include "i# the percentage mortality of trap!nesting bees and wasps due to parasitoids and predators\ which was correlated with the species richness of these natural enemies^"ii# seed set of allogamous plants due to successful pollination by trap!nesting bees^and "iii# biological control by the predacious wasps[ 3[ With increasing isolation of fragmented habitats "when traps were exposed in a cleared agricultural landscape#\ both species richness of natural enemies and per! centage mortality "parasitism and predation# declined signi_cantly[ In a comparison of habitat types "grasslands and _eld margins#\ species richness of the trap!nest community correlated with plant diversity\ but percentage mortality\ due to parasitism and predation\ with _eld age only[ The threshold distance to the nearest habitat was 095Ð429 m for a 09Ð49) decrease in mean mortality\ and the mortality increased greatly in habitats that were older than 4 years[ Accordingly\ these studies emphasize the signi_cance of a continuum of old habitat patches for the augmentation of natural enemies[ 4[ Exposure of standardized traps is an experimental approach with a small\ inter! acting and reproducing community that can be easily characterized by simple par! ameters[ Taxonomy and biology are well known\ and quick evaluations can be done using the close correlation between the number of occupied traps and species richness[ Species richness of trap!nesting bees and wasps was closely correlated with that sampled by sweep nets[ Further criteria of indicator taxa that apply to this system are ...

Genetically modified (GM) maize MON810 expresses a Cry1Ab insecticidal protein, derived from Bacillus thuringiensis (Bt), toxic to lepidopteran target pests such as Ostrinia nubilalis. An environmental risk to non-target Lepidoptera from this GM crop is exposure to harmful amounts of Bt-containing pollen deposited on host plants in or near MON810 fields. An 11-parameter mathematical model analysed exposure of larvae of three non-target species: the butterflies Inachis io (L.), Vanessa atalanta (L.) and moth Plutella xylostella (L.), in 11 representative maize cultivation regions in four European countries. A mortality–dose relationship was integrated with a dose–distance relationship to estimate mortality both within the maize MON810 crop and within the field margin at varying distances from the crop edge. Mortality estimates were adjusted to allow for physical effects; the lack of temporal coincidence between the susceptible larval stage concerned and the period over which maize MON810 pollen is shed; and seven further parameters concerned with maize agronomy and host-plant ecology. Sublethal effects were estimated and allowance made for aggregated pollen deposition. Estimated environmental impact was low: in all regions, the calculated mortality rate for worst-case scenarios was less than one individual in every 1572 for the butterflies and one in 392 for the moth.

In farmland biodiversity, a potential risk to the larvae of non-target Lepidoptera from genetically modified (GM) Bt-maize expressing insecticidal Cry1 proteins is the ingestion of harmful amounts of pollen deposited on their host plants. A previous mathematical model of exposure quantified this risk for Cry1Ab protein. We extend this model to quantify the risk for sensitive species exposed to pollen containing Cry1F protein from maize event 1507 and to provide recommendations for management to mitigate this risk.A 14-parameter mathematical model integrating small- and large-scale exposure was used to estimate the larval mortality of hypothetical species with a range of sensitivities, and under a range of simulated mitigation measures consisting of non-Bt maize strips of different widths placed around the field edge.The greatest source of variability in estimated mortality was species sensitivity. Before allowance for effects of large-scale exposure, with moderate within-crop host-plant density and with no mitigation, estimated mortality locally was <10% for species of average sensitivity. For the worst-case extreme sensitivity considered, estimated mortality locally was 99·6% with no mitigation, although this estimate was reduced to below 40% with mitigation of 24-m-wide strips of non-Bt maize. For highly sensitive species, a 12-m-wide strip reduced estimated local mortality under 1·5%, when within-crop host-plant density was zero. Allowance for large-scale exposure effects would reduce these estimates of local mortality by a highly variable amount, but typically of the order of 50-fold.Mitigation efficacy depended critically on assumed within-crop host-plant density; if this could be assumed negligible, then the estimated effect of mitigation would reduce local mortality below 1% even for very highly sensitive species.Synthesis and applications. Mitigation measures of risks of Bt-maize to sensitive larvae of non-target lepidopteran species can be effective, but depend on host-plant densities which are in turn affected by weed-management regimes. We discuss the relevance for management of maize events where cry1F is combined (stacked) with a herbicide-tolerance trait. This exemplifies how interactions between biota may occur when different traits are stacked irrespective of interactions between the proteins themselves and highlights the importance of accounting for crop management in the assessment of the ecological impact of GM plants.

Trap-nesting bees and wasps (Hymenoptera Aculeata) colonizing crop and fallow fields in an agricultural landscape were studied using 20 sown fields (pea, barley, rye, clover-grass mixtures, Phacelia tanacetifolia) and 20 fields with naturally developed vegetation (1- and 2-year old fields, both mown and unmown, and old meadows). Fourteen species of Apoidea, 4 of Sphecidae, 1 of Eumenidae and 4 of parasitoids were reared from reed nests exposed in these 40 fields of 10 field-types. Fields with naturally developed vegetation had twice as many species as sown fields, due to the distribution pattern of the 14 bee species, whereas the 9 predatory species (wasps and parasitoids) showed a rather uniform distribution. None of the trap-nesting bees were found in Phacelia fields, despite contrasting expectations of beekeepers. Old meadows showed a particularly high abundance and species richness, since only 10% of all traps were exposed, but 32% of all bee nests were sampled in old meadows, including 4 bee species that were not found elsewhere. Accordingly, species richness of fields with naturally developed vegetation showed a significant increase with age. Variability in Hymenoptera species numbers could be explained by corresponding differences in plant species numbers. The alternative hypothesis that field size or field connectivity influenced species richness was not supported. Habitats with great floral diversity appeared to offer better and richer food resources for the flower-visiting bees, whereas food availability apparently did not influence predatory wasps. The bees Osmia caerulescens and Megachile versicolor that had colonized early-successional fields took twice as long to provision cells as those that colonized late-successional meadows characterized by a greater plant species richness. In contrast, the eumenid wasp Ancistrocerus gazella took a similar period of time to provision cells in both field types. In addition, bee and wasp species of plant-species-poor fields were on average significantly larger than those of plant-species-rich fields. Thus, body size appeared to be a good predictor of colonization ability. Management by cutting greatly increased plant species richness in early-successional set-aside fields and thus doubled species richness of bees. Cutting of early-successional habitats can be expected to benefit insects and plants in general, whereas older grassland should show the greatest insect diversity when both mown and unmown parts are present.

Importance of mathematical model [of \ud exposure of non-target Lepidoptera to Bt-maize pollen expressing Cry1Ab within Europe

No abstract

Transformation of crops, including maize (Zea mays L.), with the cry1Ab gene from Bacillus thuringiensis to combat lepidopteran pests results in pleiotropic effects regarding lignin biosynthesis. Lignin patterns in stems and leaves of two genetically modified Bt-maize varieties (Novelis T and Valmont T) were studied along with their non-Bt near-isolines (Nobilis and Prelude, respectively). Molecular-level based thermochemolysis using tetramethylammonium hydroxide (TMAH) in combination with gas chromatography-mass spectrometry (GC-MS) was used to quantitate the total lignin contents and to identify monomeric lignin subunits including p-hydroxyphenyl (P), guaiacyl (G), and syringyl (S) moieties. The results were supplemented and confirmed by cupric oxide oxidation. The stems of the transgenic lines had higher concentrations of total lignin than the respective isogenic lines: Valmont T/Prelude by 18% and Novelis T/Nobilis by 28%. In contrast, differences in the total lignin concentration of leaves between the transgenic and the respective near-isogenic lines were marginal. There were significant modifications in the ratio of p-hydroxyphenyl/guaiacyl/syringyl molecular marker units of stem lignin between transgenic and isogenic lines. The guaiacyl units (in particular the G18 marker) accounted chiefly for the higher total lignin contents in the transgenic lines. The leaf lignin patterns did not show significant differences in molecular markers between isogenic and transgenic lines. TMAH-induced thermochemolysis--conducted in both the on-line and off-line modes--provided detailed information on the molecular composition of lignin, thus proving superior to the established "wet chemistry" methods of lignin determination.