Naturen er bedre i økologiske hegn og skel

Det glædelige er at selv ret unge økologiske hegn og relativt nyomlagte bedrifter tilsyneladende også har stor betydning for agerlandets natur. En mere varieret hegnsvegetation giver flere levemuligheder også for andre arter, både insekter og højere dyr. Med omtanke kan landmanden altså påvirke og beskytte naturen i skel og hegn via sin daglige drift og dermed bidrage til at forbedre naturen i agerlandskabet

Competitive Performance of Transgenic Wheat Resistant to Powdery Mildew

Genetically modified (GM) plants offer an ideal model system to study the influence of single genes that confer constitutive resistance to pathogens on the ecological behaviour of plants. We used phytometers to study competitive interactions between GM lines of spring wheat Triticum aestivum carrying such genes and control lines. We hypothesized that competitive performance of GM lines would be reduced due to enhanced transgene expression under pathogen levels typically encountered in the field. The transgenes pm3b from wheat (resistance against powdery mildew Blumeria graminis) or chitinase and glucanase genes from barley (resistance against fungi in general) were introduced with the ubiquitin promoter from maize (pm3b and chitinase genes) or the actin promoter from rice (glucanase gene). Phytometers of 15 transgenic and non-transgenic wheat lines were transplanted as seedlings into plots sown with the same 15 lines as competitive environments and subject to two soil nutrient levels. Pm3b lines had reduced mildew incidence compared with control lines. Chitinase and chitinase/glucanase lines showed the same high resistance to mildew as their control in low-nutrient treatment and slightly lower mildew rates than the control in high-nutrient environment. Pm3b lines were weaker competitors than control lines. This resulted in reduced yield and seed number. The Pm3b line with the highest transgene expression had 53.2% lower yield than the control whereas the Pm3b line which segregated in resistance and had higher mildew rates showed only minor costs under competition. The line expressing both chitinase and glucanase genes also showed reduced yield and seed number under competition compared with its control. Our results suggest that single transgenes conferring constitutive resistance to pathogens can have ecological costs and can weaken plant competitiveness even in the presence of the pathogen. The magnitude of these costs appears related to the degree of expression of the transgenes

Feral genetically modified herbicide tolerant oilseed rape from seed import spills: are concerns scientifically justified?

One of the concerns surrounding the import (for food and feed uses or processing) of genetically modified herbicide tolerant (GMHT) oilseed rape is that, through seed spillage, the herbicide tolerance (HT) trait will escape into agricultural or semi-natural habitats, causing environmental or economic problems. Based on these concerns, three EU countries have invoked national safeguard clauses to ban the marketing of specific GMHT oilseed rape events on their territory. However, the scientific basis for the environmental and economic concerns posed by feral GMHT oilseed rape resulting from seed import spills is debatable. While oilseed rape has characteristics such as secondary dormancy and small seed size that enable it to persist and be redistributed in the landscape, the presence of ferals is not in itself an environmental or economic problem. Crucially, feral oilseed rape has not become invasive outside cultivated and ruderal habitats, and HT traits are not likely to result in increased invasiveness. Feral GMHT oilseed rape has the potential to introduce HT traits to volunteer weeds in agricultural fields, but would only be amplified if the herbicides to which HT volunteers are tolerant were used routinely in the field. However, this worst-case scenario is most unlikely, as seed import spills are mostly confined to port areas. Economic concerns revolve around the potential for feral GMHT oilseed rape to contribute to GM admixtures in non-GM crops. Since feral plants derived from cultivation (as distinct from import) occur at too low a frequency to affect the coexistence threshold of 0.9% in the EU, it can be concluded that feral GMHT plants resulting from seed import spills will have little relevance as a potential source of pollen or seed for GM admixture. This paper concludes that feral oilseed rape in Europe should not be routinely managed, and certainly not in semi-natural habitats, as the benefits of such action would not outweigh the negative effects of management

Oviposition site selection of an endangered butterfly at local spatial scales

As pre-hibernating larvae of the marsh fritillary (Euphydryas aurinia) have limited mobility essential resources need to be available at a very local scale. We surveyed larval webs (2011-2013), the host plant devil's bit scabious (Succisa pratensis) (2012), and derived variables from digital orthophotos and digital elevation models (Normalized Differenced Vegetation Index, accumulated sun hours, slope, aspect) to explain the presence-absence and abundance of larval webs at three different spatial grain sizes (5 x 2.5 m, 10 x 10 m, 25 x 25 m) across seven study sites in northern Jutland, Denmark. Two-component hurdle models indicated that host plant abundance was the only important predictor of presence-absence and abundance of larval webs across the seven sites. The strength of the host plant effect on larval web prevalence increased when enlarging spatial grain size. For presence-absence (and less for abundance), the effect of host plants on larval webs varied across study sites. Using mixed effects models, we additionally analysed presence-absence of larval webs (in 1 x 1 m plots) in relation to detailed host plant measurements (abundance and size), vegetation height, and environmental variables (soil temperature, air temperature and soil moisture) across four of the sites. This showed that larval webs were located in the densest parts of the host plant patches. Given the low mobility of pre-hibernating larvae (< 0.5 m), our results suggest that females select dense parts within large patches of host plants as oviposition sites. Future management should concentrate on establishing large patches of the larval host plant