Effects of competition and mowing on growth and reproduction of the invasive plant Erigeron annuus at two contrasting altitudes

Invasive plants are often abundant at frequently disturbed sites such as roadsides, because they benefit from reduced competition or increased nutrient availability. In Switzerland, roadsides are subjected to regular mowing, and to persist in these sites, plants must be able to compensate for the biomass removal. However, the ability to tolerate competition and mowing might decline under less favourable growth conditions, such as those at higher altitudes. I investigated how competition and mowing affect growth and reproduction of Erigeron annuus (L.) Pers., an invasive plant common on Swiss roadsides, and how these effects change with altitude. The experiment was replicated in common gardens at altitudes of 400m and 1,000m asl, representing growth conditions in the main distribution area of E. annuus and at its altitudinal limit, respectively. Vegetative growth was negatively affected by competition at both sites, but especially at 1,000m. The number of capitula was not affected by competition at 400m, but was reduced at 1,000m. Plants regrew vigorously after mowing in both gardens. The effects of mowing on reproductive output were positive at 400m, but negative at 1,000m. These results imply that E. annuus is able to tolerate competition and mowing at low altitudes, but both of these factors hinder its reproduction at higher altitude

Distribution, growth performance and genetic variation of Erigeron annuus in the Swiss Alps

We investigated whether local adaptation has been important in enabling the invasive apomictic species Erigeron annuus to extend its altitudinal range in the Swiss Alps. We first conducted a field survey along several major roads crossing the Swiss Alps to study the distribution and growth performance of E. annuus along an altitudinal gradient. We then used amplified fragment length polymorphism to assess genetic variation within and among populations originating from different altitudes. To complement the molecular analyses, we compared the performance of genotypes with different distributions (i.e. local, occasional, widespread genotypes) in two common gardens at 400m and 1,000m a.s.l. Although E. annuus was seldom found above 1,000m, plant performance in field populations did not decrease with increasing altitude. However, there was a significant decline in genotypic diversity within populations, and highland (711-1,100m) populations were more differentiated (Gst=0.55) than lowland (200-530m) populations (Gst=0.33). In the common garden experiment, local genotypes (i.e. those restricted to a single population) grew less vigorously than widespread genotypes, and were less likely to reproduce. We found no evidence for on-going adaptive changes and conclude that any selection acting on particular genotypes at the altitudinal limit is weak. This leads us to propose that the patterns in the distribution of genotypic diversity in E. annuus are governed by processes of occasional sexual reproduction, dispersal and extinction that are to a large extent independent of altitud

Simulating evolutionary responses of an introgressed insect resistance trait for ecological effect assessment of transgene flow: a model for supporting informed decisionmaking in environmental risk assessment

Predicting outcomes of transgene flow from arable crops requires a system perspective that considers ecological and evolutionary processes within a landscape context. In Europe, the arable weed Raphanus raphanistrum is a potential hybridization partner of oilseed rape, and the two species are ecologically linked through the common herbivores Meligethes spp. Observations in Switzerland show that high densities of Meligethes beetles maintained by oilseed rape crops can lead to considerable damage on R. raphanistrum. We asked how increased insect resistance in R. raphanistrum – as might be acquired through introgression from transgenic oilseed rape – would affect seed production under natural herbivore pressure. In simulation experiments, plants protected against Meligethes beetles produced about twice as many seeds as unprotected plants. All stages in the development of reproductive structures from buds to pods were negatively affected by the herbivore, with the transition from buds to flowers being the most vulnerable. We conclude that resistance to Meligethes beetles could confer a considerable selective advantage upon R. raphanistrum in regions where oilseed rape is widely grown

Effects of competition and mowing on growth and reproduction of the invasive plant Erigeron annuus at two contrasting altitudes

ISSN:0253-1453ISSN:1420-906

UAAD Founders\u27 Day

Because today is the birthday of Thomas Edison who was born in 1847 in Ohio, I suppose that you would expect me as today\u27s speaker to have a special obligation to be inventive. Some of you probably know that for several years, Edison\u27s birthday has been observed as National Science Youth Day, which sounds to me like a rather interesting invention itself. Youth is not a science and science is certainly not a youth, but I am perfectly willing to go along with the national celebration and wish a happy birthday to any science youth that I might happen to encounter. I would encourage you to do the same

Distribution, growth performance and genetic variation of Erigeron annuus in the Swiss Alps

ISSN:1387-3547ISSN:1573-146

Transgene Expression and Bt Protein Content in Transgenic Bt Maize (MON810) under Optimal and Stressful Environmental Conditions

Bt protein content in transgenic insect resistant (Bt) maize may vary between tissues within plants and between plants growing under different environmental conditions. However, it is unknown whether and how Bt protein content correlates with transgene expression, and whether this relationship is influenced by stressful environmental conditions. Two Bt maize varieties containing the same transgene cassette (MON 810) were grown under optimal and stressful conditions. Before and during stress exposure, the upper leaves were analysed for transgene expression using quantitative RT-PCR and for Bt content using ELISA. Under optimal conditions there was no significant difference in the transgene expression between the two investigated Bt maize varieties whereas Bt protein content differed significantly. Transgene expression was correlated with Bt protein content in only one of the varieties. Under stressful environmental conditions we found similar transgene expressions as under optimal conditions but Bt content responded differently. These results suggest that Bt content is not only controlled by the transgene expression but is also dependent on the genetic background of the maize variety. Under stressful conditions the concentration of Bt protein is even more difficult to predict.ISSN:1932-620

Transgene behavior in genetically modified teosinte hybrid plants: transcriptome expression, insecticidal protein production and bioactivity against a target insect pest

Background In 2009, Spanish farmers reported a novel weed, now identified as a relative of maize’s ancestor, teosinte, in their maize fields. Introgression of the insect resistance transgene cry1Ab from genetically modified (GM) maize into populations of this weedy Spanish teosinte could endow it with additional defense mechanisms. The aims of this study were: (1) to test if hybridization between GM maize and weedy plants from Spain is possible; (2) to understand the relationship between transgene transcription activity, concentrations of the expected transgene product (Cry1Ab protein) and the bioactivity of the latter on target insect pests following transgene flow from GM maize into Spanish teosinte plants. Results We demonstrated that hybridization between GM maize and the weedy Spanish teosinte is possible, with no observable barrier to the formation of crop/weed hybrids when teosinte served as pollen donor. When GM maize plants were used as pollen donors, significant crossing incompatibility was observed: hybrid plants produced only few “normal” seeds. Nevertheless, viable F1 seeds from GM pollen crossed onto teosinte were indeed obtained. The cry1Ab transgene was stably expressed as mRNA in all crossings and backgrounds. Similarly, toxicity on neonate Ostrinia nubilalis, presumably due to Cry1Ab protein, was consistently expressed in teosinte hybrids, with mortality rates 95% or higher after only 4 days exposure, similar to rates on parental GM maize plants. Nevertheless, no strong correlations were observed between transgene transcription levels and Cry1Ab concentrations, nor between Cry1Ab concentrations and insect mortality rates across all of the different genetic backgrounds. Conclusions Our results establish fundamental parameters for environmental risk assessments in the European context: first, we show that crop/weed hybridization in fields where maize and teosinte exist sympatrically can lead to potentially catastrophic transfer of resistance traits into an already noxious weed; second, our results question the viability of using gene dosage to model and predict ecological performance in either the intended crop plant or the undesired teosinte weed. Significant questions remain that should be addressed in order to provide a scientific, sound approach to the management of this novel weed.ISSN:2190-4715ISSN:2190-470

Teosinte in Europe - Searching for the Origin of a Novel Weed

A novel weed has recently emerged, causing serious agronomic damage in one of the most important maize-growing regions of Western Europe, the Northern Provinces of Spain. The weed has morphological similarities to a wild relative of maize and has generally been referred to as teosinte. However, the identity, origin or genetic composition of ‘Spanish teosinte’ was unknown. Here, we present a genome-wide analysis of single-nucleotide polymorphism (SNP) data for Spanish teosinte, sympatric populations of cultivated maize and samples of reference teosinte taxa. Our data are complemented with previously published SNP datasets of cultivated maize and two Mexican teosinte subspecies. Our analyses reveal that Spanish teosinte does not group with any of the currently recognized teosinte taxa. Based on Bayesian clustering analysis and hybridization simulations, we infer that Spanish teosinte is of admixed origin, most likely involving Zea mays ssp. mexicana as one parental taxon, and an unidentified cultivated maize variety as the other. Analyses of plants grown from seeds collected in Spanish maize fields and experimental crosses under controlled conditions reveal that hybridization does occur between Spanish teosinte and cultivated maize in Spain, and that current hybridization is asymmetric, favouring the introgression of Spanish teosinte into cultivated maize, rather than vice versa.ISSN:2045-232