Seed viability of common ragweed (Ambrosia artemisiifolia L.) is affected by seed origin and age, but also by testing method and laboratory

Plant science

Explaining variability in the production of seed and allergenic pollen by invasive Ambrosia artemisiifolia across Europe

To better manage invasive populations, it is vital to understand the environmental drivers underlying spatial variation in demographic performance of invasive individuals and populations. The invasive common ragweed, Ambrosia artemisiifolia, has severe adverse effects on agriculture and human health, due to its vast production of seeds and allergenic pollen. Here, we identify the scale and nature of environmental factors driving individual performance of A. artemisiifolia, and assess their relative importance. We studied 39 populations across the European continent, covering different climatic and habitat conditions. We found that plant size is the most important determinant in variation of per-capita seed and pollen production. Using plant volume as a measure of individual performance, we found that the local environment (i.e. the site) is far more influential for plant volume (explaining 25% of all spatial variation) than geographic position (regional level; 8%) or the neighbouring vegetation (at the plot level; 4%). An overall model including environmental factors at all scales performed better (27%), including the weather (bigger plants in warm and wet conditions), soil type (smaller plants on soils with more sand), and highlighting the negative effects of altitude, neighbouring vegetation and bare soil. Pollen and seed densities varied more than 200-fold between sites, with highest estimates in Croatia, Romania and Hungary. Pollen densities were highest on arable fields, while highest seed densities were found along infrastructure, both significantly higher than on ruderal sites. We discuss implications of these findings for the spatial scale of management interventions against A. artemisiifolia

A Case Study of the Introductory Psychology Blended Learning Model at McMaster University

This paper provides a brief review of blended learning as a didactic method, and discusses the issues and challenges of using blended learning models in post-secondary education. Blended learning refers to mixed modes of instruction that combine traditional face-to-face classroom teaching methods and online learning materials. The paper will address challenges faced by large classrooms with a diverse student body, and the ways blended learning models can help alleviate those concerns (i.e. technologically savvy students, the need for course scheduling flexibility). In addition, a case study of blended learning in higher education in the context of a unique first year Introductory Psychology program at McMaster University will be discussed. Lastly, the important learning benefits offered by blended learning systems, along with the potential barriers to their implementation will be addressed. Cet article présente un bref compte rendu de l’apprentissage hybride en tant que méthode didactique. Il traite des problèmes et des enjeux relatifs à l’utilisation des modèles d’apprentissage hybride dans le domaine de l’enseignement postsecondaire. L’apprentissage hybride renvoie aux modes d’enseignement mixtes qui combinent les méthodes d’enseignement traditionnel en présentiel et l’accès à des documents d’apprentissage en ligne. L’article traite des difficultés rencontrées dans les grands groupes comprenant une diversité d’étudiants et des façons dont les modèles d’apprentissage hybride peuvent contribuer à atténuer ces préoccupations (c.-à-d. les étudiants calés en technologie, la nécessité d’une offre de cours souple). De plus, l’article traite d’une étude de cas sur l’apprentissage hybride dans l’enseignement supérieur dans le cadre de la première année d’un programme d’introduction à la psychologie à l’Université McMaster. Enfin, l’article aborde les importants avantages offerts par les systèmes d’apprentissage hybride ainsi que les obstacles potentiels à leur mise en œuvre

A Case Study of the Introductory Psychology Blended Learning Model at McMaster University

This paper provides a brief review of blended learning as a didactic method, and discusses the issues and challenges of using blended learning models in post-secondary education. Blended learning refers to mixed modes of instruction that combine traditional face-to-face classroom teaching methods and online learning materials. The paper will address challenges faced by large classrooms with a diverse student body, and the ways blended learning models can help alleviate those concerns (i.e. technologically savvy students, the need for course scheduling flexibility). In addition, a case study of blended learning in higher education in the context of a unique first year Introductory Psychology program at McMaster University will be discussed. Lastly, the important learning benefits offered by blended learning systems, along with the potential barriers to their implementation will be addressed. Cet article présente un bref compte rendu de l’apprentissage hybride en tant que méthode didactique. Il traite des problèmes et des enjeux relatifs à l’utilisation des modèles d’apprentissage hybride dans le domaine de l’enseignement postsecondaire. L’apprentissage hybride renvoie aux modes d’enseignement mixtes qui combinent les méthodes d’enseignement traditionnel en présentiel et l’accès à des documents d’apprentissage en ligne. L’article traite des difficultés rencontrées dans les grands groupes comprenant une diversité d’étudiants et des façons dont les modèles d’apprentissage hybride peuvent contribuer à atténuer ces préoccupations (c.-à-d. les étudiants calés en technologie, la nécessité d’une offre de cours souple). De plus, l’article traite d’une étude de cas sur l’apprentissage hybride dans l’enseignement supérieur dans le cadre de la première année d’un programme d’introduction à la psychologie à l’Université McMaster. Enfin, l’article aborde les importants avantages offerts par les systèmes d’apprentissage hybride ainsi que les obstacles potentiels à leur mise en œuvre

The role of fruit heteromorphism in the naturalization of Asteraceae

Background and Aims Fruit heteromorphism is considered to be a bet-hedging strategy to cope with spatially or temporally heterogeneous environments. The different behaviours of the fruit morphs of the same species might also be beneficial during naturalization, once the species has been introduced to a new range. Yet, no study to date has tested the association between fruit heteromorphism and global-scale naturalization success for a large set of plant species. Methods We compiled two large datasets on fruit heteromorphism in Asteraceae. One dataset was on native species in Central Europe (n = 321) and the other was on species frequently planted as ornamentals (n = 584). Using phylogenetic linear and logistic regressions, we tested whether heteromorphic species are more likely to naturalize outside their native range, and in more regions of the world than monomorphic species. We also tested whether the effect of heteromorphism is modulated by life history and height of the species. Key Results We show that heteromorphic species were more likely to naturalize outside their native range. However, among the naturalized species, heteromorphic and monomorphic species did not differ in the number of world regions where they became naturalized. A short life span and tall stature both promoted naturalization success and, when life history and height were included in the models, the effect of fruit heteromorphism on the ability to naturalize became non-significant. Nevertheless, among tall plants, heteromorphic ornamental species were significantly more likely to become naturalized in general and in more regions than monomorphic species. Conclusions Our results provide evidence that in Asteraceae the production of heteromorphic fruits is associated with naturalization success. It appears, however, that not fruit heteromorphism per se, but a successful combination of other biological traits in fruit heteromorphic species, namely short life span and tall stature, contributes to their naturalization success

Forest type interacts with milkweed invasion to affect spider communities

Abstract Non-native tree plantations constitute a large part of forestation worldwide. Plantations are prone to invasion by exotic herbaceous plant species due to habitat properties, including understory vegetation structure. We established 40 sampling sites in 10 plantation forests. Sites were selected according to tree species (native poplar forests and exotic pine plantations) and common milkweed (Asclepias syriaca) density (invaded and non-invaded sites) in a full factorial design. We collected spiders with pitfall traps. We found a significant effect of A. syriaca invasion on spider functional diversity (Rao's quadratic entropy), with invaded sites having a lower functional diversity than non-invaded sites. A larger effect of invasion with A. syriaca on the RaoQ of spiders was observed in pine compared to poplar plantations. Spider species were larger, and web-building spiders were more frequent in poplar forests than in pine plantations. We found no effect of A. syriaca invasion on species richness or abundance of spiders. Species composition of spider assemblages in the two forest types was clearly separated according to non-metric multidimensional scaling. We identified seven species associated with pine plantations and six species associated with poplar plantations. The similar species richness and the higher functional diversity of non-invaded sites suggested that these trait states were less similar than invaded sites and that functionally different species were present. In contrast, the invaded sites had lower functional diversities and thus more uniform trait state compositions, suggesting that environmental filtering played an important role in species sorting, making invaded plantations low-quality secondary habitats for the original spider fauna