Effects of Selection Regime on Invasive Characteristics in an Emerging Biomass Crop, Switchgrass (Panicum virgatum L.)

Production of biomass feedstock crops could produce substantial environmental benefits, but these will be sharply reduced if these crops become invasive. Switchgrass (Panicum virgatum L.) is being bred for biomass production; these selective efforts may enhance invasive traits. To inform the assessment of invasive risk, undomesticated switchgrass strains were used as a baseline for comparison with strains bred for biomass production. In a three-year field experiment, we compared juvenile plant densities and survival, persistence of established plants, and aboveground biomass between selectively bred (cultivar) and undomesticated switchgrass strains. Cultivars had modestly greater third-year biomass and first-year plant densities than commercial ecotypes but lower survival and persistence; consequently, third-year plant densities did not significantly differ between cultivars and commercial ecotypes. Higher initial establishment and subsequent self-thinning in cultivars resulted in stands that were similar to those of commercial ecotypes. Therefore, our results do not suggest that the breeding of current cultivars of switchgrass enhanced juvenile and young-stand traits associated with invasiveness. Because biomass yields were not greatly different between cultivars and commercial ecotypes, use of the latter in biomass grasslands could provide functional benefits, including an enhanced habitat for native biodiversity and reduced pathogen loads, without incurring large losses in biomass production.

Diapause characterisation and seasonality of Aedes japonicus japonicus (Diptera, Culicidae) in the northeast of France

The invasive mosquito Aedes japonicus japonicus (Theobald, 1901) settled in 2013 in the Alsace region, in the northeast of France. In this temperate area, some mosquito species use diapause to survive cold winter temperatures and thereby foster settlement and dispersal. This study reports diapause and its seasonality in a field population of Ae. japonicus in the northeast of France. For two years, eggs were collected from May to the beginning of November. They were most abundant in summer and became sparse in late October. Diapause eggs were determined by the presence of a fully developed embryo in unhatched eggs after repeated immersions. Our study showed effective diapause of Ae. japonicus in this part of France. At the start of the egg-laying period (week 20), we found up to 10% of eggs under diapause, and this rate reached 100% in October. The 50% cut-off of diapause incidence was determined by the end of summer, leading to an average calculated maternal critical photoperiod of 13 h 23 min. Interestingly, diapause was shown to occur in part of the eggs even at the earliest period of the two seasons, i.e. in May of each year. Even though we observed that the size of eggs was positively correlated with diapause incidence, morphology cannot be used as the unique predictive indicator of diapause status due to overlapping measurements between diapausing and non-diapausing eggs. This study provides new knowledge on diapause characterisation and invasive traits of Ae. japonicus.

The Physics of Cellular Decision Making During Epithelial–Mesenchymal Transition

The epithelial–mesenchymal transition (EMT) is a process by which cells lose epithelial traits, such as cell–cell adhesion and apico-basal polarity, and acquire migratory and invasive traits. EMT is crucial to embryonic development and wound healing. Misregulated EMT has been implicated in processes associated with cancer aggressiveness, including metastasis. Recent experimental advances such as single-cell analysis and temporal phenotypic characterization have established that EMT is a multistable process wherein cells exhibit and switch among multiple phenotypic states. This is in contrast to the classical perception of EMT as leading to a binary choice. Mathematical modeling has been at the forefront of this transformation for the field, not only providing a conceptual framework to integrate and analyze experimental data, but also making testable predictions. In this article, we review the key features and characteristics of EMT dynamics, with a focus on the mathematical modeling approaches that have been instrumental to obtaining various useful insights.