Optimising sampling and analysis protocols in environmental DNA studies

Ecological surveys risk incurring false negative and false positive detections of the target species. With indirect survey methods, such as environmental DNA, such error can occur at two stages: sample collection and laboratory analysis. Here we analyse a large qPCR based eDNA data set using two occupancy models, one of which accounts for false positive error by Griffin et al. (2020), and a second that assumes no false positive error by Stratton et al. (2020). Additionally, we apply the Griffin et al. (2020) model to simulated data to determine optimal levels of replication at both sampling stages. The Stratton et al. (2020) model, which assumes no false positive results, consistently overestimated both overall and individual site occupancy compared to both the Griffin et al. (2020) model and to previous estimates of pond occupancy for the target species. The inclusion of replication at both stages of eDNA analysis (sample collection and in the laboratory) reduces both bias and credible interval width in estimates of both occupancy and detectability. Even the collection of >1 sample from a site can improve parameter estimates more than having a high number of replicates only within the laboratory analysis

Predation increases multiple components of microbial diversity in activated sludge communities

We thank Severn Trent Waters for providing an access to the Derby waste-water treatment plant, and Peter Vale for his help in facilitating waste-water sampling at the site. Further, many thanks go to Richard Duff for his essential support during media preparation and laboratory assistance. We also thank two anonymous reviewers for their constructive feedback. This project was funded by internal support from Derby University to AB and from Queen Mary University of London to PK.Protozoan predators form an essential component of activated sludge communities that is tightly linked to wastewater treatment efficiency. Nonetheless, very little is known how protozoan predation is channelled via bacterial communities to affect ecosystem functioning. Therefore, we experimentally manipulated protozoan predation pressure in activated-sludge communities to determine its impacts on microbial diversity, composition and putative functionality. Different components of bacterial diversity such as taxa richness, evenness, genetic diversity and beta diversity all responded strongly and positively to high protozoan predation pressure. These responses were non-linear and levelled off at higher levels of predation pressure, supporting predictions of hump-shaped relationships between predation pressure and prey diversity. In contrast to predation intensity, the impact of predator diversity had both positive (taxa richness) and negative (evenness and phylogenetic distinctiveness) effects on bacterial diversity. Furthermore, predation shaped the structure of bacterial communities. Reduction in top-down control negatively affected the majority of taxa that are generally associated with increased treatment efficiency, compromising particularly the potential for nitrogen removal. Consequently, our findings highlight responses of bacterial diversity and community composition as two distinct mechanisms linking protozoan predation with ecosystem functioning in activated sludge communities.Derby UniversityQueen Mary University of Londo

Survival and regeneration ability of clonal common milkweed (Asclepias syriaca L.) after a single herbicide treatment in natural open sand grasslands

Abstract Invasive species are a major threat to biodiversity, human health, and economies worldwide. Clonal growth is a common ability of most invasive plants. The clonal common milkweed Asclepias syriaca L. is the most widespread invasive species in Pannonic sand grasslands. Despite of being an invader in disturbed semi-natural vegetation, this plant prefers agricultural fields or plantations. Herbicide treatment could be one of the most cost-effective and efficient methods for controlling the extended stands of milkweed in both agricultural and protected areas. The invasion of milkweed stand was monitored from 2011 to 2017 in a strictly protected UNESCO biosphere reserve in Hungary, and a single herbicide treatment was applied in May 2014. This single treatment was successful only in a short-term but not in a long-term period, as the number of milkweed shoots decreased following herbicide treatment. The herbicide translocation by rhizomatic roots induced the damage of dormant bud banks. The surviving buds developing shoots, growth of the milkweed stand showed a slow regeneration for a longer-term period. We concluded that the successful control of milkweed after herbicide treatment depends on repeated management of treated areas to suppress further spreading during subsequent seasons