Summary1. Predictions of the identities and ecological impacts of invasive alien species are critical for risk assessment, but presently we lack universal and standardized metrics that reliably predict the likelihood and degree of impact of such invaders (i.e. measurable changes in populations of affected species). This need is especially pressing for emerging and potential future invaders that have no invasion history. Such a metric would also ideally apply across diverse taxonomic and trophic groups. 2. We derive a new metric of invader ecological impact that blends: (i) the classic Functional Response (FR; consumer per capita effect) and Numerical Response (NR; consumer population response) approaches to determining consumer impact, that is, the Total Response (TR = FR 9 NR), with; (ii) the 'Parker-Lonsdale equation' for invader impact, where Impact = Range 9 Abundance 9 Effect (per capita effect), into; (iii) a new metric, Relative Impact Potential (RIP), where RIP = FR 9 Abundance. The RIP metric is an invader/native ratio, where values >1 predict that invader ecological impact will occur, and increasing values above 1 indicate increasing impact. In addition, the invader/invader RIP ratio allows comparisons of the ecological impacts of different invaders. 2017, 54, 1259-1267 doi: 10.1111/1365-2664.12849 3. Across a diverse range of trophic and taxonomic groups, including predators, herbivores, animals and plants (22 invader/native systems with 47 individual comparisons), high-impact invaders were significantly associated with higher FRs compared to native trophic analogues. However, the RIP metric substantially improves this association, with 100% predictive power of high-impact invaders. 4. Further, RIP scores were significantly and positively correlated with two independent ecological impact scores for invaders, allowing prediction of the degree of impact of invasive alien species with the RIP metric. Finally, invader/invader RIP scores were also successful in identifying and associating with higher impacting invasive alien species. 5. Synthesis and applications. The Relative Impact Potential metric combines the per capita effects of invaders with their abundances, relative to trophically analogous natives, and is successful in predicting the likelihood and degree of ecological impact caused by invasive alien species. As the metric constitutes readily measurable features of individuals, populations and species across abiotic and biotic context-dependencies, even emerging and potential future invasive alien species can be assessed. The Relative Impact Potential metric can be rapidly utilized by scientists and practitioners and could inform policy and management of invasive alien species across diverse taxonomic and trophic groups. Journal of Applied Ecology

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Environmental DNA (eDNA) is gaining traction in conservation ecology as a powerful tool for detecting species at risk. We developed a quantitative polymerase chain reaction assay to detect a DNA amplicon fragment of the mitochondrial nicotinamide adenine dinucleotide locus of the Blanding’s turtle (Emydoidea blandingii) for detecting overwintering individuals. Seventy-eight water samples were collected from 17 wetland sites in Ontario, Canada. We used traditional field data to identify a priori positive and negative control sites. Fifty percent of positive control sites amplified. Detection was related to the number of individuals estimated from field observations in at least one region surveyed. Positive control sites had lower total dissolved solids and electrical conductivity in relation to negative control sites. Shedding rates were within the same order of magnitude for brumating and active turtles. We recommend collecting additional samples at a larger number of locations to maximize detection. Recommended sampling design changes may overshadow the additional effects of water chemistry and low eDNA shedding rates. eDNA offers tremendous potential to practitioners conducting species at risk assessments in environmental consulting by providing a faster, more efficient method of detection compared with traditional surveys.