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Risk assessment currently lacks pliable tools that can be reliably applied across a range of environmental contexts to predict the success and impact of non‐native species (NNS). An approach adopting functional responses (FR) and the Relative Impact Potential (RIP) metric may offer considerable insight and predictive power regarding invader impacts, which may include losses in ecosystem function and biodiversity. We aim to evaluate the use of FRs and the RIP metric in predicting impact in non‐native, data‐deficient bivalves.Very little is known about the potential impacts of the Gulf wedge clam, Rangia cuneata outside of its native range, and as a rapidly spreading non‐native species, it is highly suitable for this study. Comparisons of feeding activity and abundance between non‐native species and functionally analogous native species may produce reliable impact predictions where significant disparity in these factors exists. We conducted field abundance surveys and laboratory feeding studies on R. cuneata, in order to quantify FRs and the RIP metric. Clearance rates and FRs were calculated for R. cuneata and the sympatric, native unionid duck mussel, Anodonta anatina, across a range of algal concentrations at 1.0 ppt salinity.Mean ± SE clearance rates (ml g DW−1 hr−1) were found to be significantly greater for R. cuneata (294.31 ± 65.17) than for A. anatina (125.99 ± 29.59) with both species exhibiting a type I functional response. As a result of far greater field abundance of R. cuneata compared with A. anatina (37.7 m−2 ± 6.1 versus 0.7 m−2 ± 0.4 at sympatric sites) and a significantly higher feeding rate, the RIP score for R. cuneata was high (11.61) signifying likely ecological impact. Calculating the probability density function for the RIP includes uncertainty in the metric and also yielded a very high value (38.14), and these results provide the first evidence that R. cuneata should be considered a high‐risk invasive species.The results of our analyses firmly support the assertion that R. cuneata will likely continue to have significant impact in its introduced range if management action is not taken. The rate of spread of R. cuneata, its established densities and RIP score are all comparable to severely invasive bivalves; therefore, R. cuneata may pose a significant threat to both freshwater and brackish water biodiversity and function. We conclude that FRs and the RIP metric may be extremely beneficial to making reliable impact predictions for non‐native species and are particularly well suited for estimating the potential impacts of data‐deficient novel and emerging non‐natives. [ABSTRACT FROM AUTHOR]

Large river floodplains contain a high diversity of habitats and species but are highly threatened by human activities. River floodplain restoration is increasingly undertaken to reverse biodiversity loss and enhance ecosystem services., Few studies have examined the consequences on the biota of restoring lateral connectivity, a key variable that represents the exchange of materials and organisms between the river and its floodplain. We developed models to describe the richness and abundance of aquatic macroinvertebrates in 18 channels of the Rhône floodplain and predict how restoration (i.e. the increase in lateral connectivity of floodplain channels) should alter the native and alien communities., Models quantified how richness and abundance decrease for lentic taxa and increase for lotic and alien taxa with higher connectivity between the floodplain channels and the main channel. Predicted changes were weakly related to overall observed changes when all restored channels were combined, but consistent with observed changes when floodplain channels were grouped by restoration type. We highlighted that restoration interventions modifying lateral connectivity induced a change of lentic and lotic taxa richness in accordance with the predictions. Richness of alien taxa was favoured by restoration more than predicted; however, no interaction between alien species changes and native species was detected after restoration., Restoration of the ecosystem predictably transformed native communities and encouraged alien species, at least over the 4 years studied. Our findings demonstrate that lateral connectivity is a key variable driving macroinvertebrate communities in large river floodplains and that the response of macroinvertebrates to restoration of a disturbance-driven ecosystem can in part be predicted. Therefore, the outcome of restoration programmes can be optimised by quantifying lateral connectivity before and after restoration. [ABSTRACT FROM AUTHOR]