Biological invasions are a population-level rather than a species-level phenomenon.

Biological invasions pose a rapidly expanding threat to the persistence, functioning and service provisioning of ecosystems globally, and to socio-economic interests. The stages of successful invasions are driven by the same mechanism that underlies adaptive changes across species in general-via natural selection on intraspecific variation in traits that influence survival and reproductive performance (i.e., fitness). Surprisingly, however, the rapid progress in the field of invasion science has resulted in a predominance of species-level approaches (such as deny lists), often irrespective of natural selection theory, local adaptation and other population-level processes that govern successful invasions. To address these issues, we analyse non-native species dynamics at the population level by employing a database of European freshwater macroinvertebrate time series, to investigate spreading speed, abundance dynamics and impact assessments among populations. Our findings reveal substantial variability in spreading speed and abundance trends within and between macroinvertebrate species across biogeographic regions, indicating that levels of invasiveness and impact differ markedly. Discrepancies and inconsistencies among species-level risk screenings and real population-level data were also identified, highlighting the inherent challenges in accurately assessing population-level effects through species-level assessments. In recognition of the importance of population-level assessments, we urge a shift in invasive species management frameworks, which should account for the dynamics of different populations and their environmental context. Adopting an adaptive, region-specific and population-focused approach is imperative, considering the diverse ecological contexts and varying degrees of susceptibility. Such an approach could improve and refine risk assessments while promoting mechanistic understandings of risks and impacts, thereby enabling the development of more effective conservation and management strategies.

Dyeing waters: Does indiscriminate dye use threaten aquatic ecosystems?

Aquatic ecosystem conservation is imperative to reaching global biodiversity and sustainability targets. However, the ecological status of waters has been continuously eroded through mismanagement in the face of existing and emerging anthropogenic stressors, such as pollutants. There has been an emerging trend towards the use of dyes to manage algae and plants as well as to alter aesthetics within various aquatic environments. This artificial colouring has potential ecological implications through reductions in light levels and disruptions to thermoclines (i.e., temperature regime changes with depth). Abiotic regime shifts could in turn drive ecological cascades by depowering primary production, hampering top-down trophic interactions, and affecting evolved animal behaviours. Despite commercial dyes being marketed as acutely non-toxic, very little is known about the chronic effects of these dyes across ecological scales and contexts. We thus call for greater research efforts to understand the ecological consequences of dye usage in aquatic environments, as well as the socio-cultural drivers for its application. This emerging research area could harness approaches such as biological assays, community module experiments, remote sensing, culturomics, and social surveys to elucidate dye effects, trends, and perspectives under a pollution framework. A greater understanding of the potential effects of dye in aquatic ecosystems under relevant contexts would help to inform management decisions and regulation options, while helping to mediate ecocentric and anthropocentric perspectives.