Biological invasions are a major driver of biodiversity loss, and tracking non-native species introductions is essential for biodiversity monitoring and policy assessment. First records, defined as the earliest documented evidence of a species occurring in the wild outside its native range, provide a standardized metric to quantify introduction dynamics across regions and taxonomic groups. However, compiling and harmonizing such records from diverse sources remain challenging due to non-standardized terminology and heterogeneous reporting standards. Here, we describe a reproducible workflow for standardizing first records of non-native species from diverse sources. The workflow is implemented in R and is designed to ensure consistency in taxonomy, harmonize geographic locations, convert heterogeneous temporal expressions into four-digit years using explicit transformation rules, and standardize terms following Darwin Core terminology. A key innovation of the workflow is the assignment of a confidence level to each standardized first record, reflecting the uncertainty of the original temporal information. The workflow is open-source, modular, and customizable, allowing users to apply it to their own data or modify standardization rules. It is applied to produce v4.0 of the FirstRecords dataset, which contains nearly 100,000 first records of more than 30,000 taxa and is structured into linked tables covering actual records, taxonomy, locations, and data sources. This represents a 17.8% increase in the amount of available first records compared to the previous version, of which approximately 8% is due to the refinement of the workflow. By providing a transparent and automated approach to data harmonization, this workflow facilitates large-scale analyses of invasion patterns and indicator development, while maintaining data integrity.
Invasive alien species are a recognised threat to biodiversity, ecosystem functions, and human well-being. Management efforts often prioritise ecological and economic outcomes, neglecting the implications of control methods on animal welfare. We investigated the perceived impacts on animal welfare of different lethal and non-lethal methods to control invasive slider turtles Trachemys scripta in Europe. We elicited the opinions of a group of 24 herpetologists, turtle caretakers, veterinarians and welfare experts, combining the Five Domains welfare framework with a formal structured elicitation approach. Experts generally agreed that welfare impacts in traps or transport would be mostly minor, but could increase with time of exposure, turtle densities and inadequate protocols. For captive containment post-capture, concerns included inadequate diets and habitats, disease and behavioural concerns, although the latter were particularly uncertain. For lethal methods, lethal injection and properly executed shooting were judged to cause no or mild suffering only. Self-expressed confidence in the elicited estimates was relatively high, but decreased for higher impact levels, longer timeframes and less-known welfare domains such as behavioural concerns. Future research would refine welfare assessment models, particularly for the evaluation of cumulative impacts across different methods and multiple affected individuals. However, in a field as multifaceted as animal welfare, some degree of expert interpretation will likely always be necessary to guide policy: structured expert elicitation can help formalise current knowledge and make those interpretations more transparent.
Non-native species are recognized as one of the major drivers of biodiversity change globally, with profound impacts on ecosystem functions and services. Despite the high number of studies on non-native species published, mainly in the last two decades, an often-overlooked aspect is their role as mediators of resource subsidies (the cross-boundary movement of energy, nutrients, or materials). This topic may have theoretical and empirical implications because non-native species may play a major role in ecosystem connectivity by transporting—or interrupting the transport of—energy and organic matter. Therefore, the main aims of this review were to (1) assess temporal trends, geographic distribution, and methodological approaches in research on resource subsidies mediated by non-native species; (2) synthesize how non-native species alter the magnitude, direction, and dynamics of resource subsidies across ecosystems and their implications for ecosystem functioning; and (3) identify key gaps in current knowledge and define future research priorities. The review retrieved 143 publications, resulting in 212 case studies, that collectively show that non-native species can both reduce and increase resource flows across ecosystem boundaries, with implications for ecosystem dynamics and connectivity. Although terrestrial and freshwater connectivity accounted for the majority of published case studies (56%), many ecosystem linkages remain underexplored. A significant geographic bias was found, with Africa being severely understudied (2.8% of all publications), followed by Asia (7.7% of all publications). Taxonomic representation was also skewed, with the majority of studies focusing on non-native plants (28.8% of case studies), non-native fish (25.5% of case studies), and mammals (21.7% of case studies), whereas fungi (0.9%) and bacteria (2.4%) were largely neglected despite their fundamental roles in decomposition processes. Key priorities for advancing this field include long-term monitoring, the application of emerging molecular and analytical tools (e.g., telemetry, eDNA, metabarcoding, and isotopic tracers), and the integration of artificial intelligence to synthesize large datasets. The findings provide the first synthesis of resource subsidies mediated by non-native species. This information is crucial for biodiversity conservation and the effective management of ecosystems and their connectivity.
The crayfish plague pathogen Aphanomyces astaci Schikora, 1906 is one of the most damaging invasive pathogens affecting European freshwater ecosystems, causing declines in native crayfish populations. In Croatia, crayfish plague was first reported in the late 19 th century and was subsequently molecularly confirmed in 2016. However, its national distribution remains incompletely resolved because the initial molecular survey covered only a limited number of localities. To obtain an initial country-scale distribution of A. astaci , ethanol-preserved specimens of all seven crayfish species present in the country, collected across Croatia between 1998 and 2025, were analyzed. Tissue samples were screened for A. astaci using quantitative PCR (qPCR), and positive results were confirmed by Sanger sequencing. Genotype groups were assessed using pentaplex qPCR, with microsatellite genotyping and mitochondrial haplotyping applied to samples with sufficient pathogen loads. Of the 238 samples, 91 (38.2%) were A. astaci -positive. Pathogen presence was confirmed in both the Black Sea and Adriatic Sea drainages and across all investigated host species, extending its known distribution beyond previously surveyed localities. The integration of different genotyping methods yielded 11 interpretable consensus genotype profiles, including genotype groups A and B, SSR-UP-like, and a putatively novel genotype profile. However, additional genotypes may have remained undetected, for instance, in positive samples with low pathogen loads from Faxonius limosus , an invasive host widespread in Croatia and a typical carrier of genotype group E. Overall, the study shows that A. astaci is a widespread, long-established, and genetically diverse pathogen in Croatia, highlighting the need for coordinated, genotype-resolved national monitoring focused on invasive crayfish reservoirs and threatened indigenous populations.
Considering the high invasiveness of lodgepole pine (LP, Pinus contorta Dougl.) in parts of its introduced range, concerns about invasion risks in the Baltic region have been raised. In this regard, self-regeneration, dispersion distance, and factors affecting LP regeneration outside plantations were studied in Latvia, where the species is still considered as an alternative for forest regeneration. Among the 20 plantations investigated, 45% contained seedlings or saplings of LP. The density of LP within and in proximity to the plantation (up to 90 m) was similar, at 240 ± 78 and 234 ± 103 seedlings ha-1, respectively. The assessed LP plantations were still young (28 to 47 years), which might have contributed to lower pressure of propagules on the surrounding area, as the most distant seedling was found at 89 m. Site properties affecting LP regeneration included the absence of large canopy openings and bare soil, lack of competition, and, particularly, high browsing damage (24%) on seedlings over 30 cm. The regeneration densities and biotic limitations suggest that the invasion risk of LP in Latvia is currently low, nevertheless, monitoring of dispersal is still needed.
