Victoria Werenkraut

Biological invasions pose significant threats to biodiversity, ecosystem functioning, and human well-being. Urban areas are particularly prone to biological invasions as high levels of human activity and connectivity enhance the arrival of alien species, and some characteristics of these areas (e.g. disturbance levels and reduced thermal variability) facilitate their establishment. Here, we study the establishment and distribution of the highly invasive Argentine ant, Linepithema humile (Mayr, 1868), in Bariloche, a Patagonian city ~1000 km away from its native range, using a citizen science approach, complemented by outdoor ant sampling. Our findings confirm its establishment as an urban pest within a small downtown area and suggest it has not spread into surrounding urban or semi-natural habitats. However, ongoing urban development and climate change might facilitate its spread in the future. Through citizen science records, we also found other ants (including the invasive Monomorium pharaonis (Linnaeus, 1758), reported for the first time in the region) behaving as indoor pests in parts of the city where L. humile was not detected. This study highlights the value of citizen science in detecting invasive alien species and its added benefit of monitoring indoor pests that might otherwise go unnoticed using outdoor surveys and emphasize the need for coordinated management strategies from different stakeholders to address these invasions.

Invasive species impact native ecosystems through associations with local biota; however, these co‐occurrences and potential interactions remain poorly understood, particularly for small organisms like insects. Citizen science provides a valuable tool, providing broad spatial and temporal coverage to facilitate the observation of species co‐occurrences. Our aim was, using citizen science records, to detect co‐occurrences and potential novel interactions between the invasive ladybird Harmonia axyridis and local biota (plants, arthropods and fungi) in Argentina. Over 50% of the photos showed H. axyridis in association with another species, mainly from the plant families Asteraceae, Rosaceae and Lamiaceae and the arthropod families Aphididae and Coccinellidae. In addition, we report potential novel interactions including predation, parasitism, interspecific mating and mixed aggregations with local biota that have not been previously documented in Argentina, providing new insights into possible ecological impacts of this invasive ladybird. Our findings highlight how citizen science can be used as a research prioritization tool for invasive species research, revealing species co‐occurrences and also uncovering potential novel interactions between invasive species and local taxa across large spatial and temporal scales.

The Argentine ant (Linepithema humile) is a highly invasive species with a widespread global distribution. However, the dynamics of its recent expansion into southwestern Argentina remain unclear. We evaluated its spread, niche shifts, and genetic diversity using field surveys, distribution models, and mitochondrial DNA analyses. Our results revealed a strong expansion from Pampas into anthropogenic habitats (multiple urban and rural sites) in the Monte Desert, but not into natural habitats. The Argentine ant’s presence declined westward along the Río Negro Valley in the Monte Desert, and was virtually absent from the Patagonian Steppe, where it was found only in urban sites in Bariloche (ecotone with the Patagonian Forest). The distribution models identified isothermality and water balance as the key drivers of suitability. Thus, urbanization and irrigated agriculture seem to have facilitated its establishment in the Río Negro Valley by buffering climate extremes. Genetic analyses revealed widespread and novel haplotypes, which are consistent with multiple introductions and potential regional differentiation. This southward expansion underscores the critical role of urban areas and irrigated agriculture as refuges and stepping stones that facilitate Argentine ant survival in otherwise inhospitable environments. Continued monitoring of transitional zones in northern Patagonia is crucial to determining whether this front will remain stable or shift further south.

Biological invasions are one of the major drivers of biodiversity decline and have been shown to have far‐reaching consequences for society and the economy. Preventing the introduction and spread of alien species represents the most effective solution to reducing their impacts on nature and human well‐being. However, implementing effective solutions requires a good understanding of where the species are established and how biological invasions develop over time. Knowledge of the status and trends of biological invasions is thus key for guiding research efforts, informing stakeholders and policymakers, for targeted management efforts, and preparing for the future. However, information about the status and trends of alien species is scattered, patchy, and highly incomplete, making it difficult to assess. Published reports for individual regions and taxonomic groups are available, but large‐scale overviews are scarce. A global assessment therefore requires a review of available knowledge with careful consideration of sampling and reporting biases. This paper provides a comprehensive global assessment of the status and trends of alien species for major taxonomic groups [Bacteria, Protozoa, Stramenopila, Alveolata, and Rhizaria (SAR), fungi, plants, and animals] for Intergovernmental Panel of Biodiversity and Ecosystem Services (IPBES) regions. The review provides irrefutable evidence that alien species have been introduced to all regions worldwide including Antarctica and have spread to even the most remote islands. The numbers of alien species are increasing within all taxa and across all regions, and are often even accelerating. Large knowledge gaps exist, particularly for taxonomic groups other than vascular plants and vertebrates, for regions in Africa and Central Asia, and for aquatic realms. In fact, for inconspicuous species, such as Bacteria, Protozoa, and to some degree SAR and fungi, we found records for very few species and regions. Observed status and trends are thus highly influenced by research effort. More generally, it is likely that all lists for alien species of any taxonomic group and region are incomplete. The reported species numbers therefore represent minima, and we can expect additions to all lists in the near future. We identified six key challenges which need to be addressed to reduce knowledge gaps and to improve our ability to assess trends and status of biological invasions.

Main: Animals not only forage for abundant and nearby resources, but their diets can also be influenced by abiotic and geographic factors. This often results in non‐random interactions among species. We investigate how seed density, distance from nest, abiotic (e.g., climate stability, temperature, precipitation) and geographic factors (e.g., latitude, elevation and continental hemisphere) influence the removal of food items (i.e., seeds and dead arthropods) by Pogonomyrmex species.Location: South and North America, from Patagonia to the Rocky Mountains.Taxon: Genus Pogonomyrmex (Formicidae: Hymenoptera).Methods: Conducting standardised experiments, we performed a seed removal experiment and an assessment of the items retrieved by ant workers of 160 nests from eight Pogonomyrmex spp. at 16 sites extending the American continent.Results: Pogonomyrmex ants native to North America removed more seeds than their South American counterpart. In general, results align with optimal foraging theory, indicating a higher probability of seed removal near ant nests. High climate stability correlated with lower seed predation rates, emphasising seed consumption's significance in historically arid environments. Increased precipitation and temperature led to reduced removal of food resources, suggesting reduced water availability and lower mean temperatures increases the consumption of seeds by harvester ants.Conclusions: Overall, Pogonomyrmex ants' food resource use is influenced by a combination of factors such as region, distance from the nest and climate. This study underscores harvester ants' potential impact on plant distribution over large spatial scales consuming seeds from the immediate proximity of their nest and preventing establishment.

Although invasive alien species have long been recognized as a major threat to nature and people, until now there has been no comprehensive global review of the status, trends, drivers, impacts, management and governance challenges of biological invasions. The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) Thematic Assessment Report on Invasive Alien Species and Their Control (hereafter ‘IPBES invasive alien species assessment’) drew on more than 13,000 scientific publications and reports in 15 languages as well as Indigenous and local knowledge on all taxa, ecosystems and regions across the globe. Therefore, it provides unequivocal evidence of the major and growing threat of invasive alien species alongside ambitious but realistic approaches to manage biological invasions. The extent of the threat and impacts has been recognized by the 143 member states of IPBES who approved the summary for policymakers of this assessment. Here, the authors of the IPBES assessment outline the main findings of the IPBES invasive alien species assessment and highlight the urgency to act now.

Extreme events are important determinants of environmental changes at multiple geographical and temporal scales, influencing the ecology and evolution of species. Volcanism in particular can modify entire landscapes through ash deposition, affecting the survival and abundance of susceptible species and favouring tolerant ones. However, there is still a lack of information for predicting which species will be more or less affected by volcanic disturbances. We test the hypothesis that the effect of volcanic ash will differentially affect taxa according to their morphological traits. We used a ground‐dwelling beetle community that was sampled before and immediately after the last eruption of the Puyehue‐Cordón Caulle (PCC) volcano. We measure traits that might help predicting responses to the ash deposition in insect species susceptible to the PCC volcanic eruption – i.e., their abundance decreased considerably – and compared them to others that were tolerant. We examined cuticle thickness, its structures (i.e., hairs) and microsculptures, and body size. We found that traits associated with smoothness of the cuticle (fewer hairs and microsculptures) and a small body enables species to better tolerate the negative effects of volcanic ash. These results are the first to explicitly test for traits that could help to predict which species will be more tolerant to volcanic ashes, a widespread disturbance associated with volcanism.

Monitoring changes in species composition near active volcanoes is important to identify environmental factors that maintain biological diversity after major disturbances. We investigated the taxonomic composition of epigaeic beetles' assemblages in five mountains in north‐western Patagonia (Argentina) in the aftermath of the 2011 Puyehue Cordón‐Caulle Volcanic Complex eruption. The associations of beetle composition with the thermal environment, vegetation structure and soil characteristics were analysed using 10 m × 10 m plots with nine pitfall traps each, established 100 m apart in altitude on each mountain in 2005, 2006 (pre‐eruption) and 2012, 2015 and 2016 (post‐eruption). We found significant differences in beetle composition between forests and high‐Andean steppes before and after the eruption. The beetle composition of forests and high‐Andean steppes differed due to higher plant cover and lower pH and herb richness in forests. Six months after the eruption, the herbs almost disappeared and forests showed high ash accumulation and lower temperature than the high‐Andean steppes. In the medium term, plant cover, temperature and soil conditions—but not ash accumulation—remained as important correlates of beetle composition. Before the eruption, forest assemblages showed higher beetle diversity and Leiodidae indicator species, but Curculionidae predominated post‐eruption. Tenebrionidae and Carabidae were high Andean steppes indicators. Post‐eruption, the beetle composition in high‐Andean steppes did not change significantly except for an increase in Tenebrionidae indicator species. We concluded that the conservation of landscape diversity and environmental gradients maintaining the differentiation between ecoregions is essential to protect epigaeic beetle composition and for species survival after volcanic disturbances.