Citizen Science Quickly Reveals the Argentine Ant Linepithema humile (Mayr, 1868) Distribution in an Invaded Urban Area and Provides Unexpected Findings.

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.