Abstract

Invasions of exotic species in fragile and pristine ecosystems, such as those of Antarctica, is a growing ecological concern. Psychoda albipennis, a cosmopolitan saprophagous fly, has recently become established in the Maritime Antarctic South Shetland Islands archipelago, raising questions about its potential for adaptation and expansion. This study analyses wing morphological variation amongst Maritime Antarctic and Magellanic sub-Antarctic populations of P. albipennis using geometric morphometrics to infer rapid adaptive responses to the extreme Antarctic environment. The data obtained reveal significant differences in wing shape and size, with Maritime Antarctic flies exhibiting narrower and more elongated wings, an aerodynamic configuration likely favoured under stronger wind conditions. Additionally, interannual reduction in wing size in the Maritime Antarctic population suggests an adaptive thermoregulatory strategy, partially consistent with the temperature-size rule. These morphological changes are likely to be associated with selective pressures, such as wind strength and minimum temperatures, which explained 46% and 2.74% of the shape variation, respectively. Our findings support the hypothesis of rapid phenotypic response processes, reflecting an early stage of successful adaptation. Given the species' potential ecological impact, including alterations in decomposition processes and trophic networks, we emphasise the need to implement early detection and preventative management strategies. This research highlights the value of geometric morphometrics as a cost-effective and practically applicable tool for identifying adaptive patterns in biological invasions and supports the application of integrative approaches combining morphological, genomic and physiological data to anticipate and mitigate the consequences of future invasions in Antarctica.