Occurrence of the freshwater invasive snail Potamopyrgus antipodarum in Madeira Island (Portugal): distribution and impacts on benthic communities

<p> <i>Potamopyrgus antipodarum</i> (Gray, 1843) has been considered one of the most successful and widespread invasive freshwater molluscs worldwide. This snail has been present in mainland Portugal since the 1960s, but there is only scarce information regarding its presence in Madeira or Azores archipelagos. In this work, macroinvertebrate communities were sampled in six Madeira Island streams. <i>P. antipodarum</i> was found in all sampled sites, with abundances ranging from 3 to 3528 individuals per sampling area, indicating that the species arrived at Madeira recently and is now in a clear spreading phase. Our results indicate no relationship between the abundance of <i>P. antipodarum</i> and macroinvertebrates' biodiversity indices. Nevertheless, the abundance of <i>P. antipodarum</i> was extremely high in some locations, representing more than 30% of all benthic invertebrates, which triggered alterations in the food web and community structure. The future impacts of this invasion are for now unpredictable, but given <i>P. antipodarum</i> parthenogenetic reproduction and fast spread, its presence can potentially affect Madeira Island's aquatic ecosystems' ecological status and services. These results can inform environmental agencies on the importance of monitoring the presence and spread of this invasive species and call for management strategies focused on early detection and control measures. Given the endemicity and insularity of Madeira macroinvertebrate communities, the spread of <i>P. antipodarum</i> should be limited to mitigate its ecological impacts and biodiversity loss.</p>