Alien Invasive Arthropods of Malta and Sicily

Biological invasions have become a major global concern due to the potential economic and environmental ramifications they entail. Arthropods, which encompass insects, mites, spiders, millipedes, woodlice, crabs and other related organisms, are continuously being introduced into new territories. Introduced species evolve in their new environments, and this can aggravate impacts. In some cases, newly introduced genotypes can cause a harmless species to become invasive. Over the past century, this trend has surged, primarily driven by increased international trade in agricultural commodities, particularly plants, the rapid growth of the tourism industry and the ongoing effects of climate change. Most invasive species, particularly those originating from subtropical regions, tend to follow a similar distributional pattern: they first establish themselves in the Mediterranean and/or Macaronesian regions before gradually expanding northward. Once they take root in a new territory, these biological invasions pose threats to native biodiversity and can jeopardise economically significant crops. Sicily and Malta are no exceptions to the phenomenon of biological invasions and the combined count of terrestrial and freshwater alien arthropods in either of these regions exceeds 600 species. It’s worth noting that this number is likely an underestimate because many arthropod groups remain inadequately studied. A significant portion of these organisms was inadvertently introduced during historical times and has since become nearly ubiquitous in distribution, establishing themselves as native to these territories (autochthonous). Examples include the sap beetle, Carpophilus bifenestratus and the cotton aphid, Aphis gossypii. The native origins of some of these species remain a subject of debate among scientists and their precise origins are often unknown. On the other hand, a relatively small number of alien species, though documented in the scientific literature from Malta and/or Sicily (such as the false powderpost beetle, Sinoxylon unidentatum and the longhorn beetle, Callidiellum villosulum, both recorded from Malta) have not yet established themselves within these territories and should not be considered as forming part of their respective faunas. However, it’s important to acknowledge that the potential for some of these species to establish themselves in the future cannot be ruled out. This is particularly so when considering factors such as repeated introductions of a particular species and changing environmental parameters such as climate change.