Rare observation of blowflies on a remote island research station: the risk of intra-island human-assisted dispersal

Globally, biodiversity loss is accelerating, with biological invasions representing one of the greatest threats to biodiversity and ecosystem functioning. Increasingly, research visits to isolated locations, such as the sub-Antarctic islands, involve stringent biosecurity measures to limit the inadvertent import and establishment of non-native species in these regions. Notwithstanding, human activity remains the predominant source of non-native species on these islands. One such species found on sub-Antarctic Marion Island, assumed to have been introduced during logistical operations several decades ago supporting this South African-administered island, is the blowfly, Calliphora vicina. To date, this conspicuous fly has only been observed in a limited area in the south-eastern quadrant of the island near Funk Bay and Kildalkey Bay. Here we report an incident of two living flies observed and captured at the island’s meteorological research station in the island’s north-east quadrant, which we speculate is likely associated with inadvertent human-mediated dispersal by a field assistant who surveyed seal populations at Funk Bay earlier the same day. Morphological examination and molecular analyses – the latter being the first for this species on Marion Island – confirmed that these specimens represent C. vicina. Further molecular analyses suggest the Marion population possibly originated from South Africa. Our observations emphasise the importance not only of strictly applying biosecurity protocols before disembarking onto the island, but also the need for increased vigilance to detect the unintentional movement of established non-native species between sites across Marion Island.