The status and distribution of alien plants on the islands of the south coast of Western Australia.
Alien plants pose a substantial threat to island ecosystems in Australia and worldwide. A better understanding of weed distributions is necessary to more effectively manage natural resources on islands. To address this need for Western Australian islands, we created a database of all available records of alien plants on these islands. Here we report on records from all islands located along the south coast of Western Australia. From 789 individual records, a total of 116 alien plant species were recorded on the 43 islands with existing weed records. A disproportionately large number of weed species were recorded on estuarine islands and islands with a history of intensive human activity. Some of the species are known to be serious environmental weeds, including bridal creeper (Asparagus asparagoides), pig's ear (Cotyledon orbiculata), sea spurge (Euphorbia paralias), cleavers (Galium aparine), African boxthorn (Lycium ferocissimum), tree mallow (Malva arborea), arum lily (Zantedeschia aethiopica), and the annual grasses Avena, Bromus, Ehrharta, Hordeum, Lolium and Vulpia. Developing management plans to address these species, as well as surveying islands adjacent to known infestations, should be a conservation priority for south coast islands. Improved biosecurity procedures and enforcement could prevent the establishment of new island weed populations and reduce future costs associated with the management of active infestations.