Prioritising plant-parasitic nematode species biosecurity risks using self organising maps

The biosecurity risks from many plant-parasitic nematode (PPN) species are poorly known and remain a major challenge for identifying potentially invasive species. A self organising map (SOM) was used to prioritise biosecurity risks from PPN to the whole of continental Australia as well as each of the states and the Northern Territory separately. The SOM used the recorded worldwide distributions of 250 systematically selected species from 43 genera, and identified 18 different countries spanning Asia, Africa, North and Central America, Europe and the Pacific with very similar PPN assemblages to Australia as a whole. Many of the species in these countries are not recorded in Australia, and therefore pose a biosecurity risk. Analysed separately, the states and territories were identified as forming five separate clusters, each with a different region of the world, and with different characteristic PPN. Many of the PPN found in the regions clustered with an Australian state have not been recorded from anywhere in Australia, and others have very restricted distributions within Australia, thus posing different biosecurity risks. The SOM analysis ranked the risks of the different PPN based on likelihoods of establishment. The rankings confirmed the risks from frequently quarantined PPN, but more importantly identified species, which upon further investigation could be new threats. This method can be used to identify previously overlooked species for more detailed risk assessments.