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Among the most economically relevant and environmentally devastating diseases globally are those caused by Phytophthora species. In Australia, production losses in agriculture and forestry results from several well-known cosmopolitan Phytophthora species and infestation of natural ecosystems by Phytophthora cinnamomi have caused irretrievable loss to biodiversity, especially in proteaceous dominated heathlands. For this review, all available records of Phytophthora in Australia were collated and curated, resulting in a database of 7869 records, of which 2957 have associated molecular data. Australian databases hold records for 99 species, of which 20 are undescribed. Eight species have no records linked to molecular data, and their presence in Australia is considered doubtful. The 99 species reside in 10 of the 12 clades recognised within the complete phylogeny of Phytophthora. The review includes discussion on each of these species? status and additional information provided for another 29 species of concern. The first species reported in Australia in 1900 was Phytophthora infestans. By 2000, 27 species were known, predominantly from agriculture. The significant increase in species reported in the subsequent 20 years has coincided with extensive surveys in natural ecosystems coupled with molecular taxonomy and the recognition of numerous new phylogenetically distinct but morphologically similar species. Routine and targeted surveys within Australian natural ecosystems have resulted in the description of 27 species since 2009. Due to the new species descriptions over the last 20 years, many older records have been reclassified based on molecular identification. The distribution of records is skewed toward regions with considerable activity in high productivity agriculture, horticulture and forestry, and native vegetation at risk from P. cinnamomi. Native and exotic hosts of different Phytophthora species are found throughout the phylogeny; however, species from clades 1, 7 and 8 are more likely to be associated with exotic hosts. One of the most difficult challenges to overcome when establishing a pest status is a lack of reliable data on the current state of a species in any given country or location. The database compiled here for Australia and the information provided for each species overcomes this challenge. This review will aid federal and state governments in risk assessments and trade negotiations by providing a comprehensive resource on the current status of Phytophthora species in Australia.

Impact assessment is an important and cost-effective tool for assisting in the identification and prioritization of invasive alien species. With the number of alien and invasive alien species expected to increase, reliance on impact assessment tools for the identification of species that pose the greatest threats will continue to grow. Given the importance of such assessments for management and resource allocation, it is critical to understand the uncertainty involved and what effect this may have on the outcome. Using an uncertainty typology and insects as a model taxon, we identified and classified the causes and types of uncertainty when performing impact assessments on alien species. We assessed 100 alien insect species across two rounds of assessments with each species independently assessed by two assessors. Agreement between assessors was relatively low for all three impact classification components (mechanism, severity, and confidence) after the first round of assessments. For the second round, we revised guidelines and gave assessors access to each other’s assessments which improved agreement by between 20% and 30% for impact mechanism, severity, and confidence. Of the 12 potential reasons for assessment discrepancies identified a priori, 11 were found to occur. The most frequent causes (and types) of uncertainty (i.e., differences between assessment outcomes for the same species) were as follows: incomplete information searches (systematic error), unclear mechanism and/or extent of impact (subjective judgment due to a lack of knowledge), and limitations of the assessment framework (context dependence). In response to these findings, we identify actions that may reduce uncertainty in the impact assessment process, particularly for assessing speciose taxa with diverse life histories such as Insects. Evidence of environmental impact was available for most insect species, and (of the non-random original subset of species assessed) 14 of those with evidence were identified as high impact species (with either major or massive impact). Although uncertainty in risk assessment, including impact assessments, can never be eliminated, identifying, and communicating its cause and variety is a first step toward its reduction and a more reliable assessment outcome, regardless of the taxa being assessed.