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...s in other areas. However, there are many examples of species that have no significant impact in their native range but become invasive when they escape from biotic constraints or find vacant niches (=-=Mack et al. 2000-=-), though the validity of the ‘vacant niche’ concept is questionable (Herbold & Moyle 1986, Copp 2008). The base rate effect, where the probability of predicting an event accurately is dependent not o...

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...uctured on a scale of increasing stringency. Measures can be applied singly or in combination. 4. Discussion The difficulties of assessing the risks posed by non-native species are widely recognised (=-=Kolar & Lodge 2002-=-, National Research Council 2002, Hulme 2003, Copp et al. 2005b, Gozlan et al. 2005, Rejmanek et al. 2005). Trait-based approaches work well for some taxa in some habitats (Pheloung et al. 1999, Daehl...

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...ognised (Kolar & Lodge 2002, National Research Council 2002, Hulme 2003, Copp et al. 2005b, Gozlan et al. 2005, Rejmanek et al. 2005). Trait-based approaches work well for some taxa in some habitats (=-=Pheloung et al. 1999-=-, Daehler et al. 2004, Copp & Fox 2007) but not for others (Rosecchi et al. 2001, Kolar & Lodge 2002). Williamson (1999), for example, found no distinctive intrinsic attributes in the invasive non-nat...

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....1. The Invasive Attributes Spreadsheet (Module 1) The spreadsheet created by Pheloung et al. (1999) for the Australian weed risk assessment (WRA), which has also been successfully adopted in Hawaii (=-=Daehler et al. 2004-=-), was obtained from the authors and adapted for freshwater fish (Copp et al. 2005b, 2005c), and subsequently for marine fish, marine invertebrates, amphibia and plants (http://www. cefas.co.uk/4200.a...

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...yle 1986, Copp 2008). The base rate effect, where the probability of predicting an event accurately is dependent not only on the accuracy of the predictive system but also on the rarity of the event (=-=Smith et al. 1999-=-), adds to the problem.sDespite the stated difficulties, the need for such schemes is often mentioned. Lodge et al. (2006) have called for a more quantified scheme for risk assessment in the USA that ...

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...ws International Plant Protection Convention (IPPC) standards for pest risk analysis, PRA (FAO 2004) that are recognised by the World Trade Organisation Sanitary and Phytosanitary Agreement, WTO-SPS (=-=WTO 1994-=-).sAlthough the EPPO pest risk assessment scheme was originally designed to assess the risks posed by the unintentional entry of invertebrate and pathogen pests to cultivated plants, environmental imp...

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... impact in their native range but become invasive when they escape from biotic constraints or find vacant niches (Mack et al. 2000), though the validity of the ‘vacant niche’ concept is questionable (=-=Herbold & Moyle 1986-=-, Copp 2008). The base rate effect, where the probability of predicting an event accurately is dependent not only on the accuracy of the predictive system but also on the rarity of the event (Smith et...

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... al. 2005b, Gozlan et al. 2005, Rejmanek et al. 2005). Trait-based approaches work well for some taxa in some habitats (Pheloung et al. 1999, Daehler et al. 2004, Copp & Fox 2007) but not for others (=-=Rosecchi et al. 2001-=-, Kolar & Lodge 2002). Williamson (1999), for example, found no distinctive intrinsic attributes in the invasive non-native flora of the UK. The best predictors were propagule pressure and records of ...

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...very high), for responses to the questions in the scheme proved to be a reasonable compromise between parsimony and accuracy, and the use of an odd number allowed a mid-point score to be defined (see =-=Holt 2005-=-). Scores were averaged under each major heading (entry, establishment, spread, impact) as well as overall to obtain aggregate measures of risk. Summation or averaging has been used ubiquitously in si...

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...onmental risks are considered has also been published (FAO 2005). Previous studies have shown that the assessment of invasion risks has common elements regardless of the taxon or the method of entry (=-=Schrader & Unger 2003-=-, Baker et al. 2005a). Thus, the aim of the present study was to adapt the EPPO protocols and to develop a generic risk identification and assessment framework with which to assess the risks posed by ...

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...e range but become invasive when they escape from biotic constraints or find vacant niches (Mack et al. 2000), though the validity of the ‘vacant niche’ concept is questionable (Herbold & Moyle 1986, =-=Copp 2008-=-). The base rate effect, where the probability of predicting an event accurately is dependent not only on the accuracy of the predictive system but also on the rarity of the event (Smith et al. 1999),...

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...the risks posed by any non-native taxon to UK species, habitats and ecosystems.s2. MethodologysIn the initial phase of development, the latest available draft of the EPPO pest risk assessment scheme (=-=EPPO 2003-=-) was reformatted into a table and circulated to experts who carried out trial risk assessments on 34 non-native species that are already present in the UK or that could enter intentionally or uninten...

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...cheme for all non-native species 53 ment of risk better than did score averaging. A subsequent application of the conditional probability method to a study involving 256 potential quarantine species (=-=Holt et al. 2006-=-) revealed that high and low risk cases were clearly separated and that discrimination was enhanced particularly for the more borderline cases, which arguably pose the greatest decision problem.s3.6 R...