Invasive alien species (IAS) are considered one of the greatest threats to biodiversity, particularly through their interactions with other drivers of change. Horizon scanning, the systematic examination of future potential threats and opportunities, leading to prioritization of IAS threats is seen as an essential component of IAS management. Our aim was to consider IAS that were likely to impact on native biodiversity but were not yet established in the wild in Great Britain. To achieve this, we developed an approach which coupled consensus methods (which have previously been used for collaboratively identifying priorities in other contexts) with rapid risk assessment. The process involved two distinct phases: Preliminary consultation with experts within five groups (plants, terrestrial invertebrates, freshwater invertebrates, vertebrates and marine species) to derive ranked lists of potential IAS.Consensus-building across expert groups to compile and rank the entire list of potential IAS.Five hundred and ninety-one species not native to Great Britain were considered. Ninety-three of these species were agreed to constitute at least a medium risk (based on score and consensus) with respect to them arriving, establishing and posing a threat to native biodiversity. The quagga mussel, Dreissena rostriformis bugensis, received maximum scores for risk of arrival, establishment and impact; following discussions the unanimous consensus was to rank it in the top position. A further 29 species were considered to constitute a high risk and were grouped according to their ranked risk. The remaining 63 species were considered as medium risk, and included in an unranked long list. The information collated through this novel extension of the consensus method for horizon scanning provides evidence for underpinning and prioritizing management both for the species and, perhaps more importantly, their pathways of arrival. Although our study focused on Great Britain, we suggest that the methods adopted are applicable globally.

There is a need for improvement and standardization in larval descriptions for them to become useful not only for identification purposes but also in comparative and phylogenetic studies. Details of the rearing technique and equipment used should be given, the spent female crab and representative larval stages need to be deposited at a national museum and a minimum of five specimens of each stage should he used for meristic and morphometric criteria. Diagnostic features of the carapace, all appendages, abdomen, and other characters that are to be included in a standard larval description are presented with specifications concerning format and sequence of substructures. Typical configurations of larval structures are given and some possible exceptions are described. Guidelines for illustrations including the preparation, size, sequence and arrangement of figures are provided.

No abstract

No abstract

No abstract