DOI: 10.5061/dryad.4b8gthtg7
title: Data from: Pathways of introduction of alien species in Norway

description: 1. Alien species constitute one of the major threats to global
 biodiversity. Stopping alien species at an early stage, preferably before
 establishment, is crucial for the effectiveness of management actions. To
 enable early detection and prevent future introductions, knowledge of
 pathways of introduction and their absolute and relative importance is
 crucial. 2. Based on an exhaustive impact assessment of all alien species
 in Norway (multicellular neobiota), the relation of taxonomy, lifestyle
 and ecological impact of alien species to their pathways of introduction
 are investigated. This taxonomically and ecologically unbiased dataset
 contains 2,267 unique pathways of 1,180 alien species. 3. Ecological and
 taxonomic patterns indicate that terrestrial organisms were predominantly
 introduced by means of escape (mainly plants escaped from gardens),
 parasites as contaminants (mainly fungi and insects parasitising plants),
 freshwater organisms by release (mainly vertebrates), and marine organisms
 as stowaways (mainly invertebrates and algae). Unaided introductions were
 most common among insects and marine organisms. 4. Alien species with high
 ecological impact were mainly introduced along the same pathways as other
 alien species. In relative terms, high-impact species were overrepresented
 among released species, even though this pathway was subordinate in
 absolute terms. The number of pathways and the overall introduction
 pressure were important predictors of ecological impact, especially of the
 species' invasion potential and area of occupancy. 5. Introduction
 rates of novel alien species have seen recent increases in all taxa and
 along almost all pathways. This acceleration was especially pronounced for
 insects and fungi introduced as contaminants and for marine organisms
 introduced as stowaways. In absolute terms, introduction rates were
 highest for plant escapes, reaching more than five novel species per year.
 6. Synthesis and applications: Introduction of new alien species cannot be
 prevented by closing one or two introduction pathways, since none can be
 singled out as the main pathway of invasives. Yet each pathway closed
 makes a difference, as this reduces the overall introduction pressure. The
 highest priorities for management are the pathways that are easiest to
 address, such as release, and those with the highest volume, such as plant
 trade.
description: The assessments during which the pathways were recorded, followed
 the Generic Ecological Impact Assessment of Alien Species (GEIAA,
 described by Sandvik et al., <em>Biological Invasions</em>
 <em>21:</em>2803,
 2019).
description: The dataset contains three files: (1)
 README.pdf (explanations)<br>(2) Pathways.xlsx (Microsoft Excel
 spreadsheet workbook)<br>(3) pathways.txt (data file as
 semicolon-delimited plain text) The data are provided
 both in "pathways.txt" and in the "Data" sheet of
 "Pathways.xlsx".<br>The information needed to interpret
 the data is provided both in "README.pdf" and in
 "Pathways.xlsx". For questions on these
 files, please contact the first author (hanno.sandvik@nina.no)
 Information on the species contained in the current dataset is
 available from an earlier publication (Sandvik et al.,
 <em>Ecological Solutions and Evidence</em>
 <em>1:</em>e12006,
 2020) and dataset (dryad.8sf7m0cjc). The data in the datasets
 can be coupled using species names.