The Catalogue protocol

The initial compilation of the EASIN Catalogue was carried out following a formal protocol, as described below, aiming at ensuring consistency, good quality of information, standardization and avoidance of duplicate records.

Compilation of species names - standardization

Duplicate names in the initial list of alien species (produced by merging inventories from all online sources) were removed using Excel's 'Remove Duplicate' function. Because of variations across information systems in the notation of the taxon names, many taxa still had multiple entries in the table. To facilitate the process of identification of additional duplicates and also to standardize species notation according to accepted nomenclature (binomial name), the following steps were followed:

  • Names higher than species rank were deleted.

  • Conformation with international nomenclature (International Code of Botanical Nomenclature, the International Code of Zoological Nomenclature and the International Code of Nomenclature of Bacteria). When binomial name is not applicable, the following changes were made:

    • subgenus is indicated by subg. for algae, fungi and plants: ex. Solanum subg. Leptostemonum. (ICBN Art. 22.1)

    • subgenus is indicated within parenthesis for animals: ex. Branchiostoma (Amphioxus) lanceolatum. (ICBN Art. 25.1)

    • ssp., sub. and subspecies were replaced by subsp. for algae, fungi and plants: ex. Helichrysum strechas subsp. barrelieri. (ICBN Art. 5.A.1)

    • subspecies is indicated without parenthesis for animals: ex. Ornithoptera priamus priamus. (ICZN Art. 6.1 - modified)

    • variant was replaced by var. for algae, fungi and plants: ex., Magnolia virginiana var. foetida. (ICBN Art. 5.A.1)

    • forma was replaced by f.; forma specialis was replaced by f. sp.

    • sensu lato was replaced by s.l.;

    • cfr. was replaced by cf.;

    • × (used for hybrids and nothotaxa) was replaced by x. The letter " x" should be in lower case. A single letter space should be left between it and the epithet to avoid ambiguity ex. Mentha x piperita (nothospecies); x Apogropon lutosus (nothogenera), Dianthus caryophyllus x gratianopolitanus x plumarius (hybrid formula for taxon that have not binomial name). (ICBN Art. H3A.1)

    • pathovar is replaced by pv. (for bacteria) ex. Xanthomonas axonopodis pv. citri

    • cultivar status cv. preceding a cultivar is no longer used and it is replaced by single quotation marks ‘’. The name is not written in Italics, it starts with a capital letter and is not a Latin name but rather a common name ex. Pinus sylvestris ‘Repens’ (ICNCP 8th Edition 2009. Art. 14.1).

  • Special characters were substituted, according to international nomenclature codes.

  • Supplementary acronyms, numbers, and text were deleted.

  • Dots were added or deleted where necessary.

For taxon names with multiple taxon ranks (e.g. subsp. and var.), the correct taxon rank was identified through cross checking with the following international systems in a hierarchical way first in World Register of Marine Species (WoRMS) and in the Integrated Taxonomic Information System (ITIS), then in the Catalogue of Life (CoL) and in the Global Biodiversity Information Facility (GBIF).

Protocol for the correction of spelling errors

After the standardization of the species name notation, spelling errors (max. 3 characters) were identified and corrected with the Excel add-in ‘Fuzzy duplicate finder’ (AbleBits, Homel, Belarus; http// Pairs of names obtained this way (potential duplicates) were cross-checked in a hierarchical way with WoRMS, ITIS, CoL, Encyclopedia of Life (EoL), and GBIF, to assess which entry was valid. If the questioned names were both valid, they were both kept as different taxa, otherwise the invalid name was replaced by the valid one.

Checking synonyms

Synonyms present in the list were identified through a cross-check with ITIS, WoRMS, and CoL, and a further correction of invalid names and removal of duplicate records was done. Synonyms were checked in WoRMS using the “match taxa” tool provided in the WoRMS website, in ITIS by extracting them from the downloadable version of the databases, and manually in CoL.

Checking autonyms

Autonyms of subsp. and var. levels taxa were included when applicable; e.g. Lupinus albus was included as an autonym of Lupinus albus subsp. albus.

Compilation of the taxonomic tree

The taxonomy (Kingdom, Phylum-Division, Class, Order and Family) of each alien taxon was retrieved in a hierarchical way from WoRMS, ITIS, CoL, EoL and GBIF. Note that not all species names could be matched with WoRMS and ITIS, but often the taxonomy could be resolved through these sources by using the genus name instead. The taxonomy of the few alien taxa that remained unresolved after cross-checking with WoRMS, ITIS, CoL, EoL and GBIF was completed by following the source database or through literature search. The six-kingdom (Bacteria, Protozoa, Chromista, Plantae, Fungi, Animalia) taxonomic system for cellular organisms proposed by Cavalier-Smith (2004) was followed, with two additional categories, i.e. ‘viruses’ (non-cellular forms) and ‘unresolved’ (taxa with yet unresolved taxonomy).

Identification of the environment

For each species names, the environments where they can be found were identified following this procedure:


  • Present in marine databases (World Register of Marine Species: WoRMS; Flanders Marine Institute: VLIZ; Främmande arter i svenska hav, Alien species in Swedish seas; JNCC report on Non-native marine species in British seas; Marine alien species of Estonia database)

  • Listed as present in a sea in DAISIE

  • Listed as “estuaries and brackish area” or “marine habitat” in NOBANIS

  • Listed as marine in Ellenic Network on Aquatic Invasive Species (ELNAIS); Fish of Latvia;


  • Present in freshwater databases (Freshwater Animal and Diversity Assessment: FADA; Register of Freshwater Plants by CEH)

  • Listed as present in “estuaries and brackish area”, “lakes”, “watercourses” or “wetlands” in NOBANIS

  • Listed as aquatic inland in DAISIE

  • Listed as freshwater in Ellenic Network on Aquatic Invasive Species (ELNAIS); Fish of Latvia;


  • Listed as Terrestrial in DAISIE (excl. aquatic inland)

  • Listed as present in “agricultural areas”, “arctic/alpine habitat”, “boreal forest”, “coastland”, “disturbed areas”, “grass and heathlands”, “greenhouses or compost heaps”, “mixed conifer/broadleaf forest”, “riparian zones”, “rocks and lavafields”, “shrublands”, “temperate broadleaf forest”, “under human management” or “urban areas” in NOBANIS

For unresolved names, the environment was added based on literature.

Identification of pathways

Identification of pathways is based on expert contribution.

An adaptation of the framework proposed by Hulme et al (2008) has been followed. Five main pathways have been included (each one divided into more specific sub-categories): Release (Biocontrol; Game animals; Landscaping-Erosion control; Pets, Terrarium-Aquarium species; Other); Escape (Cultivation and Livestock; Aquaculture; Ornamental planting; Use of live food-bait; Pets, Terrarium-Aquarium species; Zoos, botanical gardens); Contaminant (Trade of contaminated commodities; Packaging materials; Aquaculture); Stowaway (Shipping; Aviation; Land transport); Corridor (Lessepsian migrants; Inland canals; Railroads and Highways).

However, it should be noted that EASIN will gradually align its pathways categorization to the one proposed by the Convention of the Biological Diversity (CBD, 2014) within 2016, aiming at achieving synchronization and harmonizing of information on alien species and their pathways.

Impact classification (high, low/unknown)

The impact of species present in the ‘high-impact’ or ‘worst invasive’ species lists of DAISIE, GISD and SEBI-2010 was classified as ‘high’, while for the rest species as ‘low/unknown’.