Compilation, revision, and annotation of DNA barcodes of marine invertebrate Non-Indigenous Species (NIS) occurring in european coastal regions

The script developed to create the DNA sequence reference library is available at https://github.com/tadeu95/Curated-BINs-Reference-Library (accessed on 25 January 2023). Metabarcoding datasets will be made available upon request since they belong to a study that is not published yet.The introduction of non-indigenous species (NIS) is one of the major threats to the integrity of European coastal ecosystems. DNA-based assessments have been increasingly adopted for monitoring NIS. However, the accuracy of DNA-based taxonomic assignments is largely dependent on the completion and reliability of DNA barcode reference libraries. As such, we aimed to compile and audit a DNA barcode reference library for marine invertebrate NIS occurring in Europe. To do so, we compiled a list of NIS using three databases: the European Alien Species Information Network (EASIN), the Information System on Aquatic Non-indigenous and Cryptogenic Species (AquaNIS), and the World Register of Introduced Marine Species (WRiMS). For each species, we retrieved the available cytochrome c oxidase subunit I (COI) mitochondrial gene sequences from the Barcode of Life Data System (BOLD) and used the Barcode, Audit & Grade System (BAGS) to check congruence between morphospecies names and Barcode Index Numbers (BINs). From the 1249 species compiled, approximately 42% had records on BOLD, among which 56% were discordant. We further analyzed these cases to determine the causes of the discordances and attributed additional annotation tags. Of the 622 discordant BINs, after revision, 35% were successfully solved, which increased the number of NIS detected in metabarcoding datasets from 12 to 16. However, a fair number of BINs remained discordant. Reliability of reference barcode records is particularly critical in the case of NIS, where erroneous identification may trigger action or inaction when not required.This research was funded by national funds through the Foundation for Science and Technology (FCT I.P.), grant number PTDC/BIA-BMA/29754/2017 (NIS-DNA: Early detection and monitoring of non-indigenous species (NIS) in coastal ecosystems based on high-throughput sequencing tools) and by the “Contrato-Programa” UIDB/04050/2020. Financial support granted by the FCT I.P. to S.D. (CEECIND/00667/2017) is also acknowledged. A.S.L. (UI/BD/150871/2021) and J.T.F. (UI/BD/150910/2021) are supported by the Collaboration Protocol for Financing the Multiannual Research Grants Plan for Doctoral Students with financial support from FCT I.P. and the European Social Fund under the Northern Regional Operational Program—Norte2020