DNA barcoding Diplostomum (Digenea: Diplostomidae) through the lens of taxonomy: Status and issues

Molecular barcoding is causing fundamental changes in our understanding of the species diversity in a large number of digenean families. Yet, after 16 years of barcoding, we are still far from reaching a global coverage and a clearer picture of the taxonomic diversity of Diplostomum, the most species-rich genus of the digenean family Diplostomidae, comprising important fish pathogens. Here, focusing on taxonomy, we provide an overview of the important developments during this period (2009-2025), an update of Diplostomum taxonomy and nomenclature for 49 species and species-level lineages barcoded to date, an assessment of the progress in several specific areas of current interest, such as species richness and taxonomic diversity, geographical distribution, life cycles, host specificity, and the status of barcode libraries, and identify problems with the use and interpretations of the new data gathered that may affect future work.