Challenge from nomenclature changes: the case of ascidian biodiversity

The stability of biological nomenclature is essential for estimating biodiversity and is ensured by the International Codes for Nomenclature. However, species names change over time due to advances in scientific knowledge and new technologies, such as DNA barcoding. While barcoding has significantly improved species identification, it has also revealed complexes of cryptic species that can only be distinguished using molecular methodologies. This creates challenges for taxonomists, who must provide new morphological descriptions to properly distinguish these species. As a result, modern species identification requires the use of integrative taxonomy, which combines multiple methods. In this study, using literary and systematic reviews, we analyse issues related to nomenclature changes, cryptic species and integrative taxonomy using ascidians of the Venice Lagoon as a study case. Although ascidians have been documented in this area since the 18th century, reconstructing a clear timeline of biodiversity is difficult due to frequent name changes. We discuss notable cases of name change related to the well-known laboratory species Ciona intestinalis, Ciona robusta and Botryllus schlosseri. These examples show that changes in species names can have impacts beyond biodiversity studies, including resistance within the scientific community and the need to update laboratory practices and research protocols.