Integrating molecular taxonomy and genomics to strengthen marine biosecurity: a Mediterranean perspective

The introduction of non-indigenous species (NIS) threatens marine biodiversity, ecosystem services and biosecurity worldwide. Rapid and accurate NIS identification is a fundamental first step in understanding biological introductions and managing invasive species. While traditional taxonomy remains invaluable, its reliance on morphological traits and taxon-specific expertise can significantly hinder the identification of cryptic species and early life stages. Molecular approaches, particularly DNA barcoding and eDNA metabarcoding, overcome these limitations by enabling reliable detection across diverse taxa and life stages, complementing classical methods. However, accurate molecular identification relies heavily on the integrity of curated reference databases, ideally sourced from native populations. Recent large-scale initiatives focusing on standardized genetic and genomic approaches are critical for establishing the reference libraries required for regulatory confidence. Furthermore, population-level genomic analyses are increasingly necessary to capture the complexity of marine introductions. These tools detect multiple introductions, population-level admixture and enhanced adaptive potential in novel environments. Genomic approaches also reveal complex dynamics, including intraspecific introgression between introduced populations, hybridization between closely related species and cryptic invasion of introduced alleles into native populations. This manuscript emphasizes the need for frameworks that integrate rigorous, standardized molecular taxonomy and population genomics into biosecurity frameworks providing practitioners with clear methodological guidance to enable well-informed management strategies.