Species delimitation is one of the most contested areas in modern biology, with widespread disagreement about almost every aspect of the definition and implementation of the “species” label. While this debate is intellectually stimulating, it also has real implications for conservation, where its impacts on taxonomic inflation or inertia can mean that specific populations receive adequate conservation measures or are ignored. Recently, the rise of next generation sequencing and phylogenomics has revolutionised phylogenetic understanding of many organismal groups but has simultaneously highlighted the porosity of genomes in terms of admixture across previously delineated species barriers. The extraordinary power of genomic data is increasingly being used to delineate species, and several publications in this domain have recently attracted significant attention and criticism. Here we revisit the question of species delimitation, but from a genomic context. We ask how and whether the large amounts of data provided by genomic methods can resolve the longstanding discussion on the validity and application of phylogenetic and allied species concepts, and how some recent examples can inform this debate. We argue that conserving adaptive potential is a priority for conservation, and no single species concept currently does that adequately on its own. Genomic data holds the potential to add unprecedented detail, but frequently falls short of this potential.
