When genetic and phenotypic data do not agree: the conservation implications of ignoring inconvenient taxonomic evidence

Taxonomy plays a central role in conservation programs of threatened New Zealand taxa. The role of taxonomy is especially relevant for highly vulnerable taxa, where the identification of distinct lineages is essential to define units of conservation and to appropriately allocate conservation resources. Taxonomy traditionally relied on phenotype, but in the past 30 years, the use of genetic data has become prominent in the field. While both phenotypic and genetic approaches to taxonomy have their own merit, they do not always agree. In such cases, favouring one type of data over the other when they are in conflict can have important implications for conservation management. We highlight this issue using several examples from the taxonomy of threatened New Zealand birds. We caution against biases in interpretation of each data type and advocate for a more integrative approach to taxonomy where the limitations of all approaches are carefully considered.