Mammals and meaningful taxonomic units: the debate about species concepts and conservation

Mammalian taxonomy based on the diagnosability version of the Phylogenetic Species Concept has recently been declared the only sound approach to mammalian classification. In this article, based on the underlying evolutionary ontology of species taxa, I explain the fallacy of these arguments and hold that in a ‘grey area’ after lineage sundering, completely objective species delimitation is impossible, making both lumping and splitting equally correct or incorrect. As a consequence, we may have to get used to the idea that described species are often a poor guide to the delineation of meaningful taxonomic units for conservation.