Biodiversity Realism: Preserving the tree of life

Biodiversity is a key concept in the biological sciences. While it has its origin in conservation biology, it has become useful across multiple biological disciplines as a means to describe biological variation. It remains, however, unclear what particular biological units the concept refers to. There are currently multiple accounts of which biological features constitute biodiversity and how these are to be measured. In this paper, I draw from the species concept debate to argue for a set of desiderata for the concept of "biodiversity" that is both principled and coheres with the concept's use. Given these desiderata, this concept should be understood as referring to difference quantified in terms of the phylogenetic structure of lineages, also known as the 'tree of life'.