 Microbes, and particularly Bacteria and Archaea, provide a treasure trove of problems for species concepts. They do not sexually reproduce, they are not morphologically rich for the most part (protists are, so morphology has been a large part of their historic classification), and they do not form the right sort of reproductively isolated lineages. Importantly, whatever lineage-like interpretations can be made of their descent relationships are confounded by major and promiscuous episodes of gene transfer between these otherwise distinct lineages (Doolittle 1999; Martin 1999; Gogarten et al. 2002). As soon as philosophers consider microbes, especially Bacteria and Archaea, they usually default to a pluralistic view of species concepts. It is one thing to find a concept that mostly works for animals and even plants, but it is more or less universally admitted that no single concept works across the entirety of the diversity of the tree of life, on any reconstruction of that tree (Dupré 2001; Ereshefsky 1998, 2010; Doolittle &amp; Zhaxybayeva 2009).