The Future of Systematics: Tree-Thinking Without the Tree
Abstract: The construction and use of phylogenetic trees is now the centerpiece of modern biological systematics. These trees are meant to represent the genealogical history of life and apparently derive their justification from the existence of the tree of life and the fact that evolutionary history is tree-like. However, there are a number of problems for the reality of these assumptions. The existence of species is questionable, hybridization and introgression are common phenomena, and lateral gene transfer and endosymbiosis entail that there cannot be a single tree-like hierarchy of the distribution of traits. Here it is argued that once we understand the important role of phylogenetic trees as models which contain idealizations, we can accept these criticisms and deny the reality of the tree while justifying the continued use of trees in phylogenetic theory and preserving nearly all of what defenders of the tree have called “the importance of tree-thinking”.