 Biological taxonomists often talk in terms of the patterns and processes of evolution. Perhaps there is a process or a pattern that occurs in species but not in other types of taxa. Such a process or pattern would unify the types of lineages we call ‘species.’ Let us start with process. The Biological Species Concept highlights those species bound by the process of interbreeding. The Ecological Species Concept identifies those species unified by stabilizing selection. The species highlighted by Phylogenetic Species Concepts are unified by such historical processes as genetic and developmental homeostasis. A survey of these different species concepts reveals that species are bound by different types of processes. So no single type of process is common to all species. Arguably, none of these processes are unique to species either (Mishler and Donoghue 1982).