The Network Species Model
  We propose a theoretical model for species that is focused on intrinsic organization and processes. Specifically, we regard species to be networks of organisms integrated by reproductive mechanisms (e.g., conjugation, meiosis, syngamy) regardless of degree or type of divergence, longevity, size, fate, or other criteria. Ramifications of viewing units of diversity in terms of inherent organization include the following: (1) Species, subspecies, population, deme, Evolutionary Significant Unit (ESU), and related terms cannot be distinguished on the basis of inherent organization and, consequently, do not reflect a hierarchy of organization. In other words, only one model is required to explain systems composed of organisms. (2) Temporarily isolated networks of organisms possess the same intrinsic organization and, therefore, the same ontological status as permanently isolated systems. (3) Units of diversity are recognized regardless of kind or degree of divergence. (4) Fate is not an intrinsic property of systems and is an inappropriate consideration in species models. (5) Networks are recognized at the moment they become isolated; therefore, resultant classifications reflect the causal events that generate diversity (e.g., vicariance) rather than post-vicariance events such as character evolution and, consequently, have greater historical relevance (e.g., biogeography). (6) Because the proposed model is based on organization, it is similar to models in other disciplines (e.g., astronomy, chemistry, and physics) and should lead to greater unification of thought within biology and among scientific disciplines. (7) Lineage concepts are problematic because they do not describe a unique level of biological organization and because ancestor-descendant relationships are not unique to living systems. 
David Kizirian and Maureen A. Donnelly