The phylogenic species, the cohesive species, the ecological or fossil species

The phylogenic species

Cracraft (1989) defines a phylogenic species as a nonreducible unit individuals having jointly a diagnosis differentiating from the others and including the current ancestors, individuals and their descent. The species is thus a phylum having a common parental model. For Queiroz & Donoghue (1990), the species is more small group monophyletic Polyphyletic. having a common ancestor

The cohesive species

According to Templeton (1989), the species is “the most inclusive population individuals having a phenotypical potential of cohesion by intrinsic mechanisms of cohesion (or genetic or demographic exchanges)”. According to Mayr (1996), Templeton defines a specific cohesion by gene flows but does not distinguish the internal barriers of insulation (mechanisms of insulation of the biological design) and external (geographical barriers).

The ecological species

For certain phytosociologists, a species, although similar to another, remotely by its presence in a particular habitat. The definition of an ecological species takes again the definitions morphological and biological by adding to it the concept of time and space (natural habitat). An ecological species is a unit gathering the individuals having the same capacities to exploit identical resources (Van Valen, 1992). If the ecological species are generally not hybrident in their natural environment, this event can occur if the geographical barriers are removed; what is thus opposed to the biological design.

The fossil species

The fossil species poses many problems: complete absence of alive material, elements partial on morphology of the plant, impossibility of carrying out biochemical analyzes (isozymes, DNA), etc Moreover, it is impossible of test reproductive insulation. The fossil species is always a morphological species

The various fossil species of Gingko resembled the current species morphologiquement, G. biloba.