However, it was on the right track in interpreting species in a phylogenetic context since species were joined by common ancestry. It is similar to the morphological species concept in that a diagnostic character of a species may be morphological, but differs in that any character that is diagnostic of a species, from genomic to behavior, is valid. The concept tries to emphasize diversification among taxa, with diversification sometimes resulting in reproductive isolation and at other times not. Whatever the diagnostic character may be, it would preferably be fixed in all members of a species, but may be found only in one sex, or at a particular developmental stage. As long as the character is found within the species and nowhere else, it can be used to delimit the species.
Species arise and change by many different means and exist at all steps in a continuum of change.
Forcing this diversity into a static definition will result in problems. Even in sexual groups, populations within a region may have several different characteristics than other populations of the same species. Taxonomic 'splitters' would recognize these as different species while 'lumpers' would not. Further work revealed that they differed in habitat, distribution or behavior and thus represent different species which did not diverge in morphology. These are called sibling species.