In the evolutionary process, species continually come and go. Consequently, all species on earth today were, at one time, "rare and endangered" while in their infancy, and most will become "rare and endangered" once more as they are replaced. Therefore, decisions relative to protecting rare and endangered species are largely meaningless if based on numbers alone. They must include information about their biology and evolutionary history. Lists of endangered forms currently being prepared apparently include only those which are (1) scarce (rare and of restricted distribution), (2) named, and (3) sponsored. Their biological, economic, and academic values may be more important, but apparently are not often considered. As abundantly illustrated in western shrubs, genetically rich genotypes are sometimes maintained by only a few individuals, whereas uniform, and therefore rare, genotypes may in some circumstances, be represented by many individuals in uniform environments. Wise management decisions cannot, therefore, come from numbers alone.
Stutz, Howard C.
"The meaning of "rare" and "endangered" in the evolution of western shrubs,"
Great Basin Naturalist Memoirs: Vol. 3
, Article 15.
Available at: https://scholarsarchive.byu.edu/gbnm/vol3/iss1/15