Birds of Prey (Falconiformes, Accipitriformes) of Northern Eurasia in the Biological Tetranary Nomenclature
The main disadvantage of the generally accepted trinary system of around-species nomenclature is the lack of a species concept. This leads to the fact that any lower taxon can be declared a species or subspecies, and any combination of these taxa of arbitrary rank is correct and legitimate by definition, and therefore cannot even be discussed. Ambiguity of the level of divergence of species creates a "species problem" and makes the question - species or subspecies - meaningless. The solution to the "species problem" can be the creation of a nomenclature system with an "own" species concept. The only concept whose criteria are objective (reproductive isolation and sympatry) and, more importantly, correspond to a certain level of divergence, and thus have a biological meaning, is a biological species concept. However, the use of this concept is difficult due to the uncertainty of the degree of reproductive isolation. Therefore, a revised definition of a biological species (B-species) as a category of taxonomy is proposed - this is a level of divergence that provides reproductive isolation sufficient for sympatry (with other closely related forms). Accordingly, as a physical object, the B-species can be defined as a set of sister populations that are incapable to sympatry with each other. The level of B-species is very high, therefore, for forms intermediate between subspecies and B-species, an additional category is needed - a semi-species. Unlike subspecies, which differ only in size and color, a semi-species must have at least one of the following features: 1 - obvious differences in the preference for environmental conditions; 2 - a certain assortative mating with other semi-species; 3 - reduced fertility of hybrids; 4 - significant differences in morphology, physiology, behavior, etc.; 5 - the hybridization zone is relatively very narrow (parapatry). The taxonomy of birds of prey (Falconiformes, Accipitriformes) of Northern Eurasia is presented in a new (genus, B-species, semi-species, subspecies) system of categories and nomenclature.