The opposite is also true. Selection to conditions that prevail across the entire species range can maintain uniformity in spite of no interchange of alleles across the range. See text for examples of these processes. Whether or not a pluralistic species concept is the best choice is related to the question of how many different ways there are for speciation to occur. The cladistic concept defines species throughout their evolutionary history.
Cladistic species are segments on a cladogram, joining branch-points on the phylogenetic tree.
In many situations, this is not only intuitively sensible but coincides with other species concepts. The cladistic species concept also introduces awkward nomenclature involving pseudoextinction . Taxonomic concepts may be nominalist or realist. The relevance of this distinction is the question of whether species or any other taxonomic category recognize real distinctions in nature or simply impose arbitrary distinction for human convenience. The species category.