Always a biologist is faced with the problem of identification of species of a particular group of organisms, the first tool to determinate is the morphology as decisive criterion of species, however, the existence of sibling species, different morphological types or individual genetic variations as a consequence of the mosaic evolution, becomes this approach arbitrary at the time of determinate species. Thus, the concept of biological species (BCS) arose, as a result of the unsatisfactory inference of morphological species concept, since the BCS takes other factors such as their genetic identity.
Mayr's BCS is from my point described as an evolutionary strategy to keep the genetic identity certain populations, or as he says: "keep the gene pool well-balanced and well-adapted genotypes or harmonics," (Mayr, 1996), whose mechanism of protection against any kind of destabilization by recombination, diminishes the frequency of the exchange of genes between the groups, is interbreeding isolation. Likewise, the definition and the operation of BCS consistent with one another. However, the main problem is its application, because if we follow the BCS cannot go beyond the organisms with sexual reproduction, so those asexual organisms would be excluded, that would become impractical for studies of conservation and biodiversity, since the latter seeking a universal definition and objective, thus, as a consensus of species richness and biodiversity hotspots (Agapow, 2004).
Otherwise, the geography is an unsolved problem for the BCS, as far as allopatric populations are concerned (in addition to any already existing applicability problems), according to Mayr these populations are those that have not reaching or ever reach the status of species, characterized by a certain kind of continuous isolation. However, Zink in 2004 from a study using mitochondrial DNA, argue against considering subspecies as proxies for units of conservation because he demonstrates that certain avian subspecies do not have a clear population genetic structure, and that it is inconsistently related to subspecies boundaries sensu Mayr.
Hence, as far as I’m concerned the BCS is a vicious circle around the sexual organisms (is logical that the genetic barrier to sexual organisms, is the interbreeding isolation), which more than a practical concept of demarcation is an evolutionary strategy of sexual stabilization gene, that becomes in the game of apply and not apply, turning both ambiguous and expensive for two primary approaches where the concept of species is critical and decisive, biodiversity and conservation.
Agapow, PM. Bininda, OR. Crandall, KA. Gittleman, JL. Mace, GM. Marshall, JC. & Purvis, A. 2004. The impact of species concept on biodiversity studies. Q Rev Biol. 79:161-79.
Mayr, E. 1996. What is a species and what is not?. Philosphy of Science. 63: 262–277.
Zink, R. 2004. The role of subspecies in obscuring avian biological diversity and misleading conservation policy. Proc. R. Soc. Lond. B 271, 561–564