Biological Species: Reality or Abstraction? A Fascinating Story about Two Buntings

The main issue of the species problem is the following: do species really exist or is it just an abstract taxonomic category invented by taxonomists to describe biological diversity? The dilemma “either species without evolution or evolution without species” can be solved by logically substantiating that there should be only few (or no) transitional forms between subspecies and species. In the terms of the biological concept of a species, the reinforcement hypothesis serves as such justification: in the hybrid zone, natural selection facilitates mechanisms of ethological isolation, i.e. secondary contact leads to an acceleration of the process of speciation. The key point of this hypothesis is the statement about the reduced fitness of hybrids resulted from the destruction of the co-adapted gene complexes of parental forms, the formation mechanism of which is described by the Dobzhansky—Muller model. To evaluate the effectiveness of reproductive isolation mechanisms and the viability of hybrids, I conducted a long-term monitoring of the hybrid population of the yellowhammer and the pine bunting in Altai. It turned out that the hybrids are actually characterized by the shorter life span than the birds with the parental type of phenotype. It confirms the Dobzhansky—Muller model, although the reinforcement hypothesis does not find its confirmation in this case.

speciation, phylogeny, ethological isolation, hybrid populations, yellowhammer, pine bunting, Dobzhansky—Muller model