Reorganization of species genomes during evolutionary specialization of taxa

Abstract

The study of genetic aspects of speciation and adaptation revealed several genetic parameters that distinguish evolutionarily labile (with a low level of specialization) species that are “generators” of speciation and evolutionarily conservative (highly specialized) species. In the evolutionary development of a taxon in the horizontal direction (cladogenesis or adaptive radiation), the features of low genome specialization at each step of the speciation are substituted gradually for alternative (evolutionarily conservative) ones, which are most pronounced in terminal species. In speciation, the number of acrocentric chromosomes (Robertsonian fusion) is reduced; polyploidy takes place—the emergence of fixed chromosomal rearrangements and increase in their number, as well as “dispersion” of heterochromatin and mobile genetic elements from their chromocenters and centromeric regions to the lateral regions of chromosomes. In addition, the recombination is limited, chromosomal (inversion) polymorphism forms, and the areas of chromosomal attachment to the nuclear envelope are expanded. The identified parameters of the structural and functional organization of the genome in species that are “generators” of speciation and in inert (conservative) species in terms of speciation characterize the evolutionary heteropotential of species genomes and nonequivalence of species with respect to natural selection. The first species seem to generate clusters of affiliated species, and the second create their own system of genetic adaptation (chromosomal polymorphism). They usually become eurybiontic species, which terminate phyletic lines.