Fundamentals of Evolution - Korzh O.P. - 2006

Part I. MICROEVOLUTION

Chapter 10. Speciation as a Fundamental Phenomenon of the Evolutionary Process

10.1. The Essence of Speciation

Were speciation not to exist, we would face Structure/149.html">The problem of unbounded Hybridization among all contemporary forms. This phenomenon would result in complete chaos characterized by hybrid forms with improbable combinations of traits. No single individual would be adapted to specific environmental conditions, instead combining incompatible Functions. Naturally, such forms would largely prove non-viable, and their rapid elimination could be expected. The sole «generalized» species that might emerge from such processes would possess no specialized adaptations to specific environmental conditions.

Various types of barriers exist to prevent unrestricted hybridization, allowing different species to evolve under conditions of genetic independence. As a result, each species specializes by adapting to distinct living conditions. Speciation is the most rapid and efficient mechanism for fixing new Gene combinations suited to particular environments. It serves as the foundation of evolution, since any evolutionary process of any scale can be envisioned as the adaptive transformation of populations or groups of populations—in other words, as a totality of speciation processes. According to most contemporary scientists, there is no specific regularity in The formation of higher taxa that cannot be explained by speciation. Although other views exist, suggesting that the formation of fundamentally novel complex adaptive mechanisms is associated with rapid, unexpected reorganizations.

The term «speciation» itself is used to denote two processes: an increase in the number of species and the transformation of species over time. The former process is sometimes termed cladogenesis, and the latter, anagenesis. Some researchers use the term «speciation» exclusively in the first sense, referring to the second process as phyletic evolution. In reality, however, no fundamental differences exist between these processes, as both unfold within a certain spatial framework over a given time. The sole difference lies in the increase in the number of species resulting from the first process versus the replacement of one species by another resulting from the second.

By speciation, we understand the process whereby a previously unified, genetically open system splits—with respect to its constituent components—into several genetically independent (though not necessarily closed, yet consistently stable) systems.

The ancestral form may remain largely unchanged in the process or undergo significant transformations up to complete extinction. The number of descendant forms can be one or several, depending on the Specific characteristics of the speciation process itself.

Speciation is characterized by uneven rates, a trait inherent to different geographic or ecological races of a single species across various modes of speciation. A consequence of this unevenness can be the simultaneous coexistence of the ancestral population and descendant populations at varying stages of evolutionary development.

According to modern scientific concepts, speciation is a process that takes place within a group of individuals; that is, the formation of a new species occurs through the evolutionary Transformation of a population or a group of populations. The Essence of speciation is that transformed populations acquire increasing independence, becoming more stable and competitive (exhibiting growing numbers, expanding geographic ranges, and consolidating ecological niches, among other traits).

However, The process of forming new structures, reactions, and adaptations does not invariably lead to The Emergence of a new species; therefore, form formation (morphogenesis) and speciation cannot be equated. Form formation occurs predominantly at the MOLECULAR AND CELLULAR levels, driving changes in individual organisms. It may serve as a prerequisite for speciation, yet the latter unfolds exclusively at the population-species level. Variability cannot directly transition into the process of speciation. Only through the elimination of unadapted variants, driven by the directing and accumulative action of natural Selection, can the transformation of populations and, consequently, the establishment of a new species take place.