Abstract
Punctuational theories of evolution suggest that adaptive evolution proceeds mostly, or even entirely, in the distinct periods of existence of a particular species. The mechanisms of this punctuated nature of evolution suggested by the various theories differ. Therefore the predictions of particular theories concerning various evolutionary phenomena also differ.Punctuational theories can be subdivided into five classes, which differ in their mechanism and their evolutionary and ecological implications. For example, the transilience model of Templeton (class III), genetic revolution model of Mayr (class IV) or the frozen plasticity theory of Flegr (class V), suggests that adaptive evolution in sexual species is operative shortly after the emergence of a species by peripatric speciation – while it is evolutionary plastic. To a major degree, i.e. throughout 98-99% of their existence, sexual species are evolutionarily frozen (class III) or elastic (class IV and V) on a microevolutionary time scale and evolutionarily frozen on a macroevolutionary time scale and can only wait for extinction, or the highly improbable return of a population segment to the plastic state due to peripatric speciation.The punctuational theories have many evolutionary and ecological implications. Most of these predictions could be tested empirically, and should be analyzed in greater depth theoretically. The punctuational theories offer many new predictions that need to be tested, but also provide explanations for a much broader spectrum of known biological phenomena than classical gradualistic evolutionary theories.ReviewersThis article was reviewed by Claus Wilke, Pierre Pantarotti and David Penny (nominated by Anthony Poole).
Highlights
Most punctuational theories of evolution, including the evolutionary conceptions of Wright, Mayr, Carson, Templeton and Flegr, suggest that sexually reproducing species respond evolutionarily to selection onlyFollowing a short period of time, estimated by paleontological data to correspond to 1-2% of the existence of the species, polymorphism accumulates in the gene pool; and in each generation, new mutations occur in the presence of different alleles
I show that punctuational models of evolution have considerable evolutionary and ecological implications that could be tested empirically, and should be analyzed theoretically in greater depth
Microevolutionary elasticity and adaptation to past condition According to the classical gradualistic theories, all species respond to selection as if they were plasticine while, according to punctuational theories, most species are resistant to selection as if they were lead or respond to selection as though they were rubber – at first, they respond readily to selection pressure; as the average phenotype of the organism deviates from its original state, selection is less and less effective and, at a certain point, the response ceases (Table 2)
Summary
Most punctuational theories of evolution, including the evolutionary conceptions of Wright, Mayr, Carson, Templeton and Flegr (for comparison see Table 1), suggest that sexually reproducing species respond evolutionarily to selection (are evolutionarily plastic) only. The Genetic Revolution model implicitly and the Frozen Plasticity model explicitly suggest that frequency-dependent selection plays an important role in stabilization of the gene pool of a species. According to these two theories, macroevolutionary frozen species are microevolutionarily elastic. Of evolutionarily stable strategies indicates that, under these conditions, selection cannot lead to long-term changes in the phenotypes of organisms (an analogy of the fixation of the “best” strategy in a population), but only to a deflection of the frequency of the individual alleles (strategies) from evolutionarily stable equilibrium The greater this deflection, the more the gene pool resists the selection; after it ceases, the allele frequencies spontaneously return to their original values. I show that punctuational models of evolution have considerable evolutionary and ecological implications (see Table 2) that could be tested empirically, and should be analyzed theoretically in greater depth
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