Table 1 Differences between various punctuational theories and models
Theory and its author | The aim | Suggested mechanism |
|---|---|---|
Shifting balance theory | to explain the ability of species with large subdivided populations cross valleys in adaptive landscape | 1. fragmentation of population to small subpopulations where an efficiency of selection is low 2. spreading and fixation of a new allele (that is detrimental when rare) in a subpopulation by drift 3. “Infection” of other subpopulations with individuals with new genotype originated from a successful population and the origination of new populations by these individuals |
Wright S. 1932 1 | ||
Genetic revolution | to explain the role of founder events in speciation | 1. change of balanced frequency of alleles in a split-off subpopulation due to sampling effect 2. selection for alleles with best effect on fitness instead of best-cooperator alleles |
Mayr E. 1954 2 | ||
Founder-flush model | to explain the role of founder events in speciation | 1. sampling effect due to rapid one-step reduction of a population size, 2. expansion of the population in an open uninhibited ecological niche, which relaxes all forms of selection allowing for surviving recombinants and mutants with suboptimal phenotypes (crossing valleys in the adaptive landscape) 3. reaching (or overshooting) the carrying capacity of a locality and the restoration of selection |
Carson H.L. 1968 3 | ||
Genetic transilience model | to explain the role of founder events in speciation | 1. sampling effect due to rapid one-step reduction of a population or to hybridization, 2. an increase of the amount of selectable genetic variability due to transformation of nonadditive (and therefore nonselectable) genetic variability to additive genetic variability and by higher survival probability for carriers of new mutations in the expanding population, which increases responsiveness of the population to selection 3. restoration of the population size limitation and selection |
Templeton A.R. 1980 4 | ||
Punctuated equilibrium | to explain the discontinuous nature of evolution and coincidence of anagenetic and cladogenetic events | various mechanisms suggested by Eldredge and Gold, including peripatric speciation and strong selection in unusual conditions on the periphery of the species’ range, peripatric speciation accompanied by genetic revolution, sorting (according to Futuyma7, without speciation, any evolutionary novelty is reversible due to gene flow), etc. |
Eldredge N. 1971 5 | ||
Frozen plasticity theory | to explain why old species are microevolutionarily elastic and macroevolutionarily frozen, how frozen species can turn plastic, and the continuously decreasing rate of macroevolution | 1. most polymorphism existing in an old species is sustained in it’s gene pool by frequency dependent selection creating interconnected network resistant to changes of allele frequencies, 2. most new (potentially useful) alleles are captured in this elastic network of alleles due to pleiotropy and its effect on (stabilized) frequencies of old alleles, 3. in small split-off populations balancing on the edge of extinction for several generations, a decrease in strength of selection, including frequency dependent selection, will occur, and most genetic polymorphism will disappear due to drift 4. after expansion of population size, now large genetically uniform population turns evolutionary plastic – new advantageous mutations can spread in the network-free population by selection 5. traits resistant to thawing accumulate in the gene pool by sorting on the basis of stability 6. accumulation of permanently frozen traits by the mechanism of sorting on the basis of stability in particular clades during macroevolution |
Flegr J. 1998 6 |