XVIII.3 Only species capable of permanent, sufficiently swift adaptation to changes in the biosphere can survive in the long-term

Only those species that were capable of coming to terms with the fact that their environment constantly undergoes irreversible changes are encountered in nature.This means that these must always be species that are capable of evolution, i.e. those that are capable of forming new organs or patterns of behavior, through which they are able to effectively react to changes in the environment, especially to new evolutionary adaptation of the species with which they interact.As soon as a species is incapable of maintaining a sufficient tempo in this evolutionary race, it is eliminated, without regard as to whether it could be otherwise very well adapted to the abiotic conditions of its environment.This phenomenon is described by the Red Queen principle.This principle, named after the characters in Lewis Carroll’s book “Through the Looking Glass”, roughly states in its commonest form that “in nature, it is necessary to run as fast as possible to at least stay in the same place”.It follows from the Red Queen principle, specifically from the necessity of keeping pace with the evolution of the other species in the biosphere, for example that species with a mutation rate reduced to zero cannot exist in nature.From a short-term perspective, such a reduced mutation rate could be advantageous for the species, as most mutations are detrimental for their bearers and reduce the average viability and fertility of the population.However, from the long-term point of view, a reduction in the mutation rate in the population is destructive, because a species that mutates slowly is not capable of sufficiently rapidly and effectively reacting evolutionarily to emerging new evolutionary features in the species with which it interacts in its environment.The necessity of adapting the tempo of one’s own evolution to the tempo of evolution of other species is apparently the reason why very varied species of organisms have very similar mutation rates measured in the number of mutations per generation without regard to their complexity, the lengths of their life cycles or the size of their genomes (Drake 1999).

The Red Queen principle was first described and employed to explain macroevolutionary processes (van Valen 1973), but is also applied at least to the same degree for cyclic and acyclic microevolutionary processes (Grant & Grant 1995).Sexually reproducing species are capable of reacting to short-term, frequently cyclically repeated changes in the environment through a shift in the frequencies of the individual alleles in the population.These shifts are simultaneously adaptive, i.e. they assist the population to better survive under the altered conditions, and also reversible, as the frequency of the alleles more or less flexibly returns to its original value on a reverse change in the conditions.In contrast, asexually reproducing species are evolutionarily plastic, react more slowly but more intensively to selection pressures, but changes in the composition of the gene pool are usually irreversible and thus primarily consist in complete loss or, to the contrary, fixation of certain alleles (Flegr 1998).Consequently, when the conditions again change, they can easily be stranded in a valley of the adaptive landscape and are not capable of sufficiently rapidly returning to the originally occupied adaptive peak.This could be the cause of the lack of success of parthenogenetic species.While sexually reproducing species can adapt in microevolution to regular fluctuations in the natural conditions and simultaneously constantly remain close to a once-occupied adaptive peak, parthenogenetic species are not capable of sufficiently rapidly following changes in the position of their adaptive peaks, so the average fitness of their individuals in the population under unpredictably changing conditions is lower than that for sexually reproducing species.

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The classical Darwinian theory of evolution can explain the evolution of adaptive traits only in asexual organisms. The frozen plasticity theory is much more general: It can also explain the origin and evolution of adaptive traits in both asexual and sexual organisms Read more
Draft translation from: Evoluční biologie, 2. vydání (Evolutionary biology, 2nd edition), J. Flegr, Academia Prague 2009. The translation was not done by biologist, therefore any suggestion concerning proper scientific terminology and language usage are highly welcomed. You can send your comments to flegratcesnet [dot] cz. Thank you.