Stochastic developmental variation, an epigenetic source of phenotypic diversity with far-reaching biological consequences.
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2015-03
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Abstract
This article reviews the production of different phenotypes from the same genotype in the same environment by stochastic
cellular events, nonlinear mechanisms during patterning and morphogenesis, and probabilistic self-reinforcing circuitries
in the adult life. These aspects of phenotypic variation are summarized under the term‘stochastic developmental variation’
(SDV) in the following. In the past, SDV has been viewed primarily as a nuisance, impairing laboratory experiments,
pharmaceutical testing, and true-to-type breeding. This article also emphasizes the positive biological effects of SDV and
discusses implications for genotype-to-phenotype mapping, biological individuation, ecology, evolution, and applied
biology. There is strong evidence from experiments with genetically identical organisms performed in narrowly
standardized laboratory set-ups that SDV is a source of phenotypic variation in its own right aside from genetic variation
and environmental variation. It is obviouslymediated bymolecular and higher-order epigeneticmechanisms. Comparison
of SDV in animals, plants, fungi, protists, bacteria, archaeans, and viruses suggests that it is a ubiquitous and phylogenetically
old phenomenon. In animals, it is usually smallest for morphometric traits and highest for life history traits and
behaviour. SDV is thought to contribute to phenotypic diversity in all populations but is particularly relevant for asexually
reproducing and genetically impoverished populations, where it generates individuality despite genetic uniformity. In
each generation, SDV produces a range of phenotypes around a well-adapted target phenotype, which is interpreted as a
bet-hedging strategy to cope with the unpredictability of dynamic environments. At least some manifestations of SDV are
heritable, adaptable, selectable, and evolvable, and therefore, SDV may be seen as a hitherto overlooked evolution factor.
SDV is also relevant for husbandry, agriculture, and medicine because most pathogens are asexuals that exploit this third
source of phenotypic variation tomodify infectivity and resistance to antibiotics. Since SDV affects all types of organisms
and almost all aspects of life, it urgently requires more intense research and a better integration into biological thinking.
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Clonal organisms, development, ecology, epigenetics, evolution, genotype-to-phenotype mapping, individuality, infectivity and resistance, phenotypic variation, stochasticity
Citation
Vogt Günter. Stochastic developmental variation, an epigenetic source of phenotypic diversity with far-reaching biological consequences. Journal of Biosciences. 2015 Mar; 40(1): 159-204.