Epigenetic variation in animal populations: Sources, extent, phenotypic implications, and ecological and evolutionary relevance
Laboratory experiments and fieldwork with asexually reproducing invertebrates and vertebrates clearly revealedthat animal populations can produce substantial phenotypic variation despite genetic identity. This epigeneticallycaused phenotypic variation comes from two different sources, namely directional environmental induction andbed-hedging developmental stochasticity. Both occur together and are mediated by molecular epigeneticmechanisms like DNA methylation, histone modifications and microRNAs. These epigenetic mechanisms arealso involved in insect polyphenism, phenotypic changes in early domestication, and gene expression change andchromatin rearrangement during speciation. Epigenetic variation is particularly important for asexual populationshelping them to stay in the game of life when the environmental conditions change. However, it is also relevant forsexually reproducing populations, as shown for genetically impoverished invasive groups, cave animals andsessile taxa that cannot evade unfavourable environmental conditions. Experiments revealed that epigeneticmarks can be transgenerationally inherited and persist for several generations. First evidence suggests thatinherited epimutations with phenotypic effects may end-up in phenotype-fixing genetic mutations by acceleratedmutation of methylated nucleotides. Refined concepts, suitable animal models, fast and affordable new omicstechniques that require only small tissue samples, and appropriate data interpretation tools are now availableenabling future investigations in ecological and evolutionary epigenetics with high accuracy.
Volume 46, 2021
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