Can epigenetic changes affect reproductive success?

Question

This is prompted by niallhaslam's answer to this question [Since Darwinian times, has there been any striking/notable effects of evolution on humans?]. A comment by Alan Boyd asks whether epigenetic changes count as evolution.

Transgenerational epigenetic inheritance can occur, and does increase the natural variation of a species (although this review is more about plants, this does apply to animals too) [1]. Based on this alone I'm inclined to say that epigenetics can affect the fitness of a species, and thus could contribute to evolution.

I am interested to know if, in practise, this does occur, and whether epigenetics have been shown to affect the reproductive success of a species? Because the changes are not permanent I could imagine that they actually have very little impact "species-wide", as environmental effects (infections, toxic exposures) also affect epigenetics. So, is there any evidence for epigenetics affecting the reproductive success of a species? This also includes whether epigenetics can influence traits enough to create a new sub-species.

1. Becker, C., & Weigel, D. (2012). Epigenetic variation: origin and transgenerational inheritance. Current opinion in plant biology. doi:10.1016/j.pbi.2012.08.004.

Answer 1

This article deals with the effect of phenotypic variation brought on by epigenetic patterns, and how these are inherited to the next generation. Their conclusions?

Our results show that epigenetic variation is inherited in chickens, and we suggest that selection of favourable epigenomes, either by selection of genotypes affecting epigenetic states, or by selection of methylation states which are inherited independently of sequence differences, may have been an important aspect of chicken domestication.

However, I personally prefer this article, as it has a more profound implication on reproductive success and addresses your question specifically. They found the there is a species-level difference in DNA methylation between humans and chimps, but more importantly that this difference is responsible for the causation of numerous lethal diseases/conditions, which has a direct impact of the fitness of the species as a whole.

Finally, we found that differentially methylated genes are strikingly enriched with loci associated with neurological disorders, psychological disorders, and cancers. Our results demonstrate that differential DNA methylation might be an important molecular mechanism driving gene-expression divergence between human and chimpanzee brains and might potentially contribute to the evolution of disease vulnerabilities. Thus, comparative studies of humans and chimpanzees stand to identify key epigenomic modifications underlying the evolution of human-specific traits.

In summary, evidence has shown that epigenetics does seem to play an active role in the evolution of species, although the exact mode of inheritance of DNA methylation from generation to generation is unknown.

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References

• Nätt, Daniel, Carl-Johan Rubin, Dominic Wright, Martin Johnsson, Johan Beltéky, Leif Andersson, and Per Jensen. “Heritable Genome-wide Variation of Gene Expression and Promoter Methylation Between Wild and Domesticated Chickens.” BMC Genomics 13, no. 1 (February 4, 2012): 59.

• Zeng, Jia, Genevieve Konopka, Brendan G. Hunt, Todd M. Preuss, Dan Geschwind, and Soojin V. Yi. “Divergent Whole-Genome Methylation Maps of Human and Chimpanzee Brains Reveal Epigenetic Basis of Human Regulatory Evolution.” The American Journal of Human Genetics 91, no. 3 (September 7, 2012): 455–465.