Extended epiphenotypes: Integrating epigenotypes into host behavioural manipulation by parasites.

Biologists have long known that environmental context can create diverse phenotypes from identical genotypes. Thus, cells of the same foetus can grow into various organs depending on the molecular environment. Also, animals of the same genetic heritage can show different behaviours in different environments. Conrad Hal Waddington conceptualized epigenotypes in the 1930s, whereby modifications of genetic material could generate alternative modules of development arising out of nonvariant genetic information. His concept paved the way for a neo‐Darwinian synthesis by creating bidirectionality between the environment and genes.In a completely independent intellectual universe, Richard Dawkins introduced the idea of extended phenotype in the early 1980s. The hypothesis posits that the appropriate phenotype of genetic information is not limited to the organism but can 'extend' beyond the environment. Parasite manipulation of host behaviour presents a dramatic example of such extended phenotypes.In this perspective, we propose a synthesis between the earlier concept of epigenotypes and the later idea of extended phenotypes, namely a novel concept of extended epiphenotypes.Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]