Hidden variation mapped

Abstract

Many biological systems are insensitive to a certain degree of environmental variation. Because such systems present some buffering properties (for example, crosstalk between pathways, redundancies and feedback loops), phenotypic variation may occur within the developing system yet be buffered at the level of its output. This buffering allows the accumulation of mutations affecting the system, for example, the activity of signaling pathways, without affecting its end product. Such cryptic genetic variation may have an important function in phenotypic evolution (Wagner, 2005). For instance, it has been proposed that the epidemic aspect of several complex genetic diseases in modern human societies could be explained by the uncovering of cryptic genetic variation in response to the abrupt change of lifestyle in recent generations (Gibson, 2009). Consequently, it is of key interest to study the genetic architecture and molecular nature of cryptic variation that segregates in natural populations. The extent of such cryptic genetic variation has so far been underestimated because of the difficulty in detecting it. In this issue, cryptic genetic variation affecting somatic sex determination mechanisms is revealed among wild isolates of the nematode Caenorhabditis elegans (Chandler, 2010). Using a quantitative genetic approach, the author detected several genomic regions underlying this variation. This work opens interesting perspectives for understanding the evolution of sex determination at the intraspecific level and highlights the importance of considering cryptic variation when studying an apparently invariant system.