Sedentary (or "residential") individuals remain in the region of their birth, while their migratory compatriots set forth on long open-water journeys. The developmental choice of the residential versus migratory "life history" is known to be influenced by environmental factors, but is not well understood at the genetic level. Researchers now report that fish that are very closely related genetically show dramatically different patterns of actual gene expression if they have adopted different lifestyle fates. Moreover, and perhaps more surprisingly, less-related individuals from geographically different populations nonetheless exhibit very similar patterns of gene expression if they have adopted the same fate--residential or migratory. Thus, the researchers found that levels of expression of a great many genes depend primarily on an individual's future lifestyle.
The findings, which illuminate how programs of gene expression have evolved to control profoundly different developmental outcomes, are reported in the April 18th issue of Current Biology by Drs. Thomas Giger, Carlo Largiadèr, and Laurent Excoffier of the University of Bern, along with colleagues from France, Ireland, Denmark, and the UK.
Salmonid fish, which include trout and whitefish as well as salmon, show exceptional levels of life-history variation--that is, residential and migratory types often co-occur within a single population of young fish. Before reaching sexual maturity and leaving their natal stream, migratory individuals undergo dramatic morphological, physiological, and behavioral changes that prepare them for adulthood in open fresh and salty waters.
In their innovative work, which is based on studying the gene expression profiles of hundreds of genes at a time in different fish populations, t