Because the gradual increase in temperatures worldwide is still relatively new, researchers have had difficulty in finding examples of genetic changes in organisms that are adapting to the warmer temperatures. Instead they have seen examples of phenotypic plasticity, which is where animals make adaptive changes based on existing conditions that are not brought about by genetic changes. Now though, for the first time, researchers in Alaska have found evidence of genetic changes in pink salmon that have come about over the past few decades as the fish have been migrating upstream earlier than they used to. In the new paper published in Proceedings of the Royal Society B, the team describes how they found a genetic marker for late spawning fish diminishing over time as water temperatures increased. The pink salmon in the study were part of a group that spawns in a stream near Juneau, Alaska. Prior research had shown that the salmon have been swimming upstream to spawn on average two weeks earlier than they did just forty years ago. In addition, the researchers found that average water temperature in the stream had risen one degree during that same time span. To find out if any genetic changes have come about as a result, the researchers turned to a genetic marker that has been bred into some, but not all of the fish during the late 1980s, that tended to make them spawn a little bit later then the others in their group. Because genetic samples of the fish have been taken on a regular basis since the 1970s, the team was able to see that the late spawning marker showed a decrease from 20% of the fish population on average to just 10%; a clear sign that genetic change over just a few decades had occurred. At the same time they found no other changes in other genes that had been marked as a control. The researchers say the evidence shows that salmon have evolved genetically over just a couple of generations which by implication means, that other animals are likely doing the same. Overall, they say, their study shows just how quickly organisms can evolve to deal with ongoing temperature changes. What they dont know yet, however, is how earlier spawning impacts the fish in other ways, such as when the young fish swim back down stream and on out into the ocean.
Environmental Protection News, 13 July 2012 ;http://www.eponline.com ;