Alaskan Salmon Evolve Along With the Climate
Source: NIcholas Bakalar, The New York Times
Alaskan salmon are apparently evolving to adapt to climate change.
Researchers have suspected that temperature-driven changes in migration and reproduction behaviors which have happened in many species may be evidence of natural selection at work. Now there is genetic evidence to confirm the hypothesis.
For their study, published online last week in Proceedings of the Royal Society B, the scientists studied Alaska pink salmon in a small stream near Juneau where there have been complete daily counts of all adult fish since 1971.
The salmon migrated in two distinct populations, one appearing toward the end of August, the other starting in September. In 1979, scientists introduced a neutral genetic marker into the later-migrating population so it could be identified and tracked without affecting its fitness.
In the 1980s, the genetically marked late migrators made up about a third of the population. But as streams started warming earlier in the year, the proportion began to decrease rapidly to just 5 percent by 2011 even though overall abundance did not change.
These were rapid changes, not gradual evolutionary shifts. The late-migrating fish practically disappeared within a few years.
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