Preserving Evolution

A recent visit to the Galápagos Islands to collect fishes for genetic studies hints at rapid evolution.

When Charles Darwin went to the Galápagos Islands in 1835 to survey the region's wildlife, he preserved the specimens he collected in "spirits," or alcohol. Since his time, most scientists have stored specimens in formaldehyde, a better preservative for body shape and structure. Turns out Darwin's method paid off. Today, his specimens can still be used to make molecular comparisons between species, while the formaldehyde in more recent collections has degraded DNA, making it unusable.

To address the lack of available genetic material in his own studies, Academy Senior Aquatic Biologist John McCosker, who has been working out the evolution of Galápagos fishes with numerous colleagues for more than 25 years, recently collected eels and other fishes around the islands-and stored them in spirits. Incidentally, he observed something while there that may say more about fish evolution than the new genetic material ever will.

The most recent El Nino event of 1997-1998 turned Galápagos coral reefs to rubble and changed fish population dynamics of the area. Fishes such as certain damselfish that were once rare became common while common species became rare. At the interface of these repopulated habitats, McCosker and colleague Gerard Wellington noted hybridization between different damselfish species-what may be a precursor to evolution.

This surprising find suggests that evolution is taking place much faster than Darwin himself thought-perhaps even in a human lifetime.


Galápagos marine iguanas. Our group (McCosker, Wellington, Baldwin) was particularly interested in the survival of marine animals subsequent to the 1997/ 1998 El Niño event. Marine iguanas suffered because of their dependence on marine algae as a food source. Although smaller in average size, many individuals seemed to have survived. Photo: J. McCosker

The red-spotted barnacle blenny was also hard hit during the El Niño, and its population is currently depleted, but making a comeback.
Photo: Paul Humann

The Four-eyed fish, Dialommus fuscus, is a remarkable feat of evolution. It feeds on insects above the tideline. Photo: Earl Herald

Bartolome Island vista. Memorable view of Galápagos seen by mostvisitors. Photo: J. McCosker