by TFH Magazine on September 16, 2011 at 9:42 am
By David E. Boruchowitz
The biological concept called “sweepstakes dispersal” describes the accidental traversing of a barrier and colonization by an organism, and it can have significant evolutionary consequences. For example, the chance arrival from South America in the Galápagos Islands—via the Humboldt Current—of a gravid iguana clinging to a floating log could explain the biologically unique iguana species found there today.
A study released today reports on the genetic studies of snails in the genus Cerithideopsis, found on both shores of Mexico and Central America, that indicate that the snails arrived about 750,000 years ago in the Atlantic from the Pacific and then some of them moved back to the Pacific about 72,000 years ago.
The most likely means for them to accomplish this twice-in-a-million-years travel is to hitch rides on waterfowl. Stuck to the legs or feathers of shorebirds, the snails could fortuitously overcome the landmass barrier that otherwise prevents genetic mixing between Atlantic and Pacific populations of many organisms.