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| Tom Devitt and a map showing the range of Ensatina eschscholtzii in California. The colors correspond to the different subspecies. |
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If you've skimmed a high school biology textbook, you've probably seen the picture:
multicolored salamanders meander around California, displaying subtle shifts
in appearance as they circle its Central Valley. This is Ensatina eschscholtzii,
and it's so well known because it is a living example of speciation in
action. Adjacent populations of
the salamander look similar and mate with one another — but where the two
ends of the loop overlap in Southern California, the two populations look quite
different and behave as distinct species. The idea is that this continuum of
salamanders — called
a ring species — represents
the evolutionary history of the lineage as
it split into two.
Ensatina has been recognized as a ring species since the 1940s, when biologist Robert C. Stebbins trooped up and down California to investigate its range. Since then, several generations of scientists in Stebbins' institution, the Museum of Vertebrate Zoology at UC Berkeley, have continued these studies, digging deeper into Ensatina's history and biology. At this point, one might think we'd know it all. What more could there be to learn after 60 years of research on a common salamander? "Lots!" says Tom Devitt, a graduate student at the museum. Tom studies Ensatina to flesh out its evolutionary history — but not just for Ensatina's sake. This classic example sheds light on the
basic evolutionary processes that shape all life.
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