Discovering a ring species
Of course, since this all would have happened millions of years ago, Robert
wasn't around to observe any of it. He based his ideas on the morphology,
or body form, of the subspecies in this case, their color patterns.
First, neighboring subspecies were more similar to one another than to those
across the ring and seemed to blend into one another. From this, he hypothesized
that Ensatina represented a ring species. Robert also noticed that
the northern coastal form, called picta, had a pattern of colors that
seemed to encompass the other subspecies. It was easy to imagine how the more
specialized southern forms could have evolved from picta. Based on this,
Robert hypothesized that the two southward-moving Ensatina lineages
had both emerged from picta's immediate ancestors.
|The subspecies Ensatina eschscholtzii picta.