David B. Wake and Kay P. Yanev, 1986.
Geographic variation in allozymes in a 'ring species,'
the plethodontid salamander Ensatina eschscholtzi of western North
America.
Evolution 40(4),1986,pp 702-715
ABSTRACT
The ring species Ensatina eschscholtzi
(a plethodontid salamander) of western North America has a circle of subspecies
surrounding the Central Valley of California which come into contact and
are sympatric in southern California. We examined 26 proteins in 19 populations
(maximum of 10 specimens per population) collected throughout the range
in order to gain an understanding of the degree of differentiation in
the group. Allozyme differentiation is profound, with genetic distances
in excess of 0.5 (Rogers or Nei) between populations. Naturally hybridizing
populations differ by genetic distances greater than 0.4. (see Genetic
distances map Two general classes of color morphs, blotched and unblotched,
are segregated geographically, but they do not form discreet genetic units.
Both are deeply differentiated, and genetic distances among populations
of either class exceed those measured between the classes where they are
sympatric in southern California. This study disclosed little evidence
of gene exchange around the ring of populations and sampling of many additional
populations in regions between populations sampled thus far will be required
to determine whether smooth intergradation occurs. Although distances
measured exceed those between some co-occurring species of plethodontid
salamanders, we find no evidence of borders between cryptic species.
Genetic distances map
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