Hybridization Between Two Species of Garter Snakes

Hybridization Between Two Species of
   Garter Snakes

   BY

   HOBART M. SMITH

   University of Kansas Publications
   Museum of Natural History

   Volume 1, No. 4, pp. 97-100
   August 15, 1946

   UNIVERSITY OF KANSAS
   LAWRENCE
   1946




   UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY
   Editors: E. Raymond Hall, Chairman, Donald S. Farner,
   Donald F. Hoffmeister

   Volume 1, No. 4, pp. 97-100
   Published August 15, 1946

   UNIVERSITY OF KANSAS
   Lawrence, Kansas


   PRINTED BY
   FERD VOILAND, JR., STATE PRINTER
   TOPEKA, KANSAS
   1946

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   Hybridization Between Two Species of Garter Snakes

   By

   HOBART M. SMITH


The chief characters distinguishing _Thamnophis radix_ (Baird and
Girard) and _T. marciana_ (Baird and Girard) in southern Kansas are:


             _marciana_                             _radix_

  1. lateral light line involving only   1. lateral light line involving
     the 3d scale row anteriorly.           rows 3 and 4 anteriorly.

  2. dorsal light line without distinct  2. dorsal light line with
     edges, varying in width from less      straight, even edges, 1-1/2
     than 1 to nearly 3 scale rows, at      scale rows wide.
     various places on body.

  3. several anterior lateral spots      3. _usually_ no anterior
     fused across lateral light             lateral spots fused across
     stripes.                               lateral light stripes.

  4. 2 posterior upper labials not       4. 2 posterior labials
     light-centered, unlike others.         light-centered, like others.

  5. A well-developed, white,            5. typically no well-developed
     black-edged crescent behind angle      postrictal crescent.
     of jaws (postrictal crescent).

Typical specimens of _radix_ are available from several localities in
Morton County of southwestern Kansas (Spring Creek; twelve miles and
eighteen miles north of Elkhart; Elkhart); from the State Lake and Meade
in Meade County; from Hunters, Harper County; Coolidge, Hamilton County;
and Ingalls, Gray County.

Typical _marciana_ is available from Spring Creek, Morton County;
Liberal, Seward County; and Clark County (no locality). An overlap of
range with _radix_ is evident, and from Spring Creek in Morton County
typical specimens of both species are available. Accordingly, at
present, I conclude that the two forms are correctly regarded as
distinct species.

Yet there is a rather marked tendency of _radix_ to approach the
characters of _marciana_ in southwestern Kansas. Two specimens (one from
Morton County, one from Gray County) have the dorsal stripe slightly
broken up by infiltration of the ground color onto the edges of the
scales. All southwestern _radix_ develop the distinct postrictal
crescent so characteristic of _marciana_, and occasional specimens fail
to have light centers in the last two labials. Finally, one specimen
from Meade, Meade County (No. 5434), appears to be actually
intermediate, and may be regarded as a hybrid. The middorsal stripe is
not sharp-edged; the lips are barred exactly as in _marciana_, the
postrictal crescent is well defined, and the lateral light stripe
extends onto the fourth scale row only very slightly. I refer the
specimen to _T. radix_ on the basis of the middorsal light stripe which
still is not as irregular as in _marciana_, upon the nature of the
lateral dark spots (not fused), and upon the slight extension of the
lateral light stripe onto the fourth scale row. Yet the specimen is
definitely atypical of _radix_; no other of the 135 specimens examined
deviates so strongly from the normal condition.

Because the two kinds of garter snakes in question maintain their
distinctness at other places where they occur on common ground, it seems
best to interpret specimen No. 5434 as a hybrid rather than an
intergrade.


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