Chapter I

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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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