Evolutionary Relations of Southwestern Ringneck Snakes (Diadophis punctatus)

Gehlbach, Frederick

Southwestern ringneck snakes include the large Diadophis punctatus regalis, the much smaller D. p. arnyi and D. p. stictogenys, and secondary intergrades between the two morphotypes. Large and small ringnecks of opposite sexes from allopatric populations, placed together with other snakes in species discrimination trials, always ate the nonringneck species and never exhibited cannibalism. Occasional copulation or attempted copulation was observed; and fertile eggs were laid by a ♀ of D. p. regalis from Arizona, mated with an intergrade from Texas. Southwestern ringnecks differ from D. p. punctatus and D. p. edwardsi in apparent envenomation of their snake and lizard prey. Ancestral ringnecks were small, like D. p. arnyi and D. p. stictogenys, and associated with mesic, transcontinental, Arcto-Tertiary forests. Pliocene events disrupted the range, and D. p. regalis evolved large size in response to xeric Madro-Tertiary woodland evolution. Wisconsin-age environments allowed secondary intergradation in westcentral Texas, followed by introgression of D. p. regalis genes eastward and D. p. arnyi-stictogenys genes westward. Apparent reproductive isolation of regalis-like and arnyi-like populations in the Guadalupe Mountains, New Mexico-Texas, is evidence of a tertiary contact and different fitness of the regalis and arnyi gene pools.

Evolutionary Relations of Southwestern Ringneck Snakes (Diadophis punctatus)

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