Water snakes

38 p. : ill., maps ; 24 cm.Includes bibliographical references (p. 35-38)."A new interpretation of the sipedon-fasciata complex of the water snake genus Natrix is proposed. Natrix fasciata is elevated to specific status with the inclusion of three fresh-water races, fasciata, confluens, pictiventris; pending studies on the salt-marsh snakes, the forms clarki, compressicauda, and taeniata are retained as additional races of fasciata. The remaining members of the complex, namely, sipedon, pleuralis, and insularum, are left in the species Natrix sipedon. Sympatry between the species sipedon and the species fasciata is demonstrated over a wide area, with specific instances listed from Arkansas, Florida, Georgia, Illinois, Louisiana, Mississippi, North Carolina, Oklahoma, and Tennessee. The two species are allopatric in many other areas; for example, from east central North Carolina to Georgia their respective ranges meet on opposite sides of the Fall Line. Intermediate specimens that combine characters of both sipedon and fasciata are described from several localities near the Fall Line in South Carolina and Georgia where there is evidence of recent disturbance of the habitat by mankind. Such intermediate specimens are believed to be the products of hybridization. Many specimens of sipedon from near the common boundary of the two species in the Carolinas and extreme southeastern Virginia exhibit head patterns that include a dark postocular element grossly similar to the dark postocular stripe that is characteristic of fasciata. This phenomenon is interpreted as convergence. Natrix sipedon occurs on the Outer Banks of North Carolina and in brackish waters along the inner (mainland) edge of Pamlico Sound. Natrix fasciata in the same general region is confined to fresh-water habitats on the mainland, except that it apparently has fortuitously reached the Shackleford Banks, which lie close inshore. On this island, on the adjacent mainland, and at the head of the Pungo River estuary, in all of which fresh- and brackish-water habitats are in close proximity, there is evidence of hybridization between sipedon and fasciata"--P. 33-34