A REEVALUATION OF POPULATIONS OF THE CORN SNAKE ELAPHE GUTTATA (REPTILIA: SERPENTES: COLUBRIDAE) IN TEXAS

摘要

Three hundred thirty-seven preserved specimens of the corn snake Elaphe guttata from Texas, six from Arkansas, 51 from Louisiana and 20 from Missouri were examined and assigned to one of three subspecies. Based upon the number of dorsal body and tail blotches, the number of ventrals and subcaudals, the degree of ventral pigmentation and the presence or absence of paired subcaudal stripes, each specimen was assigned to Elaphe guttata emoryi (great plains rat snake), E. guttata meahllmorum (southwestern rat snake) or E. guttata guttata (corn snake). When collection localities for the Texas specimens were plotted on a map by subspecies, the resulting distribution of the three subspecies represents a departure from the previous ranges for these subspecies in the state. Eastern specimens are newly assigned to the subspecies E. guttata guttata, part of the central and all of the northwest specimens represent E. guttata emoryi, and E. guttata meahllmorum are restricted to southern Texas. A zone of intergradation exists between E. guttata emoryi and E. guttata meahllmorum along the southern part of the Edwards Plateau and the Rio Grande River basin from Val Verde to El Paso counties. A suspected contact between populations of E. guttata emoryi and E. guttata guttata occurs in Milam County, Texas.