Geographic variation in whole venom profiles from the mottled rock rattlesnake (Crotalus lepidus lepidus) in Texas

Venom variation in the mottled rock rattlesnake (Crotalus lepidus lepidus) was assessed by polyacrylamide gel electrophoresis. Whole venom samples were stained for general protein, the banding recorded, and these profiles were used to compare the variation within and between populations in Texas. Analyses using agglomerative methods (phenetic clustering methods and neighbor joining analyses) and ordination from Principal Components analyses provide several geographically correlated groups of rattlesnake venom profiles. Evidence is provided for differences in venom profiles of geographically distinct populations. Venom profiles of C. lepidus collected along the Rio Grande River, though geographically disparate, are generally homogeneous. Thus, the analyses support previously hypothesized dispersal of C. lepidus in Texas along these Rio Grande canyons. A potential region of population interchange between eastern plateau populations and those of the west Texas mountain ranges was identified at the southern end of the Davis Mountains in Brewster Co. Lethality assessments using LD, analyses reveal variation in venom toxicity to range from 2.20-0.72 mg/kg across the geographic range for this subspecies.