the International Commission on Zoological Nomenclature (ICZN) to suppress the changes proposed in 1996 to merge two of these species. In 2000, the ICZN agreed and voted to retain the historical taxonomic arrangement of subspecies within this evolutionary lineage. Accordingly, the subspecies tetrataenia was reaffirmed for the San Francisco garter snake and the races concinnus and infernalis retain their historical definition. The San Francisco garter snake cohabits ecosystems that also host a subspecies of two other garter snake species: the coastal garter snake (Thamnophis elegans terrestris), a subspecies of the western terrestrial garter snake (T. elegans), and the Santa Cruz garter snake (Thamnophis atratus atratus) a subspecies of the aquatic garter snake (T. atratus). These three subspecies are known to prey upon the same foods; however, their preferences are slightly different. Herpetologist Sean Barry notes that the three subspecies divide up the food resources as follows: the San Francisco garter snake eats primarily small frogs; the coastal garter snake eats principally slugs; the Santa Cruz garter snake eats preferentially minute fish and amphibian larvae. DNA analysis While the findings of the ICZN have given the San Francisco garter snake unique taxonomic standing for now, a molecular study challenges the subspecific status of this population. Janzen analyzed sequences in mitochondrial DNA to determine relationships within the subspecies of the common garter snake (T. sirtalis). Janzen found that molecular evidence differed, often sharply, with the territorial boundaries of subspecies named on phenotypic variation. He further deduced that local environmental forces were more significant in shaping the color patterns shown by the common garter snake subspecies than shared common ancestry, and concluded all morphologically based subspecies in the western U.S. to be subject to revision. This result strongly suggests that the color traits that are diagnostic for T. s. tetrataenia are the result of local selection, rather than long-term isolation from the other subspecies of T. sirtalis in central California. On the other hand, the article places the three nearest populations of T. s. infernalis to T. s. tetrataenia in Sonoma County, Contra Costa County, and Santa Clara County into a separate group that exhibits an "elevated rate of molecular evolution". The authors suggest that sequencing nuclear DNA may provide a more precise analytical tool to crack some of the ultimate taxonomic quandaries of the San Francisco garter snake and its relatives. Outlook for this subspecies Many of the factors that led to