It has always interested scientists that the Jefferson Salamanders and Blue-spotted Salamanders hybridized.  In New York there are four types that are named depending on the number of chromosomes and which species contributed those chromosomes.  Scientists use a shorthand to describe the chromosome compliment-- J stands for one compliment of Jefferson Salamander and L is one compliment of Blue-Spotted.  JJ salamanders are pure Jefferson Salamanders and LL are pure Blue-spots.  JJL was formerly known as the Silvery Salamander, Ambystoma platineum, and JLL were Tremblay's Salamander, Ambystoma tremblayi.  These species consist entirely of females and depend on the males of the parent species to stimulate egg production, although currently it is believed no genetic information is passed on by the male.  The spermatophores of Jefferson and Blue-spots are of different sizes and this acts as a barrier to the other species.  Silvery Salamanders then, breed only with Jefferson males, while Tremblay's breed with Blue-spots.
    Jefferson Salamanders and Blue-spotted Salamanders hybrids may be found wherever Blue-spots or Jeffersons exist. It is interesting to know that the original hybridization event that occurred to create these species probably involved another species, the Small-mouthed Salamander, Ambystoma texanum, which is not found in New York.  The texanum genes have been lost in these particular lineages, although there still are Jefferson x Blue-spot x Small-mouth Hybrids in other areas of the Great Lakes region.
    Identifying the hybrids is nearly impossible in the field and can not be confirmed without chromosomal analysis.  Since there are no males, the only problems to be encountered will be with females.  Jefferson Salamanders are fully twice the size of adult Blue-spotted Salamanders so this will help.  To ID a possible hybrid look for a salamander that is similar to the parent species it's size most closely resembles, but with the diagnostic features of the other parent species.  For example the Possible Silvery pictured is nearly the size of a Jefferson and has distinct blue patches that are large in size as opposed to the small flecking somtimes seen in true Jefferson's.  Still I will never identify an individual as a hybrid based on morphology alone.  Chromosome counts are really the best way.