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Posted by chrish on September 19, 2002 at 08:54:30:
In Reply to: DNA TESTING posted by bam171bam on September 19, 2002 at 07:51:52:
It is unlikely that you could "test the purity" of Black Rat Snakes using molecular markers simply because there is unlikely to be any purity.
I suggest you read Burbrink's recent molecular work on the group where he discovered that the eastern rat snakes (E of the Mississippi) are actually a separate species (E. alleganiensis) which means that there are black rats of that species, and black rats which are E. obsoleta. I don't know what he used to determine this (I believe it was an mtDNA locus). It hasn't been widely accepted, but it does point out that the variation in obsoleta is not going to be as simple as black rats having one locus and others having another.
You might, at best, be able to come up with some probabilistic model of where the snakes could have come from based on haplotype frequencies. Hardly conclusive data.
Furthermore, rat snake subspecies intergrade over a large area of their ranges. In fact, it could be said that there are as many intergrade rat snakes as there are "pure" rat snakes. I wouldn't regard any of these KY snakes we have seen pics of as pure anything. Clearly they are a "mixture" of black rat and gray rats.
This also illustrates one of the arguements many people make against the subspecies concept: they are non-diagnostic descriptions. You can find a large number of animals that don't fall into one subspecies or another.
