IMHO they are just easterns and I'm not sure that the isolations we’re talking about is sufficient to allow complete speciation on any time frame. Even if FL influence does or did at one time extend this far north, the primary influence is now that of the eastern king.

As for how long it takes for a population to phenotypically differentiate, I think that can it can happen very quickly especially if the form is question is highly variable and the selection pressure is relatively strong.

Eastern patterns that are highly OBX like are also found in mainland areas of N.E. North Carolina and S.E. Virginia that are sandy, high and dry with little vegetation. Kings found on the barrier islands, at least those most likely to manifest the typical OBX phenotype, generally inhabit the interface between the salt marsh and dune habitats. In such locations, vegetative cover can be sparse and any pattern that enhances detection from predators would be quickly selected for. It’s also possible that the general lightening of the pattern could also allows for a longer foraging periods given that it would reflect more light (hence heat) than a typical eastern’s pattern would. All in all it’s simply a matter of selection pressures altering the frequency that a given phenotype is observed. OBX kings are just an extreme example because the shift in gene frequency is assisted by a fair degree of isolation.

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