Epigenetics is also not “outside of the double helix” it involves methylation of the double helix molecule.
Biologically there is only one definition of species - it is how it is interpreted that comes into issues with “lumpers” and “splitters”.
You seem the ultimate “lumper” - lumping species that not even the most extreme professional lumpers (taxonomists) want to lump together.
Lumping foxes, wolves, dogs, jackels and a variety of other animals into the same family is not a problem.
The problem arises out of the idea that DOGS and WOLVES and COYOTES which can and do breed freely, prolifically if we let them, and in the most fertile manner are DIFFERENT SPECIES ~ not in your wildest imagination ~ it would be like pronouncing Black Humans to be a different species than White Humans.
I'm sorry. Does not compute. Doesn't work. Even isolation to separate ranges (Northern high latitudes and Equator) is insufficient to justify identifying mere racial differences as constituting the basis of declaring a group to be a species.
As Shakira sang, "the hips don't lie".
Histone Acetylation, DNA Methylation and Epigenetics
There may be another method used to affect gene expression that I'm forgetting.