When it comes to "species" there are actually three definitions out there ~ one of them refers to what we now call clades. Another to what we now call subspecies. And another to what we now call Salmon. The EPA interprets the endangered species act to allow them to treat each batch of salmon that favor one crick over another as a totally separate species!
Looking at all these critters at the level of their DNA it's pretty obvious that Dogs, Wolves, Coyotes and mixes thereof are NOT KITTY KATS!
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.