what's the difference between a melanistic and a black cat?
and is it true that melanistic animals are more disease resitant?
>I only found a study regarding melanism and disease with insects
Melanism is just the overabundance of melanin. Melanism has developed multiple, different times. For example, black jaguar's have at least one mutated MC1R gene to thank. Domestic black cats have 2- deletion in the ASIP gene to thank. I'm not sure why exactly it makes them a little more disease resistance though. Here's some stuff for you to read if you're interested.