Panthers is a common name created by the people rather than a different speciation. they're leopards who exhibit melanism (the gene that determines how much color and how strong of color is cranked to the max). And because their coloration is successful in where they live, this trait has been passed on to their offspring, to the point that there are numerous sightings. (Leopards with their spots, blends with the light being broken by the trees, and their lighter bellies to blend with the sky if they're moving from above.)