Answer:
Larger jaws and teeth may become more common in jaguar species over a period of time for a few reasons. To start off with, the genetic pool needs to prompt the species to have multiple offspring of different genealogy lines (non-inbred). Those offspring with the new attributes would have to adapt and survive. They wouldn't necessarily need to do better than the normal variation of jaguar, they just need to do well enough to mate. In terms of mating, the offspring with the mutation would have to mate with each other since the mutation would most likely be recessive. Over time, with more offspring that contain the mutation and keep breeding together, the recessive gene would become dominant (I think that's how that works) within the population. Once the population is high enough, there would be a competition between the normal variation and new variation of jaguars. Assuming the new variation out-competes the normal variation, natural selection had occurred and you have a result. I hope this helps!