Ancient Jaguars

[tigerluver]

Really enjoyed your posts, thanks @Balam !

Good catch on P. balamoides, seems like at least two studies think it's Arctotherium.

Agreed, the next step for the P. atrox in South America idea would be testing one of the remains that are attributed to P. atrox.

We can try to get a rough estimate of the divergence then using the branch lengths. Using the 0.02 scale, the branch length of the P. leo and P. pardus split is about 0.036. The P. onca an P. onca mesembrina split branch length is 0.021. So the genetic gap between P.leo/P. pardus is 1.71 times the gap between P. onca/P. onca mesembrina. In other words P. onca and P. onca mesembrina are 1.71 times more closely related than P. leo/P. pardus. We then have to find a way to calibrate this change to time to find a rate of change. I found a study that estimates the divergence of P. leo/P. pardus at 4.35 MYA. So the rate of change over time would be 4.35 MYA divided by 0.036, equaling 121.1 MYA/1 unit of change. Using stoichiometry, P. onca and P. onca mesembrina would have diverged 2.54 MYA. This is around the divergence of P. leo and the cave lions. By this, P. onca mesembrina would be its own species but most closely related to the jaguar. Molecular dating is fickle however and the confidence intervals are wide.

Evidence into the possibility that P. onca mesembrina is its own taxon is that despite the fossils being around only 10 kya old, they are distinct from extant P. onca. This would mean there was no interbreeding which can define speciation depending on the timespan. 

This could explain why there is a large gap in size noted by Chimento and Agnolin (2017) between P. onca mesembrina and fossil P. onca. They were indeed distinct populations and perhaps size served as a sympatric barrier. 

I wonder if the cave paintings simplify rosettes into spots or if they were accurate. They probably are simplified but if not could show a difference in the coat pattern of P. onca? mesembrina. 

It is still possible P. atrox existed in the region prior to the time of these cave paintings. However, I am leaning toward digging into P. onca? mesembrina more. Reply