Rock Cap Polypody

On making a video on Polypodium, we immediately smacked into the fickleness or inconstancy of the genus, especially P. appalachianum (P.a.) and P. virginianum (P.v.), the regional representative. P.v. seems to be the normal local fern, which is a tetraploid derivative of P.a. and P. sibiricum the range of which now much further to the north. P.a. is known for more rounded pinnae, which are widest near the middle -- in contrast with P.v.'s pointer pinnae and a more deltoid blade. But the two species mix it up. Genetics: 2n = 148 (tetraploid) for P.v. vs 2n = 74 for P.a. and P.s. Much of the mixing: past 15 ma. It's a very recognizable group, and while not common here, shows up in very predictable places. We're pretty sure both P.v. and P.a. are represented in this short video; the videos taken south of here seem to show more of the Appalachian rock cap. (-jcs; 8/4/2024, all content is our own)