Those incestuous ferns

A jagged, fissured promontory of conglomerate sandstone overlooks a gorge in Jackson County, Ohio. I have made a few trips to this scenic southeastern county in the last week or so, for various purposes, and on each visit took time to inspect some rocks.

Cliff-faces are always of interest to the botanist, as they often harbor interesting saxicoles - rock-loving plants. And ferns lead the list. Of the approximately 80 species of ferns that reside in Ohio, a good-sized handful only grow on exposed rock faces.

The delicate little beauty above is mountain spleenwort, Asplenium montanum. You'll have to inspect craggy sandstone cliffs to find it. With a toughness belying its fragile appearance, mountain spleenwort lodges itself in the smallest of crannies, deriving sustenance from the meager soil that collects in such places.

Worn and winter-weary is this little fern, the pinnatifid spleenwort, Asplenium pinnatifidum. It's a close relative of the mountain spleenwort, but isn't shy about breaking taboos and mating with its kin.

Here's the evidence. This rocky shelf hosts a pure mountain spleenwort (left), and its hybrid with the pinnatifid spleenwort (right). The hybrid is known as Trudell's spleenwort, Asplenium x trudellii. One might make the case that it is even better looking than either of its parents. The specimen in my photo shows "hybrid vigor"; it is more robust than either parent species.

The fern world is fraught with cross-breeding. At least 21 hybrid combinations have been documented in Ohio alone. The spleenworts are among the worst of the lot when it comes to fidelity to their species. The eight spleenwort species known from Ohio are augmented and confused by six different hybrid combinations.

But it's this rampant infidelity that adds another layer of interest to our most ancient lineages of plants.