Silver Ferns on Marble Mountains at 10,500'

Among the genus of fern Astrolepis - which is renowned for growing primarily in desert mountains and often out of cracks in bare rock - there are only a handful of species. This species is Astrolepis integerrima, distinguished from other species in the genus by the dense coat of scales and trichomes on its upper (adaxial) leaf surface.

And among the different populations of Astrolepis integerrima that exist throughout arid regions of North America, there are various ecotypes - that is populations of the same species that all vary slightly morphologically and genetically, but not quite enough to be considered separate species or even subspecies. Their differing characteristics and morphology is the result of their particular geography and geology and climate patterns having slowly "sculpted" them - evolutionarily speaking - over the last however thousand to tens of thousands to perhaps hundreds of thousands of years. A prime example of natural selection at work.

And THIS particular ecotype of Astrolepis integerrima was more stunning than any I have ever encountered, especially since it was seemingly everywhere on this mountaintop at 10,500' (3200 m) that was composed entirely of MARBLE. That is, metamorphosed limestone. It was growing next to giant Agaves (salmiana ssp. crassispina), oaks (Quercus crassifolia), and even a cool carnivorous plant (Pinguicula moranensis).

The new growth and emerging leaf blades almost resembled feathers that were slowly uncoiling, so dense were the scales and trichomes on the blade that you could barely see any photosynthetic tissue through it. Hairs of course are an adaptation to many things, primarily drying out, full sun and frost. Surely, in the high mountains of Mexico all three of those factors made for this particular ecotype of this extremely fuzzy, silver fern.