Still can’t get over just how small this species is. Asplenium trichomanes subsp. quadrivalens.
This species prefers acidic rocks typically; but this smaller subspecies is really only associated with dolostone outcroppings that retain moisture or stay fairly wet. The divisions of the maidenhair spleenwort is really not by size necessarily, but is associated directly with substrate and separation by long distances between prefered habitats. Although this speciation event isn’t traditional allopatric speciation(speciation by large scale geographic divergence and separation) this species is definitely one exception that had been funnelled under that cause, micro-allopatric speciation for quite some time due to the presence of this species in many countries that span the northern hemisphere of the globe. The truth later was found that Asplenium trichomanes subsp. quadrivalens was far more rare overall than its acidic sandstone loving lineage, and it was more associated with North Eastern North America. Thus it was due to edge niche shift in a place that shared both habitats(like RRG for example). This then referred this speciation event to Parapatric Speciation; the specific way it has been phrased is really “Gradual speciation by habitat splitting”
The more common acidic/sandstone loving lineage is referred to now as A. trichomanes subsp. trichomanes.
I’ll be posting more calcareous maidenhair spleenwort in the next few posts.
