Comparing Scapania Species in Coastal PNW

Scapania is like the Sphagnum or liverworts--instantly recognizable to genus but then agonizing to go beyond that point. The unequally bilobed leaves with their ovate-reniform lobes are an instantly recognizable feature. There are about a dozen species in coastal BC, many clustered in subalpine habitats. I will try to add more to this table as I am able to dig up records. Using a combination of habitat and leaf features, it is possible to get to species. It turns out the shape, relative size and attachment of the characteristically unequal leaf lobes is the key to figuring this genus out. Three words from this table should be off-putting so I will explain them up front: Dorsal lobe refers to the overlapping part of the lateral leaf that you see on top when you look down at Scapania from above. It is generally smaller than the underlying ventral lobe, which is most visible and prominent when looking at the underside of the shoots. Ventral leaf decurrency refers to the way the leaf is attached to the underside of the lobe. Instead of attaching transversely across the stem, a decurrent leaf runs down along the edge of the stem for a while. This great photo by Richard Droker shows the ventral side (on the left) next to the dorsal side (on the right) of Scapania bolanderi. You can see that the leaf margin begins to parallel and descend along the stem. It is "decurrent".

Each species below is linked to an iNaturalist observation that attempts to demonstrate the features in this table. If you want to get very deep in to Scapania, try the provisional Bryophyte Flora of North America Key to Scapania (link to pdf treatment of all species of family Scapaniaceae in North America north of Mexico).

Posted on Ιανουάριος 17, 2023 1114 ΜΜ by rambryum