Persistent P's Permeating the Polytrichiaceae

In lab group last week we read an article about the moss family Polytrichiaceae. These are the mosses that have fabulous little lamellae on their leaves. Some species are quite common and can be found in open disturbed edge habitat. They can be recognized by their star-shaped form when viewed from above and they are often one of the largest mosses that you will see in the field.


Bell, Neil E. and Jaakko Hyvönen. 2010. Phylogeny of the moss class Polytrichopsida (BRYOPHYTA): Generic-level structure and incongruent gene trees. Molecular Phylogenetics and Evolution 55: 381-398. 

Species are typically grouped into the larger category of genera based on the morphology of the plants, their physical appearance. Thus all the members of the genus Atrichum (the smooth capped mosses) look similar to each other and the same for other genera such as Polytrichum (the hairy capped moss). Sometimes it ends up that these morphological groupings are confirmed by the DNA sequence data and all the members of the genus did descend from a common ancestor. Other times the DNA data shows that the members are not descended from a recent common ancestor and are instead distantly related. The morphology and the DNA evidence tell a different story. In this study both Polytrichastrum and Oligotrichum are composed of members that are distantly related. The later genus has a distinct geographic pattern with all the northern members being related to each other and all the southern members in the other group. Overall I think that it is pretty cool to explore these morphological hypotheses with DNA data. You never know what there is to be found. 

Another paper on this group of mosses by the same authors.
Bell, Neil E. and Jaakko Hyvönen. 2010 A phylogenetic circumscription of Polytrichastrum (Polytrichaceae): Reassessment of sporophyte morphology supports molecular phylogeny. American Journal of Botany 97: 566-578.