Bryophytes are the mosses, liverworts and hornworts, together comprising three of the four living groups of land plants (the fourth being tracheophytes, the large group that includes all of the familiar flowering plants, conifers and ferns). These frequently overlooked and fascinatingly diverse lineages probably retain features that were found half a billion years ago in the earliest land plants.

Scottish Bryophyte Diversity Research

In partnership with conservation agencies and long-established specialist societies we conduct research targeted at priority conservation species and globally rare habitats in Scotland and the UK. For example we have recently investigated the relationship between Orthodontium gracile, a very rare and threatened UK species that is probably now not found anywhere else in Europe, and Orthodontium lineare, a superficially very similar introduced species from the Southern Hemisphere. Through a molecular phylogenetic study of the entire genus worldwide we have been able to show that despite their close superficial resemblance, the lineage our native O. gracile belongs to diverged from that of of O. lineare tens of millions of years ago. We have further shown that O. gracile also occurs in the Himalaya and is much more closely related to a very different Asian species than it is to O. lineare.

 Rhytidium rugosum, a lime-loving moss that is fairly rare in Scotland and the UK

This link between Scotland and the Himalaya is typical of the long-range disjunctions that characterise many of the rarer elements of our bryophyte flora. Our western oceanic bryophyte communities have very few parallels anywhere else in the world, with a number of species otherwise found only in western North America, Macaronesia or the Himalaya. Ecologically similar communities occur in oceanic southern temperate regions (New Zealand, Eastern Australia, Western Patagonia) but are largely unrelated taxonomically. A target for future research will be the "mixed northern hepatic mat" communities of rare liverworts found in the mountains of the far north and west of Scotland, a number of which (such as Plagiochila carringtonii, pictured here) are disjunct with the Himalaya.

Plagiochila carringtonii (the pale plants in the centre) with Pleurozia purpurea

Plagiochila carringtonii

Bryophyte Phylogenetics and Architectural Evolution

We have world-leading taxonomic and phylogenetic expertise in several bryophyte groups, including the moss class Polytrichopsida, complex thalloid liverworts and "early-diverging" pleurocarpous lineages.

Marchantia quadrata (previously Preissia quadrata), a complex thalloid liverwort often found on limestone and mica schist ledges in the Scottish mountains

The focus on early-diverging pleurocarps relates to research into the evolution of plant architecture in mosses. The pleurocarps comprise around half of all moss species and appear to have undergone a relatively recent rapid evolutionary radiation founded on a mode of branching of the fertile modules that allows reproduction to be partially decoupled from vegetative growth. This innovation may have made more complex branching forms viable in pleurocarpous mosses, in turn allowing them to exploit a wider range of habitats. The early-diverging pleurocarpous lineages, now largely restricted to the Southern Hemisphere, show a greater diversity of architecural forms and may provide clues about how pleurocarpy evolved.

Mniodendron comatum, a "dendroid" (tree-like) moss endemic to New Zealand

Hymenodontopsis bifaria, one of the simplest dendroid mosses. The species is still treated in the genus Pyrrhobryum in the Flora of New Zealand (as P. bifarium), although both molecular data and branching archtecture reveal its closer affinities to the main group of pleurocarpous mosses (including Mniodendron comatum above).