Which moss is which? Identification of the threatened moss Orthodontium gracile using molecular and morphological techniques

Placing the regionally threatened moss Orthodontium gracile in the big picture - Phylogeny, genome incongruence and anthropogenic dispersal in the order Orthodontiales

The Orthodontiaceae is a small family of predominantly Southern Hemisphere temperate and South East Asian mosses that has a key phylogenetic position for research into the evolution of pleurocarpy. In the United Kingdom it is represented by the rare conservation priority species Orthodontium gracile and the abundant exotic O. lineare, introduced from the Southern Hemisphere around a century ago. Although the two species are superficially very similar and difficult to tell apart in the field, very little is known about how closely they are related or about the phylogeny, biogeography and evolutionary history of the genus Orthodontium as a whole. Phylogenetic inference and divergence time estimation were used to explore relationships within the genus globally, date major lineage splits, detect reticulate evolutionary processes and test monophyly of taxa. It was shown that Orthodontium gracile belongs to a Holarctic and Asian clade that diverged from the exclusively southern temperate lineage of O. lineare approximately 53 Ma and that it is sister to the Himalayan and South Siberian bispecific genus Orthodontopsis, which we now recognise as a single species within Orthodontium, O. lignicola. Orthodontium lignicola is quite distinct from O. gracile morphologically but may have a closely overlapping centre of extant diversity in the Himalaya, in contrast to O. lineare which is morphologically similar but biogeographically dissimilar. The introduced European populations of Orthodontium lineare were shown to share plastid and nuclear haplotypes with four collections from Tasmania and Southern Chile, but to be distinct from other Chilean and South African haplotypes. Finally, well-supported incongruence between nuclear and plastid sequences in some Western North American populations of Orthodontium gracile strongly implies one or more chloroplast capture or horizontal genome transfer events involving this species and the regionally sympatric O. pellucens. An appeal is made for targeting phylogenetic research at the intersection points of practical conservation, taxonomic uncertainty and wider biological questions and for the factoring of historical evolutionary and phylogenetic diversity into conservation assessments.

Challenges in the DNA barcoding of plant material

DNA barcoding, using a short gene sequence from a standardized region of the genome, is a species identification tool which would not only aid species discovery but would also have applications ranging from large-scale biodiversity surveys through to identification of a single fragment of material in forensic contexts. To fulfill this vision a universal, relatively cheap, scalable system needs to be in place. The mitochondrial locus being used for many animal groups and algae is not suitable for use in land plants, and an appropriate alternative is needed.Progress has been made in the selection of two alternative regions for plant DNA barcoding. There are however many challenges in finding a solution that fulfills all the requirements of a successful, universally applicable barcode, and in the short term a pragmatic solution that achieves as much as possible and has payoffs in most areas has been chosen. Research continues in areas ranging from the technicalities of sequencing the regions to data analysis and the potential improvements that may result from the developing technology and data analysis systems.The ultimate success of DNA barcoding as a plant identification tool for all occasions depends on the building of a reference database and it fulfilling the requirements of potential users such that they are able to achieve valid results through its use, that would be more time consuming and costly, and less reliable using other techniques.