Typically a plant of the bogs of the north and west, there are several populations of Sphagnum magellanicum in the south of England, though very few in Sussex. In West Sussex there are records from Heyshott Common, Black Down, and Iping Common, and the older East Sussex records are from Waldron Down (Francis Rose, 1962) and near Lavender Platt on Ashdown Forest (Francis Rose, 1983). It is likely that these latter are no longer present.

More recently, David Streeter found it in a small valley-side flush near Wych Cross in 2009, where it can still be found, and Rod Stern and the BBS Southern Group recorded it the following year at Broadwater Warren. Then Tom found it at Millbrook in 2014. Still, it is certainly rare in Sussex, so I was delighted to receive an email in February from Rose Dudeney announcing that she had found it at a new site on the Forest.

Sphagnum magellanicum with some S. papillosum. Photo: Rose Dudeney

First off, though, apologies to Rose for taking rather too long to go and visit the site; I did have a walk to the spot a few months ago, but I wasn’t in bryophyte mode and didn’t have appropriate footwear, so didn’t find it in the time available. However, today I made a visit specifically to find it, and once I’d got my bearings it didn’t take long to locate.

The distribution of Sphagnum magellanicum in Sussex. The green square is the new record

Near the crest of a boggy valley, there are a couple of Sphagnum magellanicum hummocks sitting slightly elevated from the wet bog as it drains down into the valley. Surrounded by other Sphagna, and slightly intermixed with S. papillosum, there are also cushions of the much finer S. capillifolium ssp. rubellum close by, with which it can be easily compared. The area also included lots of Star Sedge (Carex echinata) and Round-leaved Sundew (Drosera rotundifolia), and the main body of the bog comprised S. denticulatum and S. flexuosum. On its drier edges could be found S. compactum.

Sphagnum magellanicum hummock in the foreground

Sphagnum capillifolium ssp. rubellum

As the books make clear, Sphagnum magellanicum is normally quite distinctive in the field; like the other species in section Sphagnum it is a large, chunky plant with hooded leaves, and it has a very characteristic deep red colouration. Even so, it was worthwhile checking it microscopically too, and the chlorocysts were smooth, which, in transverse section are in the centre of the leaf and don’t reach either face of the leaf.

Leaf cells of Sphagnum magellanicum

Transverse section of Sphagnum magellanicum leaf

Tom noted that it might be prudent if much of the woodland below what is now bog is opened up because he suspects it used to cover a much larger area. There certainly was much less tree cover in the valley as the aerial photograph from the 1940s shows, in comparison with the recent view, and the trees will be drying out the bog.

The area east of Duddleswell in the 1940s. The Sphagnum magellanicum site is roughly in the middle of the image

The same area today, with woodland now extending up the valley from Great Birch Wood

The plant was originally named by Samuel Elisée Bridel-Brideri in the second volume of Muscologia recentiorum (1798) from material from the Magellan Straits (‘In Freto Magellanico’), and it has been a long-studied species, often used as a model in peatland ecology.

However, it may not be quite what it seems. A recent study[1] has shown that there are genetically distinct populations around the world, and that those in South America are differentiated from those in North America and Europe, and even in the latter regions there are several groups.

Furthermore, a subsequent study on Norwegian material[2] showed that two morphs of S. magellanicum can be separated genetically. In the field these have either shorter branches with blunt tips and deep red colouring in the more open part of mires, or longer and more pointed branches with less red colouring in plants nearer the mire edges. The authors suggest that these could be separate European species.

Interestingly, at the Ashdown Forest site today there appeared to be plants that corresponded with both these morphs, so maybe our local Sphagnum collection includes something new. In any event, assuming that Bridel’s original description only applies to the South American species, we may well get a new name for what we have long known as Sphagnum magellanicum. Congratulations to Rose for such a good find.

Chunky Sphagnum magellanicum

Rather more elongate branches of Sphagnum magellanicum? mixed with S. palustre

[1] Kyrkjeeide, M. O., K. Hassel, K. I. Flatberg, A. J. Shaw, N. Yousefi, and H. K. Stenøien (2016). Spatial genetic structure of the abundant and widespread peatmoss Sphagnum magellanicum Brid. PLoS One 11 : e0148447. https://doi.org/10.1371/journal.pone.0148447

[2] Yousefi, N., K. Hassel, K.I. Flatberg, P. Kemppainen, E. Trucchi, A.J. Shaw, M.O. Kyrkjeeide, P. Szövényi and H.K. Stenøien (2017). Divergent evolution and niche differentiation within the common peatmoss Sphagnum magellanicum. American Journal of Botany, 104: 1060-1072. doi:10.3732/ajb.1700163.