Lycophites: Extant and Extinct.

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Fir clubmoss overlooking Rossett Gill.

There are eight species of clubmoss found living in Britain and Ireland today. These are lycophytes, which are a vascular plant (despite their non-vascular name-sake), which include quillworts and the clubmosses. Of these eight species of clubmoss, seven are of the order Lycopodiales and are strictly referred to as clubmosses and one is of the order Selaginellales, which are referred to as lesser clubmosses or spikemosses.  Clubmosses can be found throughout Britain and Ireland and many species are found in upland or mountainous areas and hence have strongholds in the Scottish Highlands, the English Lake District and Wales. Also found in the UK, are extinct lycophytes. These include Devonian representatives, such as Asteroxylon, from the Rhynie Chert and Upper Carboniferous representatives, such as Lepidodendron and Sigillaria from the various Coal Measures. As a result, lycophytes are one of the oldest lineages of vascular plants. 

While I've always been interested in the group due this link between the fossil counterparts (that are common in the surrounding Pennine Coal Measures) and the living counterparts, my experience has always been limited to one of the most common species- the fir clubmoss (Huperzia selago). However, six of the eight species of clubmoss can be found in the English Lake District, and this summer I took it upon myself to see as many as I could.

Stag's-horn Clubmoss (Lycopodium clavatum) below Bowfell Buttress (left) and on Great Knott (right). 

Alpine Clubmoss (Diphasiastrum alpinum) at Great Knott.

Fir Clubmoss (Huperzia selago) at Sargeant's Crag (left) and Rossett Pike (right). 

Lesser Clubmoss (Selaginella selaginoides) at Greenup Gill (left) and Blea Crag (right).

By the 8th August 2020, I had managed to find five or the six Cumbrian clubmosses, with the missing species being the interrupted clubmoss (Lycopodium annotinum) which is restricted to a single site- the eastern flanks of Bowfell. Despite looking for it near to its sole locality, I failed to find it, although I am planning a return trip, as I've now got access to an accurate grid-reference from the rare plant register of Cumbria [4].

Moving further afield, I've also seen clubmosses and lesser clubmosses/spike mosses in Malaysian Borneo and the Indian Himalayas. These include Selaginellas that look rather different to our native species, but are more typical of the genus. 

An unidentified Selaginella species from the banks of the Teesta (near Teesta V), Sikkim, Indian Himalaya.

As well as Selaginella, I also found a 'true clubmoss' which bares a striking resemblance to our own stag's-horn clubmoss and given it's widespread distribution, very well could be. 

An unidentified clubmoss - potentially Stag's-horn Clubmoss (Lycopodium clavatum), or a similar species such as L. japonicum from Temi Tea Estate, Sikkim, Indian Himalaya.

Lycophytes are an interesting group and are often considered 'living fossils' (this term has been heavily criticised, especially in recent times, due it's ambiguous definition and its resulting misinterpretation of the evolutionary process).

The relatives of living lycophytes can also be found in the British rock record. During the Pragian age of the Devonian (410.8 Ma- 407.6 Ma) a fossil can be found with a striking resemblance to the fir clubmoss. The fir clubmoss is the most primitive of Britain's clubmosses- supposedly not having changed much from Devonian ancestors [1]. It closely resembles a fossil clubmoss called Asteroxylon mackiei from the Rhynie Chert and Windyfield Cherts of Scotland, as well as many other ancestral clubmoss-like plants [2]. It is worth noting that the first clubmosses are in fact recorded from before the Devonian, in the Silurian rocks of Australia [5].

 

Following on from the Devonian, during the Carboniferous, further fossil analogues can be found. The British lesser clubmoss belongs to the genus Selaginella and is unique among the the other clubmosses as it's reproduction is heterosporous, meaning it has both male and female aspects of its life cycle [1]. This is in common with fossil lycophytes, with some attributing Carboniferous lycophytes to the extant Selaginella. If true, Selaginella would be the longest living genus of higher land plants [3].

Many of these fossil lycophytes bare a striking morphological resemblance to modern clubmosses. This is most evident in the uncommon leafy shoots of Lepidodendron. I've collected many specimens of lycophytes, the majority from the Pennine Middle (and Lower) Coal Measures Formation, which preserves a variety of flora from the Langsettian substage (314.5 Ma- 313.4 Ma).

 Leafy shoots of Lepidodndron sp. (possibly L. simile) from the South Wales Coal Measures (section of a rock core nr Merthyr Tydfil) next to fir clubmoss (Huperzia selago) specimen collected from the Black Mountain, South Wales (found dead and already desiccated).

Lepidodendron sp. (or potentially Lepidophloios sp.) imprint in iron stone concretion from the Pennine Coal Measures from Providence Bay, Parton. 

Lepidodendron sp. from the Pennine Coal Measures from Pow Ghyll, Cumbria (left) and Lepidodendron sp. (among other plant fossils) from the South Wales Coal Measures from Clyne Valley, Swansea (right). 

Extant lycophites offer an insight into deep time and the ecosystems they inhabit and they are an evolutionary link between the 'alien' landscape of the Carboniferous (among other periods). To research, find and photograph these unusual, primative plants over the last few weeks has been a joy and really interesting, as well as expanding my knowledge of botany.

EDIT 1: I finally saw the 'complete set' of Lake District clubmosses, after a return trip to below Bowfell Buttress. There were large stands of the interrupted clubmoss (Lycopodium annotinum) which are now only found at this single site within England. A truly spectacular plant, and well worth the hike up Rossett Gill. 

 Interrupted clubmoss (Lycopodium annotinum) below Bowfell Buttress. 

Edit 2: Following a summer of clubmosses, I started my MSc at Royal Holloway in Surrey, where I was very close to the Thames Basin heathlands- a stronghold for marsh clubmoss. This gave me the opportunity to find the species in it cone during the autumn. 

 

Marsh clubmoss (Lycopodiella inundata) in cone at Chobham Common 

Edit 3: As part of my MSc course, at Easter, I enjoyed a field-course to the Scottish Highlands around Glen Roy. Here I found a variety of clubmosses in stunning settings including a number of unusual fir clubmosses that superficially resemble ssp. arctica, however, considerably more research is required. 

Fir clubmoss (Huperzia selago) at Creag Dubh

Alpine Clubmoss (Diphasiastrum alpinum) at Alt Coire Ardair.  

[1] Merryweather, J., 2020. Britain's Ferns. A field guide to the clubmosses, quillworts, horsetails and ferns of Great Britain and Ireland. Princeton University Press.

[2] University of Aberdeen. Asteroxylon. https://www.abdn.ac.uk/rhynie/aster.htm accessed on 08/08/2020. 

[3] University of Hamburg. History of Palaeozoic forest fossil and extant Lycophytes. http://www1.biologie.uni-hamburg.de/b-online/kerp/seite6.html accessed on 08/08/2020.

[4] Porter, M. and Halliday, J., 2014. The rare plant register of Cumbria: the rare, scarce and threatened vascular plants of Cumbria. Trollius Publications. 

[5] Rickards, R., B. 2000. The age of the earliest club mosses: the Silurian Baragwanathia flora in Victoria Australia. Geological Magazine.137, 2, pp:207-209.