Following on from a randomised survey of all British lichens in the Natural History Museum’s collection (see previous blog), I completed my week there finding out more about one particular British lichen, Lobaria amplissima. For all 109 specimens of the lichen, as well as recording the same information as in the previous survey, I was particularly looking for the presence or absence of cephalodia* and apothecia**.
Lobaria amplissima is a large, ‘leafy’ lichen, normally green but paler when dry. It is sensitive to toxins making it a good indicator of ecosystem health. It is found on Ash, Oak and Sycamore, often in old woodlands and predominantly to areas in the west of the UK where the air is cleanest – North and West Scotland, Cumbria and Devon and Cornwall.
Combined with information in other local and national databases, the data recorded may make it possible to identify more precisely any changes in the geographical distribution of the species over time, and any correlation between environmental changes and the presence of nitrogen-fixing cephalodia and/or the sustainability of colonies.
Lobaria amplissima is relatively unusual in that as well as the symbiosis between a fungus and a green alga in the ‘leafy’ structure (thallus), a cyanobacterium is also involved. The cyanobacteria form brown-black gall-like structures called cephalodia, which can be seen in the photo above as small black nodules. The alga and cyanobacteria provide food to the fungus through photosynthesis and, in addition, the lichen gets added nitrogen from the cyanobacteria in the cephalodia, which may be an advantage in nitrogen-deficient environments.
In the photo above, the red-brown cup-shaped structures are apothecia, the fruiting bodies from which spores are released. They mean the lichen is reproducing sexually, an indicator of the vitality of the organism. Organisms which only reproduce asexually can be vulnerable to environmental changes since mutation is the only way new genetic combinations can appear.
Thanks to Dr Holger Thus for the opportunity to work with this wonderful collection and delve a little deeper into these amazing organisms.