Tuesday, 4 December 2012

Lichens and leaves

Just when I thought the season couldn't get any more odd, I spotted a Willow making new leaves on a couple of shoots:

New Willow leaves
This is the same Willow specimen that has the opening catkins on it, so it has obviously been thoroughly confused: the leaves on this specimen of Willow normally appear after the catkins, rather than at the same time. I have received reports that Daffodils are making good growth in a nearby location, so something odd is happening.

This is a good time of year to have a look at lichens. Although they are present all year round, they are often hidden by leaves and plants, so they are now more visible and accessible.

Lichens are a combination of a fungus and a photosynthetic partner. They are usually described as a symbiotic relationship between the fungus and either an alga or a cyanobacterium, but I see it more as a boss-victim relationship for reasons that I have previously explained numerous times. Either way, lichens can be found in wildly varying shapes and colours and are very important as pioneer species, converting wood and rock into soil over time.

There are several reproductive strategies used by lichens: some create fruit bodies which are purely fungal, and eject spores into the atmosphere in the hope that they will land on a nearby victim in order to create a new specimen. Others create little packages of fungal material combined with trapped algae which are ejected as 'starter packs' of lichens ready to go. Still others grow on fragile material such as soil and simply fracture into a new specimen.

Some lichens use more than one of these reproductive techniques, and can therefore be found in different states, depending on which strategy they have currently chosen. This specimen of Hypotrachyna(Parmelia) revoluta is very unusual, in that it has produced purely fungal fruitbodies. One is visible just to left of centre:

Hypotrachyna(Parmelia) revoluta with fruitbody (orange)
Hypotrachyna revoluta is very much a western species and can be found mostly on wood, but sometimes on rock. New to my Species list.

Ramalina calicaris, on the other hand, regularly produces fruitbodies, and they can be seen here as little cups on the tips of most of the branches:

Ramalina calicaris

The orange material to the lower left and upper right of the branch is the alga Trentepohlia, which is one of the victims of choice used as part of many lichens. It is no coincidence that Trentepohlia and lichens are often found in the same location, since the lichen has probably formed principally due to the prior existence of the alga in that precise location.

Evernia prunastri is readily identified by the bifurcating branches, which make it look like antlers:

Evernia prunastri
The upper surface can be grey or green, but the underside (shown) is almost white.

Platismatia glauca is another new species for me. It is usually found on the upper side of horizontal branches:

Platismatia glauca
New to my Species list

Lecanora chlarotera is a very common lichen on Willows. I think there are few trees without some of this somewhere on the trunk:

Lecanora chlarotera

I love the colour of those fertile fruitbodies, somewhere between olive and brown. Notice how straight the line of fruitbodies is on that sample. I have a strong suspicion that these lichens are spread by slugs, perhaps even after the spores have passed through them and been left in the trail they leave behind.

Peltigera sp. lichens have very leafy structures and can grow very large. This specimen has been tentatively identified as Peltigera lactucifolia, but the orange fruitbodies seem to be the wrong shape (round, rather than elongate). Research ongoing by the good and great, but I think it's actually Peltigera horizontalis.

Peltigera cf. lactucifolia

Pannaria rubiginosa is a very attractive lichen with a distinctive appearance:
Pannaria rubiginosa
The victim in this case is the cyanobacterium Nostoc, which can often be found as a green/brown jelly on paths and carpark surfaces.

That's another two species for my species list, which must be nearing a total of 1450. I'll update it before the year runs out.

1 comment:

Inishowen Tourism Society said...

Nice Collection of Species.