All you have to do is look

Lichens are always described as a fungus and one or more algae (or cyanobacteria) living in symbiosis. The fungus provides structure and anchoring for the partnership and the algae transform sunlight into food via photosynthesis. I'm not so convinced that the partnership is quite as symbiotic as we're led to believe: in a symbiotic relationship, the partners cooperate to mutually benefit each other, but I think the fungus has the upper hand in a lichen for a number of reasons:

1) The methods of reproduction are all either purely fungal (via fungal fruitbodies that produce fungal spores), or are controlled by the fungal partner (broken or ejected fragments of lichen contain the fungus with a convenient bundle of algae already confined, ready for the next specimen).

2) The algae that are found in lichens can happily exist independently of the partnership: the fungal component cannot.

3) The fungal partner benefits from the food produced via photosynthesis which it cannot perform by itself, but what does the alga receive in return, apart from a place to live?

4) The alga can only reproduce within the confines of the lichen body: as the lichen grows, there is more space for the alga to grow.

I rather think the partnership is heavily weighted in favour of the fungal partner. 

This is a specimen of Graphis scripta (so-called because the spore-producing fruitbodies closely resemble handwriting):

Thallus of the lichen Graphis scripta

Notice the shape of the lichen: it is much wider than it is tall, and for a while I wondered why this characteristic shape is the norm for so many of our crustose lichens. The answer is quite simple: in percentage terms, a tree expands in girth much more quickly than it expands in height. The lichen grows at a common rate (perhaps a millimetre per year) in all directions from its starting point, but the bark of the tree expands more quickly horizontally than it does vertically. Over the years the lichen takes on this characteristic shape in response to the growth of the tree.

Here's another example:

Thallus of the lichen Pertusaria hymenea

I have actually been photographing the above specimen for perhaps 8 years now, and it's beginning to show its age: The thallus has been eaten away in a number of areas, most likely by slugs or snails. The bark of the tree has also split on the left, and this has almost split the original lichen into multiple specimens. Finally, Ivy has been growing on the tree and some of its tendrils have been pulled away, taking some of the thallus with them (you can see traces of the Ivy tendrils at the lower edge of the lichen, to the left of centre, looking like a fossil, and in the pale line to the right of the image).

(The dark blotches to the upper right and lower centre are the liverwort Frullania dilatata.)

I took a close-up of a much younger specimen of the Pertusaria, and you can see that it is much more rounded at this stage, but the vertical cracks that will spread it horizontally have started to appear:

I suppose the spaces get filled in with new thallus body as the lichen grows. So here we have a fungus that not only knows how to garden (it cultivates the alga), but has also learned a bit of DIY to plaster over the cracks.

(Click here for an image of the Pertusaria from 2004)

Stirrings

I thought I would take a look at the likely suspects today and found encouraging signs that our wildlife is at least having a try at this early point of the year.

A single Snowdrop was just opening; the rest were still firmly closed.

And a single Lesser Celandine bud had appeared:

The closely-related Ivy-leaved Water Crowfoot has started to come into growth on the muddy entrance to the field:

The jelly fungus Tremella mesenterica, or Witches Butter, appears to grow on dead Gorse branches, but in fact it's parasitic on the almost-invisible crusting fungus Peniophora incarnata, which grows on dead Gorse: 

This stacked dependency is a recurring theme in our wildlife: without the Gorse there would be no Peniophora and without the Peniophora there would be no Mesenterica. When you consider that Gorse is also the specific host for some moths, beetles and other fungi, you begin to see that removal of one species can have a significant impact on the whole series of its dependent species.

I also spotted the Hawthorn associate Tubaria furfuracea:

Award yourself bonus points if you can identify the leaf to the left of the image.

Brief seasons

In my previous post I showed an image of the December Moth and mentioned that they had emerged immediately after a thaw. Within 24 hours of the photograph, we were plunged into the coldest spell of weather in over 20 years. I haven't seen a single specimen since - and I have read similar reports from elsewhere, so I suppose their local season was perhaps 48 hours long. That might just explain the urgency with which they seek a mate.

Similarly, I found a few specimens of the Winter Moth over a couple of days:

Winter Moth (male)

Again, their season appears to have been dramatically curtailed this year.

The temperature reached -17 Celsius in the garden, which is by far the lowest I have recorded here. It will be interesting to see how different species are affected by this dip in overwintering temperature: some species overwinter as eggs, some as larvae, others as pupae and some as adults, and it is difficult to predict how a lengthy period of such low temperatures will affect the various alternatives.

Oddments

We had lying snow for around 10 days and I saw no moths during that time: earlier species would have died off, and new specimens would be staying underground until the snow went away. Sure enough, the same day the snow thawed, I found two specimens of the December moth:

Male December Moth

These feed on broad-leaf trees as larvae, and adults can be found from October to January; their eggs staying dormant until the trees have leaves in April or May.

Note the very feathered antennae. These perform a very similar function to the gills on the underside of mushrooms. Feathered antennae are more sensitive, making it easier to find the female, thereby increasing the chances of reproduction. Mushroom gills increase the surface area for spore production, making more spores available and again increasing the chances of reproduction.

As I was taking the shots of the male above, I spotted a minute (3mm) Springtail on the wall just below it:

It looks to be the same species as the one I showed on a mushroom earlier in the year.

A trip to the frozen high area yielded very little. I did see the empty seedpods of Yellow Rattle:

Empty seedpods of Yellow Rattle

And this frozen puddle on the path had an entertaining spiral pattern:

Ice spiral on frozen puddle

I just realised that the images for today are all virtually monochrome.

Background research

At this time of year I tend to do a lot of background research, since most of our wildlife is under the snow hibernating. During the summer, I bought a copy of "A Practical Guide to Nature Study" by J.H.Crabtree. It was published in 1924, so the material is at least 90 years old. The book deals with tools and techniques that assist with the task of studying our wildlife, and much of it is still relevant today. Having said that, as a keen photographer (he wrote books on photography, too), I'm sure he'd be astonished with our progress from film to digital.

J.H. shares his wealth of experience in collection, preservation and examination of plants, fungi and insects as you might expect, but his narrative is also peppered with references to the contemporary lack of education and awareness of the wildlife around us. He seems surprised that even in the early 20th century most school pupils couldn't identify many of our most common birds, trees or flowers. Given that I recently showed a photograph of a Bullfinch to a class of 11 year olds and was given a universal reply of 'Robin', I'm not sure that we've made a lot of progress.

Confused?

Well, the snow that we were promised duly arrived, although we haven't been hit nearly as badly as other areas. This is the time of year to spend some time in anticipation of what next year will bring, and as I checked the Willow trees in my garden, I saw the sheaths of next year's leaves growing from the point where this year's leaf has been shed:

Willow leaf sheath

That's quite normal and I'd expect to see that happening at this time of year. What I didn't expect to see, however, is the catkin beginning to open:

Opening Willow catkin

I'd expect to see that happening around the end of February, but something has completely confused this particular tree because many of the catkins were in the same condition. This early opening will have a short-term adverse effect on the tree because these flowers will be destroyed by the frost, requiring the tree to make a second set of flowers later in the spring.

This, of course, will impact our willow-dependent moths and other insects. Bees such as Andrena clarkella are only seen during the normal flowering season for willows, and this tree might flower too late to support them. On the other hand, it might just be possible that some of the other dependent species could extend their season a little due to the later availability of some pollen and nectar.

In our natural environment nothing ever happens in isolation.

Seasonal images

We're expecting snow later in the week, and that kind of weather is often preceded by interesting morning skies. This is the view from my bedroom window this morning:

Croaghan Hill, 8am, 24/11/2010

Stormy weather had brought down some small branches, and I found this specimen of the lichen Xanthoria parietina:

The green and yellow cups look like tiny cup mushrooms, and that's exactly what they are: the reproductive components of lichens are controlled by the fungus. In this case the cups are purely fungal and produce only fungal spores. The spores are ejected to land some distance away and must land on the appropriate alga to form a new specimen of the lichen.

The Candle Snuff fungus - Xylaria hypoxylon -  grows on dead wood:

This nice little image of a Mycena growing in moss is tinged with more than a hint of sadness:

 

Mycenas are a tricky little group, and I'm sad to report that my friend and Mycena guru Gerry Shannon is no longer with us. He was a very jovial and enthusiastic mycologist who specialised in the LBJ's that we found. He will be sadly missed.