The struggle for survival.

Mrs Talpa is off to church and so I was left to amuse myself with a rather wet visit to a local graveyard, where I came across this wonderfully lichen-encrusted gravestone.

Lichens are, of course, composite organisms formed by a symbiotic association between a fungus and photosynthetic partner, usually a green alga or a cyanobacterium.

Lichens can survive in some of the most extreme environments on Earth - the Arctic tundra, hot deserts, rocky marine coasts, toxic slag heaps and even on gravestones in the North East of Scotland!

What I find particularly striking in this photograph are the regular tessellations formed by the collision of individual colonies as they grow and expand: the front lines of the battles for space and resources are all too clear. Best seen zoomified.

It is all part of what Herbert Spencer, and later Charles Darwin, described as the 'Survival of the Fittest'. How appropriate that this battle for life should be raging on a gravestone!