Most of the photographs I have seen of these two lichens are greatly enlarged to show detail, but this doesn’t really tell me what I might actually see without a hand lens or magnification. Are they significantly different at first glance?
L. pygmaea is larger (to 1cm tall) and found lower down the shore, amongst the barnacles, where it copes with submersion. It often forms extensive patches.
L. confinis is smaller (to 0.5cm) and found just above the high-water line, typically with Verrucaria maura and Caloplaca marina. It often forms small tufts, but sometimes larger, fragmented swards.
Without close inspection they look very similar, but based on size and location it is often possible to tell them apart without rolling around in the seaweed with a hand lens. But not as much fun.
Thank you for your help, Nigel.
The reason I asked was because I found a small tufty patch tucked in a cranny rather further down the shore than the other patches I've found. I will need to check at high water just how much it gets washed over. The tides are rather variable at the moment and although it would have been underwater at the previous high tide on the day I found it, it may well be high and dry now as the tides have become much shallower. It was certainly above barnacle level so is probably L confinis. I tried to photograph it but as it was in shadow and growing on Hydropunctaria/Verrucaria maura I couldn't actually see it at all when I downloaded it onto my laptop.
I shall no doubt continue to slither around on the rocks and seaweed trying not to fall into rock pools on my hunts. It is fun, isn't it?
You (and others) might be interested in this recent Radio 4 interview with Pat Wolseley, who once contributed on iSpot and is a co-editor of the The Lichens of Great Britain and Ireland (the big, technical guide).
That is a very interesting interview, which I have listened to a couple of times now. Thanks for the link.
When I no longer need to keep looking up some of the terms I should be using in order to describe lichens accurately for an observation (and still getting it wrong!), I may perhaps decide to invest in The Lichens of Great Britain and Ireland. At the moment though, although I have an occasional foray into looking at woodland and farmland lichens, my main interest is in those on the coast, so A Field Key to Coastal and Seashore Lichens by Frank S. Dobson is enough for me to be going on with.