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I still find it far too easy to overlook some species, not just because many are only visible as tiny fruits, but simply because I don’t expect to see any in a given place. If not expected, one’s eyes often simply don’t register. When we moved into our bungalow two years ago, I quickly located the shapeless yellow powdering of Caloplaca citrina on the mortar along with the white thallus of Lecanora albescens (which paints the inner surface of Pickering Castle’s outer keep walls white) and the tiny white-rimmed fruits of L. dipersa. It was obvious from a standing position that the concrete yard by the south wall was painted with the black orbs of Verrucaria nigrescens and the white counterparts of Aspicula calcarea. All of these are calcicoles, preferring basic substrates.
However, it wasn’t until the Autumn of 2005 that I realised I had completely overlooked some pale yellow, one inch wide thalli, scattered here and there. On hands and knees, a hand lens revealed tiny, half-millimetre orange fruits on the survace of each thallus, but no powdering (soredia) so – not C. citrina, but what then? Then I recalled a trip with the late Prof. Oliver Gilbert and Dr. Chris Hitch to Appleton Roebuck disused, concreted arifield in 1993 when Oliver discovered Caloplaca crenulatella in various places. At that time, the official B.M. Handbook listed that species as “very rare, on hard limetstone in Cumbria”. By 2000, Dobson’s handbook quoted it as “recently reported on old concrete, near the ground”. His 2005 enlarged handbood quoted “many sites, particularly urban areas”. So, my yellow orbs were crenulatella and either nobody noticed it previously or it is on of those galloping colonisers.
Local trees bordering the A170 are virtually devoid of lichen, excpet for the ubiquitous, dull greenish Lecanora conizaeoides, due to vehicle exhaust fumes. This species can tolerate almost anything, having originated from the sulphur-impregnated areas of volcanic Iceland. One only has to step a relatively short distance away to find some excellent species. In the field (Oaklands) just to the east of the Keldholme/Sinnington crossroads, some mature trees bore excellent rosettes of Parmelia subrudecta and Physcia aipolia, the latter not seen elsewhere in Yorkshire. The road through Howldale, past the old quarry, has at least one tree bearing the vivid green rosette of Parmelia glabratula (now renamed). The peculiar and unexplainable aspect of rows of trees is that just a single one out of a line of similar species might bear a special lichen. The trunk of a single tree down Ings Lane, past the aircraft factory, is the only site in Yorkshire where I have found masses of the green/grey Physconia distorta.
So, why not examine the mortar of yor dwelling with a hand lens – you will probably be quite surprised.
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Text copyright © Ryedale Natural History Society 2006.