Diploschistes caesioplumbeus (images of British lichens)

Initially a parasite on Lecanora gangaleoides, invading and killing the host and taking over the algae, then extending as a thick, cracked, smooth to slightly lustrous, pale to lead-grey crust; apothecia sunken in the thallus, opening via minute pores in the thallus surface. On sunny coastal rocks in the west and south-west, rare elsewhere.

Refs: Smith et al. (2009), 379; Purvis et al. (1992), 237; Dobson (2005), 166 (photo); Dobson (2011), 172 (photo).

D. actinostomus is a very similar but paler, cosmopolitan species, apparently not initially parasitic on other lichens. It has recently been discovered in Kent (see Smith et al. (op. cit.)) and might be elsewhere in Britain, good illustration in Wirth et al. (2004)).

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Images of British Lichens