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digitata (L.) Hoffm., ffid C. squamosa (Scop.) Hoffm. were observed, but in these
species no additional lichen compound occurred.
Discussion
Rhodocladonic acid is restricted to areas infested by mites in C. bacilliformis and C.
nomegica. From this follows some assumptions:
. The genetic material needed for the synthesis of a particular lichen compound may
Ue presint in a specimen without being expressed in the phen_otype. Hence, a.chemical
difference between two specimens may not neccessarily rcflect a genetic difference.
This contradics a general assumption in lichenology rccently explessed, e.g., by Brodo
(1986: 137) as 'th-e presence oiabsence of chemical compounds is an expression of
the genotype'.
. The production of some lichen substances may sometimes be qiggereq by ecological
facton- There are apparently no previous reports of ecological factors influencing the
presence or absence'of a iictreri compound., although it is well.known that light
intensity may influence the amount of cortical pigment g_odlced in many lichens
Geview'ed by Rundel l9?8, Lawrcy 1986). Carlil-(1986, 1987) has suggested from a
Uio"tr"-i""Lpoint of view that ctrimicat strains differing in the.degree of oxidation of
fhe tichen co'mpound only, such as norstictic and salazinic acid in some Uszea species,
might be due io differerit metabolic activities in plants of the same genoqrpe caused
Ui?ffo*t energy supplies of the plans. Carlin gave no evidence supporting his
theory, however.
. Ctadonia bacilliformis and C. rurttegrica are chemically more closely relate/ to the
other species of sect. Cocciferae than previously realizcd, and this suPports the current
U*ono-i" arrangement of rhe nvo species. The genetic material necded for producing
rhodocladonic aIiC occun in at least two species of subsecl Ochroleucae' although
utoUfy not expressed. The absence of rhodocladonic acid from the hymenium in this
subsection is probably the result of a rpduction.
. If so, absence of a particulal lichen compound may be a derived chafacter state'
. In this particular instance, it is temp'$ng to regard the production of rhodocladonic
acid as a iefence mechanism against furttrer grazing of the mite. The biological roles
oflichen substances have been-much debated, and an antiherbivore.role has often been
assumed @undel 1978, Lawrey 1986). It is.known that feeding and development -of
some artt[opodes, including -mites, on lichens , may_ result in formation of e3{s
(reviewed by Genon 1973). See Seyd & seaward (1984) for a comPrehensrve revrew
of the known associations of oribatid mitcs and lichens.
The distribution of Cladonia norvegica *
Ctdonia nontegica was known mainly from the humid spruce forests in 'Cenral
No"""t by Tgniberg & Holien (1934).- It was reported as new to.Sweden by Muhr
ifSSOi'-d to West-Germany by Wirth (1987I bo$ 1eporu *9t" pTd on material
;;;*1ff"id tl"dociaaonic oiA ina mites in the thallui (examined by me, but not
*See also the following PaPer by Kuusinen et a1' ' ed'