Intrathalline Variation in Concentration of Lichen Substances in Pseudevernia furfuracea

Abstract

In Pseudevernia furfuracea olivetoric acid and atranorin decrease toward the base of the laciniae while physodic and chloratranorin increase. Oxyphysodic acid shows a contrasting pattern of intrathalline distribution: when olivetoric acid is absent (chemical race I) it decreases from the apex to the base of the laciniae, but when olivetoric acid is present (chemical races II and IV) the relative concentration of oxyphysodic acid increases in the same direction. Biogenetic considerations of these lichen products and some hypotheses of the origin of chemical variation in this species are discussed. For many years Pseudevernia furfuracea (L.) Zopf has been the subject of numerous chemical studies such as those developed by Culberson (1965) and Culberson et al. (1977). Current evidence suggests that in this species there are three races, having either physodic acid (race I), olivetoric acid (race III), or both (race II), as the major substances in the medulla. Moreover, some studies have attempted to correlate this chemical variation with ecological or geograph- ical factors (Hale 1968; Halvorsen & Bendiksen 1982; Hawksworth & Chapman 1971), but only a corre- lation with the distribution of the chemical races in an European northwestern-southeastern gradient has been observed. Oxyphysodic acid (3-hydroxyphysodic acid) is an- other substance found in P. furfuracea thalli and it is usually associated with physodic acid, although it is not always detected in chemical strain II, where olivetoric acid is present as well (C. Culberson, pers. comm. 1987). Culberson et al. (1977) did not detect this acid with physodic and olivetoric acids in spec- imens of the latter race. The low sensitivity of TLC may be responsible for this, but alternatively the con- centration of oxyphysodic acid could vary signifi- cantly along the laciniae, or even be absent in places, depending on the physiological activity of each part of the thallus. In a previous paper (L6pez & Manrique 1989) we described a new infrequent (1.3%) chemical race in Spain that contains olivetoric, physodic, and oxy- physodic acids together (race IV). For this reason we decided to investigate more thoroughly the chemistry of P. furfuracea. Intraspecific variation in chemistry as well as variations in substance concentration with-