Different altitudinal distributions of the two chemical varieties of Pseudevernia furfuracea collide with the conserved physiological response of transplanted lichens

Abstract

The lichen Pseudevernia furfuracea consists of two varieties, furfuracea and ceratea, which differ in secondary metabolites and geographical distribution. The aim of this work is to test the hypothesis that they also differ in altitudinal distribution possibly because they differ in some physiological responses to climatic factors. An extensive sampling was carried out in the South-eastern Alps, from 760 to 2100 m above sea level (a.s.l.), which showed that var. ceratea (with olivetoric acid, OA, as major and physodic acid, PA, as minor) is restricted to the highest altitudes, between 1500 and 2100 m, while var. furfuracea (with PA) is still widespread at the lowest altitudes. Subsequently, three areas (A-C) with different precipitation levels (A<B<C) were selected. In each area, thalli were sampled at the tree line and transplanted in situ and at four ex situ sites at 960–1090 m a.s.l. on northern and southern slopes, near and far from lakes. Chlorophyll fluorescence, malondialdehyde, and ergosterol were quantified before and after transplantation, while microclimatic conditions were monitored during exposure. After six months, the three parameters generally decreased, with no significant intervarietal difference, except for ergosterol, which was lower in var. ceratea in A,B. As these differences are negligible overall, the adaptive significance of the different chemistry of the two varieties must be interpreted as a result of different defence capabilities against herbivory, if not as a mere consequence of the accumulation of OA (a precursor of PA) caused by the climatic conditions prevailing at higher altitudes.