Spatial trends in usnic acid concentrations of the lichen Flavocetraria nivalis along local climatic gradients in the Arctic (Kongsfjorden, Svalbard)

The dibenzofuran usnic acid is an important secondary lichen metabolite, having many postulated biological roles, but evidence from field surveys is scanty. Trends in usnic acid concentrations and lobe width in the arctic lichen Flavocetraria nivalis were analysed along local longitudinal and altitudinal gradients in the Kongsfjorden area, northwestern Spitsbergen. Temperature was measured along the same gradients during 1 year. Other environmental variables were also estimated. The model that best explains the variability in usnic-acid levels includes the parameters effective temperature sum, frost sum and temperature range. Temperature range indicates a relationship between high usnic acid levels and humidity, whereas the two first parameters indicate a relationship with low temperatures, which could be direct or indirect. Much of the variability in usnic acid levels and lobe width could not be explained by the selected models. Thus, the secondary metabolism and lobe growth in this lichen is a complex matter, involving numerous environmental and possibly also intrinsic factors.