Eutrophication threatens the biochemical diversity in lichens

Abstract

AbstractLichens respond sensitively to ambient nitrogen levels. Global change, which includes the increase of nitrogen-polluted environments, causes the decline of species sensitive to eutrophication, whereas some species tolerant of high nitrogen levels increase. Lichens produce hundreds of carbon-based secondary substances (so-called lichen substances), most of which are unique to the lichen symbiosis. In the present paper, correlative patterns between the eutrophication tolerance of lichen species and their secondary chemistry are analyzed using two data sets, one classifying the eutrophication tolerance of more than 500 Central European lichen species, and another of epiphytic lichens from more than 1200 plots from the Netherlands. Analyses show that, in general, the diversity of lichen secondary metabolites decreases along with increasing tolerance to eutrophication. Most notable is the reduced diversity of depsides and depsidones, the two largest groups of lichen substances, but dibenzofurans and fatty acids are also generally found in lichens sensitive to eutrophication. Conversely, anthraquinones and pulvinic acids are found most frequently in lichens from nitrogen-rich environments that can result from eutrophication. A family-wide analysis of the datasets indicates that loss of chemical diversity is not due to a single species-rich lichen family, but a characteristic of many lichen families.