Circumboreal lichen diversification

Abstract. Lichens are one of the most important groups of organisms for monitoring environmental change, yet little is known about their worldwide diversity patterns. In higher plants, by contrast, there are well known patterns of Tertiary diversification and range fragmentation and Pleistocene extinctions and range shifts that have resulted in the vegetation patterns and world diversity hotspots we know today. It might be assumed that tree-dwelling lichen species follow similar distribution patterns, but the evidence is that this is not always the case. In particular, we note that while there are many lichen species that occur in East Asia and eastern North America (in agreement with many plants), there are also many species that occur in western North America and western Europe. The latter distribution is rare in plants at upper latitudes, and conspicuously at odds with the distribution of the trees on which epiphytic lichens grow. Circumboreal species are often treated as a distinct distributional type because they are found in all four regions, but it is possible that they conceal similar patterns of diversification in their DNA. We propose examining genetic structure within a model species of the boreal forest, Mycoblastus sanguinarius, in four different parts of its range: East Asia, western and eastern North America, and Europe. Specifically we will examine whether relationship patterns are congruent with the ‘East-East, West-West’ distribution types of many lichen species and to what extent its modern distribution and genetic diversity centers diverge from those of its common substrate trees. The results will be an important contribution to understanding diversification patterns and gene flow in a representative species.