Genomic analysis of dispersal and adaptation in Steinpilz mushrooms

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Ectomycorrhizal fungi (EMF) are critical components of terrestrial ecosystems that play essential roles in nutrient recycling. There is a pressing need to study their population dynamics and life histories so as to better understand how ecosystems function and persist. In particular, we need to learn how EMF disperse, colonise new habitats, persist, adapt to their hosts and in the longer term speciate.The Steinpilz (Boletus edulis) is arguably the most important commercially harvested wild mushroom. It has a broad geographic distribution and has obligate mycorrhizal associations with several tree species, raising questions about whether local adaptation occurs to whichever host is locally dominant. B. edulis also tends to be locally abundant, allowing the systematic sampling of sporocarps through time.This project will exploit a large collection of B. edulis samples to deliver arguably the most comprehensive population genomic study of any wild fungus. Whole genome resequencing and state of the art population genomic approaches will be used to elucidate key processes on both ecological and evolutionary timescales.First, systematic repeated sampling of multiple woodland patches from Bielefeld (Germany) and Thetford Forest / Barnham (UK) will be used to track individuals over <11 years and to reconstruct patterns of genet turnover and local dispersal. While our sampling focuses mainly on sporocarps, ITS genotyping of root tips will also be used to confirm the presence / absence of B. edulis. Individual sighting histories will be used to test the hypothesis that genet longevity is related to genotype, with selection favouring either specific alleles or more heterozygous genotypes. We will also investigate the possibility that local adaptation to specific host trees results in biased patterns of dispersal and / or longevity.Second, we will investigate whether host specialization may be a route to ecological speciation by collecting sporocarps associated with four host trees (beech, oak, birch and pine) from four localities (Bielefeld, Thetford / Barnham, Spain and Sweden). This will allow us to test whether host-associated genets represent partially reproductively isolated host races, and if so, to identify genomic regions involved in early speciation. Replicated sampling will allow us to confirm causal relationships while excluding local candidate factors such as climate, interactions with other fungi, or abiotic factors. We will also use DNA barcoding to verify host associations and archive the dried sporocarps at the fungarium of the Senckenberg Museum of Natural History, Görlitz.Overall, this project will produce an unprecedentedly detailed picture to date of how EMF populations become established, spread and evolve. Understanding these processes is essential for predicting ecosystem responses to climate change. This project will also generate molecular resources and type specimens for future research on marketable boletes.