IMC11 Programme Book 1.2-177 Population genomics of the globetrotter Serpula lacrymans reveal tight bottleneck and local adaptations. I. Skrede1, C. Murat2, J. Hess1, J.H. Sønstebø1, S. Maurice1, A. Kohler2, D. Barry3, N. Högberg4, D. C. Eastwood5, F. Martin2, H. Kauserud1 1Department of Biosciences, University of Oslo, Oslo, NORWAY, 2Interactions Arbres- microorganismes, INRA-Lorraine University, Champenoux, FRANCE, 3Alcina, Montpellier, FRANCE, 4Department of Forest Pathology, Swedish Agricultural University, Uppsala, SWEDEN, 5Department of Biosciences, University of Swansea, Swansea, UNITED KINGDOM Abstract: The bolete Serpula lacrymans is likely the most devastating fungal wood-decayer of construction materials in temperate regions worldwide. From its native range in North East Asia is has spread to most other continents, including Europe and Southern Oceania, as well as other parts of Asia (Japan). In this study, we performed population genomics analyses of 39 isolates from these three regions in order to assess differences across the invasive populations. More specific, we wanted to analyse the demographic history and level of intra-geographic structuring and local adaptations in the invasive populations. The three populations, Europe, Japan and New Zealand (the latter only represented by three isolates) were strongly differentiated. The European population had clearly gone through a tight bottleneck during its establishment while the Japanese population is far more diverse. Long genomic blocks without genetic diversity in Europe suggest a single founding event, with no secondary migration from the native regions. In both regions, there was a clear geographic substructuring, indicating dispersal limitations. Coalescence simulations was used to study the time since the populations diverged and the changes in effective population size. In scans for genetic adaptations in the two populations, we identified three outlier loci subject to purifying selection. These were linked to transport and decay, and support that these functions are particularly important in the human-made habitats of S. lacrymans worldwide. Of the three isolates from New Zealand, one had an admixed genomic make up with genetic elements from both the European and the Japanese populations. Since the original ‘out of Asia’ dispersal events, our analyses indicate that the dry rot fungus has travelled between continents, also giving rise to admixed genotypes.

CONIFERAE. Agathis australis: Auckland City. Dacrydium cupressinum: Canterbury, Christchurch. Pinus radiata: Wellington, city. Podocarpus spicatus: Wellington, city; Wallaceville. UNKNOWN HOSTS. Auckland, Mt. Albert; Mt. Eden; Sandringham.

Hymenophore pileate or more usually resupinate, when pileate pilei effused-reflexed, when resupinate indefinite in size and shape, membranous, loosely attached; hymenial surface ferruginous, irregular, sometimes plane, rugose, nodulose, or coarsely reticulate when pores are angular, 1-4 mm diameter, reticulations entire, to 1 mm tall, edges somewhat acute; margin indefinite, with abundant coarse rhizomorphs. Context at first white, drying grey or various shades of brown, 0.5-5 mm thick, basal layer duplex, of hyphae to 8 µm diameter, walls chestnut and so thickened that lumena are capillary, sparsely branched, septate with one or two clamp connections at septa, often with brief lateral, coralloid branches arising from them, intermediate layer of hyaline hyphae of two types (1) 7-8 µm diameter, walls 1-2.5 µm thick, or so thickened that lumena are capillary (2) 3-4 µm diameter, walls 0.5 µm thick, both freely branched, septate, with clamp connections. Hymenial layer to 100 µm deep, a close palisade of basidia and paraphyses, separated from the context by a dense intertwined layer of hyaline hyphae. Basidia clavate, 20-28 x 4-6 µm, bearing 4 spores; sterigmata slightly arcuate, slender, to 6 µm long. Paraphyses subclavate, 16-24 x 4-5 µm. Spores elliptical or slightly obovate, sometimes flattened on one side, 8-12.5 x 4.5-6 µm walls smooth, chestnut or ferruginous, 0.25 µm thick.

DISTRIBUTION: Common in temperate and subtropical regions.

HABITAT: Effused on building timbers in confined areas, causing a destructive brown cubical rot, and from timber spreading to adjacent masonry, soil, etc.

Although only a few collections are stored in the herbarium, S. lacrymans is common throughout New Zealand, and causes a decay of building timber brought in contact with moisture, or inadequately ventilated. It is equally destructive to boxes and woodwork in glasshouses, cool frames, and the like. Specimens vary appreciably in appearance and size, and configuration of the hymenial surface, according to the conditions under which they have developed. Some may appear as thick, effused-reflexed or dimidiate pilei, most are resupinate often appearing as large sheets with rhizomorphs which may project for metres beyond margins of fructifications. The hymenial surface may be conspicuously porose-reticulate, gyrose when resembling certain species of Phlebia, or plane.

TYPE LOCALITY: Europe.