Fungal conservation genetics: Effects of forest fragmentation on genetic diversity in dead wood dependent fungi in space and time

During the last centuries, the boreal forests of Fennoscandia have been transformed due to various anthropogenic activities, including forestry. Natural forests have declined and become fragmented. These transformations have led to a reduction in species and populations restricted to natural-like forests. While the loss of species is well studied, much less is known about how forest loss and fragmentation have affected genetic variation within species. Within-species genetic diversity represents a basic diversity component that a sustainable nature management should protect, including genetic diversity. For this purpose, it is important to be aware of whether populations are losing genetic variation, at which rate and what are the factors underlying this decline. In the FunGen project, we are focusing on wood decay fungi of boreal forests, i.e., a group of organisms providing important ecosystem services such as nutrient cycling. Several studies have drawn attention to the decline of the diversity of wood-inhabiting fungi. For these species, reduced genetic variation may mean reduced chances of survival because of decreased fruiting rate, spore production, spore viability and stress tolerance, establishment rate, growth rate and competitive ability. Reduced genetic variation may also mean poor ability to adapt with the changing climate. In the project FunGen, we investigated how forest fragmentation has influenced population dynamics and subsequently genetic variation within wood decay fungi at different spatial scales. We have sampled ca. 300 fruiting bodies for each targeted species (4) from several populations (ca. 20) in Europe (Norway, Sweden, Finland, Poland, Estonia, and Russia). We can conclude that there are different patterns of genetic diversity, some species like Phellopilus nigrolimitatus have relatively large population sizes with weak genetic structure, while other species such as Amylocystis lapponica tend to have smaller population size with more divergence between populations, with small and isolated populations more likely to be affected by forest history (WP1 and WP2). We reintroduce three rare and threatened fungi in three southern boreal landscapes: Nordmarka, Østmarka and Telemark, totaling nine forests (WP4). This translocation experiment has been yearly monitored and will extend above the duration of FunGen. Together with Fylkesmannen I Oslo and Bymiljøetaten, we are also testing the success of species restoration for other fungi and provided guidelines and recommendations for nature management authorities. Using DNA metabarcoding, we assessed bacterial and fungal diversities present in 45 logs, prior to the translocation experiment. We observed a stronger biogeographic structuring of the fungal communities within landscape compared to the bacterial communities that were clearly more affected by forest management practices (WP4). Finally, taking advantage of the big sampling size, we dig into an understudied field of fungal ecology by revealing the fungal diversity living inside fungal fruit bodies. Our results show that fungicolous fungi can make up a large proportion of the sporocarps and that a wide, hitherto largely overlooked, diversity of partly host-specific fungicolous fungi exists (WP3). For WP1 we have finalized the sampling and will focus on three categories of the IUCN classification: least concern, near threatened and vulnerable. Our conclusions are likely to hold the focal rare and threatened species studied, as found similar trends in other wood dependent species.

FunGen has generated new empirical knowledge on how wood decay fungi have been affected genetically by forest loss and fragmentation in the Fennoscandia. Improved understanding of forestry effects on species and genetic diversity has the potential to enable better informed management and conservation decisions that account for biodiversity. We investigated if regionally extinct red-listed species can be re-introduced to their former habitats that are situated beyond the dispersal distance range and written precautionary principles. Another fundamental finding is on DNA-based assessment and biomonitoring of bacteria, fungi and insects in wood or fruit bodies, which has the potential to advance the use of this analytical tool in national monitoring programs. On a longer-term perspective, the findings and experimental designed in FunGen has allowed to build larger networking, including stakeholders, for successive multilateral research collaboration frameworks and EU-funded schemes.

Forest loss and fragmentation is recognized as one of the main global threats to biodiversity. The boreal forests of Fennoscandia have undergone dramatic changes during the last centuries, where intensive forest management and short rotation times have led to the loss and fragmentation of natural forests, resulting in biodiversity decline. However, very little is known about how genetic variation within species, the basic biodiversity component, has been affected by habitat fragmentation. FunGen aims to analyse how polypores, a group of wood-dependent fungi providing essential ecosystem services in boreal forests, have been affected genetically. First, in a broad-scale landscape genetics study, we will correlate the spatial distribution of genetic variation within common (non-red-listed) and rare (red-listed) polypore species with forest characteristics, current and historic forest connectivity, climatic and spatial data. We will also analyse genetic variation among fungaria collections. In this way we will address temporal changes in genetic variation. Secondly, by a pairwise comparison of genetic variation of fruit bodies from 12 forests (six isolated and six well-connected forests), we will address the effect of fragmentation on the current populations. Thirdly, we will assess the effect of fragmentation on the next generation populations, by analysing airborne spores. Finally, we will investigate whether populations of red-listed fungal species can be restored by placing inoculated wood pieces in old-growth and culture forests. The population genetic analyses will mainly use a high throughput sequencing approach (RADseq). The project will provide new knowledge about how genetic variation is affected by habitat fragmentation. In addition to running costs, we apply funding for two post doctoral positions (3+2 years) to accomplish our goals. An interdisciplinary team of national and international experts have been assembled to carry out this ambitious project.