Biodiversity in the dark: root-associated fungi in the Arctic

Abstract

In her PhD thesis, Synnøve Smebye Botnen investigated the diversity and community ecology of Arctic fungi, from beforehand a poorly studied group of organisms. Climate change will have major impacts on Arctic ecosystems and in this regard, we need baseline information about the existing and putatively unique arctic biodiversity. As elsewhere, arctic plants live in symbiosis with various root-associated fungi that e.g. feed the host plants with essential nutrients. To assess the diversity of these fungi in the arctic, and which environmental factors influence them, Botnen used a technique called DNA-metabarcoding, relying on modern high-throughput DNA sequencing methods. Her main study area was Svalbard. The DNA-based methods revealed an extensive diversity of root-associated fungi in the arctic, where the majority still are lacking scientific names. To illustrate, a single plant root system at Svalbard may host as many fungi as the number of plant species at entire Svalbard. Only a minor proportion of these fungi produce macroscopically aboveground fruit bodies. Botnen revealed that climate conditions have a significant effect on the distribution of arctic fungi, as well as other environmental factors. This means that the ongoing climate change will re-distribute the fungal diversity. Not only the physical environment shapes the fungal communities; Botnen revealed that some types of root-associated fungi can be highly host specific. However, when it comes to ectomycorrhizal fungi – one specific group of root-associated fungi – Botnen revealed that they typically colonize different host plants and show little host specificity. In addition to empirical studies, Botnen also conducted a method study, where specific elements of the DNA-metabarcoding approach was evaluated. These analyses revealed that the DNA-metabarcoding method provides a very robust framework to study changes in communities of fungi and microorganisms. Taken together, results from the thesis provides baseline information about the extensive diversity of arctic fungi. This baseline information is much needed to better understand the expected changes in arctic ecosystems. However, most of all, the thesis illustrates that we barely have scraped the surface of this largely unknown fungal diversity, calling for intensified research efforts on this topic.