Fungal endophyte diversity in tundra grasses increases by grazing

•Tundra grasses at 70°N are hosts to a diversity of fungal endophytes.•Reindeer and small rodents promotes the diversity of these fungal endophytes.•Laser dissection of stained endophytes represent a method for the exploration of fungal endophytes.

Fungal endophytes are species rich and ubiquitous, yet, apart from the genus Epichloë, their ecology is largely unknown. Here we explore how herbivores affect the diversity of fungal endophytes in tundra grasslands. We assess both hyphal morphological and taxonomic diversity in grass individuals.By microscopic examination we identified endophytes to be present in all sampled grass individuals whereas identification to taxonomic units were only achieved in a subset of the individuals using laser micro dissection pressure catapulting and culturing for endophyte isolation. Hyphal morphological diversity was significantly higher in grasses exposed to grazing, along with 45 % more taxonomic units achieved.Our results suggest that grazing is an important mediator of fungal endophyte diversity in tundra grasslands. Furthermore, we suggest laser dissection of stained endophytes as a method for further exploring the ecological role of fungal endophytes.