The important role of northern flying squirrels (Glaucomys sabrinus) for fungal spore dispersal

Background/Question/Methods

Northern flying squirrels (Glaucomys sabrinus) are keystone species as they consume fungi and facilitate the dispersal of fungal spores. The spores remain viable post-digestion in the fecal pellets which allows plant rootlets far from the original fungi to be inoculated; therefore northern flying squirrels facilitate the growth of mycorrhizae and vascular plants. Given shifting distributions of northern flying squirrels and the closely related southern flying squirrels (G. volans), a seed generalist, we wished to understand the implications of turnover in squirrel species on mycorrhizal networks. We hypothesized that at a sympatric site where food availability is consistent between groups, the dietary differences will show the evolved preferences; northern flying squirrels will rely on fungal taxa and be most active in areas with higher fungal diversity whereas southern flying squirrels will depend upon mast seeds and be found within mast crop habitats. We quantified the relative frequency of spores in over 100 fecal pellets of both northern and southern flying squirrels. We deployed 30 radio collars on flying squirrels and surveyed for fungal fruiting bodies (mushrooms and truffles) over six months. Using the home range from each individual squirrel, we created maps of the relative use of available habitats.

Results/Conclusions

We identified a higher proportion of fungal spores, specifically truffle spores, in northern flying squirrel fecal pellets compared to southern flying squirrels. Among both species, truffle spores appeared more frequently within the individual pellets compared to other mushroom spores. Moreover, we found a temporal association in both species between high fungal consumption, measured via overall spore load, and the availability of fungal fruiting bodies. Northern flying squirrels were spatially associated with fungal communities and areas of the woodlot that support the growth of mushrooms and truffles. Comparatively, southern flying squirrels were associated with fluctuations in mast seed abundance and found in proximity to habitats that support seed crops. Our findings suggest that northern flying squirrels can be important dispersers for fungal fruiting bodies, especially for truffles, throughout woodlots. In contrast, southern flying squirrels are more reliant on tree seeds and played a lesser role in the dispersal of fungal spores. These implications should be considered for determining strategies on how we can best manage our forests for future conservation.