Plant migrations in response to climate changes – can fungal symbionts play a role in establishment success?

Background/Question/Methods

Climate change is prompting plants to migrate and establish novel interactions in new habitats. Because of the pivotal roles fungal symbionts have on plant health and function, it is important to understand the ecological consequences of these shifts in plant-fungi interactions with range expansion. Here we examine how the diversity of root-associated fungi varies along the host’s current range and extended range according with climate change predictions and assess the relative influence of seed provenance and environment in structuring the host fungal communities. We collected sugar maple seeds from across the species current range, then planted them in (i) temperate and (ii) mixedwood/transitional forests and in the (iii) boreal region (beyond range but predicted future range in response to climate change). We used amplicon sequencing to quantify root fungal communities and mycorrhizae to: (1) characterize and compare their community composition in sugar maple seedlings seeded across the three forest regions (2) compare the relative influence of geographic location and seed provenance on the two types of fungal communities; and (3) examine how the diversity and specialization of these fungi change across the latitudinal gradient.

Results/Conclusions

We found that variation among sites and regions were the main drivers of the differences in host fungal communities. Seed provenance played a secondary yet significant role in shaping the fungal communities. Along the latitudinal gradient, we observed a striking decrease in diversity and richness in the mutualistic arbuscular mycorrhizae fungi. Yet, there were no reductions in the diversity and richness in root-associated fungi from temperate to boreal regions. We further detected clines in host specificity with more specialization in areas within the current sugar maple range compared to beyond for the mycorrhizae and no changes in specificity were observed for general root-associated fungi. Here, we provide evidence that seedlings associate with specific fungal assemblages in the various forest regions, and therefore these differences in microbial communities can play a role in the ability of sugar maple to establish in new areas. Additionally, the different responses between the two fungal groups highlights the need for an integrated approach including the examination of various microbial groups to improve our understanding of plant range shifts and plant-microbe interactions.