Leaf microbiomes are a neighborhood affair in northern forests

December 03, 2020

Forest leaves are teeming with bacterial life - but despite the vast extent of bacteria-covered foliage across the world, this habitat, known as the phyllosphere, remains full of mysteries. How do bacteria spread from tree to tree? Do certain types of bacteria only live on certain types of trees?

A new paper published in the Ecological Society of America's journal Ecological Monographs addresses some of these questions. The findings reveal that the leaf microbiomes of sugar maple trees vary across the species' range, changing in accordance with the types of trees in the surrounding "neighborhood."

Geneviève Lajoie, now a post-doctoral researcher at the University of British Columbia and the paper's lead author, performed the research as a Ph.D. student at the Université du Québec à Montréal. She and her field assistant spent a summer in hot pursuit of bacteria-covered foliage, camping at remote parks and rushing to get their leaf samples back to the lab for analysis before new conditions altered the leaves' resident microbes.

The team sampled foliage at sites across Québec, Ontario and the northeastern United States. Lajoie's analysis zeroed in on the iconic sugar maple - a species that is abundant at the southern end of the study range, but tapers off at more northern latitudes where conifers dominate the landscape. In fact, at the northern reaches of the study range, at sites like Monts-Valin National Park, sugar maples become anomalous enough that tracking them down among their evergreen neighbors was a challenge.

"To reach the site, we drove up north from Québec City and witnessed the gradual transition from the mixed deciduous forest of the Saint Lawrence Valley to a boreal landscape dominated by conifers," Lajoie said. "Going sampling over the next days, we were looking for sugar maple populations - our focal species. Even though we knew it could be found in the park despite it being the northern limit of its range, encountering these beautiful trees seemingly out of place but still thriving were particularly amazing moments for me."

However, despite being outliers on a conifer-dominated landscape, these northernmost sugar maple trees had adopted leaf microbiomes that blended in with their coniferous neighbors. LaJoie found a pattern along the latitudinal gradient of her study area: southern sugar maples, which are surrounded by lots of other sugar maples, tended to share a relatively similar microbiome - one that was distinct from other tree species in the area. But in more northern areas, where sugar maple trees are few and far between, the species hosted bacterial communities that resembled the microbiomes of other more dominant species.

The observations echo similar patterns that have been observed among animal microbiomes. Ground-dwelling animals, for instance, tend to have relatively similar microbiomes, possibly through increased contact with the feces of other animals, while canopy-dwelling animals have gut microbiomes that are less similar to each other.

While gut microbiomes are a hot research topic in the human health sciences, the forest phyllosphere remains a study system that is not well understood - and according to Lajoie, the fields of plant ecology and microbiology have been growing mostly in parallel for many years. This study's findings provide a more complete picture of the plant-microbe relationship: what kinds of bacteria go on which trees, and how this pattern varies depending on how well a tree fits in with the crowd.
Journal article:
Lajoie, Geneviève, and Kembel, Steven W. 2020. "Host neighborhood shapes bacterial community assembly and specialization on tree species across a latitudinal gradient." doi.org/10.1002/ecm.1443

Geneviève Lajoie1,2 and Steven W. Kembel11Département des sciences biologiques, Université du Québec à Montréal, Montréal, QC, Canada; 2Department of Botany, University of British Columbia, Vancouver, BC, Canada

Author contact:
Geneviève Lajoie

The Ecological Society of America, founded in 1915, is the world's largest community of professional ecologists and a trusted source of ecological knowledge, committed to advancing the understanding of life on Earth. The 9,000 member Society publishes five journals and a membership bulletin and broadly shares ecological information through policy, media outreach, and education initiatives. The Society's Annual Meeting attracts 4,000 attendees and features the most recent advances in ecological science. Visit the ESA website at https://www.esa.org.


Ecological Society of America

Related Bacteria Articles from Brightsurf:

Siblings can also differ from one another in bacteria
A research team from the University of Tübingen and the German Center for Infection Research (DZIF) is investigating how pathogens influence the immune response of their host with genetic variation.

How bacteria fertilize soya
Soya and clover have their very own fertiliser factories in their roots, where bacteria manufacture ammonium, which is crucial for plant growth.

Bacteria might help other bacteria to tolerate antibiotics better
A new paper by the Dynamical Systems Biology lab at UPF shows that the response by bacteria to antibiotics may depend on other species of bacteria they live with, in such a way that some bacteria may make others more tolerant to antibiotics.

Two-faced bacteria
The gut microbiome, which is a collection of numerous beneficial bacteria species, is key to our overall well-being and good health.

Microcensus in bacteria
Bacillus subtilis can determine proportions of different groups within a mixed population.

Right beneath the skin we all have the same bacteria
In the dermis skin layer, the same bacteria are found across age and gender.

Bacteria must be 'stressed out' to divide
Bacterial cell division is controlled by both enzymatic activity and mechanical forces, which work together to control its timing and location, a new study from EPFL finds.

How bees live with bacteria
More than 90 percent of all bee species are not organized in colonies, but fight their way through life alone.

The bacteria building your baby
Australian researchers have laid to rest a longstanding controversy: is the womb sterile?

Hopping bacteria
Scientists have long known that key models of bacterial movement in real-world conditions are flawed.

Read More: Bacteria News and Bacteria Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.