ecosystem importance: fungi's positive ecosystem effect (Introduction)

by David Turell , Friday, October 20, 2023, 19:47 (189 days ago) @ David Turell

How does an infection help? It does:

https://ecoevocommunity.nature.com/posts/mycorrhizal-fungi-influence-global-forest-dive...

"I was introduced to the Janzen-Connell hypothesis and negative conspecific density dependence (CDD) around 2015, when I was working on my Master’s degree. It was fascinating that pathogens, by definition harmful organisms, could actually generate and sustain community level plant diversity. Specialized (or relatively specialized) pathogens could create a zone of repulsion under adult trees, reducing the recruitment of their offspring, and leaving space for other species. This negative ‘conspecific density dependence’ (CDD), prevents any one species from dominating and allows a diversity of species to establish. I was working with a professor and her PhD student to see whether this applied within species – are species more successful when grown under genetically more dissimilar individuals of the same species? Because I was excited by all things mycorrhizal fungi, I was hired as a work study student to score all the seedling roots for arbuscular mycorrhizal fungi (the mycorrhizal relationship 70-80% of plant species worldwide depend on).

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"In this study, we used census data across 43 large-scale forest inventory plots worldwide, including nearly 3 million stems and over 4,000 species. Ultimately, we found that EM tree species show weaker negative CDD, likely due to greater host specificity or pathogen protection compared to tree species associating with arbuscular mycorrhizal fungi. This, coupled with the well-known global latitudinal gradient in mycorrhizal types – with ectomycorrhizal plants increasing with absolute latitude – suggests forest mycorrhizal strategy is an essential component of the overall weakening of CDD and lower tree diversity observed at higher latitudes. We also showed that both mycorrhizal types exhibit positive conmycorrhizal feedbacks, with trees benefitting from the presence of heterospecific neighbors that form the same mycorrhizal type, potentially by tapping into shared neighboring mycorrhizal fungi. This positive mycorrhizal feedback at the community level may explain why many forest stands exhibit mycorrhizal bimodality globally, with stands where both mycorrhizal strategies coexist occurring far less than expected by chance. Collectively, these findings suggest that mycorrhizal interactions may play a foundational role in global forest diversity patterns and structure. These findings bring to light the important role of the forest fungal microbiome, mutualisms, and positive feedback in maintaining global patterns of forest biodiversity." (my bold)

Comment: More evidence of how delicately it all fits together. And the underlying issue is maintaining a tenuous food supply for humans.