Investigating drivers of plant-soil feedback strength in tropical tree species

Tropical rainforests support the highest plant diversity in the world. Most of this

diversity is comprised of exceedingly rare and seemingly similar tree species. Explaining

the mechanisms allowing the coexistence of so many types of trees has therefore been a

central focus of ecology for decades. An increasing body of research shows that

conspecific negative density dependence (CNDD) driven by specialist fungal natural

enemies inhibits the establishment of trees beneath conspecific adults, thereby preventing

any one species from becoming dominant. Additionally, the strength of these processes

seems to be important in influencing the local relative abundance of tree species.

However, the fungal communities driving CNDD have remained a black box due to the

difficulties associated with working with unculturable microbial species. Using modern

genetic barcoding techniques, we can now identify and quantify the fungal species

associating with tropical trees, allowing us to link fungal community composition to the

strength of CNDD in tropical forests. As a first step toward this goal, the Dirzo lab

conducted an expedition to the Los Tuxtlas Biological Preserve in 2014 to determine the

relative importance of host specificity and spatial structure in driving root associated

fungal community composition. We are currently conducting an experiment to link

root associated fungal community composition to CNDD strength across a range of host

species, focusing on differences between locally rare and abundant tree species.