Studying the Ecology of a Rhizomorphic Fungal Species in the Amazon Rainforest

By: Cristina Toapanta, Plant Pathology Graduate Student

Plant Pathology Graduate Student Cristina ToapantaAll organisms in the natural world have an important and unique role, or niche, they play in the ecosystems they belong to. How do you fully understand and reveal the role of an organism in the rainforest, one of the most complex and biodiverse ecosystems in the world? For me, my challenge is to unveil the role of a fungus found throughout the rainforest in Yasuní National Park in Ecuador, its role in nutrient cycling in this ecosystem, and to what extent it is involved in the death of several tree species.

As a forest pathologist originally from Ecuador, this is a challenge I wholeheartedly embrace since I have a unique opportunity to work in this amazing forest ecosystem and to help tell the story of this important fungus. What I reveal from my research is my way to give back to the local people and the forest, while also helping others understand the importance that fungi play in life.

The fungus I study is placed within the Polyporus genus. Polyporus and other wood decay fungi are well known for producing secondary metabolites and other compounds that can be useful for bioremediation, prospecting and medicinal purposes. If you look around the forest you can see the presence of wood decay fungi all over the surfaces of trees and the forest floor as they are vigorous colonizers of the rainforest. Since Polyporus can be found ubiquitously throughout gaps in the forest and it may appear to be playing a significant role in this ecosystem, my research is ultimately trying to specifically piece together what that role is.

Plant Pathology Graduate Student Cristina ToapantaTo answer these questions, we started working on the taxonomy of this group to recognize the particular morphological features of the rhizomorphic species of Polyporus while understanding the phylogenetic relations within the group and other related taxa. The phylogenetic work is crucial to place this group of fungi in an evolutionary context based on the strategies the group has evolved to successfully occupy a niche in the forest ecosystem. Although we found areas in the forest with abundant rhizomorphs on wood debris and living trees, there are areas where it is not ubiquitous. For this reason, we would like to recognize which abiotic and biotic factors lead to abundant colonization of rhizomorphs. We are also looking at soil data regarding nutrient distribution, topography and other environmental variables, in order to model the potential niche of this fungus in this forest ecosystem.

My fieldwork has involved searching for trees colonized with rhizomorphs to identify symptoms after the rhizomorphs colonize trees. Fortunately, we have been able to follow up on those trees to observe disease progress on the susceptible hosts. In order to measure the role of this fungus in the carbon cycle in the forest, other assays in the laboratory are investigating decay rates in different types of wood. Parallel tests include the addition of particular nutrients to culturing media to assess the growth and development of this fungus. Ultimately, these assays will help us understand the unique processes involved in the development and growth of this fungus.

Plant Pathology Graduate Student Cristina ToapantaThe amount of work in the field and laboratory can be exhausting and sometimes overwhelming, but what motivates me is my love for the forest.

Hopefully, at the conclusion of my research, I will be able to understand the biology and ecology of this fungus and this information will be used for forest dynamic studies and for bioprospecting purposes. Optimistically, one day I will be able to achieve my research goals and help preserve the forest while helping the indigenous communities in Yasuní. The way we can achieve this is by staying focused on the research goals and above all being respectful to the people and the forest where we are working.