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Browsing by Subject "Pathogenicity"

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    Terrestrial Rhizomorphic Species Of The Polyporaceae Family In The Yasuní National Park In Ecuador: Taxonomy, Life History And Pathogenicity Traits
    (2023-09) Toapanta, Cristina
    The Yasuní National Park is the biggest natural reserve in the Amazon of Ecuador with an area of 9,829 km2. This tropical rainforest received the world’s interest for the oil reserves it holds, the presence of indigenous communities living in voluntary isolation, and the remarkable biodiversity present in this area. Those qualities have resulted in numerous conflicts between the indigenous communities, illegal loggers, and the personnel of oil companies. Despite the conflicts, the diversity of animals and plants has been widely explored and the result of those investigations has positioned this forest among the most biodiverse places on Earth; however, little is known about the diversity of fungi, despite the numerous and important roles they play to maintain the equilibrium of forest ecosystems. To provide information about the diversity of fungi in this forest, the diversity of an important group of fungi within the Polyporaceae family has been studied. The focus was on fungi capable of developing above-ground rhizomorphs. This study took place in the 50-ha Yasuní Forest Dynamic Plot. At this location a random stratified sampling method was used to survey and collect basidiocarps and rhizomorphs, phylogenetic analyses were conducted, and macro and micro morphological descriptions were made. Pure isolates were obtained as well to provide cultural characterization of the taxa present in Yasuní. Four new species were described, Atroporus yasuniensis, Atroporus tagaeri, Neodictyopus sylvaticus, and Polyporus taromenane, and a new variety Polyporus leprieurii var. yasuniensis. This adds new information and essential knowledge about an important group of little-known fungi inhabiting the forest floor of this highly diverse ecosystem. Another objective of this research was to identify the species that have abundance and distribution patterns for ‘core-species’. In-situ observations and surveys showed that Polyporus leprieurii var. yasuniensis is highly abundant and well-distributed along all topographic habitats in Yasuní, including ridges, slopes, and valleys. To identify the biological and ecological characteristics that made this fungus so prevalent in this ecosystem, in-situ and ex-situ investigations were carried out to explore its wood-decay capacity on eleven species of tropical woods; its response in dual competition studies against sixteen fungal isolates obtained from the forest; the capacity it has to withstand harsh environmental conditions like droughts and floods; and the ability of rhizomorphs to sequestrate metal ions from the environment. The results obtained demonstrated that P. leprieurii var. yasuniensis has a broad decay capacity in tropical woods. Being able to produce biomass loss on high and low-density woods, with most mass loss reported on low density wood. It was also reported that the production of sclerotial plates and the development of melanized mycelium are important defense mechanisms used by this fungus to inhibit the growth of antagonist fungi. In-situ and ex-situ observations demonstrated that this fungus can remain active for long periods under challenging environmental conditions, as long as it remains attached to its substrate. Finally, metal ion sequestration by rhizomorphs was confirmed with high concentrations of metal ions present on rhizomorphs as compared to its woody substrate. This portion of the research adds knowledge to understand the biological and ecological traits behind this highly adapted fungus. Lastly, because of the interaction P. leprieurii var. yasuniensis has with trees by the formation of rhizomorphs and mycelium mats on tree surfaces, surveys among the colonized living and dead substrates were performed to identify host preference. Additionally, due to the similarities this fungus shares with Armillaria spp. (production of melanized rhizomorphs and wide wood decay capacities), Koch’s postulates were carried out on four species of tropical trees (Ochroma pyramidale, Schizolobium parahyba, Tectona grandis, and Gmelina arborea) by inoculating trees with fungus-colonized wood, fresh rhizomorphs, or uncolonized wood for controls. Due to the small number of observations on living and dead substrates, statistical analyses were not run to find significant associations between the taxa of hosts and substrates. However, it was observed that the fungus can be present in common and rare taxa of trees, suggesting its association with trees could be stochastic. On the other hand, Koch’s postulates were not proven but it was confirmed that the fungus-infected wood inoculum and fresh rhizomorphs can successfully attach to plants. Additionally, the decay symptoms on the wounds of trees and the incidence of highly abundant sites accompanied by fully colonized trees (mother trees), suggest this fungus could exhibit a pathogenic lifestyle under still undiscovered conditions. This research has provided valuable information about the taxonomy, biology, and ecology of a fungus with abundance and distribution patterns for ‘core-species’. This adds information to understand the forest dynamics of Yasuní, a sensitive ecosystem that is prone to rapid and drastic changes induced by land transformation and the effects of climate change.