Hidden Diversity: Foliar Endophytic Fungi in Coexisting Mexican Oaks

Goretty Mendoza Juárez, Roberto Garibay Orijel, Bernardo Águila Salgado, Yesenia Vega Sánchez, Felipe García Oliva, and Antonio González Rodríguez

Published May 2026 in International Oaks No. 37: 1497–156

Abstract

Microorganisms are natural components in ecosystems and their association with plants is thought to have originated 400 million years ago, with the establishment of the first terrestrial plants. Since then, complex biological interactions between hosts and microorganisms have emerged. For example, foliar endophytic fungi (FEF), which live inside leaves without causing visible symptoms, can enhance stress tolerance in their hosts, improve nutrient acquisition, and provide protection against pathogens. Given that oaks are conspicuous hosts of FEF in Mexico’s temperate forests, and that oaks in section Quercus (White Oaks) and in section Lobatae (Red Oaks) frequently coexist, there is a wide range of distinct microhabitats for the establishment of different fungal groups. Therefore, in this study we aimed to evaluate if phylogenetically close groups of oaks (i.e., belonging to the same section) harbor phylogenetically close groups of FEF. To this end, we extracted leaf DNA from White and Red Oaks in the Cuitzeo Basin, Michoacán, to identify fungal groups through metabarcoding techniques based on next-generation sequencing of the Internal Transcribed Spacer (ITS) region. Additionally, we measured 14 foliar oak traits as potential drivers of FEF community composition. Our results showed evidence of phylogenetic differentiation of FEF communities across oak sections and particularly between the widely co-occurring Q. castanea (a Red Oak) and Q. obtusata (a White Oak). Leaf tannin concentration, total nitrogen concentration, total phosphorus concentration, and C:N and C:P ratios were the foliar traits that influenced phylogenetic composition of FEF communities. Our results highlight the importance of phylogenetic relatedness among host trees and their traits in shaping endophytic microbial communities in temperate forest ecosystems.

Keywords

biological interactions, functional traits, microhabitats, phylogenetic relatedness

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