Niche Differentiation and Co-Occurrence Network of Fungal Communities Associated with Host Affiliations in an Extremely Arid Desert Ecosystem

Abstract

Background: Desert shrubs represent high productivity and play essential roles in maintaining the biodiversity and stability of ecosystem functioning in arid desert ecosystems. These xerophytic plants provide specific biotic and abiotic conditions for the resident specialist microorganisms. However, a robust understanding of the structural composition of the fungal microbiome associated with desert plants and especially the relationship between above- and belowground communities is currently lacking. In this study, we examined the endophytic fungal communities associated with the root, stem, and leaf tissues of five desert shrubs using Illumina MiSeq sequencing of internal transcribed spacer 2 (ITS2) sequences.Results: A total of 337 operational taxonomic units (OTUs) of endophytic fungi were identified at a 97% sequence similarity level. Pleosporales were dominant and played an irreplaceable role as keystone species in maintaining the connectivity and complexity of the fungal networks. Desert shrub identity significantly affected the community composition of the endophytic fungi in different tissues. Compared with the fungi in the aboveground tissues, root-associated fungi represented the most abundant reservoir of biodiversity in the desert habitat and displayed significantly high tissue specificity. Interestingly, the aboveground stems and leaves showed higher taxonomic overlap with underground root tissues than with each other. The root fungal network revealed the highest connectivity, and the interspecies relationships between desert fungal OTUs revealed a high percentage of co-presence rather than mutual exclusion. In addition, members of Hypocreales played a central role in connecting the above- and belowground fungal networks.Conclusions: This study represents the first example of research revealing plant-fungus endophytic associations in an extremely arid desert ecosystem with the simultaneous consideration and comparison of above- and belowground niches. Understanding the complex host-microbe interactions associated with desert plants could provide a basis for the exploitation of plant-fungus associations in the manipulation of the shrub microbiome for ecological restoration purposes.