engleski

Worldwide and host-dependent variation in fungal endophyte diversity in twigs of eleven tree genera

Arboreal fungal endophytes are a highly diverse group of organisms associated with asymptomatic tissues and some of them are latent pathogens. The knowledge of fungal endophytes is limited, because previous studies mainly focused on foliar fungal endophytes of a limited number of host species and locations. We assessed the fungal endophyte diversity in twigs of congeneric native and exotic tree species belonging to eleven angiosperm and gymnosperm genera in mostly temperate regions of 32 countries on six continents. We describe how host taxonomy and geographic location affect endophyte diversity and how diversity differs between native and exotic trees. More than 400 samples were collected on both hemispheres and fungal communities were assessed by high-throughput sequencing. Sampling was done in winter, because trees are mostly traded in winter, when deciduous trees lack foliage. We found around 15, 000 fungal Exact Sequence Variants (ESVs) associated with the tree genera. ESV richness varied among sampled taxa, but did not differ between native and exotic hosts. ESV richness in most of the northern hemisphere tree genera peaked at 45-50 degrees of latitude, but the pattern for southern hemisphere genera was not clear. The endophyte communities of angiosperms and gymnosperms differed ; around 30% of all ESVs were found in a single genus and less than 1% was found in all genera. Distinct geographic patterns among and within continents were found and the similarity of the endophyte communities decreased with distance between sampling locations in most genera. This study reveals fungal endophyte diversity on an unprecedented scale as a result of the wide geographic and taxonomic diversity of the samples. The geographic differences in ESVs in particular suggest that international live plant trade can facilitate the exchange of geographically isolated fungal communities, which could threaten tree-based resources in importing countries.

Arboreal fungal endophytes, n angiosperm and gymnosperm genera, fungal diversity, international plant trade

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