Seagrass‐associated fungal communities follow Wallace's line, but host genotype does not structure fungal community

AIM: To test whether or not fungal communities associated with the widespread seagrass, Syringodium isoetifolium can be differentiated on either side of Wallace's line, a boundary line separating Asian and Australasian fauna. Additionally, we examine whether host multilocus genotype predicts fungal community composition. LOCATION: A total of 77 samples were collected from 14 sampling sites spanning the Indonesian archipelago. METHODS: We sequenced the fungal ITS1 gene using Illumia MiSeq technology and used a clustering‐free Divisive Amplicon Denoising Algorithm to infer ribosomal sequence variants. Data were analysed via non‐metric multidimensional scaling, Mantel tests and permutational multivariate analysis of variance. Binary and quantitative null models were used to determine whether results significantly deviated from random. Host genotype was determined by genotyping at 18 microsatellite loci and standard genetic analysis was performed in the R package APE. RESULTS: Significant differences in fungal community composition were detected on either side of Wallace's line (p = <.001 R² = .040). A significant distance decay of similarity pattern was observed between ribosomal sequence variants and geographical distance (p = .001 R² = .227) and several fungal ribosomal sequence variants were significantly associated with sampling sites found either east or west of Wallace's line. MAIN CONCLUSIONS: Fungi are generally considered to have excellent dispersal potentials and marine fungi have the potential to disperse far and wide in an environment that has no obvious barriers to dispersal. Despite this assumed excellent dispersal potential, we show that fungal communities on either side of Wallace's line are significantly different from one another. We speculate that limited dispersal and differences in habitat type are responsible for the observed pattern. Work examining biogeographical patterns in marine fungi is still in its infancy and further research is required to fully understand marine fungal biogeography.