Conclusion
Although foliar fungal endophyte community assembly within this natural system was structured by deterministic selective forces (particularly host identity), there was no consistent evidence of deterministic successional trends in endophyte communities. A fair amount of variation in endophyte community composition remained unexplained. This could be due to several reasons. Variables which were not measured here, e.g. competitive interactions between endophyte species (Crowther et al. , 2014), could be more important for structuring endophyte communities. Alternatively, stochastic processes of community assembly may have been more important than deterministic processes in structuring foliar fungal endophyte composition (Hubbell, 2001). These stochastic processes include drift, dispersal limitation, speciation and extinction events acting together to shape the observed community composition (Vellend, 2010). Additionally, the scale at which endophyte communities were quantified may not accurately reflect the scale at which processes of endophyte community assembly are operating and thus ultimately obscure our ability to detect strong patterns (Harrison and Griffin, 2020). Thus, continued work to gain a deeper understanding of how fungal endophyte communities organise themselves through space and across time within natural systems will be essential to appreciate the functions and ultimately the ecosystem services these microbes are able to deliver.