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.