Leaf traits and host plant-fungal endophyte associations in a tropical forest

Background/Question/Methods

Foliar fungal endophytes are abundant and diverse in the leaves of tropical plants. Their presence can reduce herbivory and pathogen damage. However, factors affecting the species composition of fungal- host assemblages are poorly understood.  Previous studies often do not adequately control for confounding effects of local site (source pool of fungal spores), leaf age, light regime, or host species attributes on relative abundances of endophyte species across different host plant species. In order to address these questions, we studied the colonization and diversity of endophytic fungi associated with eight host plant species growing intermixed over 18 months in a common garden under high and low light regimes in the Barro Colorado Nature Monument.  

Results/Conclusions

We found that the identities and relative abundance of dominant endophyte species varied across different host species. Endophyte diversity decreased with increasing leaf age, suggesting succession of the fungal communities within each leaf. We also found dramatic differences in culturable endophyte abundances across host plants species and across study years. Endophyte abundance but not diversity varied with light environment, with the response to light environment differing across plant host species. Endophyte abundance was negatively correlated with maximum photosynthesis rate and leaf toughness, but no relationship was observed between endophyte abundance and nitrogen content, insect herbivory or phenolic content. We discuss how host plant life-history trade-offs, local source pools of fungal spores, and light regimes may affect the relationships among tropical host plants and their fungal symbionts.