Ohia Fungal Endophytes on Oahu

Fungal endophyte (FE) communities may be influenced not only by abiotic environmental conditions, but also by varying degrees of affinity to their host plants. The landscape-dominant woody genus Metrosideros (Myrtaceae) contains many morphologically distinct taxa that occupy different habitats throughout the Hawaiian Islands. This study used Metrosideros along an elevation gradient on O'ahu to test the relative importance of environment versus host taxon on FE composition and diversity. Variation in FE communities due to geographic distance (across and within sites) was also examined. The fungal ITS1 region was sequenced from surface-sterilized leaf samples (N=176). Analyses revealed that variation in FE diversity was significantly explained by Metrosideros taxon, site, and geographic distance. Considerable overlap in FE communities among host taxa and among sites was detected, however, and evidence for host-specificity of leaf FEs was weak and restricted to 700-1,000 m above sea level. FE communities did not vary with elevation (environment); however, the elevation ranges examined may be too narrow for the detection of elevation/environmental effects. Lastly, a significant pattern of isolation by distance on FE community composition was detected across the island as well as within each of the four sites. These results suggest that within O'ahu Metrosideros, leaf FE communities vary in diversity and composition across space, some of this variation is associated with host taxonomic effects and distance, and very little is associated with environmental variation across the island's elevation gradients.