The species-area relationship (SAR) has been observed so frequently that it is thought to be a ubiquitous phenomenon.  However, while SARs have been quantified for many macro-organisms, the spatial scaling of microbial richness and diversity remains inherently difficult to quantify and has not successfully been characterized for most ecosystems. Our investigation was designed to characterize fungal species richness and diversity patterns across a deciduous NE Ohio forest and determine if fungal SARs exist among senesced leaf habitat patches. Leaf surface area was quantified and fungal ITS clone libraries (~ 110 clones per leaf) were generated from the largest and smallest Acer saccharum and Fagus americanus leaves gathered at two replicate sites in each of three habitats (upland, riparian, vernal pool). Diversity indices calculated from rarefaction curves were compared using a mixed model ANOVA with log-transformed leaf size used as a continuous index of patch area, and leaf species and habitat type as fixed effects. Multivariate community analysis was also used to determine if fungal community composition was affected by resources (leaf species) or location (habitat or site).
Results/Conclusions

2653 sequences containing both forward and reverse primer sequences were clustered into 97% similarity operational taxonomic units (OTUs) using BlastClust. A significant area X leaf species interaction indicated that the fungal SAR was different depending on the type of leaf patch that was colonized. Analyzing only A. saccharum leaves, there was a significant effect of leaf size, with increased diversity in larger leaves (P = 0.0534 for S_obs, P < 0.05 for Simpson and Shannon indices).  The significant SAR detected for A. saccharum had a power law z-value of 0.17. Analyzing only F. americanus leaves, there was no significant effect of leaf size on any diversity index (P > 0.1), and therefore the power law z-value on this leaf type was not significantly different from zero. Redundancy analysis showed that 21% of the variance in OTU relative abundance was explained by differences between habitats, an additional 21% was explained by site-to-site differences within habitats, and 5% was explained by leaf species (P < 0.05). Additional investigation is being conducted to help determine the cause of variation in fungal SARs among leaf species and determine whether these patterns change through an annual cycle of decomposition.