Processes shaping the distribution of foliar fungal endophyte species remain poorly understood. Despite increasing evidence that these cryptic fungal symbionts of plants mediate interactions with pathogens and herbivores, there remain basic questions regarding the extent to which dispersal limitation and host specificity might shape fungal endophyte community composition in rainforests. To assess the relative importance of spatial pattern and host specificity, we isolated fungi from a sample of mapped trees in lowland Papua New Guinea. Sequences of the internal transcribed spacer (ITS) region were obtained for 2079 fungal endophytes from three sites and clustered into molecular operational taxonomic units (MOTUs) at 95% similarity. Multivariate analyses suggest that host affinity plays a significant role in structuring endophyte community composition whereas there was no evidence of endophyte spatial pattern at the scale of tens to hundreds of metres. Differences in endophyte communities between sampled trees were weakly correlated with variation in foliar traits but not with tree species relatedness. The dominance of relatively few generalist endophytes and the presence of a large number of rare MOTUs was a consistent observation at three sites separated by hundreds of kilometres and regional turnover was low. Host specificity appears to play a relatively weak but more important role than dispersal limitation in shaping the distribution of fungal endophyte communities in New Guinea forests. Our results suggest that in the absence of strong ecological gradients and host turnover, beta diversity of endophyte communities could be low in large areas of contiguous forest.
Bibliographical noteFunding Information:
We thank I. Schmitt and D. Balhorn for their role in initiating this research, S. Sau, B. Isua, and B. Andreas for field assistance, and E. Treiber and P. Lenz for extensive laboratory work. In particular, we would like to acknowledge the contributions to the project of J. Fankhauser, a promising young scientist who left us too soon. We thank the customary landowners of Ohu, Wamangu and Wanang for providing access to their forested lands and for their commitment to forest preservation. We also thank the field assistants, students and New Guinea Binatang Research Center staff contributors to the Wanang plot census. We acknowledge the PNG Forest Research Institute, the PNG National Research Institute, the Center for Tropical Forest Science and Swire and Sons Pty. Ltd., for their partnership and support. This material is based upon work supported by the U.S. National Science Foundation under grants DEB-0816749 and DEB-0515678) and National Institutes of Health under grant ICBG 5UO1TW006671. JBV was supported by Dayton and Wilkie Fellowships from the Bell Museum of Natural History, and Crosby and Doctoral Dissertation Fellowships from the University of Minnesota Graduate School.
© 2015 John Wiley & Sons Ltd.
- DNA barcoding
- community ecology
- species interactions