Interannual variation and host affiliations of endophytic fungi associated with ferns at La Selva, Costa Rica

Abstract

Ferns are an ancient and diverse lineage of vascular plants that differ morphologically, chemically and in growth habits from the angiosperms with which they co-occur. We used a culture-based approach coupled with phylogenetic analyses to characterize the incidence, diversity and composition of fungal endophyte assemblages in ferns, with a focus on healthy aboveground tissues of seven species of eupolypods at La Selva, Costa Rica. Endophytes were isolated from every individual plant and were similarly abundant and diverse in frond blades and stalks, in different vegetation types, in epiphytic vs. terrestrial species, and between sampling years. However, abundance, diversity and community structure differed significantly among fern species, and composition differed markedly between sampling years. Phylogenetic classification using separate and combined datasets revealed that as for many Neotropical angiosperms, the majority (95%) of endophyte taxa were Ascomycota, with particular dominance by Sordariomycetes, Eurotiomycetes and Dothideomycetes. However, our data suggest higher phylogenetic richness and stronger host affinities in fern associated endophytes relative to those studied in angiosperms thus far.

• Ascomycota
• diversity
• fungal endophytes
• host affiliation
• tropical forest

Acknowledgments

We thank the College of Agriculture and Life Sciences (CALS) at the University of Arizona (UA) for supporting this work.

MD was supported by a CONACYT doctoral fellowship from the government of Mexico; CALS; and the School of Plant Sciences (UA).

We thank the Organization for Tropical Studies for supporting MD’s participation in a tropical field course on ferns, led by R. Moran, a post-course scholarship to MD that facilitated this research and logistical support in Costa Rica. We thank A. Rojas-Alvarado and S. Lobo-Cabezas from the Costa Rican National Museum for fern identification, F. Santos for assisting with field collections in 2008, A. Laetsch for assistance with DNA extractions and M. Gunatilaka, M. Hoffman, J. U’Ren, M.J. Epps, D. Sandberg, J. Riddle and R. García-Sandoval for technical assistance.