URen, Jana M. , Lutzoni, Francois , Miadlikowska, Jolanta , Arnold, A.E. .
Community analysis of symbiotrophic and saprotrophic Ascomycota from multiple biogeographic provinces reveals the ecological novelty of the endolichenic symbiosis.
Endophytic and endolichenic fungi occur in healthy tissues of every plant and lichen species surveyed to date, forming symbioses in a range of terrestrial communities. Phylogenetic analyses suggest a close evolutionary relationship between these guilds, but to date, sampling has been insufficient to diagnose the similarity or distinctiveness of these symbiotrophs relative both to each other and to co-occurring saprotrophs. We examined the diversity, ecology, and evolutionary connections among endophytes, endolichenic fungi, and fungi from dead leaves in tree canopies and leaf litter in Arizona (Chiricahua Mountains), North Carolina (Appalachian Mountains) and Florida (subtropical scrub forest). ITS rDNA sequences of 2700 symbiotrophic fungi from 10 lichen and 10 plant species per site, and 1400 saprotrophs from four plant species per site, revealed a surprisingly high diversity of symbionts relative to those associated with senescent tissues, as well as an association between community-level diversity and phylogenetic dispersion among hosts. Each major host lineage was dominated by different classes of Pezizomycotina, with the congruence among plant and fungal phylogenies in temperate sites suggesting diffuse coevolution between plants and fungi. In general, endophytes and endolichenic fungi were taxonomically similar, but endolichenic fungi were more similar to endophytes from bryophytes than from conifers, ferns or angiosperms. Endolichenic fungi had consistently low similarity to saprotrophic fungi, whereas endophytes had a higher degree of overlap to fungi from senescent leaves. However, leaf litter contained numerous fungi that were never found among symbiotrophs. Our data suggest that endophytic fungi act as an ‘ecological nexus’ connecting otherwise distinct assemblages of endolichenic and saprotrophic fungi, and that endophytism represents an ecologically and evolutionarily more flexible symbiosis relative to endolichenic associations. These data also underscore the evolutionary distinctiveness of symbiotrophs relative to saprotrophic taxa. Additional analyses will examine biogeographic factors that structure these diverse fungal communities.
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1 - University of Arizona, Division of Plant Pathology and Microbiology, Dept. of Plant Sciences, 1140 E. South Campus Drive, P.O. Box 210036, Tucson, AZ, 85721, USA
2 - Duke University, Department of Biology, 139 Biological Sciences Building, PO Box 90338, Durham, North Carolina, 27708, USA
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Cottonwood C/Snowbird Center
Date: Wednesday, July 29th, 2009
Time: 1:30 PM