PARENT SESSION
Contributed Oral Session 109: Agroecology: Soils; Nutrient Cycling
Thursday, August 11, 8:00 AM - 11:30 AM, Meeting Room 513 A, Level 5, Palais des congrès de Montréal
Endophyte communities decrease in diversity as leaves age.
Herre, Edward*,1, Van Bael, Sunshine1, Rojas, Enith1, 1 Smithsonian Tropical Research Institute, Balboa, ANCON, Panama
ABSTRACT- This study was designed to investigate factors affecting the composition of foliar endophytic fungal communities in the leaves of a tropical tree, Theobroma cacao. Previous work in a wide range of woody dicots has shown that fungal endophytes colonize leaves via spores that germinate and subsequently penetrate the surfaces of leaves that are flushed endophyte-free. Further, point time samples of different-aged leaves have suggested that the diversity of these communities increases monotonically with leaf age. Precise leaf ages were not known, however, and this sampling method potentially confounded effects of leaf age per se and the composition of the fungal community available for colonization at the different times that the leaves that were flushed. Therefore, we sampled the composition of the endophyte communities in a cohort of simultaneously flushed leaves over a period of 6 months. Further, we collected detailed spatial data on the distributions of endophytes in the leaves, and conducted in vitro interaction trials among common and rare morphospecies. Consistent with previous reports, overall diversity of the endophytes was very high. Further, the density of endophyte infection (proportion of 2mm2 leaf fragments producing a fungal isolate) was extremely low in youngest leaves (within one week of flush) and increased to saturation at roughly 1 month. However, we found that, after an initial increase, diversity (the number of morphospecies/isolate) drops, with a consistent subset of the morphospecies emerging over time as the most common components to otherwise very diverse communities. Further, the most common endophyte morphospecies dominated over the rarer species in vitro interaction trials. Overall, we interpret these results to suggest that foliar endophyte communities are the products of semi-random colonization followed by differential proliferation and competitive displacement among an extremely diverse potential fungal flora. We briefly discuss the implications for host-plant defense and biocontrol.
Key words: fungal endophytes, diversity, tropical forests, community ecology