Linking endophytes and ecosystem functioning

OMACINI M

Fayetteville, Arkansas, USA

Simposio; . 5th International Symposium on Neotyphodium/Grass Interactions; 2004

  Predicting the impact of endophyte-grass symbioses on ecosystem functioning requires a mechanistic understanding of how endophytes alter the amount and quality of resources for plants, consumers and decomposers at various spatio-temporal scales.  Recent experiments have shown that endophytes can modify energy transfers through aboveground insect food-webs but so far the  impact of foliar endophytes on belowground processes has been largely overlooked. In this presentation, I focus on the functional significance of Neotyphodium infections  for both the grass hostand neighbo­ring non infected plants. Using the annual ryegrass Lolium multiflorum as a model system, and carefully designed microcosms experiments, we have explored alternative pathways for an effect of fungal endophytes on litter decomposition processes. Endophyte infection slowed down the decomposition of aboveground litter produced by the host plant (a substrate quality effect). We also found that litter produced by endophyte-infected L. multiflorum  affected the decomposition rate of  litter derived from a different, endophyte-free grass species (a microenvironment effect). These results imply that endophyte effects on tissue quality for aboveground herbivores can also be transmitted to components of soil food webs with important potential consequences for ecosystem functioning. In another experiment, we observed significant endophyte effects on the activity of arbuscular mycorrhizal fungi. Endophyte infection inhibited  host-plant root colonization by AM fungi but indirectly promoted AM  colonization of conspecific uninfected neighbors. Overall, our findings suggest that Neotyphodium endophytes should be considered when looking at possible feedback interactions between plant and soil communities. However, further research is required to investigate the extent and significance of these mechanisms in natural communities.