PARENT SESSION
Oral Session #53: Co-evolved species interactions: Mutualisms and parasitism. Presiding: A. Krist.
Wednesday, August 8, 2001. 1:00 PM to 4:45 PM. Hall of Ideas F.
Effects of endophyte genotype on Arizona fescue performance.
Sullivan, T.1, Faeth, Stanley1, 1
ABSTRACT- Fungal endophytes are ubiquitous, yet relatively understudied, members of the phytosphere. In agricultural grasses, endophytes of the genus Neotyphodium interact mutualistically with their plant hosts, providing protection from herbivores, increasing water and nutrient uptake, and drought resistance. The relationship between Neotyphodium and their hosts in natural systems, however, is not as clear. In Arizona fescue, Neotyphodium does not confer herbivore resistance or any other obvious benefit. Nevertheless, Neotyphodium is very common in Arizona fescue populations, and since the endophyte is only transmitted asexually via the host's seeds, Neotyphodium is presumably maintained by positive selection. Our reciprocal transplant experiments show geographic differences exist between Arizona fescue/Neotyphodium symbionts, as predicted by co-evolutionary theory. In addition to these interpopulation differences, clonal lines in a common garden experiment show significant differences between lineages for various growth and reproductive parameters. The recent development of microsatellite markers for Neotyphodium gives us the ability to identify specific lineages in natural populations, the amount of genetic variation present in these populations, as well as the performance of specific Neotyphodium genotypes in the native and non-native populations. Most of the genetic variation in Neotyphodium occurs between populations, and this variation also explains the geographic differences in plant performance and reproduction
KEY WORDS: Neotyphodium, endophytes, mutualism