THE EFFECT OF THE FUNGUS ATKINSONELLA HYPOXYLON (CLAVICIPITACEAE)ON THE REPRODUCTIVE SYSTEM AND DEMOGRAPHY OF THE GRASS DANTHONIA SPICATA.

The Balansiae (Clavicipitaceae, Ascomycetes) consists of five genera of fungi that parasitize grasses, sedges and rushes. Most or all species produce alkaloids that are toxic to mammalian and insect herbivores. Previous reports suggest that infected grasses are more vigorous than uninfected grasses and that the proportion of infected individuals is greater in older populations. In this study individual plants or genotypes of the grass Danthonia spicata (L.) Beauv. Infected by the fungus Atkinsonella hypoxylon (Peck) Diehl. were compared with uninfected genotypes from the same population. Danthonia spicata typically bears dimorphic chasmogamous and cleistogamous flowers but in the study population infected plants were partially sterilized, producing only cleistogamous flowers; uninfected plants produced chasmogamous and cleistogamous flowers. Two experimental comparisons were conducted by propagating infected and uninfected genotypes into clones, or ramets, which were then planted back into their native site. Infected ramets had higher survival and growth rates, but lower flower production, than uninfected ramets both in random field transects and in field competition studies between D. spicata and the grass Anthoxanthum odoratum L. The results indicate infected individuals have higher survival and growth rates but reduced fecundity compared to uninfected individuals.