PARENT SESSION
Poster Session # 20: Predator - Prey / Mutualism - Parasitism Ecology.
Thursday, August 7 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.
Effects of fungal infection and competition on a grass.
Maas, Martha*,1, Fowler, Norma1, 1 University of Texas- Austin, Austin, Texas, USA
ABSTRACT- Individual plants of Nassella leucotricha, a perennial bunch grass common in central Texas, are sometimes infected by the fungus Atkinsonella texensis. Infected N. leucotricha plants do not set seed; instead, their flowering culms produce fungal fruiting bodies. However, previous studies have also indicated that infected plants are on average larger than uninfected plants. We hypothesized that infected plants are larger because they put resources into vegetative growth that would have gone into culms, flowers and seeds. To investigate the effects of infection on plant performance we conducted a factorial experiment with two levels of infection status (infected or uninfected), two levels of simulated herbivory (unclipped or clipped), and two levels of interspecific competition (alone or with 2 individuals of the grass Bothriochloa ischaemum in the pot). Each of the eight treatment combinations was replicated 20 times, for a total of 160 target plants. We found that infection status did not affect final total above-ground plant dry biomass. However, infection status did affect resource allocation: infected plants allocated a greater proportion of their above-ground dry biomass to non-flowering culms and associated leaves than did uninfected plants. As hypothesized, infection by A. texensis evidently diverts resources normally used by this grass for reproduction into vegetative growth. As expected, the presence of two B. ischaemum plants in a pot reduced N. leucotricha total above-ground dry biomass. Competition reduced average total biomass by 63%, and average vegetative biomass by 52%. In contrast, infection increased average vegetative biomass by 55%. Presumably, this infection-induced increase in vegetative size would improve a plant's survival in the future.
Key words: Atkinsonella texensis, competition, Nassella leucotricha, fungal infection