Division of Science, Mathematics, and Computing and Dean of the College Present
Ghosts of Photosynthesis Past and the Green Trojan Horse:
Effects of Atmospheric Change and Infection on Competition in Plant Communities
Changes to the global atmosphere, including increasing levels of carbon dioxide and tropospheric ozone, can significantly alter plant physiology, competition, and community composition. However, much less is known about the effects of these atmospheric changes on viral plant disease, despite the profound effects such diseases can have on their hosts and communities. I used open top chambers in the field to examine the effects of rising carbon dioxide and ozone on the probability of disease establishment and proportion of plants infected by barley yellow dwarf virus (BYDV), an economically and environmentally important pathogen of plants in the grass tribe. I examined the effects of both gases on within-host viral fitness, viral spread and host competition in monocultures and mixtures of two grasses: the epidemiologically important host Avena fatua and the poor viral host Setaria lutescens. Elevated levels of carbon dioxide alone increased the probability of disease establishment in Avena, but elevated levels of both atmospheric gases reduced the probability of disease establishment. In mixtures of Avena and Setaria, within-host viral fitness and transmission rates in both Avena and Setaria were enhanced. In addition, when Avena and Setaria were grown in competition, carbon dioxide reduced the benefits to Avena of growing in mixtures across infection treatments. Although presence in mixtures significantly suppressed growth in Setaria, CO2 increased reproductive output in infected plants. These results suggest an important role for infection in grassland communities under changing global atmospheres.
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