UC Riverside

Virus ecology in wild plants is a relatively new field of study that has emerged from disciplines of ecology, entomology, and plant pathology. In this dissertation, I critically review progress in plant virus ecology thus far to identify and address major research gaps, then perform a series of empirical studies to address these deficiencies. My analysis revealed that there is a deficit in research on perennial dicot plants, a weak understanding of the factors shaping virus community composition within and between hosts, and a lack of manipulative studies quantifying impacts of crop viruses on wild plant health. To address these understudied areas, I developed a wild, perennial plant study system consisting of keystone perennial hosts in local Riverside county reserves: Cucurbita foetidissima, C. palmata, and Datura wrightii. In Chapter 1 and Chapter 2, I characterized virus communities in several reserves then employed methods from community ecology to determine the factors that shape the virus communities in hosts, populations, and reserves. In Chapter Three, I determined the origins of the most prevalent aphid-transmitted virus in this system, Cucurbit aphid-borne yellows virus (CABYV). And lastly, in Chapter 4, I used manipulative experiments combined with field observations to quantify CABYV effects on cucurbit performance and evaluate how virus infection modifies host interactions with a key aphid vector, Aphis gossypii. Overall, I found that crop-associated viruses are prevalent in the perennial target hosts, which often support multiple infections. Differences between hosts and reserves structure cucurbit virus communities, with some viruses emerging as keystone species. One of these species, CABYV, negatively affects its wild hosts in ways that are relevant for both virus and host persistence within the community.