Ecosystem simplification, biodiversity loss and plant virus emergence

Abstract

Plant viruses can emerge into crops from wild plant hosts, or conversely from domestic (crop) plants into wild hosts. Changes in ecosystems, including loss of biodiversity and increases in managed croplands, can impact the emergence of plant virus disease. Although data are limited, in general the loss of biodiversity is thought to contribute to disease emergence. More in-depth studies have been done for human viruses, but studies with plant viruses suggest similar patterns, and indicate that simplification of ecosystems through increased human management may increase the emergence of viral diseases in crops.

Figure 1

Schematic of the relationship between habitat heterogenenity and disease risk. Disease is greatest in fully cultivated plants, intermediate in wild plants that are tended by humans in anthropic habitats, and lowest in fully wild plants. On the other hand, biodiversity is highest in the habitats of wild plants, and lowest in those of cultivated plants.

Figure 2

Spillover and spillback between wild and domestic hosts. Spillover occurs when a virus moves from its natural (either a domestic or a wild host) into a new host (either wild or domestic). Spillback occurs when a virus moves from the new host back into the natural host. Natural host here means the source of the virus in this ecosystem, but does not necessarily mean the host where the virus originally evolved (this is often unknown).