Nematodes network too: diversity, abundance and dispersal via plant produce trade networks

The dispersal of invasive species, such as plant pests, can have major economic, environmental and social impacts worldwide. Movement of plant pests from farms to both foreign and domestic markets is facilitated by trade networks, such as plant produce trade networks. While many potential pathways of invasive plant pest entry are regulated, few studies have examined the diversity, abundance and dispersal of soil microorganisms, such as nematodes, on plant produce while en route between origin and destination to quantify the risk of invasive plant pest introductions via these pathways. Here it is shown that a large range and number of live nematodes are dispersing locally and nationally via plant produce trade networks, with the potential to also move internationally. Up to 98% of samples tested carried free-living nematodes and up to 40% carried plant-parasitic forms. Diversity of nematodes varied between countries and regions, and numbers on samples generally decreased with increasing distance from the farm to market. These findings may have implications for plant biosecurity surveillance as well as human health. Moreover, nematodes provide a model for other potentially invasive species dispersing via plant produce trade networks.