Cultivated alien plants with high invasion potential are more likely to be traded online in China.

Biological invasions have become a worldwide problem, and measures to efficiently prevent and control invasions are still being developed. Like many other parts of the world, China is undergoing a dramatic increase in plant invasions. Most of the currently 933 established (i.e., naturalized) plant species, of which 214 are categorized as invasive, have been introduced into China for cultivation. It is likely that many of those species are still being traded, particularly online, by plant nurseries. However, studies assessing whether naturalized and invasive species are currently being traded more or less than non-naturalized aliens are rare. We extracted online-trade information for 13,718 cultivated alien plant taxa on 1688.com, the largest website for domestic B2B in China. We analyzed how the presence in online-nursery catalogues, the number of online nurseries that offer the species for sale, and the product type (i.e., seeds, live plants and vegetative organs) differed among non-naturalized, naturalized non-invasive and invasive species. Compared to non-naturalized taxa, naturalized non-invasive and invasive taxa were 3.7 to 5.2 times more likely available for sale. Naturalized non-invasive and invasive taxa were more frequently offered as seeds by online nurseries, whereas non-naturalized taxa were more frequently offered as live plants. Based on these findings, we propose that, to reduce the further spread of invasive and potentially invasive plants, implementation of plant-trade regulations and a monitoring system of the online horticultural supply chain will be essential.