Harnessing Citizen Science and Collections Data for Invasive Plant Surveillance

Our main source of information about the distribution of invasive plants in the United States comes from occurrence records in three categories: biological collections (physical plant specimens in museums), citizen science (opportunistic observations by untrained civilians), and invasion monitoring (structured observation by government or non-profit agencies). This study compiles a set of 3.1 million occurrence records of 3,578 introduced plant species in the continental United States, and infers spatial, temporal, and taxonomic biases by comparing the three categories of data. We find that citizen science contributes the largest bulk of records, and does better capturing visually conspicuous plants and very widespread invasives relative to the other data sources. Citizen scientists also manage to record data more uniformly across state boundaries than professional collectors. However, cryptic grass-like plants are likely to be under- sampled by citizen science, and collections generally do a better job capturing the breadth of non- native species diversity nationwide (especially in remote, unmodified environments). Invasion monitoring information seems less useful than either of the other two sources in describing introduced plants, except perhaps in some parts of the northwest. These results can help guide decision-making around invasive plant research, surveillance, and policy