Flows of invasive ants worldwide to the United States

<p>International trade and human movements have accidentally transported thousands of species worldwide at an unprecedented scale. The resulting biological invasions are among the greatest drivers of species extinctions and can cause enormous economic losses. Understanding how globalization affects the accidental transport of species is urgent to prevent new invasions. However, global trade networks have had mixed success so far in explaining intercontinental species movements. Here, we show that commonly used proxies of global trade flows such as general imports and agricultural imports differed greatly from flows of alien ants from their donor regions to the United States. The analysis of 97 individual commodity flows revealed instead that plants and fruit imports, which are a small subset of all agricultural commodities, were associated with invasion flows. All 95 other commodities differed from flows of alien ants, including most "agricultural" commodities which had extremely heterogenous geographic origins. This highlights the need to know precisely which commodities serve as introduction pathways for a particular taxonomic group in order to explain invasion flows and identify likely source regions of future invasions in a world of changing trade relationships.</p>