Flows of invasive ants worldwide to the United States

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.