Biological invasions in soil: DNA barcoding as a monitoring tool in a multiple taxa survey targeting European earthworms and springtails in North America

Biological invasions are increasingly recognized as a potent force altering native ecosystems worldwide. Many of the best documented cases involve the massive invasions of North America by plant and animal taxa native to Europe. In this study, we use DNA barcoding to survey the occurrence and genetic structure of two major groups of soil invertebrates in both their native and introduced ranges: Collembola and earthworms. Populations of ten species of earthworms and five species of Collembola were barcoded from both continents. Most of these species exhibited a similar genetic structure of large and stable populations in North America and Europe, a result supporting a scenario of multiple invasions. This was expected for earthworm species involved in human economic activities, but not foreseen for Collembola species de facto unintentionally introduced. This study also establishes that invasive species surveys employing DNA barcoding gain additional resolution over those based on morphology as they allow evaluation of cryptic lineages exhibiting different invasion histories.