Disentangling invasion processes in a dynamic shipping - boating network

The relative importance of multiple vectors to the initial establishment, spread, and population dynamics of invasive species remains poorly understood. This study used molecular methods to clarify the roles of commercial shipping and recreational boating in the invasion by the cosmopolitan tunicate, Botryllus schlosseri. We evaluated i) single vs. multiple introduction scenarios, ii) the relative importance of shipping and boating to primary introductions, iii) the interaction between these vectors for spread (i.e., the presence of a shipping-boating network), and iv) the role of boating in determining population similarity. Tunicates were sampled from 26 populations along the Nova Scotia, Canada, coast that were exposed to either shipping (i.e., ports), or boating (i.e., marinas) activities. A total of 874 individuals (~30 per population) from 5 ports and 21 marinas was collected and analyzed using both mitochondrial cytochrome c oxidase subunit I gene (COI) and 10 nuclear microsatell...