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Despite the importance of dispersal behavior in the eco-evolutionary responses of species to global environmental change, its role in the invasion dynamic of stowaway invaders has been poorly studied, especially in low-mobile species (i.e. with direct development). Here we use peracarid crustaceans as a target group to understand the role that local dispersal plays in the initial stages of the stowaway pathway in species inhabiting transport hubs (specifically marinas). Thus, we performed field experiments to quantitatively explore differences in species' propensity to disperse when comparing species with low and high invasion potential (considered here as the ability for successful anthropogenic dispersal). At the community level, we found that widespread introduced species (with high potential for invasion; HPI) exhibited higher propensity for local dispersal than closely related species that fail to spread (with low potential for invasion; LPI). From a functional perspective, high invasion potential, in synergy with omnivorous feeding and a tube-dweller lifestyle, was instrumental in determining differences in trait composition between assemblages that vary in their natural tendency to disperse. In addition to anthropogenic dispersal on ships, we show that unaided dispersal may play a crucial role at the beginning of the stowaway pathway, even in low-mobile species. Knowledge of dispersal behavior should be more fully integrated into research on managing the risk of this growing invasion pathway. This may help to predict rates of spread and provide new insights into the proximate causes of stowaway organisms' invasion success. [ABSTRACT FROM AUTHOR]

Commercial ships inadvertently transfer vast numbers of living organisms beyond their evolutionary ranges, sometimes resulting in invasions of distant marine habitats. Biofouling on ship hulls translocate organisms that cling to the undersides and interstices of ships that function as hard substrate habitat for biota. Because biofouling accumulates over space and time continually, it poses risk to all ports visited. To better understand the potential magnitude of the biofouling vector in the United States, we compiled information on ship-specific dimensions as well as actual arrival histories of the fleets of ships calling at U.S. ports (2011-2014) in an effort to calculate wetted surface area (WSA) flux to the U.S. The annual mean flux of WSA from overseas bioregions to the U.S. is 333 km2 year−1. An additional 177 km2 year−1 of WSA moves among the eight distinct biogeographic regions of the lower 48 United States. We confirm that over 90% of all global marine bioregions (120 of 132 identified by IUCN) are visited by commercial ships within five port calls of arriving to the U.S. Our analysis is the first ever to quantify the extent of WSA flux among global marine bioregions and underscores the urgent need for management approaches and technologies that will reduce associated invasion risks. [ABSTRACT FROM AUTHOR]

Ships' hulls can transport aquatic nuisance species, but there is little quantitative information about the magnitude of vessel biofouling on a global or regional scale. There does not exist a robust method to estimate the wetted surface area (WSA) of a particular fleet of ships, especially across the diversity of possible vessel types. An estimate of the total WSA of ship arrivals into a port or region is essential to determine the potential scope of biofouling and to inform management strategies to reduce the future invasions. Multiple statistical models were developed so commonly available ships' parameters could be used to estimate the WSA for a given set of fleet data. Using individual ship characteristics and publicly available data from ~120,000 active commercial ships in the world fleet, the method results in a total global minimum WSA estimate of approximately 325 × 10 m. The size of the global fleet employed here is greater than the commonly cited vessel number of approximately 80,000-90,000, as we include ships <100 gross tons. Over 190,000 vessels were initially identified, representing a WSA of 571 × 10 m, but active status of only 120,000 vessels could be confirmed. Reliable data were unavailable on the operating status of many additional and especially smaller vessels. This approach, along with a contemporary and comprehensive estimate of global WSA, when combined with knowledge of the different operational profiles of ships that may reduce biofouling (port residence times, steaming speeds, extent of antifouling coatings, cleaning frequency, etc.), can inform current numerical models and risk assessments of bioinvasions. [ABSTRACT FROM AUTHOR]

Invasive species possess unique traits that allow them to navigate the invasion process in order to establish and spread in new habitats. Successful hull fouling invaders must resist both physical and physiological stressors associated with their voyage. We characterised attachment strength and drag coefficient of common fouling species in order to estimate the velocity required to dislodge them from boat hulls. We hypothesized nonindigenous fouling species would possess biomechanical properties that enable them to remain attached to hulls more successfully than similar native species. Indeed, the well-known invasive ascidian Styela clava had both high attachment strength and low drag coefficient and its dislodgment velocity was well above that of fast moving vessels. In contrast, the native congener Styela gibbsii had low attachment strength and higher drag coefficient. Colonial invasive species employed a different hitchhiking strategy; despite their low attachment strengths, Botrylloides violaceus and Didemnum vexillum had low drag coefficients allowing them to be transported on slower-moving vessels, such as sailboats and barges. The biomechanical adaptations of invasive species show promise in predicting future invaders and informing vector management strategies at the first node in the invasion process: transport by the vector. [ABSTRACT FROM AUTHOR]

The smooth shelled blue mussel, Mytilus galloprovincialis Lmk (Bivalvia: Mollusca) arrived in Pearl Harbor, Oahu, Hawai'i on 22 June 1998 as a member of the fouling community of the USS Missouri, and mussel spawning activity was observed within 2 h of the vessel's arrival. Small mussels (<10 mm shell length, approximately 6 weeks post-metamorphosis) were collected on 30 September 1998 from a submarine ballast tank in Pearl Harbor, indicating that a successful recruitment event had taken place very soon after the first arrival of the species at this location. We suggest that even if M. galloprovincialis is not able to establish permanently within Pearl Harbor, the fact that it has been able to successfully spawn and recruit to another shipping vector within the Harbor indicates that a ‘stepping stone’ model of range expansion from temperate to temperate region via an intermediary subtropical environment is quite feasible for this species. Data from worldwide distributions of mussels of the family Mytilidae indicate that preferred habitats are eutrophic continental shelf regions, which suggests that successful establishment within Pearl Harbor is possible. However, oceanic coral-reef environments are not preferred habitat types, suggesting that M. galloprovincialis is not likely to become widely distributed in the Hawaiian Islands. [ABSTRACT FROM AUTHOR]