Adapted for invasion? Comparing attachment, drag and dislodgment of native and nonindigenous hull fouling species
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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.
KeywordsHull fouling Biomechanics Dislodgment velocity Attachment strength Drag coefficient
The authors wish to thank N. Backe, B. Claman, T. Goodman, M. Herborg, J. Nelson and C. Simkanin for field and laboratory assistance. We are grateful to Megan Mach for creating the illustrations in the manuscript. Detailed comments by L. Brown, K. Demes and two anonymous reviewers improved earlier versions of this manuscript. Conference travel support was provided by the Canadian Aquatic Invasive Species Network (CAISN). Research funding was provided by the Aquatic Invasive Species program of Fisheries & Oceans Canada as well as a Natural Sciences and Engineering Research Council (NSERC) Postgraduate Scholarship and a University of British Columbia (UBC) Affiliated Fellowship to CCM.
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