Examining Inducible Defenses to Novel Predators Across Native and Introduced Populations

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Marine Ecology Progress Series

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An invading species should be more likely to establish if it can successfully identify and defend against predators in the recipient range, such as through the expression of inducible defenses. Inducible defenses are behavioral or physiological changes induced by the presence of the predator or related cues that reduce an organism’s susceptibility to predation. The few studies that have examined inducible defenses in the context of biological invasions used introduced species that invaded many generations before rather than newly introduced prey naïve to predator cues. Therefore, we examined if inducible defenses may have benefited the purple varnish clam Nuttallia obscurata during the early stage of its introduction from Asia to the Northeast Pacific. Once we established that non-native N. obscurata increased burrowing depth in the presence of invaded-range predators, in particular Dungeness crabs Metacarcinus magister, we compared burrowing depth in aquaria of tethered N. obscurata collected from 2 introduced populations, viz. Oregon, USA, and British Columbia, Canada, versus those collected from a native population in Miyagi Prefecture, Japan. The physical presence of M. magister caused N. obscurata from the USA and Canada to increase their burrowing depth, while specimens from Japan did not. Whereas these findings suggest that inducible defenses may contribute to the continued success of N. obscurata in the Northeast Pacific, they do not support the idea that N. obscurata expressed inducible defenses in the early stage of invasion. Nonetheless, this mechanism may be important for the initial establishment of some species and population growth and expansion for other species once they learn the cues of local predators.


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