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 that reduce an organism’s susceptibility to predation. The few studies that examined inducible defenses in the context of biological invasions used introduced species that invaded years or decades before rather than newly introduced prey naïve to predator cues. Therefore, we set out to examine if inducible defenses may have benefited the early stage of invasion of the purple varnish clam (Nuttallia obscurata), a species native to Asia and introduced to the Northeast Pacific. Once we established that non-native N. obscurata increased their burrowing depth in the presence of their invaded-range predators, in particular Dungeness crabs (Metacarcinus magister), we compared burrowing depth in aquaria of tethered N. obscuratacollected from two introduced populations, Oregon, USA and British Columbia, Canada, versus a native population in Miyagi Prefecture, Japan.
Results/Conclusions
Specimens of N. obscurata from the USA and Canada responded similarly to M. magister cues, while specimens from Japan did not increase their burrowing depth. This suggests that while inducible defenses may contribute to the continued success of N. obscurata in the Northeast Pacific, it is unlikely they influenced the initial survival of newly arrived N. obscurata. 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.