Differences in anti-predator traits of a native bivalve following invasion by a habitat-forming seaweed

Invasive habitat-forming species cause large changes to the abiotic environment, whichmay lead to lethal and sublethal effects on native fauna. In this study, we tested whether morphological anti-predator traits of an infaunal bivalve, Anadara trapezia, differed between areas invaded by the habitat-forming seaweed Caulerpa taxifolia and uninvaded habitats in estuaries in New South Wales, Australia. Caulerpa changes the abiotic environment in ways that may affect traits of native species. In particular, there is lowerwater flow, lower dissolved oxygen in thewater and sediments aremore silty and anoxic than in unvegetated habitat. To test our hypotheses, we collected Anadara from Caulerpa and uninvaded habitats andmeasured shell thickness, shell strength and resistance to opening of valves.We found that all three traits were reduced inAnadara fromCaulerpa habitat comparedwithAnadara fromuninvaded habitats. These findings are consistent with the idea that trait modifications in native fauna in response to invasive habitat-forming species can potentially increase susceptibility to predation. Additional keywords: Anadara trapezia, bivalve, Caulerpa taxifolia, invasive seaweed, predation, shell strength, traits. Received 19 August 2011, accepted 3 November 2011, published online 13 December 2011