Meeting Abstract

S10-1.1  Saturday, Jan. 7  Costs and benefits of alternative defensive morphologies and population variation in phenotypic plasticity of the barnacle Chthamalus fissus JARRETT, JN; Central Connecticut State University

The barnacle Chthamalus fissus resides in the high intertidal along the coast of Southern California and Northern Baja California. Juvenile C. fissus exposed to the spine feeding predatory snail Mexacanthina lugubris lugubris may develop either a narrow or bent defensive morphology which are both better defended against this predator compared to the conic morph. This appears to be the only reported case in which there exists more than one “plastic” morphological response within a species population to a single predator. Here I report costs and benefits associated with the three morphs, species specificity of the defensive response, variation among populations of this barnacle in the degree of plasticity, and population variation in spine morphology of the predator. The evidence suggests that populations of C. fissus north of the historic northern range limit of M. l. lugubris are less able to respond to predator cues thus making them more vulnerable to predation by this predator whose population continues to extend north.