The different morphs of Chthamalus anisopoma: a phenotypic response? Direct molecular evidence

Chthamalus anisopoma is a rock-inhabiting barnacle which appears in two rad ically different morphs: the shell may be either conical or bent at a right angle. Based on field experiments, it was previously concluded that the tw o morphs are phenotypic variants, with the bent morph being induced by the presence of a predator gastropod. In the present study we used molecular da ta in order to examine directly the degree of genetic similarity between th e two morphs. We compared the sequences of two mitochondrial DNA segments p reviously shown to exhibit substantial inter- and intra-specific variabilit y in barnacles: the 12S mt rDNA and the cytochrome C oxidase subunit 1 (CO1 ). The sequences obtained for the different C. anisopoma morphs showed comp lete identity (12S rDNA) or very high similarity (> 99.5%, CO1). We thus pr ovide direct genetic evidence indicating that barnacles of the different mo rphs originate from a common gene pool. This supports previous conclusions that predation in this case is an inductive factor rather than selective. ( C) 2000 Elsevier Science B.V. All rights reserved.