EVOLUTION AND SYSTEMATICS IN HALIOTIDAE (MOLLUSCA, GASTROPODA) - INFERENCES FROM DNA-SEQUENCES OF SPERM LYSIN

Abalone taxonomy and systematics have remained unresolved: neither sta ble species-level nomenclature nor a cladistic hypothesis of relations hips among species have been established. To infer the phylogeny of th e genus Haliotis and to identify species using molecular data, we comp ared complementary DNA (cDNA) sequences of sperm lysin from 27 species -group taxa from California, Japan, Australia, New Zealand, Taiwan, Bo rneo, Madagascar, South Africa, Greece, France, Italy and the Azores. The lysin cDNA sequences reveal that 22 of the 27 taxa are clearly dis tinguishable by > 20 nucleotide differences. Of the remaining 5, H, co ccinea from the Azores may be a subspecies of H. tuberculata, if not a sibling species (10 nucleotide differences). The other four taxa are most probably the same species as one of the 22 taxa: the lysin sequen ces are almost identical between H. madaka and N. discus hannai, H. co nicopora and H., rubra, H. diversicolor supertexta and H. diversicolor aquatilis, and H. tuberculata lamellosa and H. tuberculata tuberculat a. The phylogeny of lysin cDNA suggests that there are three groups am ong the 27 species-group taxa: (1) all California species and 3 Japane se species (H. gigantea, H. discus hannai, and H. madaka); (2) 1 New Z ealand species (H. ir is); (3) 1 Japanese species (H. diversicolor aqu atilis), Indo-West Pacific species and European species. These groups can be assigned to three previously recognized subgenera (Nordotis, Pa ua and Padollus) in the genus Haliotis. Two historical hypotheses are proposed to explain the biogeography and evolution within these abalon e: (1) Tethyan distribution of the ancestral abalone during the Cretac eous, followed by extinction in most of the habitat, but radiation in California and Southeast Asia which later spread to the other areas; ( 2) North Pacific rim distribution of the ancestral abalone, followed b y dispersal to the other areas during the Paleogene.