Limpets of the genus Nacella (Mollusca, Gastropoda) of the southwestern Atlantic coasts: species identification based on molecular data.

DE ARANZAMENDI, M.C., GARDENAL, C.N., MARTÍN, J.P. Y BASTIDA, R

JOURNAL OF MOLLUSCAN STUDIES

OXFORD UNIV PRESS

Año: 2009 vol. 75 p. 241 - 251

0260-1230

ABSTRACT Several species of the genus Nacella show high phenotypic intraspecific variability and only a few morphological characters can be used to identify them, so that their taxonomic status is unclear. In this work molecular markers were used to determine if the most frequent forms of the genus observed along the coast of Patagonia and Tierra del Fuego in Argentina (Nacella magellanica, Nacella deaurata,Nacella show high phenotypic intraspecific variability and only a few morphological characters can be used to identify them, so that their taxonomic status is unclear. In this work molecular markers were used to determine if the most frequent forms of the genus observed along the coast of Patagonia and Tierra del Fuego in Argentina (Nacella magellanica, Nacella deaurata,Nacella magellanica, Nacella deaurata, Nacella delicatissima and Nacella mytilina) are true species, or if some are morphotypes of a single species. Maximum Parsimony and Bayesian phylogenetic analyses of the partial sequence of the mitochondrial cytochrome oxidase I and cytochrome b genes showed a polytomy comprising most of the individuals of the genus Nacella analysed. Using cytochrome b, among all species tested, onlyand Nacella mytilina) are true species, or if some are morphotypes of a single species. Maximum Parsimony and Bayesian phylogenetic analyses of the partial sequence of the mitochondrial cytochrome oxidase I and cytochrome b genes showed a polytomy comprising most of the individuals of the genus Nacella analysed. Using cytochrome b, among all species tested, onlyb genes showed a polytomy comprising most of the individuals of the genus Nacella analysed. Using cytochrome b, among all species tested, onlyNacella analysed. Using cytochrome b, among all species tested, only N. mytilina formed a well-supported clade. Interspecific genetic distances among the four Nacellaformed a well-supported clade. Interspecific genetic distances among the four Nacella species were very low and similar to the intraspecific ones. On the contrary, intersimple sequence repeats (ISSRs) fingerprint analyses confirmed the differentiation of N. magellanica, N. deaurata andN. magellanica, N. deaurata and N. mytilina. The specimens of N. delicatissima were intermixed with the individuals of N. magellanica. The specimens of N. delicatissima were intermixed with the individuals of N. magellanica and N. deaurata, suggesting that N. delicatissima is not a separate species but an infrequent morphotype of each of the other two species. ISSR–PCR was more useful in revealing genetic differences among closely related species than mitochondrial DNA sequences. These results could be explained by recent speciation processes in these limpets of the Southwestern Atlantic.N. deaurata, suggesting that N. delicatissima is not a separate species but an infrequent morphotype of each of the other two species. ISSR–PCR was more useful in revealing genetic differences among closely related species than mitochondrial DNA sequences. These results could be explained by recent speciation processes in these limpets of the Southwestern Atlantic.