Molecularly assisted taxonomic studies of marine red algae from the north-western Pacific: establishing the ordinal and family positions of the genus Lukinia and the monospecific status of the genus Sparlingia (Rhodymeniales)

Abstract

ABSTRACT The main aim of our study was to determine the taxonomic position of Lukinia dissecta, the species of a monotypic genus endemic to the boreal western-Pacific Ocean preliminarily placed with some doubt by several authors in the order Gigartinales. To address its ordinal and family affinities, we sequenced the plastid rbcL marker and additionally provided critical cystocarp details. Based both on a phylogenetic analysis using Bayesian inference and a maximum likelihood approach as well as cystocarp structure, we conclude that Lukinia belongs to the family Rhodymeniaceae of the order Rhodymeniales. The critical anatomical features that support this conclusion are the carposporophytes, which develop on a stout fusion cell within a large chamber formed by a domed, ostiolate pericarp, with the carposporangia borne in a dense mass on a few distal gonimolobes and most gonimolobe cells becoming carposporangia. To explore a further issue regarding the presence of Rhodymeniaceae in eastern-Russian waters, we also sequenced the rbcL of Sparlingia stipitata in order to ascertain whether it is an independent taxon or a morphological form of the widespread S. pertusa. A comparison of the obtained sequences with those of S. pertusa available in GenBank has revealed a low divergence (1 ± 0.1%) from S. pertusa, which supports the assignment of S. stipitata populations from Russian waters to S. pertusa.