Morphological and molecular assessment of Lithophyllum okamurae with the description of L. neo-okamurae sp. nov. (Corallinales, Rhodophyta)

ABSTRACT

Lithophyllum okamurae has been widely reported in the Pacific Ocean with identification based on morpho-anatomical observations. Two infraspecific taxa, L. okamurae f. okamurae and f. angulare, described from Japan, have been recorded in the temperate region of Japan. We assessed branched Lithophyllum samples morphologically referable to L. okamurae using morpho-anatomical data and DNA sequences (psbA, rbcL and partial LSU rDNA) obtained from herbarium specimens, including type material, as well as recently field-collected material in Japan. The molecular analyses showed that these ‘L. okamurae’ samples contained two species: L. okamurae and a cryptic new species which we describe as L. neo-okamurae sp. nov. Because the holotype of L. okamurae f. angulare was conspecific with original material cited in the protologue of L. okamurae, it is a heterotypic synonym of L. okamurae f. okamurae. Lithophyllum okamurae and L. neo-okamurae were morphologically similar in having warty, lumpy and fruticose thalli and in often forming rhodoliths. Lithophyllum okamurae can be morpho-anatomically distinguished from L. neo-okamurae by the thallus with tapering or plate-like protuberances (knobby protuberances in the latter) and by having smaller tetrasporangial conceptacle chambers (167–314 µm; 248–380 µm in L. neo-okamurae). Our LSU rDNA sequence data from L. okamurae f. angulare (=L. okamurae f. okamurae) was identical to that of the type of L. margaritae, which has nomenclatural priority over L. okamurae. However, considering that psbA and rbcL sequences of L. margaritae type material could not be generated in the present study, we refrain, for the moment, from proposing the taxonomic synonymy between these two taxa until the status of L. margaritae and its synonyms from the type locality (Gulf of California) are clarified.

KEYWORDS:

• Lithophyllum margaritae
• LSU rDNA
• Morpho-anatomy
• Non-geniculate coralline algae
• Northwestern Pacific Ocean
• psbA
• rbcL
• Rhodolith

Acknowledgements

AK thanks Jazmin J. Hernández-Kantún for providing DNA sequences of L. margaritae and Akira Kurashima for providing some examined specimens. The authors are grateful to the Herbarium of TRH (Kristian Hassel, Tommy Presto) PC, UC and HAK (Hajime Yasui). The manuscript was improved by the comments from two anonymous reviewers.

DISCLOSURE STATEMENT

No potential conflict of interest was reported by the authors.

SUPPLEMENTARY MATERIAL

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Additional information

Funding

This research was mainly supported by Japan Society for the Promotion of Science (JSPS KAKENHI Grant Number 26850123, 17K07908) to AK. Acquisition of some molecular data was carried out at the CNRS-UMS 2700 (Service de Systematique Moleculaire) with funds from the Action Transversale du Museum National d’ Histoire Naturelle. VP acknowledges support by Universidade da Coruña (Contrato programa-Campus Industrial de Ferrol). JH-S was supported by the International Education and Research Laboratory Program, University of Tsukuba.