Phylogenetic position of Newhousia (Dictyotales, Phaeophyceae) and the description of N. sumayensis sp. nov. from Guam

ABSTRACT

The calcified encrusting brown algal genus Newhousia is reported from three new archipelagos in the Pacific: (1) Society Islands, French Polynesia; (2) Guam, Mariana Islands; and (3) Vanuatu. Newhousia presents a simple morphology consisting of small, rounded, two-layered calcified blades with limited interspecific variability in morphological features. Consequently, resolving cryptic diversity in Newhousia requires molecular phylogenetics. Bayesian and maximum likelihood phylogenetic trees, based on the concatenated cox1, cox3, psbA, rbcL and 18S rDNA sequences, supported a sister relationship of Newhousia with Lobophora/Zonaria clade. Analyses revealed five distinct evolutionary lineages within Newhousia. Genetic variation between the lineage from Guam and the two hitherto known Newhousia species, N. imbricata from Hawaii and N. yagha from Papua New Guinea, warrant the description of one new species, N. sumayensis sp. nov. The other two lineages, from the Society Islands and Vanuatu, were identified as geographically distinct populations of N. imbricata with limited genetic variation, rather than independent species. In the Society Islands, N. imbricata is common between depths of 10 m and 20 m as unattached spherical structures, or attached to hard substrate. In Guam, N. sumayensis sp. nov. grows abundantly in sciophilous habitats at depths of 10–21 m. We provide the first documentation of spores for this genus and of structures resembling plurilocular antheridia. Increased sampling throughout the Indo-Pacific region is required to further elucidate the distribution range and patterns of species richness in Newhousia.

KEYWORDS:

• Endemism
• Mariana Islands
• Marine biodiversity
• Molecular phylogeny
• Society Islands

ACKNOWLEDGEMENTS

CV is indebted to Ghent University for a grant as postdoctoral research (16/PDO/141). CV’s mobility was supported by The Research Foundation – Flanders (FWO) grant V406219N. CV is an International Research Fellow of the Japan Society for the Promotion of Science. TS is indebted to the University of Guam for supporting studies to document and conserve the natural heritage of Guam and the larger Micronesian region. We thank Théo Gromberg for his assistance in taking the SEM photographs. We are indebted to Gary Saunders for providing DNA material of a Newhousia specimen from Vanuatua. The authors thank the Japan Society for the Promotion of Science (JSPS) for additional financial support including a Grant-in-Aid for Science.

DISCLOSURE STATEMENT

No potential conflict of interest was reported by the authors.

SUPPLEMENTARY MATERIAL

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Funding

This research work was supported by a LABEX CORAIL research grant under the program ALGALREEF. This work makes use of resources and facilities provided by UGent as part of the Belgian contribution to EMBRC-ERIC [FWO GOH3817N and I001621N]. Any opinions, findings and conclusions or recommendations expressed in this manuscript are those of the authors and do not necessarily reflect the views of NASA, NSF or any of their subagencies. AS and MP are supported by the U.S. National Science Foundation [DEB-1754117] ; the U.S. National Fish & Wildlife Foundation [NFWF 0810.18.059023]; and the National Oceanic and Atmospheric Administration (NOAA) Papahānaumokuākea Marine National Monument. Sample collections, specimen observations and species descriptions conducted in Guam were possible through funding by the National Aeronautics and Space Administration (NASA; nasa.gov) and the National Science Foundation (NSF; nsf.gov) under grant numbers 80NSSC17M0052 and OIA-1946352 awarded to TS and managed through the Guam EPSCoR offices of NASA and NSF.