Molecular confirmation and morphological reassessment of Udotea geppiorum (Bryopsidales, Chlorophyta) with ecological observations of mesophotic meadows in the Main Hawaiian Islands

ABSTRACT

Udotea geppiorum is reported to form meadows in deep-water, soft sediment habitats in the Main Hawaiian Islands. The identification of the species, initially published as U. argentea in the archipelago, is revised and confirmed based on morphological assessment and comparative DNA sequencing with western Pacific specimens. Udotea geppiorum is fully corticated and newly shown to display discrete concentric segments arranged in a ‘tongue and groove’ manner, which are connected by medullary siphons running along the entire segment interface. Udotea geppiorum is phylogenetically nested among a cluster of Udotea spp. recently circumscribed within Udotea sensu stricto. This cluster of species is separate from the remainder of the family Udoteaceae, which includes several genera and Udotea spp. sensu lato that lack or exhibit incomplete cortication. Based on field observations conducted in O‘ahu and Maui, U. geppiorum can be found from 20 m to > 90 m depth with a peak in abundance at mesophotic depths of 60–85 m, where it forms extensive meadows that support associated diversity.

KEYWORDS:

• Bryopsidales
• cortex
• flabellata
• Harvey
• psammophytic
• siphons
• tufA
• Udoteaceae
• Yamada

Acknowledgements

Collaborative fieldwork in mesophotic habitats was funded by several awards to the University of Hawai‘i by the National Oceanic and Atmospheric Administration (NOAA) Coastal Ocean Program, NOAA Undersea Research Program’s Hawai‘i Undersea Research Laboratory, NOAA Coral Reef Conservation Program and NOAA’s Office of Ocean Exploration. TS is thankful for an invitation to participate in the Maui HURL mesophotic algae campaign led by Dr Heather Spalding (November 2006). ARS thanks support from the National Science Foundation (DEB-1754117). TS acknowledges support from a G.E. Burch Fellowship for funding residency and research at SMS. We are also thankful to Prof. Kazuhiro Kogame (SAP Herbarium, Hokkaido University, Sapporo) for providing a high-quality picture of Yamada’s syntype and Mike Guiry for discussion on the taxonomic history of U. flabellata and U. flabellum. We also thank Dr Monica Paiano (UHM) and Larissa A. Santos (SMS) for assistance with molecular work. This is SMS contribution No. 1115.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary information

The following supplementary material is accessible via the Supplementary Content tab on the article’s online page at http://dx.doi.org/10.1080/09670262.2019.1668061

Supplementary fig. S1. Photographic illustration of a shallow U. geppiorum specimen collected off Kalaeloa south-west O‘ahu from ~6 m depth by Dr R. Okano (BISH720045). Image downloaded from the Macroalgal Herbarium Portal.

Supplementary fig. S2. Photographic illustration of Yamada’s syntype from Palau (SAP8601). The specimen is identical to fig. 1 in Yamada (1930).

Supplementary fig. S3. Photographic illustration of Udotea flabellata J.V.Lamouroux nom. illeg. syntype held at NY (Harvey’s ‘Friendly Isl. Alg. no. 94’, NY02112272). Image downloaded from the Macroalgal Herbarium Portal.

Supplementary fig. S4. Photographic Illustration of U. flabellata J.V.Lamouroux nom. illeg. at MICH (Harvey’s ‘Friendly Isl. Alg no.94’, MICH1306130). Note M.J. Wynne’s annotation ‘Udotea geppiorum Yamada 1930 syntypes!’. Image downloaded from the Macroalgal Herbarium Portal.

Supplementary fig. S5. Photographic illustration of Hawaiian specimen of U. geppiorum (ARS08534) sequenced for the present study and deposited in BISH under accession BISH775782.

Supplementary table S1. Newly and previously published tufA accessions included in the phylogenetic analyses.

Author contributions

T. Sauvage, K.A. Peyton and D.L. Ballantine wrote the manuscript. K.A. Peyton conducted submersible dives and field observations. D.L. Ballantine conducted morphological observations. T. Sauvage and R.M. Wade conducted molecular work and phylogenetic analyses. A.R. Sherwood, S. Keeley and C. Smith contributed to data interpretation and revision of the manuscript. All authors read and approved the final manuscript.