New Ulvaceae (Ulvophyceae, Chlorophyta) from mesophotic ecosystems across the Hawaiian Archipelago

Abstract

Ulvalean algae (Chlorophyta) are most commonly described from intertidal and shallow subtidal marine environments worldwide, but are less well known from mesophotic environments. Their morphological simplicity and phenotypic plasticity make accurate species determinations difficult, even at the generic level. Here, we describe the mesophotic Ulvales species composition from 13 locations across 2,300 km of the Hawaiian Archipelago. Twenty-eight representative Ulvales specimens from 64 to 125 m depths were collected using technical diving, submersibles, and remotely operated vehicles. Morphological and molecular characters suggest that mesophotic Ulvales in Hawaiian waters form unique communities comprising four species within the genera Ulva and Umbraulva, each with discrete geographic and/or depth-related distributional patterns. Three genetically distinct taxa are supported by both plastid (rbcL and tufA) and nuclear (ITS1) markers, and are presented here as new species: Umbraulva kaloakulau, Ulva ohiohilulu, and Ulva iliohaha. We also propose a new Umbraulva species (Umbraulva kuaweuweu), which is closely related to subtidal records from New Zealand and Australia, but not formally described. To our knowledge, these are the first marine species descriptions from Hawai'i resulting from the collaboration of traditional Hawaiian nomenclature specialists, cultural practitioners and scientists. The difficulty of finding reliable diagnostic morphological characters for these species reflects a common problem worldwide of achieving accurate identification of ulvalean taxa using solely morphological criteria. Mesophotic Ulvales appear to be distinct from shallow-water populations in Hawai'i, but their degree of similarity to mesophotic floras in other locations in the Pacific remains unknown.

Nuevo registro de Ulva australis (Ulvaceae, Chlorophyta) en el norte de Chile

“…La filogenia inferida del alineamiento de las secuencias del gen rbcL y tufA, junto al bootstrap del análisis ML, se muestran en la Figura 1. La filogenia obtenida concuerda con varios estudios realizados con anterioridad en este grupo (Kraft et al 2010, Kirkendale et al 2013, Spalding et al 2016 Los especímenes analizados poseen un talo laminar membranoso, diestromático y su color varía desde un verde oscuro hasta un verde claro. El talo de 3-19 cm de alto, de forma variable desde pequeñas rosetas orbiculares a formas lobuladas.…”

The Age of Discovery is still with us

“…Spalding et al. in the current issue contribute to this process by recognizing several new deep‐water species of sea lettuces (Ulvaceae), collected from depths to 125 m using a variety of submersibles (Fig. ), remotely operated vehicles, and technical divers.…”

“…Their taxonomic concepts were guided by molecular analyses, following what has become a standard practice. In what seems to be the norm for Ulvaceae, Spalding et al. also note an “absence of clear morphological markers for these species reflects the common problem worldwide of achieving proper ulvoid identifications using morphological criteria,” this providing at least a modicum of solace for those of us with past indiscretions. However, the taxonomic component of the paper, while expertly accomplished, is not what prompted me to nominate this work as an ‘Algae Highlight’.…”

“…My journey is perhaps unique but not unusual. When queried, the authors of Spalding et al. spoke of similarly convoluted life‐paths. Heather [Spalding] diverted from what might well have been a rewarding career in the design of dental hygiene products(!).…”

“…It is clear that each of us did not set out to be phycologists, and discovered our calling often by chance, be it an encounter with an inspirational mentor, or an uninspiring alternative. But what, you might ask, does this reminiscing have to do with the paper by Spalding et al. describing deep‐water green algae from the Hawaiian Islands? What struck me about this work was not nostalgia or the science, per se , but the sense of adventure, of exploring, phycologically speaking, uncharted waters and discovering the unexpected.…”