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Taxonomic reassessment of the Indo-Pacific Scytosiphonaceae (Phaeophyceae): Hydroclathrus rapanuii sp. nov. and Chnoospora minima from Easter Island, with proposal of Dactylosiphon gen. nov. and Pseudochnoospora gen. nov.

Wilfred John E. Santiañez, Erasmo C. Macaya, Kyung Min Lee, Ga Youn Cho, Sung Min Boo and Kazuhiro Kogame
From the journal Botanica Marina


A new and putatively endemic species of Hydroclathrus, Hydroclathrus rapanuii, is described from the geographically isolated Easter Island in the southeastern Pacific based on morphological and molecular phylogenetic data. It is distinguished from other Hydroclathrus by thalli of unevenly furrowed thin membranes, and angular, block-like plurangial sori. Our phylogenetic analyses indicated that H. rapanuii is closely related to the generitype Hydroclathrus clathratus. We also report on the morphology and phylogeny of Chnoospora minima from Easter I. and elsewhere in the Indo-Pacific Ocean, noting the previously unreported presence of hollow portions in its medulla. Although not collected from Easter I., we herein propose the recognition of two new genera, Dactylosiphon gen. nov. and Pseudochnoospora gen. nov., based on our three-gene phylogeny and their known morphologies and anatomies. Dactylosiphon is based on the three species currently assigned to Colpomenia (C. bullosa, C. durvillei, and C. wynnei) that are genetically and morphologically (i.e. thalli with erect and finger-like tubes arising from a common saccate base) distinct from other members of Colpomenia. The monotypic genus Pseudochnoospora is represented by the decumbent, branching, and inter-adhesive species currently known as Chnoospora implexa. With the above proposals, we further increase the genus-level diversity of Scytosiphonaceae in the Indo-Pacific Ocean.


WJES is funded by the Ministry of Education, Japan (MEXT) under the Monbukagakusho Scholarship Grant. ECM is funded by the Chilean Millennium Initiative (NC120030) grant. We are indebted to Carolina Sandoval for her assistance in collecting and preparing voucher specimens of the Hydroclathrus and Chnoospora from Easter Island used in this study. We thank S. Kawaguchi, A. Kato, A. Kurihara, A.D.R. N’Yeurt for the Chnoospora samples and P.J.L. Geraldino for the Rosenvingea orientalis sample. We also thank our reviewers for their insightful comments and suggestions that have considerably improved this manuscript. The scans of the type specimen of Chnoospora minima and Chnoospora implexa we examined in this study were courtesy of the Herbarium Hamburgense, University of Hamburg, Germany (HBG) and the Trustees of the Natural History Museum, London (BM), respectively.


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Received: 2017-10-25
Accepted: 2017-12-15
Published Online: 2018-1-10
Published in Print: 2018-1-26

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