Lagourgue L. auteur aut IRD Verbruggen H. auteur aut IRD Ampou E. E. auteur aut IRD Payri Claude auteur aut IRD text journalArticle eng text/pdf born digital access Tydemania Weber-van Bosse is a genus belonging to the family Udoteaceae (Bryopsidales, Chlorophyta) and currently thought to be monospecific throughout its distribution range in the Indo-Pacific. We tested the assumption that Tydemania is a single species using species delimitation methods, morphological observations and phylogenetic reconstructions of large datasets. Our molecular and morphological data recovered two distinct groups, which we argue are the type species T. expeditionis Weber-van Bosse and T. gardineri A. Gepp & E. Gepp. The latter is currently considered a synonym of the former and we resurrect this name from synonymy. T. gardineri is distinguished morphologically from T. expeditionis by the complete absence of glomeruli, whereas T. expeditionis can have glomeruli and flabella, glomeruli alone, or flabella alone. The two species can also be distinguished by the shape and length of the stalks at the base of the flabellum, the diameter of the main axis and of the flabella siphons at the apices. In addition, they have different geographic distributions, with T. gardineri restricted to the Western Indian Ocean, and T. expeditionis extending from the Red Sea, throughout the Indian Ocean and into the West Pacific, including the Coral Triangle, the Philippines and Japan. From our dataset and literature search, we hypothesize that its south-western distribution limit is in northern Madagascar. Finally, we confirm the synonymization of T. mabahithae with T. expeditionis based on specimens from the type locality of the former and the lack of flabella in several other specimens of T. expeditionis. specialized Bryopsidales Indo-Pacific macroalgae molecular data morphology phylogeny species delimitation OCEAN INDIEN PACIFIQUE MADAGASCAR MAYOTTE TANZANIE INDONESIE PAPOUASIE NOUVELLE GUINEE VANUATU NOUVELLE CALEDONIE FIDJI MER ROUGE 034 55 1 89-99 2020 0967-0262 https://www.documentation.ird.fr/hor/fdi:010077101 10.1080/09670262.2019.1654618 0967-0262 [F B010077101] https://www.documentation.ird.fr/hor/fdi:010077101 https://www.documentation.ird.fr/intranet/publi/depot/2020-11-19/010077101.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2019-11-05 2025-02-24 fdi:010077101 fre