The diversity of red algae is significantly increasing; in the recent interest of climate changes, taxonomic and biogeographic studies are needed in untouched regions such as ecological important islands. We examined a collection of
Gelidium specimens gathered during the 2010 Atimo Vatae expedition
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The diversity of red algae is significantly increasing; in the recent interest of climate changes, taxonomic and biogeographic studies are needed in untouched regions such as ecological important islands. We examined a collection of
Gelidium specimens gathered during the 2010 Atimo Vatae expedition based on the morphology and DNA sequencing of mitochondrial
cox1 and plastid
rbcL. Both morphological and molecular datasets demonstrated the presence of three species in Madagascar;
G. leptum G.H.Boo, L.Le Gall and H.S.Yoon, sp. nov., described here, and
G. sclerophyllum W.R.Taylor and
G. usmanghanii Afaq-Husain and Shameel.
Gelidium leptum is distinguished by thin, slender, flattened thalli with irregular branches, compactly arranged thick-walled cells in medulla, sparse rhizoidal filaments at both sides of branches, and elongate sori of tetrasporangia.
Gelidium sclerophyllum, previously considered as endemic to the Tropical Eastern Pacific, is first reported in the Indian Ocean and Hawai’i;
G. usmanghanii, previously reported to occur in Pakistan and Oman, also presents a first record in the Southern Hemisphere. Phylogenies inferred from
cox1 and
rbcL sequences suggests that each of the three species likely diverged from different ancestors. The Madagascan
Gelidium comprises two geographical elements; Madagascan endemic (
G. leptum) and widespread species (
G. sclerophyllum and
G. usmanghanii).
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