Diversity, systematics and biogeography of French Polynesian Lobophora (Dictyotales, Phaeophyceae)

ABSTRACT We re-evaluated the diversity of Lobophora using an integrative taxonomic approach based on a broad sampling across French Polynesian archipelagos. Our results show that French Polynesia supports at least 37 Lobophora species of which ~57% (21) are endemic. This level of endemicity is comparable to that presently known in the Caribbean and the western Indian Ocean, while French Polynesian coastlines cover a much smaller length. With a third of the species in common, French Polynesia shares considerable biogeographic affinities with the Melanesian Islands, situated over 4000 km to the west. Distribution ranges of a few species reach the western Indian Ocean, and two species also occur in the Atlantic. We hypothesize that Lobophora species in French Polynesia have mainly evolved into endemic species from colonizers originating from the Central Indo-Pacific. These rare dispersal events to ocean archipelagos followed by a long period of isolation and speciation represent an important process responsible for the high level of endemism in remote archipelagos. While south-eastern Pacific Islands could be considered an ‘evolutionary graveyard’ for the genus Lobophora as little local radiation occurred, this may simply be due to recent evolutionary history. Based on these new data, the diversity of Lobophora represents ~10% of French Polynesian seaweed diversity. Eighteen new species of Lobophora are here described from French Polynesia. Highlights Lobophora species diversity and biogeography in French Polynesia were investigated. Twenty-three species of Lobophora were newly identified, and 18 new species were described. This is the first inter-archipelago diversity and biogeographic study for a macroalgal genus in the French Polynesian region.