The calcified encrusting brown algal genus Newhousia is reported from three new archipelagos in the Pacific: (1) Society Islands, French Polynesia; (2) Guam, Mariana Islands; and (3) Vanuatu. Newhousia presents a simple morphology consisting of small, rounded, two-layered calcified blades with limited interspecific variability in morphological features. Consequently, resolving cryptic diversity in Newhousia requires molecular phylogenetics. Bayesian and maximum likelihood phylogenetic trees, based on the concatenated cox1, cox3, psbA, rbcL and 18S rDNA sequences, supported a sister relationship of Newhousia with Lobophora/Zonaria clade. Analyses revealed five distinct evolutionary lineages within Newhousia. Genetic variation between the lineage from Guam and the two hitherto known Newhousia species, N. imbricata from Hawaii and N. yagha from Papua New Guinea, warrant the description of one new species, N. sumayensis sp. nov. The other two lineages, from the Society Islands and Vanuatu, were identified as geographically distinct populations of N. imbricata with limited genetic variation, rather than independent species. In the Society Islands, N. imbricata is common between depths of 10 m and 20 m as unattached spherical structures, or attached to hard substrate. In Guam, N. sumayensis sp. nov. grows abundantly in sciophilous habitats at depths of 10–21 m. We provide the first documentation of spores for this genus and of structures resembling plurilocular antheridia. Increased sampling throughout the Indo-Pacific region is required to further elucidate the distribution range and patterns of species richness in Newhousia. |
