Genetic differentiation and host usage of coral and fire coral-associated barnacles (Cirripedia: Pyrgomatinae and Wanellininae) across the Indian and Pacific Oceans.

This article investigates the genetic differentiation of coral-associated barnacles across the Indian and Pacific Oceans using two molecular markers, COI and 12S, from seven genera and 20 species. Molecular phylogenetic analyses revealed two major sister-clades within pyrgomatinid barnacles: the Cantellius clade, which generally lacks clear Indo-Pacific genetic divergence except for Cantellius sextus, and the major clade, where species such as Darwiniella angularis, Galkinius maculosus, Nobia grandis, and Hiroa stubbingsi show distinct genetic separation between Indian and Pacific populations. The fire coral-associated barnacle Wanella milleporae also exhibits genetic differentiation corresponding to populations in the Red Sea, Phuket (Indian Ocean), and the Pacific Ocean. The study suggests that Pleistocene glaciations, larval development duration, and host specificity influence the observed genetic divergence, contributing to the biogeographical patterns of coral barnacles in the Indo-Pacific region.