Phylogeography of the intertidal barnacle Chthamalus barnesi in the northwestern Indian Ocean

The phylogeography of intertidal invertebrates in the northwestern Indian Ocean is poorly known due to difficulties in crossing diverse political regions for sampling. This study, based on mitochondrial cytochrome c oxidase subunit 1 (cox1) and nuclear sodium-potassium ATPase alpha-subunit (NaK) sequences, is the first assessment of the phylogeography of the intertidal barnacle Chthamalus barnesi in the Indian Ocean and includes all peripheral seas of the northwestern region. Our phylogenetic analyses defined 1 monophyletic clade, suggesting that C. barnesi does not comprise any cryptic species. Phylogeographic analyses showed no clear differentiation among populations of C. barnesi, except in the Red Sea. This isolated population apparently did not leave the Red Sea during post-Pleistocene glaciation. High phi ST values between the Red Sea and other populations is further indication of isolation. Low values of phi ST among the Persian Gulf, Gulf of Oman and the northeastern Arabian Sea indicate gene flow among these populations. Analysis of molecular variance revealed no significant genetic differentiation among these 3 areas. Phylogeographic analyses suggested that there may be 2 major populations (Red Sea and northwestern Indian Ocean) of C. barnesi in the Indian Ocean resulting from interactions between the Pleistocene glaciation and present-day ocean currents. Among these populations, the Persian Gulf seems to have a higher probability of being the ancestral population. After the Red Sea, the Persian Gulf has the highest genetic diversity of the cox1 gene. This evidence suggests that the Arabian Sea population may have originated from the expansion of the Persian Gulf population after the Pleistocene glaciation.