Global phylogeography of the intertidal limestone bio-eroding barnacle Lithotrya (Pollicipedomorpha: Lithotryidae): centre of origin in the Central Indo-Pacific and dispersal to Western Indo-Pacific and Western Atlantic

Limestone bio-eroding invertebrates are important eco-engineers in marine systems. However, no studies have focused on the speciation and phylogeography of these significant species. We aim to investigate the diversity and phylogeography of intertidal limestone bio-eroding barnacles of the genus Lithotrya on a global scale using genetic markers. Phylogenetic analyses identified 11 mOTUs distributed across two major clades. The first major clade, Central Indo-Pacific, comprises six mOTUs distributed across eastern and north-western Australia, Philippines, New Caledonia, and Papua New Guinea. The second major clade, termed Global clade, includes the monophyletic Western Indo-Pacific clade (comprising three regional mOTUs), the widely distributed Greater Central Indo-Pacific mOTU, and the Atlantic mOTU. Time estimations have revealed more recent divergence among the three mOTUs in the Western Indo-Pacific clade and older divergences among clades distributed in the Central Indo-Pacific. Phylogenetic results support the hypothesis that the mOTUs in the Western Indo-Pacific and Atlantic originated from the Central Indo-Pacific during the Miocene. Our study, therefore, supports the ‘centre of origin’ model in the Coral Triangle to explain the diversity patterns in the Indo-Pacific. While four valid species of Lithotrya have been reported to date, the discovery of 11 mOTUs in this study highlights the significant underestimation of bio-eroding species diversity.