A molecular phylogeny of the Indo-West Pacific species of Haloa sensu lato gastropods (Cephalaspidea: Haminoeidae): Tethyan vicariance, generic diversity, and ecological specialization

Abstract

The cephalaspidean gastropod genus Haminoea has been considered a worldwide radiation with species living in intertidal and shallow areas with algae, seagrass sandy-mud, mangroves, and coral reefs. Recently this monophyletic status was questioned and it was suggested that Haminoea proper only included Atlantic plus eastern Pacific species, whereas the Indo-West Pacific species were a separate radiation belonging to the genus Haloa. In this work we used an extended dataset of Haminoea sensu lato including to our best knowledge representatives of all Indo-West Pacific species, plus a large representation of Atlantic and eastern Pacific species. Bayesian and maximum likelihood molecular phylogenetic analyses using three mitochondrial (COI, 12S rRNA, 16S rRNA) and two nuclear genes (28S rRNA and Histone-3) were employed to study relationships and diversification including also the closely related genus Smaragdinella. Our results support a monophyletic Atlantic + eastern Pacific Haminoea clade and a monophyletic Indo-West Pacific radiation with five genera all defined by unique morphological characters and ecological requirements, namely Haloa proper with tropical and sub-tropical species spread across the Indo-West Pacific, Lamprohaminoea including only colourful species of tropical and sub-tropical affinity, Bakawan gen. nov. with species associated with mangrove habitats across the tropical eastern Indian Ocean and western Pacific, Papawera gen. nov. restricted to temperate waters of Australasia, and Smaragdinella the only cephalaspidean genus inhabiting intertidal hard substrates across sub-tropical and tropical regions of the Indo-West Pacific. This result suggests the role of the closure of the Tethys seaway structuring the phylogeny of worldwide “Haminoea” snails and of ecology driving the phylogenetic structure of the Indo-West Pacific radiation.