Sibling speciation by life‐history divergence in Dendropoma (Gastropoda; Vermetidae)

Dendropoma meroclista has been found on six islands and one continental site between Hawaii and Kenya; it occurs in shallow‐subtidal and low‐intertidal habitats and has either no, or very limited, planktic development. A very similar form has been found only in the Indian Ocean (Sinai and Madagascar), where it forms gregarious masses on exposed intertidal ledges. This form also produces many more, smaller eggs than the described species and has a planktotrophic larva. While adult anatomies of the two forms are indistinguishable, the Sinai‐Madagascar form has a smaller protoconch with distinctive sculpture. These apparent sibling species provide a case of speciation occurring by life‐history divergence within a very conservative morphology and present a surprising example of wider distributional range in the species with little apparent capacity for dispersal.