Colpomenia bullosa crust masquerading as Ralfsia verrucosa (Phaeophyceae) in southeast Australia

We analyzed nuclear ribosomal internal transcribed spacer (ITS) and plastid rbcL genes from the crustose brown algae from Kainga Reef, Australia and Isle of Man UK, and compared their morphologies. Unexpectedly, both ITS2 and rbcL showed that the crusts from Kainga Reef on the south coast of New South Wales, previously identified as Ralfsia verrucosa, were the crustose phase of Colpomenia bullosa. In addition, the crusts from Isle of Man were also not R. verrucosa but an undescribed species of the genus. Morphologically the C bullosa crusts were indistinguishable from Ralfsia sp. from the Isle of Man, long thought to be R. verrucosa. The erect phase of C. bullosa has not been found in Australia but exists, introduced, at the same latitude in New Zealand. It is likely that the crusts of C. bullosa are not native to Australia and for reasons yet unknown repeatedly reproduce themselves there. Our study also shows that the taxonomy and biogeography of R. verrucosa, the most common crustose species in temperate to cold waters of the world, needs to be re-examined.