Unraveling theAsteromenia peltataspecies complex with clarification of the generaHalichrysisandDrouetia(Rhodymeniaceae, Rhodophyta)

Abstract

The senior author was fortunate in 1996 to dive on the remote Houtman Abrolhos Islands of Western Australia and view in situ the stunning “ Asteromenia peltata ” that is so strikingly illustrated by John Huisman (viewable on AlgaeBase). Five years later, during excursions to Bermuda and Lord Howe Island (tropical eastern Australia), he observed and collected specimens referable to this species in both these localities. Based on their respective appearances in the field, it seemed unlikely that these entities from geographically remote regions represented the same species. Our molecular results not only confirm this suspicion, but further indicate that A. peltata sensu lato constitutes a complex of at least five distinct species. We restrict A. peltata to one of two species found in the western (sub)tropical North Atlantic, the second described herein as A. bermudensis sp. nov. Samples from Western Australia represent an undescribed species, A. exanimans sp. nov., while two entities collected from Lord Howe Island (A. anastomosans (Weber-van Bosse) comb. nov. and A. pseudocoalescens sp. nov.) conform to records variously reported as Asteromenia peltata and Drouetia coalescens . Specimens of D. coalescens from South Africa are also not representative of the genus Drouetia , but form a novel lineage within the Rhodymeniaceae. We included two species of Halichrysis in our molecular analyses and, in combination with observations of salient anatomical features, provide arguments for maintaining Asteromenia, Drouetia, and Halichrysis as distinct genera.