Sponges of the family Dysideidae (Dictyoceratida) are renowned for their diversity of secondary metabolites, and its genus Lamellodysidea, particularly Lamellodysidea herbacea, is the most studied taxon biochemically. Despite its importance, the taxonomic status of L. herbaceawhether it is a distinct species or a species complex-has never been assessed. Recent biochemical proWling revealed anti-plasmodial activity of brominated compounds in Lamellodysidea of the PaciWc. Here, we present a comparative chemotaxonomic and molecular analysis of selected Dysideidae from the PaciWc and the Indian Ocean (New Caledonia, Great Barrier Reef, Fiji, Mayotte, Guam, Palau). We investigated the phylogenetic relationships between the populations and assessed their bioactive (PBDE) compounds in order to unravel the taxonomic status of this commercially important group of sponges and assessed patterns of dispersal and biochemical variation. The molecular phylogeny was based on the internal transcribed ribosomal spacer and compared against a PBDE phylogeny for several specimens. Molecular data revealed a diversity of IndoPaciWc L. herbacea populations, also reXected by diVerent PBDE compound proWles. Molecular and biochemical data also revealed a Lamellodysidea species new to science. Several specimens misidentiWed as Lamellodysidea were detected based on their position on diVerent clades in the molecular phylogeny and their production of diVerent halogenated compounds (brominated vs. chlorinated). The direct comparison of molecular and biochemical data also provided evidence for the occurrence of a host switch event and support for the theory that abiotic factors, such as sedimentation, aVect the chemical constituents produced in L. herbacea.