Phylogenetic relationships within the order Hadromerida (Porifera, Demospongiae, Tetractinomorpha) as indicated by ribosomal RNA sequence comparisons

Despite advances of recent years no stable higher order classification of the Porifera has yet emerged. We present the first approach to addressing this problem using nucleic acid sequencing. In order to resolve relationships at various taxonomic levels it is necessary to utilize a range of species, genera and families. We have focused on one well defined order of Demospongiae, the Hadromerida, and have used 18 S rRNA sequencing to evaluate relationships between seven species belonging to five genera and four families. One species of the order Dictyoceratida has been included to indicate divergence between orders in two subclasses of the Demospongiae. Existing ordinal and familial groups are confirmed and some rearrangement of genera is indicated following sequence alignment and comparison using parsimony analysis. These data can serve as a baseline for molecular approaches to resolving relationships between other sponge groups.