On the molecular phylogeny of sponges (Porifera)*

Abstract

In the past decade molecular genetic markers have been introduced for research on the evolution and systematics of sponges. Historically, sponges have been difficult to classify due to lack of complex characters with the result that hypothesised phylogenetic relationships for various sponge taxa have changed rapidly over the past few years. Here, we summarize the current status of systematic and phylogenetic hypotheses proposed for sponges. We discuss the relationships among the three classes, Calcarea (calcareous sponges), Hexactinellida (glass sponges) and Demospongiae, as well as those among the members within each class. While molecular phylogenies of hexactinellids corroborate previous morphological hypotheses, phylogenetic hypotheses based on rDNA sequence analyses in Calcarea largely conflict with the previous, typological classifications. Many demosponge taxa have only recently been shown to be para– or polyphyletic and thus their new clades and other phylogenetic relationships have only now begun to be tested using current molecular approaches.