The Phylogeny of Calcareous Sponges (Calcarea, Porifera)

Calcareous sponges (Class Calcarea) are one of the three recent classes of phylum Porifera.
They play an important role for our understanding of early metazoan evolution because they are probably more closely related to eumetazoa ('Coelenterata' + Bilateria) than to the other main sponge taxa Demospongiae and Hexactinellida. However, supra-specific relationships within Calcarea remain largely unresolved as a high degree of morphological homoplasy did not allow a well-supported phylogenetic classification to date.
(Click here to read more about the Calcarea on Gert Wörheide's homepage)

In a project funded by the German Research Foundation (DFG) , we combine morphology with multi-locus DNA sequence markers and lipid biomarkers.
First results of rDNA gene analyses showed that many classically recognized taxa are not monophyletic, a hypothesis which will be tested with independent protein coding genes (Dohrmann et al., 2006). Fatty acid biomarkers, on the other hand, were found to show a low variability within Calcarea, whereas being clearly distinct from other sponge groups, thus confirming calcarean monophyly (Schreiber et al., 2006).
By combining genetic, biochemical and palaeontological data we aim to contribute to the understanding of phylogenetic relationships of Calcarea, a still enigmatic key taxa for investigating early metazoan evolution.

Publications

Schreiber A., Wörheide G., Thiel V. (2006) The fatty acids of calcareous sponges (Calcarea, Porifera). Chemistry and Physics of Lipids 143, 29-37.

Dohrmann, M., Voigt, O., Erpenbeck, D., Wörheide, G. (2006): Non-monophyly of most supraspecific taxa of calcareous sponges (Porifera, Calcarea) revealed by increased taxon sampling and partitioned Bayesian analysis of ribosomal DNA. Molecular Phylogenetics and Evolution 40(3), 830-843.

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