Meeting Abstract
Although sponges (phylum Porifera) are basal metazoans with relatively simple body plans, some groups of sponges possess a wide diversity of siliceous spicules that form a mineralized skeleton. Recent investigations of the Order Astrophorida have established a molecular phylogeny based on gene sequences encoding the large (28S) subunit of nuclear ribosomal RNA and subunit I of mitochondrial cytochrome oxidase (coxI). This molecular phylogeny conflicts with traditional arrangements of Astrophorida and suggests a novel pattern of gain and loss of morphological traits, including spicules. We expanded a previously published morphological character matrix of Astrophorida to include nested traits based on an ontology of morphological characters and modified the character matrix to include only the presence and absence of traits. We obtained 28S and cox1 sequences of Astrophorida from GenBank, aligned these sequences using MAFFT, and constructed a molecular phylogeny by implementing a relaxed clock model in MrBayes. We tested whether morphological traits were correlated with this phylogeny by calculating measures of phylogenetic signal implemented in the R-based software package ‘arbor’. Of the 24 morphological traits examined, 14 displayed significant phylogenetic signal. Ongoing work examines phylogenetic correlations among these traits and their impact on the diversification of Astrophorida.
